GERMAN ATV-DVWK

RULES AND STANDARDS

Standard
ATV-DVWK-A 198E

Standardisation and Derivation of

Dimensioning Values for Wastewater
Facilities

April 2003
ISBN 3-924063-63-X

Publisher/marketing:
ATV-DVWK German Association for Water, Wastewater
and Waste,
Theodor-Heuss-Allee 17 y D-53773 Hennef
Tel. ++49-22 42 / 8 72-120 y Fax:++49 22 42 / 8 72-100
E-Mail: vertrieb@atv.de y Internet: www.atv-dvwk.de
ATV-DVWK-A 198E

User Notes

This ATV Standard is the result of honorary, technical-scientific/economic collaboration which has been
achieved in accordance with the principles applicable therefor (statutes, rules of procedure of the ATV
and ATV Standard ATV-A 400). For this, according to precedents, there exists an actual presumption
that it is textually and technically correct and also generally recognised.

The application of this Standard is open to everyone. However, an obligation for application can arise
from legal or administrative regulations, a contract or other legal reason.

This Standard is an important, however, not the sole source of information for correct solutions. With its
application no one avoids responsibility for his own action or for the correct application in specific cases;
this applies in particular for the correct handling of the margins described in the Standard.

The German Association for Water, Wastewater and Waste, ATV-DVWK, is the spokesman in Germany for
all universal questions on water and is involved intensively in the development of secure and sustainable
water management. As politically and economically independent organisation it operates specifically in the
areas of water management, wastewater, waste and soil protection.

In Europe the ATV-DVWK is the association in this field with the greatest number of members and, due to
its specialist competence it holds a special position with regard to standardisation, professional training and
information of the public. The ca. 16,000 members represent the experts and executive personnel from
municipalities, universities, engineer offices, authorities and businesses. The emphasis of its activities is on
the elaboration and updating of a common set of technical rules and standards and with collaboration with
the creation of technical standard specifications at the national and international levels. To this belong not
only the technical-scientific subjects but also economical and legal demands of environmental protection
and protection of bodies of waters.

Publisher/Marketing: Setting-up and printing:

ATV-DVWK German Association for Water DCM, Meckenheim

Wastewater and Waste
Theodor-Heuss-Allee 17
D-53773 Hennef
Tel.: ++49-22 42 / 8 72-192 ISBN:
Fax: ++49- 22 42 / 8 72-100 3-924063-63-X
E-Mail: vertrieb@atv.de
Internet: www.atv-dvwk.de Printed on 100 % recycled paper

© ATV-DVWK Deutsche Vereinigung für Wasserwirtschaft, Abwasser and Abfall e. V., Hennef 2002

All rights, in particular those of translation into other languages, are reserved. No part of this Standard may be reproduced in any form
- by photocopy, microfilm or any other process - or transferred into a language usable in machines, in particular data processing ma-
chines, without the written approval of the publisher.

2 April 2003
 ATV-DVWK-A 198E

Authors
This Standard has been elaborated by the ad-hoc Working Group “Dimensioning-Principles for Wastewater
Facilities“ within the ATV-DVWK Main Committee ES “Drainage Systems” and KA “Municipal Wastewater
Treatment”.

The following are members of the Working Group:

Prof. Dr.-Ing. Dr. h. c. R. Kayser, Braunschweig (Chairman)

Dr.-Ing. E. Meißner, München
Dipl.-Ing. H. Schmidt, Erkrath
Prof. Dr.-Ing. Th. Schmitt, Kaiserslautern
Dr.-Ing. M. Schröder, Aachen
Bauass. Dipl.-Ing. G. Willems, Essen

April 2003 3
ATV-DVWK-A 198E

Contents
User Notes ............................................................................................................................................... 2

Authors .............................................................................................................................................................3

1 Area of Application ...........................................................................................................................6

1.1 Preamble ................................................................................................................................... 6
1.2 Objective.................................................................................................................................... 6
1.3 Scope ........................................................................................................................................ 6

2 Symbols..............................................................................................................................................7
2.1 General...................................................................................................................................... 7
2.2 Surface Parameters and Runoff Coefficients............................................................................ 8
2.3 Flow/Discharge Parameters ...................................................................................................... 9
2.4 Concentration Parameters ........................................................................................................ 9
2.5 Sludge Parameters.................................................................................................................... 11
2.6 Load Parameters....................................................................................................................... 11
2.7 Other Characteristic Values ...................................................................................................... 11

3 Preparatory Work for the Derivation of Dimensioning Values ...................................................12

3.1 Initial Situation ........................................................................................................................... 12
3.2 Data Gathering .......................................................................................................................... 12
3.2.1 Flow Measurement.................................................................................................................... 12
3.2.2 Sampling for the Derivation of Loads ........................................................................................ 13
3.3 Data Required for Dimensioning ............................................................................................... 13
3.3.1 Flow Data .................................................................................................................................. 13
3.3.2 Loads and Concentrations ........................................................................................................ 14
3.3.2.1 For the Size-Classification and the Determination of the Design Capacity of Wastewater
Treatment Plants 14
3.3.2.2 For the Dimensioning of Combined Sewer Overflows 14
3.3.2.3 For the Dimensioning of Wastewater Treatment Plants 15

4 Determination of Data about the Actual Condition ......................................................................16

4.1 General Documents and Data................................................................................................... 16
4.2 Determination of Discharge Data .............................................................................................. 16
4.2.1 Data on Water Consumption ..................................................................................................... 16
4.2.2 Data on Sewage Flow ............................................................................................................... 17
4.2.2.1 Determination of Essential Flow Data 17
4.2.2.2 Determination of the Annual Mean Dry Weather Flow 18
4.2.2.3 Determination of the Wastewater Flow 18
4.2.2.4 Determination of the Infiltration Water Flow 18
4.2.2.5 Determination of Daily Peaks and Nightly Minima 19
4.2.2.6 Determination of the Combined Wastewater Flow to the Wastewater Treatment Plant 20
4.2.3 Flow Data on the Basis of Empirical Values ............................................................................. 21
4.3 Determination of Loads and Concentrations............................................................................. 22
4.3.1 Determination through Evaluation of Measured Values............................................................ 22
4.3.1.1 Sampling Frequency and Necessary Parameters 22
4.3.1.2 Examination of Available Information 23
4.3.1.3 Location of the Sampling 23
4.3.1.4 Summary of Measured Data and Calculation of the Daily Load as well as the Values of the
Concentration Ratio 24

4 April 2003
 ATV-DVWK-A 198E

4.3.1.5 Determination of the Relevant Loads on the Basis of Weekly Means 25

4.3.1.6 Determination of the Relevant Loads as 85 % Values 26
4.3.1.7 Determination of the Relevant Concentrations 26
4.3.1.8 Determination of the Peak Factor for Nitrogen 26
4.3.2 Estimation of Pollutant Loads and Concentrations on the Basis of Empirical Values ...............27

5 Forecast Data.....................................................................................................................................28

6 Costs and Environmental Effects ...................................................................................................28

7 Relevant Regulations, Standards and Standard Specifications ................................................28

8 Literature [Translator’s note: Apart from [4] no known translation available in English] ......30

Appendix A: Explanatory notes for surface characteristic values and catchment area related
values..................................................................................................................................................31
A1 Surface characteristic values .....................................................................................................31
A 1.1 Surface areas.............................................................................................................................31
A 1.2 Calculated value “Impermeable surface” Aimp ............................................................................32
A 1.3 Degree of paving and runoff coefficients ...................................................................................32
A 1.4 Numerical example for surfaces and surface parameters .........................................................35
A. 1.5 Catchment area related values ..................................................................................................36
A2 Surface reference parameters ...................................................................................................36

Appendix B 1: Summary of flow values from the English translations of respective ATV-DVWK
Standards ...........................................................................................................................................38

Appendix B 2: Summary of flow values from the original German ATV-DVWK Standards ...................39

Appendix C: Example for the evaluation of measured values....................................................................40

C1 Flows ..........................................................................................................................................40
C 1.1 Summary of measured values ...................................................................................................40
C 1.2 Daily flows ..................................................................................................................................41
C 1.3 Determination of the dry weather flow .......................................................................................41
C 1.4 Determination of the wastewater flow as annual mean .............................................................42
C 1.5 Determination of the infiltration water flow .................................................................................43
C 1.6 Determination of the maximum and minimum dry weather flow ................................................43
C 1.7 Maximum and minimum wastewater flow ..................................................................................44
C 1.8 Determination of the combined wastewater flow .......................................................................44
C2 Loads and concentrations ..........................................................................................................45
C 2.1 Summary of measured values ...................................................................................................45
C 2.2 Planning of sampling..................................................................................................................46
C 2.3 Determination of the relevant COD load on the basis of weekly means ...................................47
C 2.4 Determination of the relevant COD load as 85 % value ............................................................48
C 2.5 Ratio values of important parameters ........................................................................................48
C 2.6 Determination of the concentrations ..........................................................................................49
C 2.7 Determination of the peak factor for the nitrogen loading..........................................................50

April 2003 5
ATV-DVWK-A 198E

1 Area of Application 1.2 Objective

This Standard is concerned with the definition,

collection, evaluation and examination of data as
1.1 Preamble well as with the subsequent derivation of dimen-
sioning values based on these for wastewater
In the course of the self-monitoring of wastewater treatment plants and drainage systems. Forecast
treatment plants data are collected which can data for various time horizons can subsequently
form a valuable basis with the planning of expan- be derived from measured data. With this Stan-
sion or optimisation of both drainage systems dard the objective is pursued, globally for all
and also wastewater treatment plants. Unfortu- ATV-DVWK Standards and Advisory Leaflets, as
nately, in the past, the collection and evaluation far as possible and practical to standardise the
often took place unilaterally, either for wastewater derivation of values for the dimensioning of
treatment plants only or for sewer systems only. drainage systems and municipal wastewater
Terms and symbols were not always harmonised treatment plants as well as the symbols for di-
with each other, frequently the same symbols mensioning values.
with different significance have been used in dif-
ferent standards. The reason was the lack of The discharges, loads and concentrations neces-
clear specifications. sary for dimensioning are, as previously, laid
down in the appropriate ATV-DVWK-Standards.
After even more municipalities, associations and
operating companies are managing data banks in The following are introduced in this standard:
which a great deal of basic data for water man-
agement planning are kept, a clear definition and – a homogeneous system for symbols;
common further processing of these data have – for hydraulic calculations a mathematical de-
gained in significance. termination of the dry weather flow dissociated
from meteorological records;
The planning of wastewater facilities should as – for the interface sewer - wastewater treatment
far as possible take place on the basis of meas- plant a new approach for the determination of
ured values. As the planning process for the ex- the combined wastewater flow QCWW;
pansion of existing wastewater facilities or new – the concentration of the frequently to be de-
construction measures in individual locations as a termined COD as master parameter and the
rule spread over several years, this time should, if ratios to the less frequently determined other
possible, be used to widen the data base. A reli- parameters (e.g. BOD5, filterable solids, nitro-
able databasis is a basic prerequisite for an ecol- gen and phosphorus), in order to keep the
ogically and economically practical planning, costs for chemical analysis within limits.
construction and operation of wastewater facili-
ties. Should, after the publication of this Standard, di-
vergent definitions be given in other ATV-DVWK-
Sewer systems and wastewater treatment plants Standards then the latter apply.
are to be operated for the same flow. Due to the
different planning horizons the sewer system can
be dimensioned for another flow than that for 1.3 Scope
the wastewater treatment plant. Previously the
permitted combined wastewater flow was deter- The here summarised terms and bases for the
mined primarily according to dimensioning data determination of
or the hydraulic capacity of the wastewater – catchment areas,
treatment plant. In order to make possible an op- – flows/discharges,
timisation between permitted charging of the – loads and
wastewater treatment plant and the dimensioning – concentrations
of stormwater tanks, an approach using a band-
width of the permitted combined wastewater flow
is recommended.

6 April 2003
 ATV-DVWK-A 198E

concern all ATV-DVWK Standards and Advisory AC,Sep [AE,Tr] – area with separate sewer sys-
Leaflets which deal with dimensioning and appli- tem
cation of simulation models for drainage systems, AC,Comb [AE,Mi] – area with combined sewer sys-
combined wastewater or stormwater treatment tem
facilities and wastewater treatment plants (see AC,Ind [AE,G] – commercial/industrial area
Chap. 7, ATV-DVWK Standards).
Further differentiation in lower case, for exam-
ple:
p [b] – with paved surface (AC,p) [AE,b]

2 Symbols np [nb]
s [k]
– non-paved surface (AC,np) [AE,nb]
– with sewers (AC,s [AE,k] and, for ex-
ample, AC,s,p [AE,k,b])
2.1 General ns [nk] – without sewers (AC,ns) [AE,nk]

A common system is introduced for all symbols – Types of flow: [in German upper case, 1 or 2
according to which, behind the respective main letters], for example:
term (A for surfaces, Q for flows/discharges, C, S WW [S] – wastewater flow (QWW) [QS]
and X for concentrations and B for loads), an in- DW [T] – dry weather flow (QDW) [QT]
dex or further indices separated by commas can Inf [F] – infiltration water flow (QInf) [QF]
follow. Alternatively, instead of the index style Comb [M] – combined wastewater flow
one can work with lowered hyphen. Special indi- (QComb) [QM]
ces are continued in later chapters, however, Thr [Dr] – throttle flow (QThr) [QDr]
they can also be selected sensibly, for certain
applications in the respective Standards. – Periods of time: lower case, for example:
Authors’ afternote: a – year
In agreement with EN 752-1 it is differentiated m – month
between “wastewater” (water changed by use t – a certain period of time, e.g. from
and discharged to a sewer system, e.g. domestic 13.7.02 to 18.9.02
wastewater and/or commercial/industrial waste- w – week
water) [in German: Schmutzwasser] and “sew- d – day
age” (wastewater and/or surface water conveyed h – hour
by a sewer) [in German: Abwasser]. min – minutes
With no details: interval ≤ 5 minutes
Translator’s note:
While the main terms remain unchanged as they – Divisor for wastewater flows:
are recognised internationally, the indices used x in h/d, (24, 16, x for general)
reflect the English translation of the individual xQmax in h/d for peak values
German parameter. For simplicity and clarity
these have been chosen to match as far as pos- – Mean values for periods, e.g.:
sible the German indices. Where this is not pos- aM – annual mean
sible the original German symbol is placed in mM – monthly mean
square brackets after the English version. This pM – mean for a period
procedure is not intended to create new symbols wM – weekly mean
for the English-speaking engineering community 2wM – 2-weekly mean
but serves solely to make German sym- dM – daily mean
bols/indices comprehensible to non-German hM – hourly mean
speakers.
For the main meanings below the indices are
specified in the following order:
− Catchment areas (AC) [AE], further sub-
division, for example:

April 2003 7
ATV-DVWK-A 198E

2.2 Surface Parameters and Runoff from the locality, others first result through multi-
Coefficients plication using a runoff coefficient and represent
numerical values.
As the conceptual limitation of catchment areas
in practice continues to cause confusion, the ar- In Appendix A further explanatory notes can be
eas which are possible within water management found on surface parameters and the values de-
are listed below. The majority are assignable rived from these.

Symbol Unit Designation

English German

AC A_C AE A_E ha Catchment area; e.g. of a wastewater disposal region

AC,s A_C,s AE,k A_E,k ha Catchment area served by sewers or covered by a drainage
system
AC,ns A_C,ns AE,nk A_E,nk ha Catchment area not served by sewers or not covered by a
drainage system
AC,p A_C,p AE,b A_E,b ha Sum of all paved surfaces of a catchment area; is to replace
Ared, i. a. in ATV-A 128E (1992)
AC,np A_C,np AE,nb A_E,nb ha Sum of all non-paved surfaces of a catchment area

AC,Ind A_C,ind AE,G A_E,G ha Commercial and/or industrial catchment area

Aimp A_imp Au A_u ha Impermeable surface area, application-related numerical value:

Aimp = AC,s ⋅ Ψ or Aimp = AC,p ⋅ Ψ [Au = AE,k ⋅ Ψ or Au = AE,b ⋅ Ψ ]
(dependent on terms of reference), if required also sum of sev-
eral flow-effective surface components: Aimp = Σ(AC,i ⋅ Ψi)
[Au = Σ(AE,i ⋅ Ψi)]
PD I/ha Population density, quotient of number of inhabitants and
ED E/ha catchment area
IG I_G IG I_G % Surface ground slope; area-weighted average slope of a catch-
ment area
γ γ - Degree of paving of a catchment area, γ = AC,p/AC [γ = AE,b/AE]

Ψ Ψ - Runoff coefficient; application-related ratio to quantify the flow-

influencing part of the precipitation; calculation as quotient of
stormwater flow and associated precipitation dependent on
application, e.g. as Ψm, Ψpeak [Ψm, Ψs]
Ψm Ψ_m Ψm Ψ_m - Mean runoff coefficient; quotient of stormwater flow volume
and precipitation volume for a defined period of time (e.g. dura-
tion of a single rainfall event, period of time); previously mean
discharge coefficient
Ψs Ψ_s Ψs Ψ_s - Peak runoff coefficient; quotient of maximum runoff rate qmax
and associated maximum rainfall intensity rmax; mainly for flow
time procedures and block rainfall; previously runoff coefficient
during storm peak
ΨA128 Ψ_A128 ΨA128 Ψ_A128 - Application-related runoff coefficient in accordance with ATV-A
128E (1992) and ATV-DVWK–M 177 (2001) for the determina-
tion of the numerical value Aimp from the size of the paved
surface AC,p [AE,b]

8 April 2003
 ATV-DVWK-A 198E

2.3 Flow/Discharge Parameters

Symbol Unit Designation
English German

fWW,QCW f_WW,QCW fS,QM f_S,QM - Factor for the calculation of the wastewater
flow with QCW [QM]
QD Q_D QH Q_H l/s Domestic wastewater flow
QInd Q_Ind QG Q_G l/s Commercial and/or industrial wastewater flow
QWW Q_WW QS Q_S l/s Wastewater flow (QD + QInd [QH + QG])
QWW,max,85 Q_WW,max,85 QS,max,85 Q_S,max,85 l/s Maximum hourly wastewater flow derived from
the daily wastewater flow undercut on 85% of
the days
QInf Q_Inf QF Q_F l/s Infiltration water flow
QDW Q_DW QT Q_T l/s Dry weather flow (QWW + QIW [QS + QF])
QR Q_R QR Q_R l/s Stormwater [rainfall] flow
QComb Q_Comb QM Q_M l/s Combined wastewater flow to the wastewater
treatment plant
QR,Sep Q_R,Sep QR,Tr Q_R,Tr l/s Unavoidable stormwater runoff in sanitary
sewers of areas with separate sewer system
QThr Q_Thr QDr Q_Dr l/s Throttle flow with combined sewer overflows
and stormwater tanks
Qa Q_a Qa Q_a l/s Annual flow
Qd Q_d Qd Q_d l/s Daily flow
QDW,d Q_DW,d QT,d Q_T,d l/s Daily dry weather flow
QDW,d,aM Q_DW,d,aM QT,d,aM Q_T,d,aM l/s Average daily dry weather flow (quotient of
sum of daily flows of all dry weather days and
the number of dry weather days of a year
QDW,aM Q_DW,aM QT,aM Q_T,aM l/s Dry weather flow as annual mean
Qd,Conc Q_d,Conc Qd,Konz Q_d,Konz m3/h Daily flow for the calculation of concentrations
from loads
Qh Q_h Qh Q_h m3/h Hourly flow
Q2h Q_2h Q2h Q_2h m3/h 2-hourly average of the flow
QWW,x Q_WW,x QS,x Q_S,x m3/h, l/s Wastewater flow as fraction x of QWW,d [QS,d],
e.g. flow as daily peak
QDW,max Q_DW,max QT,max Q_T,max l/s Peak dry weather flow (interval ≤ 5 minutes)
QDW,h,max Q_DW,h,max QT,h,max Q_T,h,max m3/h, l/s Maximum hourly dry weather flow
QDW,2h,max Q_DW,2h,max QT,2h,max Q_T,2h,max m3/h, l/s Maximum dry weather flow as 2-hourly mean
qInf q_Inf qF q_F l/(s•ha) Area-specific infiltration water flow rate,
qInf = QInf / AC,s [qF = QF / AE,k]
qR q_R qR q_R l/(s•ha) Area-specific stormwater discharge rate,
qR = QR / AC,s [qR = QR / AE,K]
qInd q_Ind qG q_G l/(s•ha) Industrial/commercial wastewater discharge
rate, qInd = QInd / AC,s [qG = QG / AE,k]
wd w_d wd w_d l/(I•d) Inhabitant-specific daily water consumption
wWW,d w_WW,d wWW,d w_WW,d l/(I•d) Inhabitant-specific daily wastewater yield

2.4 Concentration Parameters 2 h interval. Average annual values are, for exam-
ple, required with the calculation of pollution load
Concentrations without additional details apply for
simulation. For differentiation, grab samples re-
24-h composite samples, with index, for example,
ceive the additional index GS, this also applies for
2h is defined as the average concentration in a
qualified grab samples.

April 2003 9
 ATV-DVWK-A 198E

Symbol Unit Designation

English German

CXXX C_XXX CXXX C_XXX mg/l Concentration of the parameter XXX,

in the homogenised sample

CXXX,GS C_XXX,GS CXXX,SP C_XXX,SP mg/l Concentration of the parameter XXX,

in the homogenised grab sample

SXXX S_XXX SXXX S_XXX mg/l Concentration of the parameter XXX,

in the filtered sample (0.45 µm membrane filter)

XXXX X_XXX XXXX X_XXX mg/l Concentration of the filter residue,

XXXX = CXXX - SXXX

CXXX,2h C_XXX,2h CXXX,2h C_XXX,2h mg/l Average concentration in a 2-h interval

CXXX,aM C_XXX,aM CXXX,aM C_XXX,aM mg/l Annual average value of a concentration

CBOD C_BOD CBOD C_BOD mg/l Concentration of BOD5 in the homogenised sample

SBOD S_BOD SBOD S_BOD mg/l Concentration of BOD5 in the sample filtered with 0.45 µm mem-
brane filter

CCOD C_COD CCOD C_COD mg/l Concentration of COD in the homogenised sample

SCOD S_COD SCOD S_COD mg/l Concentration of COD in the sample filtered with 0.45 µm mem-
brane filter

CN C_N CN C_N mg/l Concentration of total nitrogen in the homogenised sample as N

(CN = CorgN + SNH4 + SNO3 + SNO2)

CTKN C_TKN CTKN C_TKN mg/l Concentration of Kjeldahl nitrogen in the homogenised sample
(CTKN = CorgN + SNH4)

CorgN C_orgN CorgN C_orgN mg/l Concentration of organic nitrogen in the homogenised sample
as N (CorgN = CTKN – SNH4 or CorgN = CN – SNH4 – SNO3 – SNO2)

SinorgN S_inorgN SanorgN S_anorgN mg/l Concentration of inorganic nitrogen as N

(SinorgN = SNH4 + SNO3 + SNO2)

SNH4 S_NH4 SNH4 S_NH4 mg/l Concentration of ammonia nitrogen in the filtered sample as N

SNO3 S_NO3 SNO3 S_NO3 mg/l Concentration of nitrate nitrogen in the filtered sample as N

SNO2 S_NO2 SNO2 S_NO2 mg/l Concentration of nitrite nitrogen in the filtered sample as N

CP C_P CP C_P mg/l Concentration of phosphorus in the homogenised sample as P

SPO4 S_PO4 SPO4 S_PO4 mg/l Concentration of phosphate in the filtered sample as P

SALK S_ALK SKS S_KS mmol/l Alkalinity

XSS X_SS XTS X_TS mg/l Concentration of suspended solids

(0.45 µm membrane filter, drying
at 105 °C)
XorgSS X_orgSS XorgTS X_orgTS mg/l Concentration of organic suspended solids

XinorgSS X_inorgSS XanorgTS X_anorgSS mg/l Concentration of inorganic suspended solids

10 April 2003
 ATV-DVWK-A 198E

2.5 Sludge Parameters

Symbol Unit Designation

English German

QSl,d Q_Sl,d QSchl,d Q_Schl,d m3/d Daily volume of sludge

QWS,d Q_WS,d QÜS,d Q_ÜS,d m3/d Daily volume of waste (activated) sludge
SVI SVI SVI SVI l/kg Sludge Volume Index
DRSl DR_Sl TRSchl R_Schl kg/m3 Concentration of the dry solids (evaporation residue) of sludge
oDRSl oDR_Sl TRSchl oTR_Schl % Percentage of organic dry solids of sludge
DSWS DS_WS TSÜS S_ÜS kg/m3 Concentration of dry solids (filter residue) of waste (activated)
sludge

2.6 Load Parameters

Traditionally, with loads, the period of time is the first index before the index for parameter.

Symbol Unit Designation

English German

Bd,XXX,2wM B_d,XXX,2wM Bd,XXX,2wM B_d,XXX,2wM kg/d 2-weekly average of the daily load of a substance,
e. g. for 2-weekly average of the daily COD load
Bd,COD,2wM
Bh,XXX B_h,XXX Bh,XXX B_h,XXX kg/h Hourly load of a substance (Bh,XXX = CXXX,h · Qh), e. g.
for hourly BOD5-load Bh,BOD
B2h,XXX B_2h,XXX B2h,XXX B_2h,XXX kg/h Hourly load of a 2-hour interval (B2h,XXX = CXXX,2h ·
Q2h), e. g. for 2-h TKN load B2h,TKN
B2h,XXX,max B_2h,XXX,max B2h,XXX,max B_2h,XXX,max kg/h A days maximum 2-h-load as hourly load

Numbers of inhabitants or population equivalents [see EN 1085]

P I Number of inhabitants (Population)

EZ [E]
PEXXX,ZZ PE_XXX,ZZ I Population equivalents, e. g. for the characterisation
EGWXXX,ZZ EGW_XXX,ZZ [E] of the industrial wastewater, always with reference
parameter and associated inhabitant-specific load,
e. g. PECOD,120, i.e. dependent on the parameter there
can be various PEs for a specific wastewater
PT I Total number of inhabitants and population equiva-
EW [E] lents (PT = P + PE), depending on the parameter
possibly different PTs

2.7 Other Characteristic Values

Indices for the location or for the purpose of sampling (always as last index).

Indices Designation
English German

In Z Sample from the inflow to the wastewater treatment plant, e. g. CBOD,In; XDS,In [CBSD,Z; XTS,Z]
InB ZB Sample from the inflow to the biological stage, e. g. CCOD, InB [CCSB,ZB]
ESST AN Sample from the effluent of the secondary settling stage [EPST for primary settling]
EF AF Sample from the effluent of a filter
EP AT Sample from the effluent of a pond

April 2003 11
ATV-DVWK-A 198E

3 Preparatory Work for If one or more of the above criteria are not met it
has to be decided whether missing data is to be
the Derivation of determined through additional measurements, or
are to be estimated on the basis of empirical val-
Dimensioning Values ues.

3.1 Initial Situation Empirical values are enlisted for plausibility checks
of the dimensioning values derived from measured
As a rule, there are records of the sewage flow, the values. They can be used as basis for the dimen-
weather (rainfall days, dry weather days), the tem- sioning of wastewater treatment plants, if the costs
perature of the wastewater and the concentration for measurements are disproportionate compared
of certain parameters available in wastewater with utilisation, in particular for small catchment ar-
treatment plants and, in individual cases, from eas without industrial or commercial develop-
sewer networks or from stormwater tanks. With ments. Sewage flow values should, as far as pos-
these data the values for the effluent from the sible, be derived from measured values.
sewer system and for the loading of the wastewa-
ter treatment plant can be determined. The concentration of a parameter, as a rule, shows
a typical diurnal variation as for the wastewater
However, it is always to be examined whether the flow. In addition, as a result of dilution with rain
sewer system is being operated correctly, for ex- and/or infiltration water, through remobilisation of
ample whether any inadmissible overflows or non- sewer deposits or as a result of draining stormwa-
statutory discharges are present, which are not ter tanks, they can vary considerably. Average
contained in the records. It is recommended that concentration values can therefore only be derived
first, a correct situation is established. from the average values of loads and the associ-
ated flows.
As every evaluation has a very definite aim it
must first be determined which values are re-
quired, see Chap. 3.3. 3.2 Data Gathering

Then, inter alia, it is to be examined , 3.2.1 Flow Measurement

– whether the available measured values are ac- For each type of evaluation it has to be checked
ceptable or not, for example due to inaccurate when the last calibration of the flow measurement
or missing flow measurements or inappropriate equipment took place. Under certain circum-
sampling and/or analysis; stances a new calibration is to be initiated. The ex-
– whether the flow values are available with suffi- isting flow data then may be corrected appropri-
cient frequency in representative periods of time ately.
(including weekends), in order to create time se-
ries; In the ideal case, in addition to the daily flow Qd in
– whether and in which manner the laboratory is m³/d, the daily flow variation is available in the form
subject to analytical quality assurance; if re- of print-outs or on data carriers. It is recom-
quired an external examination is to be carried mended, that 5 minute or 1 hour averages of the
out; dry weather flow are applied for evaluations of the
– whether measured values [of concentrations] of daily variation on dry weather days for the sewer
volume- or flow-proportional daily composite system, and 2-hourly means for wastewater treat-
samples for the required parameters are avail- ment plants.
able;
– whether the sampling point is suitable for the
desired information (e. g. due to internal back-
flows). With the discharge of back-flows with a
high suspended solids concentration, implausi-
ble concentrations can, for example, be meas-
ured.

12 April 2003
 ATV-DVWK-A 198E

3.2.2 Sampling for the Derivation of expensive. The samplers must be equipped
Loads with a bottle exchanger, in order to obtain
twelve 2-hourly composite samples a day. A
A continuous (on-line) measurement of the con- daily composite sample is obtained by weighting
centrations of the essential parameters is desir- the sample volumes of the 2-hourly samples
able, in order to be able to limit the expense for with the inflows of the associated 2-hourly inter-
sampling and analysis and to indicate diurnal and vals.
seasonal variations and, from these, derive – Manual sampling
maxima and minima. In the wastewater treatment Grab samples are taken at half-hourly or hourly
plant inflow or in the discharge from the primary intervals and combined into 2-hourly samples.
settling stage, however, it is almost impossible to The further procedure corresponds with the
measure on-line any of the typical parameters time-proportional sampling.
without great expense for the processing of the
sample stream. As an aid the Spectral Absorption Grab samples are, as a rule taken from the sludge
Coefficient (SAC) in accordance with DIN 38404, flows. A sampling point is to be chosen at which
Part 3, with a measuring probe submerged directly the concentration is not subjected to heavy time
in the wastewater in the outflow of the primary set- variations, e.g. at the outlet of a pre-thickener; if
tling stage, can be used as an indicator for the necessary several grab samples are to be taken
variation of the organic loading. The relationship to each day in order to obtain a usable average daily
the COD is, in each case, to be derived based on value.
parallel chemical analysis. The continuous meas-
urement of the ammonia concentration is also pos- Fundamentally a rough sketch of the wastewater
sible but very expensive due to the processing of treatment plant with clear marking of the sampling
the sample stream. points should be made from which it is plain to see
which wastewater stream is sampled where.
A daily load is the product from the volume- or
flow-proportional 24-hourly mean (daily composite
sample) of the concentration of a parameter, e.g.
3.3 Data Required for Dimensioning
CCOD in mg/l, and of the flow volume of the day Qd
in m³/d. It is, for example, designated with Bd,COD in
3.3.1 Flow Data
kg/d.
For applications within wastewater engineering
Grab samples are unsuitable for the calculation
mean values and peak values are required de-
of daily loads.
pendent on the terms of reference. Mean values
are always based on a given period of time, e. g.
The diurnal load fluctuation for reasons of cost, is
daily dry weather flow QDW,d in m³/d or dry weather
formed from the 2-hourly mean of the concentra-
flow as annual mean QDW,aM in l/s. Peak values are
tion, e.g. CTKN,2h in mg/l, and from associated 2-
used when, for short intervals, specific functions
hourly mean of the flow Q2h in m³/h.
have to be maintained and safe operation has to
be guaranteed. With this also the appropriate ref-
For sampling there are the following possibilities:
erence period of time (e. g. 2h, h) is to be given;
– Volume- or flow-proportional sampler without these details the reference interval is ≤ 5
Flow-coupled samplers require a measurement minutes.
signal of the flow-meter. As a rule a daily com-
posite sample is collected. If the samplers are A summary of the necessary inflows or discharges
also equipped with a bottle exchanger, 2-hourly from the relevant ATV-DVWK Standards is to be
composite samples can also be collected to found in Appendix B.
analyse the diurnal fluctuation.
In the Standards and Advisory Leaflets listed in
– Time-proportional sampler
Appendix B it is not clearly defined with what infil-
This is employed if the conduction of the flow
tration water flow is to be reckoned. Therefore the
signals, e. g. for temporary applications, is too
following definition is made: for hydraulic dimen-

April 2003 13
ATV-DVWK-A 198E

sioning the infiltration water flow should be the 3.3.2 Loads and Concentrations
maximum monthly mean (QInf,mM,max in l/s) of a mul-
tiple annual series (see Chap. 4.2.2.4). 3.3.2.1 For the Size-Classification and the
Determination of the Design
As a rule the following values can be derived from Capacity of Wastewater Treatment
flow data measured in the wastewater treatment Plants
plant or in the sewer network:
– mean annual dry weather flow QDW,d,aM in m3/d The classification of wastewater treatment plants
or QDW,aM in l/s. into the size-category [Authors’ afternote: In Ger-
– maximum monthly mean of the infiltration water many the effluent standard depends on the size-
flow of a multiple annual series QInf,mM.max in l/s category] and the determination of the design ca-
and the annual mean of the infiltration water pacity is to be based on the BOD5 load in the in-
flow QInf,aM in l/s. flow to the wastewater treatment plant which is
– mean annual wastewater flow QWW,aM in l/s, if achieved or undercut on 85% of the dry weather
the mean infiltration water flow QInf,aM in l/s has days (Bd,BOD,In in kg/d) without internal return flows
been determined through nightly measurements plus a planned reserve of capacity.
– maximum flow as 1-hourly or 2-hourly mean
Qh,max or Q2h,max in m³/h or l/s. If only data from the effluent of the primary tanks
– maximum and minimum mean hourly dry are available then, in accordance with the [Ger-
weather flow as 1- or 2-hourly mean QDW,h,max or man] Wastewater Ordinance, the 85% value of the
QDW,2h,max and QDW,h,min or QDW,2h,min in m3/h or BOD5 load derived from these for dry weather can
l/s. be applied.
– maximum and minimum flow Qmax and Qmin in l/s
both from areas with separate as well as with If necessary, existing internal back-flows are to be
combined sewer systems if the flow data are determined and deducted.
available for short time intervals of, for example,
5 minutes. The determination of the 85% values should in any
case be based on at least 30 BOD5 load values of
For the derivation of data see Chap. 4.2.2. dry weather days distributed evenly over the period
of time considered, insofar as no significant
For hydraulic calculations with wastewater treat- changes in the catchment area (e.g. connection of
ment plants on catchment areas with pure sepa- areas, changes with indirect dischargers) occur.
rate sewer systems, the maximum inflow with wet
weather as 1-hourly mean (QDW,h,max in l/s) and in Note: The separate determination of the design
all other cases the combined wastewater flow capacity and of the dimensioning value, for exam-
(QComb in l/s) as well as the minimum flow with dry ple for the biological stage, is necessary as this is
weather as 2-hourly mean (QDW,2h,min in l/s) are re- dimensioned, dependent on the type of process,
quired. for various loads (e.g. 2- or 4-weekly mean with
activated sludge plants or 2-hourly mean with
The dimensioning of the primary settling tanks de- biofilters).
pends on the maximum inflow as 2-hourly mean
with dry weather (QDW,2h,max in m3/h) and with the
combined wastewater flow (QComb in m3/h) or with 3.3.2.2 For the Dimensioning of Combined
the maximum flow from separate systems Sewer Overflows
(QSep,h,max in m³/h).
For the dimensioning of combined sewer overflows
and subsequent stormwater retention facilities in
accordance with ATV-A 128E (1992) the mean an-
nual value of the concentration of the COD in the
inflow to the wastewater treatment plant (CCOD,In,aM
in mg/l) with dry weather is required. If it is known
through previous measurements, that the average

14 April 2003
 ATV-DVWK-A 198E

concentration is smaller than CCOD,In,aM = 600 mg/l, means are to be determined or 2 x 40 daily
the determination is only necessary for the applica- loads are required for the formation of the cor-
tion of simulation models and, if applicable, with responding 85% values. A distinct seasonal
stringent discharge requirements. variation exists if the maximum or minimum
monthly average of the load varies by more
than ± 20% of the annual mean.
3.3.2.3 For the Dimensioning of
Wastewater Treatment Plants – Relevant concentrations of nitrogen and
phosphorus: if it is required to maintain certain
For the dimensioning of activated sludge plants effluent concentrations, the relevant concentra-
with the removal of nitrogen and phosphorus the tions CTKN,InB in mg/l, SNO3,InB in mg/l and CP,InB in
following are required in accordance with ATV- mg/l are to be arived, comp. Chap. 4.3.1.7.
DVWK-A 131E (2000): – Peak factor: for the design of the oxygen sup-
ply the ratio of the highest daily 2-hourly load of
– The annual variation of the water temperature, the TKN (B2h,TKN,max,InB in kg/h) to the daily aver-
in particular the lowest and highest tempera- age (Bh,TKN,dM,InB in kg/h) is required, comp.
ture in the effluent of the biological reactors, Chap. 4.3.1.8.
from the 2-weekly means over at least two – Sludge Volume Index with the expansion of
years. If no temperature measurement in the activated sludge plants: as a result of a frequent
biological stage is available, the water tempera- seasonal variation of the Sludge Volume Index
ture of the inflow or the effluent of the primary the critical load case should be determined in
settling stage can be applied. context using the associated loading from the
– As relevant loads the maximum 2- or 4-weekly seasonal fluctuation of the Sludge Volume In-
mean of the isochronous loads of: dex (as 2-weekly average, as far as possible
– COD (Bd,COD,InB in kg/d) and ratio SCOD/CCOD,
over three years). Alternatively, it should be
if dimensioning using COD, based on the 85-percentile value at least from
– BOD5, (Bd,BOD,InB in kg/d),
the last two years. It should be noted that
– suspended (filterable) solids
changes of the process and of the sludge age
(Bd,SS,InB in kg/d), also lead to changes of the Sludge Volume In-
– nitrogen (Bd,TKN,InB; Bd,NO3,InB and, if required,
dex. The efficiency of the secondary settling
Bd,NO2,IB in kg/d) as well as stage is to be taken into account.
– phosphorus (Bd,P,InB in kg/d)
respectively for the periods with the dimension- For the dimensioning of trickling filters and rotat-
ing temperature, with the lowest and the highest ing biological contactors in accordance with
temperature. For determination see Chap. ATV-DVWK-A 281E (2001) the following are re-
4.3.1.5. quired as relevant loads:

If the intense sampling required for the forma- – BOD5, (Bd,BOD,InB in kg/d),
tion of 2- or 4-weekly average is out of propor- – Nitrogen (Bd,TKN,InB in kg/d)
tion with the use, the relevant daily loads can be
determined as those daily loads achieved or Applicable as being relevant are those loads
undercut on 85% of the days (“85 percentile which are undercut on 85% of the days. At least
value“). The data collection for this should in- 40 load values over one to three years are to be
clude at least 40 daily loads distributed evenly used. The combining of BOD5 loads and nitro-
over up to three years. The combination of gen loads which do not occur isochronously
loads which are not isochronous, for example of must be avoided. For the calculation see Chap.
the COD and of the nitrogen, must be avoided. 4.3.1.6. For small facilities the relevant loads
For the calculation see Chap. 4.3.1.6. For small can be estimated from empirical values.
wastewater treatment plants the relevant loads
can be estimated from empirical values. – Relevant concentrations of nitrogen and
phosphorus: if it is required to maintain certain
With a distinct seasonal variation of loads, at effluent concentrations the relevant concentra-
least two different (maximum) 2- or 4-weekly

April 2003 15
ATV-DVWK-A 198E

tions CTKN,InB in mg/l, SNO3,InB in mg/l and CP,InB in charges and effluents from wastewater treat-
mg/l, are to be derived, comp. Chap. 4.3.1.7. ment plants);
– local conditions (inter alia inventory documents
Treatment processes with short retention peri- with details on conditions, soil and groundwater
ods: certain biological processes such as, for ex- conditions, water levels in the surface waters,
ample, biofilters, are dimensioned for the relevant urban land use planning documents);
(highest) 2-hourly loads of COD (B2h,COD,max,InB in – surface restrictions (inter alia pipelines and ca-
kg/h) and of TKN (B2h,TKN,max,InB in kg/h). bles, contaminated soil).

Dynamic simulation: depending on the pro- The sources of information and publishers or data
gramme and planning specifications comprehen- managers can vary depending on the structure of
sive data collection is to be carried out for dynamic the administration of the Federal [German] State.
simulation. Presentation of this is dispensed with in
this Standard [1, 2].
4.2 Determination of Discharge Data
For the dimensioning of facilities for sludge
treatment the daily sludge volume QSl,d in m3/d, 4.2.1 Data on Water Consumption
the dry solids concentration DRSl in kg/m3 and the
organic fraction of the dry solids oDRSl in % are re- The potable and process water input into the
quired. It is recommended that the mean of the catchment area and the water produced in own
sludge load is based on several weeks with dry water works of industry correspond approximately
and wet weather. with the wastewater discharged to the sewer sys-
tem. Water which is not discharged, for example
The masses to be disposed of from breweries or in agriculture, is to be taken into
– screenings (depends on the bar spacing of the account. The seasonal variation of the daily water
screen) and consumption serves as plausibility check of the
– grit chamber material (also depends on whether seasonal variation of the daily wastewater flow;
a washing takes place) seasonal influences can thus be clearly recog-
nised. A trend can be better recognised in a time
can be determined as a mean only over several series of the annual water consumption than in a
weeks. With sewer systems susceptible to depos- time series of the annual dry weather flow which is
its the masses of all residues can vary extremely influenced by differing precipitation and/or infiltra-
sharply over time. tion water flow.

Attention is to be paid that in many cases the water

service area and the catchment area of the sewer
system are not congruent. The water consumed in
4 Determination of Data the catchment area can be determined through
about the Actual addition of the annual water quantities of all con-
sumers and subtraction of the water consumption
Condition outside the catchment area. This can, however,
mean expensive calculations for the water suppli-
4.1 General Documents and Data ers.

For the planning of wastewater facilities, in addition In accordance with the significance of the planning
to the dimensioning values, which characterise the task it is recommended, even if the water service
loading, further data, documents and information area and the wastewater catchment area are dif-
are required, such as for example: ferent, to take the following points into considera-
tion:
– requirements on the quality of the wastewater to
be discharged (combined sewer overflow dis- – collection of the annual water supply rates, if
possible including the inherent water production

16 April 2003
 ATV-DVWK-A 198E

of businesses, for the last 5, better 10 years, in with the discharge of groundwater from larger
order to identify a possible existing trend. construction sites are not dry weather days. If
– collection of the seasonal variation of the daily the determination of the dry weather flow takes
water consumption including the inherent water place with calculation in accordance with the
production of industries in order to obtain infor- method of sliding minimum (comp. 4), the
mation on seasonal fluctuations of the wastewa- weather records serve as plausibility check.
ter flow.
– determination of the mean specific water con- 2. Daily sewage flow Qd in m3/d.
sumption wd,aM in l/(I·d). For this the following
are to be collected: the number of inhabitants in 3. Daily sewage flow with dry weather QDW,d in
the service area (P) and the annual feeding of m3/d (combination from 1 and 2).
water into the service area as mean of the last
4. For the mathematical derivation of the daily dry
two to three years if no strong trend is present,
weather flow it is recommended, based on
otherwise from the previous year, in each case
Fuchs et al. [3], that the polygon of the sliding
reduced by the recorded water utilisation of in-
21-day minima of the daily flows be formed (in-
dustries. If a value is found for wd,aM which lies
terval 10 days before and 10 days after the day
far outside the normal range of from 100 to 150
under consideration). All up to 20% over this
l/(I·d), the reasons are to be explored.
polygon available daily flows then apply as dry
weather flows, comp. Appendix C, Chap. C 1.3.
The value of 20% corresponds approximately
4.2.2 Data on Sewage Flow with the fluctuation bandwidth of the daily dry
weather flow with constant infiltration water flow.
4.2.2.1 Determination of Essential Flow
Data Note: the procedure of sliding minima is new and
still not a rule of technology. It is accepted that the
As a rule, one finds devices for the measurement day with the smallest daily flow within the interval
of the sewage flow with associated recording facili- is to be considered as dry weather day. A duration
ties in wastewater treatment plants and, possibly, for the interval of 21 days is proposed. With a re-
at pumping stations and stormwater tanks. Atten- duction of the duration of the interval the number
tion is already drawn to the checking of measure- of dry weather days and the annual mean of the
ment devices in Chap. 3.2.1. dry weather flow increase.
5. Daily maximum and minimum flow with dry
The evaluation of sewage flow data should cover weather as peak values QDW,max and QDW,min in
one year (with little infiltration water), better three l/s or as hourly values QDW,h,max and QDW,h,min in
to five years (with a great deal of infiltration water), l/s or m3/h, if inflow data for short time intervals
as the precipitation events of only one year, under of, for example, 5 minutes or hours are avail-
certain circumstances, can lead to false initial data able.
(dry or wet year). An example for an evaluation is
contained in Appendix C. In the first place the fol- Attention: the values can, for example, be in-
lowing data are to be collected or calculated: fluenced by upstream pumping stations.

1. Days with dry weather flow. Although, as a rule, 6. Daily maximum and minimum flow with dry
it is recorded in wastewater treatment plants weather as 2-hourly mean QDW,2h,max and
whether it has rained or snowed, the definition QDW,2h,min in m3/h (only if the flow data are avail-
of a dry weather day should, however, come able on data carriers or printer carriage tape).
better from existing representative rainfall re-
corders in the catchment area in combination 7. Daily maximum flow from areas with separate
with a limiting amount of precipitation of, for ex- sewer system as hourly values QSep,h,max or as 2-
ample, 1 mm/d and normally one, and in larger hourly mean QSep,2h,max in m3/h (only if the inflow
catchment areas, up to two follow-on days [Au- data are available on data carriers or printer car-
thor’s afternote: For the emptying of stormwater riage tape).
reservoirs]. Days with melting snow and days

April 2003 17
ATV-DVWK-A 198E

The following graphical representation is recom- dicates no pronounced seasonal variation, it is

mended: appropriate to determine the wastewater flow for
a period with constant dry weather flow, e.g. in
– time series of the daily sewage flow for all days
summer, through more frequent measurements
(Qd) and separately for dry weather days
of the infiltration water in accordance with
(QDW,d), comp. Figs. C-1 to C-5.
Eqn. 3.
– time series of the daily maximum, mean and
minimum dry weather flows possibly separate
QWW ,aM = QDW ,pM − QInf ,pM [l/s] (3)
for 5-minute intervals, hourly- and 2-hourly
mean, comp. Figs C-7 and C-8.
2. With the second route the mean annual waste-
Freak values in the hydrographs of the dry weather water flow QWW,aM is determined from water
flow QDW,d indicate i. a. undetected rainy weather consumption data. For this the mean annual
days, emptying of stormwater reservoirs or false water consumption in the catchment area in-
measurements. If the associated maxima and min- cluding the water production of industry and the
ima (e. g. QDW,h,max and QDW,h,min in l/s) indicate water used by commerce and industry but not
similar deviations from the other dry weather days discharged are to be collected with sufficient
such days are, if necessary, to be omitted for the accuracy. If the water consumption indicates a
evaluation. seasonal variation, then appropriate period
means QWW,pM are to be determined.

4.2.2.2 Determination of the Annual Mean

Dry Weather Flow
If this is not possible, the mean annual waste-
water flow QWW,aM can be calculated (Eqn. 4) as
The annual mean dry weather flow QDW,aM in l/s
sum of the domestic flow QD,aM and of the indus-
which, for example, is required for pollution load
trial wastewater QInd,aM with the aid of specific
simulations, results from the arithmetic mean of all
values. The specific wastewater flow wWW,d,aM
daily dry weather flows QDW,d,aM in m3/d through
should be derived from water consumption data.
simple conversion in l/s:

QDW ,d ,aM QWW ,aM = Q D,aM + Q Ind ,aM =

QDW ,aM = [l/s] (1) w WW ,d ,aM [l/s] (4)
86.4 P⋅ + AC ,Ind ⋅ q Ind
86400

In addition the annual amount of wastewater from

4.2.2.3 Determination of the Wastewater the annual reports of the wastewater treatment
Flow plant can be included for comparison. As thor-
oughly different results can be expected it is rec-
For the determination of the wastewater flow as ommended that the results are compared with
annual mean QWW,aM in l/s or as mean of a certain each other and that the “most probable” value is
period two routes are possible: selected following critical assessment and justifica-
tion why calculation should be carried out using it.
1. With the first route, the infiltration water flow
must have been determined through night
measurements as annual mean QInf,aM in l/s 4.2.2.4 Determination of the Infiltration
(Eqn. 2) or for a certain period QInf,pM in l/s (Eqn. Water Flow
3), comp. 4.2.2.4.
The infiltration water flow is subject to seasonal
QWW ,aM = QDW ,aM − QInf ,aM [l/s] (2)
variations due to the seasonal fluctuation of the
precipitation. The assumption of a suitable infiltra-
If the infiltration water is subject to a marked tion water flow is decisive for the correct function of
seasonal variation and if it is known from water wastewater facilities and the loading of surface wa-
consumption data, that the wastewater flow in- ters [receiving water].

18 April 2003
 ATV-DVWK-A 198E

The infiltration water flow can be determined – sewage flow data are available on data carriers
through night measurements or as difference of for short time intervals of, for example, 5 min-
the dry weather flow and the wastewater flow. utes or for one hour, so that QDW,max and QDW,min
or QDW,h,max and QDW,h,min can be extracted for
1. Annual mean on the basis of night measure- each dry weather day.
ments: – the flow rate is not influenced by the operation
night measurements are, as a rule, only signifi- of upstream pumping stations.
cant in catchment areas with negligible water – a period with approximately constant infiltration
consumption at the time of measurement. Fa- water flow is detectable, this must be docu-
vourable times are the early morning hours of mented through a sufficient number of meas-
nights from Saturday to Monday. The meas- ured values for the determination of QInf,pM .
urements are to be carried out regularly at least
twice per month, in order to obtain sufficient The period can cover one or more months with as
values for the annual mean of the infiltration wa- few as possible rainy weather days. In the first in-
ter flow QInf,aM in l/s. stance, for each dry weather day, the differences
QDW,h,max – QInf,pM and QDW,h,min – QInf,pM and QDW,d –
2. Maximum monthly mean on the basis of night QInf,pM in l/s are formed as hourly flow (or, for ex-
measurements: ample, for 5 minute intervals). Then for each dry
if a distinct seasonal variation of the infiltration weather day the ratio values
water flow is present, the maximum infiltration
QDW ,h ,max − QInf ,pM QDW ,h ,min − QInf ,pM
water flow as monthly mean QInf,mM,max is deter- and
mined in l/s. For this, night measurements on at QDW ,d − QInf ,pM QDW ,d − QInf ,pM
least six days of the months involved from three
are calculated. Finally the mean maximum and
years are necessary. As such intensive meas-
minimum hourly wastewater flow is calculated by
urements are not, as a rule, undertaken, in ret-
using the arithmetic means of the ratio values and
rospect an appropriate value cannot be deter-
the period mean of the wastewater flow QWW,d,pM :
mined.
 QDW ,h ,max − QInf ,pM 
3. Maximum monthly mean as difference of the dry QWW ,h ,max,pM = QWW ,d ,pM ⋅   [l/s] (5)
 QDW ,d − QInf ,pM  pM
weather flow and of the wastewater flow:
here the variation of the dry weather flow for a
multiple year series is determined in accordance
 QDW ,h ,min − QInf ,pM 
with Chap. 4.2.2.1, Para. 4. From this the QWW ,h ,min,pM = QWW ,d ,pM ⋅   [l/s] (6)
maximum monthly mean of the dry weather flow  QDW ,d − QInf ,pM  pM
QDW,mM,max is determined. The wastewater flow
is based on Chap. 4.2.2.3, Para. 2 as annual or
period mean and is deducted. The Divisor xQmax in h/d results as follows:

An ATV-DVWK Advisory Leaflet, which deals with 24

xQ max = [h/d] (7)
the determination of the infiltration water flow is in  QDW ,h ,max − QInf ,pM 
preparation.  
 QDW ,d − QInf ,pM  pM

4.2.2.5 Determination of Daily Peaks and Maximum and minimum flow with dry weather
Nightly Minima as 2-hourly mean

Maximum and minimum wastewater flow If the daily dry weather flow is subject to no
marked seasonal variation, the annual mean of the
The maximum or minimum wastewater flow QWW,max maximum and minimum 2-hourly mean QDW,2h,max,aM
and QWW,min or QWW,h,max and QWW,h,min in l/s can be and QDW,2h,min,aM in m³/h is produced from all dry
determined with the presence of the following pre- weather days.
requisites only:

April 2003 19
ATV-DVWK-A 198E

If the daily dry weather flows show a marked sea- Schleypen and Meißner [5] is introduced. With this
sonal variation then, for the month with the highest a mean annual wastewater flow QWW,aM in l/s and a
mean dry weather flow, the mean of the maximum factor fWW,QComb are assumed.
2-hourly mean of the dry weather days
QDW,2h,max,mM is formed in m3/h and for the month The salient points of the approach are derived as
with the lowest mean dry weather flow the mean of follows:
the minimum 2-hourly mean of the dry weather
days is calculated. For small residential areas the ratio of the
85 % value to the annual mean QWW,d,85 /QWW,aM is
If the period with low daily dry weather flow is of ca. 1.5 and the divisor for the peak xQmax = 8. From
longer duration, for example, always continues for this results for the previous peak flow in accor-
the complete summer, the maximum 2-hourly dance with ATV-A 131E (1991)
mean of this period QDW,2h,max,pM in m3/h can be sig- QWW = QWW,max,85 = (1.5 · 24/8) · QWW,aM = 4.5
nificant for process layout. QWW,aM and 2 QWW,max,85 = 9 QWW,aM. For larger
towns the ratio QWW,d,85 /QWW,aM with ca. 1.15 and
Maximum flow from purely separate systems xQmax = 16 can be applied. With this 2 QWW,max,85 =
3.5 QWW,aM. Using this approach up until now in
For hydraulic calculations, i. a. in the area of the small towns relatively much and in large cities rela-
wastewater treatment plant, with purely separate tively little stormwater has been accepted in the
sewer systems the highest plausible measured wastewater treatment plant.
value of the flow QSep,h,max in l/s of a period of at
least one, better three or more years is assumed; if Editorial note: ATV Standard ATV-A 131E (1991)
necessary, a safety factor is to be taken into ac- is no longer the valid dimensioning regulator. Cur-
count. rently, for the dimensioning of single-stage acti-
vated sludge plants, ATV-DVWK-A 131E (May
2000) is valid. The explanatory notes given at this
4.2.2.6 Determination of the Combined point for the determination of the combined waste-
Wastewater Flow to the water flow serve for the better understanding of the
Wastewater Treatment Plant procedure in ATV-DVWK Standard ATV-DVWK-A
198E.
The combined wastewater flow to the wastewater
treatment plant or the effluent of the last combined Within the sense of pollution control, equal treat-
sewer overflow upstream of the wastewater treat- ment of large and small residential areas is to be
ment plant QCW has been calculated in accordance sought. In order also to ensure that, with the start
with ATV-A 131E (1991) [4] from double the [Authors’ afternote: due to rainfall] of combined
wastewater flow QWW plus the infiltration water flow wastewater flow, the ammonia concentration in the
QInf plant effluent does not increase too sharply, it
would be sensible to limit the combined wastewa-
QComb = 2 · QWW + QInf,aM ter flow QCW uniformly to
With this, QWW was derived from the value of the QComb = 6 · QWW,aM + QInf,aM [corrected from QInf,pM]
daily flow QDW,d in m³/d which is undercut in 85% of
the dry weather days. With multiplication of this Instead of the rigid factor of 6 in the equation
value by an hourly peak factor (divisor xQmax) there above a bandwidth of the factor for the wastewater
results the daily peak value QWW, which is desig- flow fWW,QCW (Fig. 1), however, shall be used for
nated below as QWW,max,85. According to the earlier calculation. Through this an optimisation between
ATV Standard ATV-A 131E (1991) [4] the infiltra- the necessary storage volume for stormwater in
tion water flow is defined as annual mean. the sewer system and the loading capacity of the
wastewater treatment plant is made possible. The
In order to obtain a margin for the optimisation of factor should be selected between 6 and 9 for
the hydraulic loading of the wastewater treatment small catchment areas and between 3 and 6 for
plant and the treatment of the stormwater, a new wastewater treatment plants of large cities. The
approach to the calculation in accordance with

20 April 2003
 ATV-DVWK-A 198E

combined wastewater flow QCW, using the factor If no water consumption data is available the in-
selected from Fig. 1, results as follows: habitant specific wastewater yield can be assumed
to be wWW,d = 100 to 150 l/(I·d). The area-specific
[l/s] (8)
QComb = fWW ,QCW ⋅ QWW ,aM + QInf ,aM industrial respectively commercial wastewater dis-
charge rate qInd in l/(s·ha) is to be estimated for ar-
The annual mean of the infiltration water flow eas with firms producing little wastewater (com-
QInf,aM is to be determined according to Chap. merce, offices, certain firms, for example, wood
4.2.2.4. If the infiltration water flow is subject to a processing) on the basis of the number of employ-
marked seasonal variation and the highest monthly ees and, if necessary, visitors. Here, it should be
mean QInf,mM,max, for example, is more than twice avoided that employees resident in the catchment
the annual mean, a higher infiltration water flow is, area are additionally included with the firms. If wa-
if necessary, to be applied in order still to ensure ter-intensive firms, for example food processing,
an emptying of the stormwater tanks with the daily are based in the catchment area surveys of the
peak of the dry weather flow. water consumption and/or the wastewater flow are
to be undertaken.
Seen as an advantage of this approach is that the
mean wastewater flow QWW,aM can present the The annual mean the dry weather flow is:
same initial basis both for the layout of combined QDW ,aM = QWW ,aM + QInf ,aM [l/s] (10)
sewer overflows and also for the combined waste-
water flow to the wastewater treatment plant.
For the infiltration water flow see Chap. 4.2.2.3. If
no measured values are available a sensible as-
sumption must be made and justified.

If no measured data are available the daily peak of

the wastewater flow can be determined with the
aid of divisor xQmax in accordance with Fig. 2. In
this the lower line can be related approximately to
QWW,max or QWW,h,max and the upper line to
QWW,2h,max. The daily peak flow with dry weather
thus results as follows:
Q DW ,max , Q DW ,h ,max resp . Q DW ,2 h ,max =
Fig. 1: Range of the factor fWW,QComb for the de- 24 ⋅ QWW ,aM [l/s] (11)
termination of the optimum combined + Q Inf ,aM
x Q max
wastewater flow to the wastewater
treatment plant on the basis of the
mean annual wastewater flow

4.2.3 Flow Data on the Basis of Empirical

Values

The annual wastewater flow QWW,aM in l/s can be

estimated on the basis of the inhabitant-specific
wastewater yield wWW,d in l/(I·d) as well as the
area-specific commercial and/or industrial waste-
water discharge rate qInd in l/(s·ha) as follows:

P ⋅ w WW ,d (9)
QWW ,aM = + AC ,Ind ⋅ q Ind [l/s]
86400 Fig. 2: Divisor xQmax dependent on the size
[number of residents] of the [catch-
ment] area [Authors’ afternotes]

April 2003 21
ATV-DVWK-A 198E

Further suitable estimated values for dimensioning flow to the biological stage are to be determined
or for plausibility checks are to be found, applica- (see Chap. 3.3.2.3):
tion specific, in the relevant ATV-DVWK Standards
– CBOD,InB in mg/l,
and Advisory Leaflets.
– CCOD,InB and, if required, SCOD,InB in mg/l,
– XSS,InB and, if required, XinorgSS,InB in mg/l,
– CTKN,InB, SNH4,InB, SNO3,InB, and, if required, SNO2,InB
4.3 Determination of Loads and in mg/l,
Concentrations – CP,InB in mg/l,
– SAlk,InB in mmol/l.
4.3.1 Determination through Evaluation
of Measured Values In order to keep the costs for chemical analysis
within limits, the relatively easy to determine COD
4.3.1.1 Sampling Frequency and is introduced as master parameter. CCOD is to be
Necessary Parameters determined frequently, if possible daily. The other
necessary parameters can be analysed less fre-
As prerequisite for the assessment of available quently. Using the ratio values determined on the
data and/or the planning of a sampling it must be basis of the measurements, loads and the relevant
known for which purpose the data are to serve. concentrations of the less frequently analysed pa-
Subsequently the necessary parameters and the rameters can be calculated.
frequency of sampling are to be laid down.
For the determination of the relevant 2- and 4-
The necessary parameters result in accordance weekly means of the COD loads (master parame-
with the relevant ATV-DVWK Standards, see ter), the calendar weekly mean of the COD
Chap. 3.3.2. (Bd,COD,wM) is introduced as auxiliary for the dimen-
sioning of activated sludge plants. At least 4 daily
The BOD5 load in the inflow with dry weather with- loads of a calendar week are required for the crea-
out internal return flows is relevant for the size tion of a weekly mean.
classification of wastewater treatment plants, see
Chap. 3.3.2.1. Note: At least 5, better 6 days of each calendar
week must be sampled in order to obtain 4 usable
The annual mean value of the concentration of the COD daily loads in the case of freak values, for
COD in the inflow with dry weather is required for example obvious errors in analysis.
the dimensioning of stormwater overflow facilities
in accordance with ATV Standard ATV-A 128E If the seasonal variation of the daily loads is
(1992), see Chap. 3.3.2.2. For this it is sufficient known, the intensive sampling can be limited to re-
once in every month with dry weather, to deter- spectively 4 to 10 weeks, for example in the cold
mine a daily COD load of the inflow to the waste- and warm seasons and, if required, to seasonally
water treatment plant not loaded by internal back- weak or high load periods. For each period the
flows. The mean concentration CCOD,In,aM is the maximum 2- or 4-weekly mean of the COD loads
quotient of the sum of the COD loads and the sum are to be formed from the means of coherent
of the flows of days from which the loads have weeks (sliding mean value).
been formed. If measured values of the raw
wastewater inflow are not available in sufficient For the determination of the parameters of the
numbers, CCOD,In,aM, can be extrapolated approxi- sewage sludge, in view of the possible heavy fluc-
mately from the mean COD load in the effluent tuations both of the volume and of the concentra-
from the primary settling stage, taking into account tion, the daily determination of the solids concen-
the measured settling effect of the primary settling tration (DRSl in kg/m3) as well as of the organic
tanks. fraction (oDRSl in %) is recommended several
times a year in periods of two and more weeks.
For the dimensioning of the biological treatment The associated daily volume (QSl in m3/d) is to be
stage with nitrogen and phosphorus removal, as a documented for the determination of the daily
rule the following necessary parameters in the in- mass of [sludge] solids.

22 April 2003
 ATV-DVWK-A 198E

4.3.1.2 Examination of Available load to the mean daily TKN load can be taken
Information up, comp. 4.3.1.8.

Using the available records of the daily sewage 2. The current routine sampling with regard to fre-
flow, the concentration of certain parameters and quency of sampling as well as the parameters
thus the calculated loads the following questions examined for the recording of the seasonal
are first to be clarified: variation is considered essentially to be suffi-
cient. In favourable cases calendar-weekly
– are the measured values plausible? Do, for ex- means of the COD loads can be created for in-
ample, the ratio values of parameters deviate teresting periods or there are available at least
significantly (more than 20%) from the values 40 evenly distributed COD loads for the deter-
according to Table 1, then the cause should be mination of the 85% value.
explored.
– is there a trend within the last 3 to 4 years with Previously unmeasured parameters can, in ad-
the sewage flow, the pollutant loads and/or the dition to the master parameter COD, be deter-
ratio values of certain parameters, for example mined in a two to four week continuous sam-
COD/N, to be observed? Are there reasons for pling. The ratio of the highest daily 2-hourly TKN
the observed trend? Is the sewage flow, for ex- load to the mean daily TKN load (peak factor)
ample, influenced by the annual precipitation? can also be determined, comp. Chap. 4.3.1.8.
Loads can, for example, be influenced through
decrease or new establishment of commercial
and/or industrial activity. If there is a trend with
the loads or with the relationship of certain pa- 4.3.1.3 Location of the Sampling
rameters which has a gradient of more than
±10% per year then the data from previous In wastewater treatment plants there are practically
years have only a limited value for application. only three locations for a representative sampling:
the raw sewage inlet, the outlet from the primary
– has a seasonal variation of the [daily] sewage
settling stage or the inlet to the biological stage
[flow] produced, the pollutant loads and/or of the
and the outlet to the surface [receiving] waters.
ratio values of certain parameters, for example
COD/N, been observed? Are there reasons for
Basically the sample from the raw sewage is to be
this variation, for example seasonal operating
taken at a location with sufficient turbulence, if
industry, tourism, infiltration water? If the
necessary mixers or a chicane are to be installed
monthly mean of the period with higher or lower
for the sampling.
loading deviates by more than 20% of the an-
nual mean, then the data is to be evaluated
If several main sewers discharge into one waste-
separately for typical periods of the year.
water treatment plant and the separate determina-
– does the frequency of the previous sampling tion of the loads of the individual main sewer is
suffice for the current questioning? necessary for a certain question, attention is to be
paid that, in addition to the sampling, flow meas-
– do the parameters previous analysed routinely
urements for each main sewer must also be avail-
suffice for the current questioning?
able.

Then the following two situations are possible for

For practical reasons the sampling for the raw
further action:
sewage, takes place usually in the outlet of the grit
1. The current routine sampling is insufficient with chamber. At this location, if applicable, the streams
regard to the frequency of sampling and/or the from different main sewers are well mixed. If a
parameters investigated. As a possible sea- pumping station is upstream from the sampling
sonal variation is to be recorded the routine point in many cases the internal return flows from
analysis is to be intensified appropriately. sludge treatment are fed in there. In particular, due
Thereby a sampling for the determination of the to thickener overflows which are [may be] heavily
relationship of the highest daily 2-hourly TKN

April 2003 23
ATV-DVWK-A 198E

loaded with suspended solids, the organic loading 4.3.1.4 Summary of Measured Data and
can also be increased. Calculation of the Daily Load as
well as the Values of the
If possible the loads of sludge liquor and faecal Concentration Ratio
matter discharges should be determined sepa-
rately with an inflow sampling. A possible dis- The calculation of the COD loads and the ratio val-
charge of filter washing water should also be re- ues of the less frequently measured parameters to
corded. the master parameter COC normally takes place in
tabular form. In Appendix C an evaluation is dem-
The advance construction of a sludge liquor equal- onstrated as an example. The following are to be
iser can be sensible. This is, in any case, expedi- listed for a period of approximately one year:
ent for all types of advanced sludge liquor treat-
ment; even without liquor treatment, in particular, 1. Date and day of the week (the latter to identify
with surge-type sludge liquor production, an equal- the effects of the weekend).
iser is strongly recommended. At many points the 2. Characterisation of the dry weather days.
fraction of the nitrogen load to the nitrogen load of 3. Wastewater temperature in the effluent from the
the plant is properly identified through the deliber- biological reactor, alternatively in the wastewa-
ate collection and volume flow measurement of the ter inflow to or effluent from the primary settling
sludge liquor. stage. The 2-weekly mean of the temperature
should be produced separately for at least two
If the sampling serves for the creation of the basis of the preceding years.
for the expansion of the biological stage of a 4. Sludge Volume Index SVI in l/kg. The 2-weekly
wastewater treatment plant, then one should bear mean should be produced for at least two of the
in mind that, with the expansion this, in many preceding years.
cases, is accompanied by process changes in the 5. Daily wastewater flow Qd in m3/d.
area of the mechanical [primary] stage. Thus, un- 6. Dry weather flow QDW,d in m3/d (combination of
der certain circumstances, consideration can be 2 and 5 or determined arithmetically, comp.
given to reducing the existing too large a primary Chap. 4.2.2.1, Para. 4).
settling tanks and/or to carry out a separate treat- 7. Measured concentrations in mg/l from 24 hour-
ment or an equalising of the centrifuge/filter efflu- composite samples from the inflow into the bio-
ent of the sludge dewatering facility. logical stage:
– COD homogenised, CCOD,InB
With a planned reduction of the primary settling – COD of the filtrates of the sample, SCOD,InB
stage the question arises whether a sampling of – BOD5 homogenised, CBOD,InB
the outflow of the (too large) primary settling stage – suspended solids, XSS,InB
provides false values. The alternative is therefore – Kjeldahl nitrogen, TKN, homogenised, CTKN,InB
seen frequently in the sampling of the inflow to the – ammonia nitrogen, SNH4,InB
wastewater treatment plant, which however, can – nitrate nitrogen, SNO3,InB
also deliver problematic values (see above). – total phosphorus, homogenised, CP,InB
– alkalinity, SAlk,InB in mmol/l
One usually makes the lesser error if one samples 8. Calculation of the COD loads in the inflow to the
the effluent of the existing primary settling stage biological stage:
and takes into account a possible later reduction of – COD daily load, Bd,COD,InB in kg/d
the volume through a slight increase of the organic (= Qd · CCOD,InB/1000).
loads. With sampling attention must be paid to the – weekly mean (calendar week) of the COD
internal back-flows (surplus [waste activated] load Bd,COD,InB,wM in kg/d, can be produced if
sludge, process water etc.) into the primary settling at least four daily loads have been deter-
stage. mined in the week.
9. Calculation of the ratio values of the concentra-
For sampling for the determination of the parame- tions:
ters of the sewage sludge see Chap. 3.3.2.3. – dissolved [filtered] to homogenised COD,
SCOD,InB / CCOD,InB

24 April 2003
 ATV-DVWK-A 198E

– BOD5 to COD, CBOD,InB/CCOD,InB 4.3.1.5 Determination of the Relevant

– suspended solids to COD, XSS,InB/CCOD,InB Loads on the Basis of Weekly
– Kjeldahl nitrogen to COD, CTKN,InB/CCOD,InB Means
– ammonia nitrogen to COD, SNH4,InB/CCOD,InB
– phosphorus to COD, CP,InB/CCOD,InB The following load cases can be differentiated for
– alkalinity to COD, SAlk,InB/CCOD,InB the dimensioning of activated sludge plants:

The inflow of sludge liquor, significant discharges Load with the dimensioning temperature
of faecal sludge and filter washing water should at The relevant 2- or 4-weekly mean of the organic
least be documented through details of the start load (Bd,COD,InB,2wM) is found in the period in which
and finish of each discharge; also necessary is the the 2-weekly mean of the temperature (T2wM) lies in
recording of the volumes discharged. These details the range of the dimensioning temperature (Tdim).
are particularly useful on days with investigations Using the ratio values CBOD,InB/CCOD,InB,
for the peak factor, as irregularities can be identi- CTKN,InB/CCOD,InB, XDS,InB/CCOD,InB and CP,InB/CCOD,InB
fied. For plants with sludge digestion and me- one finds the associated loads and concentrations
chanical dewatering the following are, for example, of the other parameters.
to be documented:
– daily volume of sludge liquor QSl,d in m3/d (can Load with the lowest temperature
be approximated with the daily volume of the It is to be examined whether the 2- (or 4-) weekly
sludge drawn from the digester). mean of the organic load for the lowest range of
– ammonia nitrogen concentration of sludge liq- the temperature is higher by more than 10% than
uor, SNH4,Sl. with Tdim. If this is the case then the proof of the
– start and finish (time) of the sludge liquor dis- maintenance of nitrification in accordance with
charge. ATV-DVWK-A 131E (2000) is based on the 2- (or
– ratio of the ammonia nitrogen load of the sludge 4-) weekly mean of the measured load. The under
liquor to the TKN load in the inflow to the bio- certain circumstances deviating ratio values
logical stage. CBOD,InB/CCOD,InB, CTKN,InB/CCOD,InB, XDS,InB/CCOD,InB
and CP,InB/CCOD,InB are to be taken into account.
So far as no data is available about later sludge
production and its properties, the back-flow loads Load with the highest temperature
can be estimated with the aid of empirical ap- For the layout of the aeration system the 2- (or 4-)
proaches [6]. weekly mean of the COD load for the range of the
highest temperature (T2wM,max) as well as the asso-
In order in particular to identify seasonal influences ciated ratio values CBOD,InB/CCOD,InB, CTKN,InB/CCOD,InB,
it is recommended that the following annual time XSS,InB/CCOD,InB and CP,InB/CCOD,InB are to be deter-
series are shown graphically: mined.

– wastewater temperature, comp. Fig. C-9 Special load cases

– Sludge Volume Index There are cases with commerce or industry which
– COD loads, Bd,COD,InB, comp. Fig. C-10 operate seasonally or in tourist areas with which
– weekly mean of the COD loads Bd,COD,InB,wM, the maximum organic and/or nitrogen loading do
comp. Fig. C-11 not fall within the three above load cases. For
– 2- (or 4-) weekly mean of the COD loads these the highest 2- (or 4-) weekly mean of the
Bd,COD,InB,2wM, comp. Fig. C-12 COD load, the associated wastewater temperature
– ratio values CBOD,InB/CCOD,InB, CTKN,InB/CCOD,InB, and the associated ratio values CBOD,InB/CCOD,InB,
XDS,InB/CCOD,InB and CP,InB/CCOD,InB, comp. Figs. CTKN,InB/CCOD,InB, XSS,InB/CCOD,InB and CP,InB/CCOD,InB
C-15 to C 17 are to be determined.

At a glance one can identify the dependencies and

dispersions of the [daily] inflows, loads and con-
centrations in a plot of the COD loads Bd,COD,InB via
the wastewater flows Qd, comp. Fig. C-13.

April 2003 25
ATV-DVWK-A 198E

4.3.1.6 Determination of the Relevant mined; this value is designated as Qd,conc in m3/d.
Loads as 85 % Values In the simplest case the mean dry weather flow of
the period sampled is to be applied. If it is required
The dimensioning of trickling filters and rotating to keep certain effluent concentrations, it is deci-
biological contactors is to be based on the relevant sive which initial concentration has to be reckoned
BOD5 and TKN loads as 85% values. With this it is with, the correct assumption to the wastewater
to be avoided that non-isochronous loads are flow, therefore, has the greatest significance. At
combined together. It is assumed that, in addition best the associated value of Qd,conc can be identi-
to BOD5 and TKN, the COD is also determined and fied from the hydrograph curve of the flow also of
that the COD analysis is more reproducible than previous years as in this way, for example, in-
the determination of the BOD5 practised in waste- creased dry weather flows caused by high infiltra-
water treatment plants. Therefore the procedure tion water flows, can be excluded. All further nec-
should be as follows: essary concentrations can be obtained with the aid
of the mean ratio values or on the basis of meas-
1. The COD load is determined which has been ured loads.
achieved or undercut in 85% of the cases. For
this at least 40 daily loads Bd,COD,InB are required If the relevant loads have been determined as 85%
in kg/d. These can be distributed over a period values in accordance with Chap. 4.3.1.6, then the
of up to three years, provided there is no trend monthly mean of the dry weather flow for the range
or seasonal variation of the BOD5 and/or of the of the dimensioning temperature is to be selected
TKN loads present, comp. Fig. C-14. If there is for the determination of the concentration.
a marked seasonal variation present then peri-
ods of similar loads are to be selected and 85%
values formed separately for these periods. In
4.3.1.8 Determination of the Peak Factor
this case every period should also cover at least
for Nitrogen
40 values.
2. For all days in which samples are taken the ratio In accordance with ATV-DVWK-A 131E (2000) the
values CBOD,InB/CCOD,InB and CTKN,InB/CCOD,InB are peak factor
formed and mean values are to be determined.
B 2 h,TKN,InB,max
Using the mean values of the ratios the relevant fN =
BOD5 load and the relevant TKN load can then B d,TKN,InB
be determined.
must be derived from measured values for the de-
termination of the oxygen transfer. For this at least
If, in special cases, activated sludge plants are to
14 days, if possible with dry weather, are to be
be dimensioned with the 85% load value, one has
sampled. The peak factor fN is determined for each
to proceed accordingly. The load cases are named
day and finally the mean value is formed. If the ra-
as under Chap. 4.3.1.5 with the exception that, as
tio value CTKN,InB/CCOD,InB indicates a seasonal
a rule, only the determination of the lowest and
variation then in the appropriate periods respec-
highest temperature is required. The relevant loads
tively 14 days are to be sampled and two mean
are the same in all cases unless, with the presence
values for fN are to be produced.
of a seasonal variation, two 85% values have to be
determined.
As, as a rule, one more or less knows the daily
variation of the TKN load, it is usually sufficient, for
example in the period from 10:00 h to 16:00 h, to
4.3.1.7 Determination of the Relevant analyse three 2-hourly samples and the daily com-
Concentrations posite sample, comp. Chap. C 2.7.

If the relevant COD load has been determined as 2-

(or 4-) weekly mean, the relevant concentration
CCOD from the relevant load Bd,COD,2wM and the
mean of the dry weather flow of the associated
sampling period (e.g. 6 weeks) are to be deter-

26 April 2003
 ATV-DVWK-A 198E

4.3.2 Estimation of Pollutant Loads and Table 1: Inhabitant-specific loads in g/(I·d),

Concentrations on the Basis of which are undercut on 85% of the
Empirical Values days, see also ATV-DVWK Standard-
ATV-DVWK-A 131E (2000)
If so few measured values are available that even
an 85% value (comp. Chap. 4.3.1.6) cannot be de- After primary settling
termined and the recording of additional values is too Raw- with retention time
Parameter
expensive, there are the following possibilities for the wastewater with QDW,2h,max
0.5 to 1.0 h 1.5 to 2.0 h
estimation of the pollutant loads.
BOD5 60 45 40
– transfer of pollutant loads from analogously or COD 120 90 80
similarly populated (structured) areas. SS 70 35 25
– derivation of pollutant loads from the number of TKN 11 10 10
connected inhabitants and inhabitant-specific P 1.8 1.6 1.6
pollutant loads as well as the connected com-
mercial and/or industrial areas using production- The monthly mean of the dry weather flow for the
specific values. range of the dimensioning temperature should be
used for the calculation of the concentrations. The
Most convenient is the derivation of the pollutant flow value should be derived from measurements
loads using inhabitant-specific loads, as are listed in (comp. Chap. 4.2.2.1) or, if that is not possible, de-
Table 1. termination should be in accordance with Chap.
4.2.3.
Production-specific values of commerce and indus-
try have, in the past, been frequently given for the The concentrations determined with this must be
purpose of comparison as population equivalents compared with the measured values of the con-
(PE). In the future, in accordance with DIN EN centrations with dry weather. With heavy devia-
1085, this must be given an index, which desig- tions, if required, a suitable value Qd,conc is to be
nates from what the value has been determined selected. It should be noted that the calculated
(e.g. PECOD,120 = 25,000 I, PEBOD5,60 = 15,000 I). concentrations of COD and BOD5 as a rule are
Always necessary is the separate determination of higher than measured concentrations. The reason
the dimensioning-relevant values for BOD5, COD, for this is that, with the specific loads in Table 1,
suspended solids, nitrogen, phosphorus and, if re- one is concerned with the 85% value and not with
quired, further parameters. The area-specific mean values. In individual cases higher inhabitant-
wastewater flow rate from commercial/industrial specific loads of suspended solids (SS) were
areas is frequently applied as qInd = 0.5 l/(s·ha) with measured.
the dimensioning of the sewer system (in the plan-
ning stage) (comp. ATV-A 118E, 1999). This pre- With heavy seasonal differences different values
sents hourly peak values for the dimensioning of for Qd,conc must be used as a basis.
sewers and drains. These are not suitable for the
determination of annual values of the wastewater For the determination of the flow in the daily peaks
flow and are to be appropriately reduced. with dry weather QDW,2h,max see Chaps. 4.2.2.5 or
4.2.3 and for the calculation of the combined
It is not permitted to derive population equiva- wastewater flow QComb, see Chap. 4.2.2.6.
lents from estimated wastewater flows from
commercial areas and then determine loads us-
ing these. As an aid a minimum value for the
loads can be found using the (estimated) number
of those employed in the commercial area.

April 2003 27
ATV-DVWK-A 198E

5 Forecast Data mensioning values from measured data. False in-

terpretations are avoided through the standardisa-
tion of the terms and symbols.
Forecasts are to be made according to the plan-
ning horizon of the facilities, if necessary sepa- Investment costs for wastewater facilities can, inter
rated according to structures, mechanical installa- alia, be limited to the required degree through the
tions, measuring and control facilities etc. In specification of realistic dimensioning values. To
Germany overall one assumes a reducing popula- that end existing measured data are to be evalu-
tion number. It depends, however, in individual ated and, if necessary, to be supplemented
cases on the attractiveness of the communities through well-directed investigations. The costs for
whether one has to reckon with an increase or de- this stand in no relation to the possible savings. In
crease of the number of inhabitants. At the same addition ways are indicated as to how the costs for
time the further development of the inhabitant- chemical analysis can be limited to a justifiable de-
specific domestic water consumption is to be taken gree without giving up any of the informative value.
into account. Currently, in many places, the spe-
cific water consumption is stagnating, frequently it
is rather decreasing

Firms are increasingly applying water-saving pro- 7 Relevant Regulations,

duction procedures. An increase of the wastewater
production and of the pollution loads from firms al-
Standards and
ready established is therefore to be expected only Standard
with mergers or the commissioning of new produc-
tion lines. Specifications
In urban land use planning normally additional resi- • Wastewater Ordinance
dential and commercial areas are identified. The
additional numbers of inhabitants are to be es- Verordnung über Anforderungen an das Einleiten
timated very accurately on the basis of the charac- von Abwasser in Gewässer (AbwV). [(German)
teristic numbers for building utilisation and to be Ordinance on the Requirements for the Discharge
assessed with possible changes (reductions) in of Wastewater into Surface Waters] Bundesge-
other areas. With the commercial/industrial areas setzblatt 2002, Part 1, No. 6 dated 2. 7. 2002
there should be differentiation between firms with • ATV-DVWK Standards
low specific water consumption and those with
medium to high water consumption (see Chap. ATV-DVWK-A 110E
4.2.3 and ATV-A 118E, 1999). If no clear plans for Hydraulic Dimensioning and Performance Verifica-
certain [new] businesses exist, one should, as a tion of Sewers and Drains
rule, assume businesses with medium water con-
sumption for the dimensioning of wastewater ATV-A 111E
treatment plants. Standards for the Hydraulic Dimensioning and
Verification of Stormwater Overflow Installations in
In larger catchment areas the forecast data for the Sewers and Drains
dimensioning of wastewater treatment plants and
for example the dimensioning of combined sewer ATV-A 112 [Not available in English]
systems may deviate from one another. Richtlinien für die hydraulische Dimensionierung
und den Leistungsnachweis von Sonderbauwerken
in Abwasserkanälen und -leitungen
6 Costs and [Standards for the Hydraulic Dimensioning and

Environmental Effects Performance Verification of Special Structures in

Sewers and Drains]

With this standard planners and examiners obtain

a differentiated work basis for the derivation of di-

28 April 2003
 ATV-DVWK-A 198E

ATV-A 116E ATV-DVWK-A 281E

Special Sewer Systems Dimensioning of Trickling Filters and Rotation Bio-
Vacuum Drainage Service – Pressure Drainage logical Contactors
Service
ATV-DVWK-M 153 [Not yet available in English]
ATV-DVWK-A 117 [Not available in English in the Handlungsempfehlungen zum Umgang mit Re-
latest version (2001)] genwasser
Bemessung von Regenrückhalteräumen [Recommendations on the handling of Stormwater]
[Dimensioning of Stormwater Retention Facilities]
ATV-DVWK-M 177 [Not yet available in English]
ATV-A 118E Bemessung und Gestaltung von Regenentlas-
Hydraulic Dimensioning and Verification of Drain- tungsanlagen in Mischwasserkanälen - Erläute-
age Systems rungen und Beispiele -
[Dimensioning and Design of Stormwater Overflow
ATV-A 126E Facilities in Combined Sewers - Explanatory Notes
Principles for Wastewater Treatment in Wastewa- and Examples -]
ter Treatment Plants According to the Activated
Sludge Process with Joint Sludge Stabilisation with • Standard Specifications
Connection Values between 500 and 5,000 Total
EN 752-1: 1995
Number of Inhabitants and Population Equivalents
Drain and sewer systems outside buildings,
Part 1: Generalities and definitions
ATV-A 128E
Standards for the Dimensioning and Design of
EN 752-2, 1996
Stormwater Structures in Combined Sewers
Drain and sewer systems outside buildings,
Part 2: Performance requirements
ATV-DVWK-A 131E
Dimensioning of Single-Stage Activated Sludge
EN 752-3, 1996
Plants
Drain and sewer systems outside buildings,
Part 3: Planning
ATV-A 134 [Not available in English in the latest
version (2000)]
EN 752-4, 1997
Planung und Bau von Abwasserpumpanlagen
Drain and sewer systems outside buildings,
[Planning and Construction of Pumping Stations]
Part 4: Hydraulic design and environmental con-
siderations
ATV-A 138 [Not available in English in the latest
version (2000)]
EN 752-5, 1997
Planung, Bau und Betrieb von Anlagen zur Versi-
Drain and sewer systems outside buildings,
ckerung von Niederschlagswasser
Part 5: Rehabilitation
[Planning, Construction and Operation of Facilities
for the Percolation of Precipitation Water]
EN 752-6, 1998
Drain and sewer systems outside buildings,
ATV-A 200E
Part 6: Pumping installations
Principles for the Disposal of Wastewater in
Rurally Structured Areas
EN 752-7, 1998
Drain and sewer systems outside buildings,
ATV-A 257E
Part 7: Maintenance and operations
Principles for the Dimensioning of Wastewater La-
goons and In-line Biological Filters or Biological
EN 1085, 1997
Contactors
Wastewater treatment – Vocabulary; Trilingual
version

April 2003 29
ATV-DVWK-A 198E

DIN 4045, 1985 [3] Fuchs, S., Lucas, S., H. Brombach, Weiß, G.
Wastewater engineering; Vocabulary and Haller, B.: Fremdwasserprobleme erken-
nen - methodische Ansätze
DIN 4049-3, 1994 [Not yet available in English] [Identification of Infiltration Water Problems -
Hydrologie – Teil 3: Begriffe der quantitativen Methodic Approaches]. KA - Abwasser, Abfall
Hydrologie 50 (2003), 28 - 32
[Hydrology - Part 3: Terms for quantitative hydrol- [4] ATV-A 131E (1991): Dimensioning of Single-
ogy] Stage Activated Sludge Plants upwards from
5,000 Total Inhabitants and Population
EN 12255-11, 2001 Equivalents
Wastewater Treatment plants - Part 11: General
data required [5] Schleypen, P. and Meißner, E.: Abflüsse aus
Kanalisationsgebieten und Zuflüsse zu kom-
DIN 38404-3, 1976 munalen Kläranlagen bei Trockenwetter- und
German standard methods for the analysing of wa- Regenwasserverhältnissen
[Flows from Areas with Sewers and Flows
ter, wastewater and sludge: physical and physical-
chemical parameters (Group C); Determination of into Municipal Wastewater Treatment Plants
absorption in the field of UV radiation (C3) with Dry Weather and Wet Weather Condi-
tions]. Korrespondenz Abwasser 46 (1999),
42 - 46
[6] ATV-DVWK-Arbeitsbericht: Rückbelastung
8 Literature aus der Schlammbehandlung - Menge und
Beschaffenheit der Rückläufe
[Translator’s note: Apart from [4] no known
translation available in English] [Loads from Sludge Treatment - Quantity and
Properties of the Return Flows]. Korrespon-
[1] ATV-Arbeitsbericht „Simulation von Kläranla- denz Abwasser 47 (2000), 1181 -1187
gen“ [7] Schmitt, T. G., Illgen, M.: Abflusswerte in der
[ATV Report “Simulation of Wastewater Bemessung und Abflusssimulation von Ent-
Treatment Plants”]. Korrespondenz Abwasser wässerungsanlagen
44 (1997), 2064-2074. [Flow values in the Dimensioning and Flow
[2] ATV-Arbeitsbericht „Grundlagen und Einsatz- Simulation of Drainage Systems]. KA - Was-
bereich der numerischen Nachkläbecken- serwirtschaft, Abwasser, Abfall 48 (2001),
Modellierung“ 1720 - 1728
[ATV Report “ Principles and Area of Applica- [8] Stier, E., Fischer, M. and Felber, H.: Betriebs-
tion of Numerical Modelling of Secondary Set- tagebuch für Kläranlagen
tling Tanks]. Korrespondenz Abwasser 47 [Logbooks for Wastewater Treatment Plants].
(2000), 893-896. F. Hirthammer Verlag, München

30 April 2003
 ATV-DVWK-A 198E

Appendix A:
Explanatory notes for surface characteristic values
and catchment area related values
Due to the large effect of the surface characteristic • Catchment area AC [ha]
values (catchment areas and parameters) and the Surface of a catchment area, e. g. surface area
surface-related characteristic values on the of a wastewater disposal catchment.
wastewater engineering calculations, standard
definitions for the comprehension of terminology as The catchment area must be clearly bounded in
well as clear specifications on the arithmetical de- accordance with the respective problem. For
termination of the individual quantities are particu- more detailed characterisation of the surface AC
larly important. The terminological determination of further indices are added, for example AC,s as
these quantities as well as their significance and catchment area with sewers (see below.) etc.
quantitative determination are explained in detail
below. Particular attention is drawn to the catch- • Sewered catchment area AC,s [ha]
ment area and the runoff coefficients. Surface of the catchment area served by sew-
ers or other types of drainage system.

A1 Surface characteristic values For construction areas the boundaries of the

catchment area with sewers are as a rule laid
A 1.1 Surface areas down corresponding with the boundaries of the
parcel of land which is connected through the
In future, with wastewater engineering calculations, drainage system. The surface of the outer area
only the terms and symbols defined in Fig. 1 are to possibly drained in the direction of the devel-
be applied. All other derived area specifications opment is not included in this. In areas with
such as, for example, Aimp, are numerical values separate sewer systems AC,s for the wastewater
which can be additionally calculated depending on and stormwater sewers may be different.
the application.
• Catchment area without drainage system
AC,ns [ha]
Catchment area without sewers or not covered
by a drainage system.

The drainage area without sewers AC,ns results

as the difference between the surface of the
catchment area AC and the surface of the
catchment area with sewers AC,s:
AC,ns = AC – AC,s (A-1)

• Paved surface area AC,p [ha]

Sum of all paved surfaces of a catchment area.

The quantity AC,p includes all paved sub-areas

in the catchment under consideration, inde-
Fig. A-1: Schematic representation for pendent of whether these surfaces are con-
catchment area definition (not a nected to the drainage system and a discharge
plan drawing!) into the sewer system takes place. The designa-
tion AC,p replaces the quantity Ared which is con-
tained, inter alia, in the ATV Standard ATV-A
128E (1992).

April 2003 31
ATV-DVWK-A 198E

Paved surfaces can be impermeable (tiled, The quantity Aimp, through the coupling with the
metal or glass roofs, asphalt roads) or be of dif- application-specific runoff coefficient ψ (see
ferent permeability (gravel paths, grassed bal- above), is event-dependent and represents the re-
last). Their flow effectiveness is described via spective “runoff-effective surface”. Aimp is deter-
application-specific runoff coefficients ψ (see A mined in the concrete application case from the
1.3). sum of all sub-surfaces AC,i connected to the
drainage system, multiplied by the associated ap-
• Unpaved surfaces AC,np [ha] plication- and surface-specified discharge coeffi-
Sum of all unpaved surfaces of a catchment cient ψi:
area as the difference between total catchment
Aimp = Σ (AC,i ⋅ ψi) (A-4)
area and paved catchment area under consid-
eration, general:
With restriction to paved sub-areas AC,p,i and ex-
AC,np = AC – AC,p (A-2) clusion of the unpaved surfaces, the following sim-
plification applies:
The possible runoff contribution of unpaved sur-
Aimp = Σ (AC,p,i ⋅ ψi) (A-5)
faces and their consideration in the design or
with flow calculations is dependent on the local
In ATV Standard ATV-A 128E (1992) Aimp is de-
circumstances (ground slope, limitation of the
fined with reference to the annual amount of storm-
parcel of land, structural facilities) and the re-
water runoff as long-term mean and limitation to
spective problem. Unpaved areas can have a
the paved surface AC,p (Ared in accordance with A
considerable contribution in particular with the
128E (1992)). For these, Aimp,A128 is determined via
consideration of less frequent heavy rainfall
the runoff coefficient ψA128,i of the paved sub-areas
events in the sewer network calculation or the
AC,p,i determined with the same reference. Paved
dimensioning of stormwater retention facilities.
sub-areas not connected to the sewer system are
evaluated here with ψA128,i = 0.0 (see A 1.3).
• Industrial catchment area AC,Ind [ha]
Area of a commercial or industrial catchment. Aimp,A128 = Σ (AC,p,i ⋅ ψA128,i) (A-6)

The industrial catchment area AC,Ind refers in If no differentiated consideration of the individual
general to the catchment of commercial or in- surfaces takes place within the drainage area, Aimp
dustrial areas identified in the development is to be set equal to the paved surface AC,p.
plan. For definition or more detailed description
further indices can be applied, e.g. as area with Stormwater runoff models as a rule contain distinct
sewers AC,Ind,s. modelling approaches for the calculation of the
losses (flow formation) and should therefore build
upon the actual connected surface area AC,s or,
A 1.2 Calculated value “Impermeable
with the disregard of the contribution to the runoff
surface” Aimp of non-paved surfaces, upon the paved surface
AC,s,p. The surface approaches used as a basis are
Application-related calculated value for quantify-
to be identified.
ing the portion of the catchment area from which
the stormwater runoff, following deduction of the
wetting effect and filling of depression storage, en-
A 1.3 Degree of paving and runoff
tirely gets runoff effective in a drainage system.
coefficients
Aimp is a calculated quantity and is a non-
• Degree of paving γ [-]
measurable surface area in a locality. It results from
corresponds with the fraction of the paved sur-
the application-related precipitation runoff balance
faces in the overall catchment area; generally:
of a catchment area:
AC ,p
hP ⋅ AC ⋅ ψ = hP ⋅ Aimp => Aimp = AC ⋅ ψ (A-3) γ = (A-7)
AC

32 April 2003
 ATV-DVWK-A 198E

As a rule the degree of paving refers to the sive influence on the result of the runoff cal-
catchment area with sewers AC,s. Indices can be culation.
employed for elucidation and further differentia-
tion, e.g.: In specialist literature there exist standard
values for different problems and dimension-
γC,s = AC,p,s / AC,s. (A-8) ing details, if required broken down for vari-
ous precipitation loads as well as types, uses
In built-up areas the degree of paving results and slopes of surfaces. The standard values
from the assessed size of the paved surface ar- can be converted, using surface-weighted
eas (see A 1.1) and the associated overall meaning, to area-specific coefficients of run-
catchment area. With planned developments off and adopted in simplified approaches for
the degree of paved areas is selected on the the determination of discharge (e.g. as coef-
basis of specifications on the type and extent of ficient of maximum discharge ψs in the time
the constructional utilisation from the develop- coefficient process). Discharge coefficients
ment plan (empirical values). for dimensioning can, quantitatively, be
specified only together with their application
• Runoff coefficient ψ [-] reference. This is to be given. It can be eluci-
application-related coefficient quantifying the dated using additional indices, for example
runoff effective precipitation fraction; calculation ψs as coefficient of peak runoff or ψm for a
as quotient of runoff and associated precipita- defined period (see below).
tion quantity, depending on the problem, as ψm,
ψs etc. b) Runoff coefficients as calculation result
of discharge modelling
The runoff coefficient of a catchment area is al- Runoff coefficients can be derived as calcula-
ways to be given as application-related ac- tion result from the application of precipitation
cording to the respective problem. It is, to a runoff modelling. These determine the resul-
large degree, dependent on the local conditions tant runoff directly from the specified precipi-
(i. a. surface properties and ground slope, type tation loading, the surface characteristic val-
of property drainage and implementation of (de- ues and the model parameters for the flow
centralised) measures of stormwater manage- formation. Here the runoff coefficients result -
ment) as well as on the precipitation event or again with different reference - as ratio value
period considered. With existing systems and of calculated discharge quantity (flow in l/s;
clearly defined sub-catchments the coefficient of flow volume in m3) to the associated, speci-
discharge can be determined mathematically via fied precipitation loading (momentary or
a discharge and precipitation measurement. mean rainfall intensity in l/(s⋅ha) or amount of
precipitation in mm together with the catch-
With runoff coefficients, in addition to the appli- ment area).
cation reference, it is to be differentiated
whether they are given as dimensioning value • Mean runoff coefficient ψm [-]
or as result of a discharge/flow calculation, see Quotient from flow volume and precipitation vol-
also [7]. ume for a defined period (e.g. limited precipita-
tion event or seasonal period).
a) Runoff coefficients for dimensioning (de-
sign) The mean runoff coefficient ψm can, depending
Runoff coefficients are used for various di- on the problem, refer to a limited, individual pre-
mensioning details. They serve for the de- cipitation event or a defined period, e.g. as an-
termination of a flow quantity (flow in l/s or nual value in the long-term mean. In this way it
m3/s; volume in m3) from a specified precipi- is used in the ATV-DVWK Advisory Leaflet ATV-
tation loading (e.g. block rain with rainfall in- DVWK-M 153 (2000) [not available in English]
tensity r in l/(s⋅ha) or amount of precipitation as event-related value - with reference to heavy
in mm together with a surface area). The size rain appropriate to the question. As long-term
of the selected runoff coefficients has a deci- annual mean value it serves in ATV Standard

April 2003 33
ATV-DVWK-A 198E

ATV-A 128E (1992) for the estimation of the and block rain. It is defined as quotient of the
discharge-effective annual amount [height] of maximum amount of precipitation runoff to the
precipitation hP,a,eff. maximum rainfall intensity defined via Eqn. (A-
11)
As dimensioning [design] value, ψm allows
ψs = qmax / rmax (A-11)
the determination of the runoff amount of pre-
cipitation of a specified precipitation loading or a with qmax – maximum runoff rate in l/(s⋅ha)
discharge volume with inclusion of the associ- rmax – maximum rainfall intensity in l/(s⋅ha)
ated surface area in accordance with Eqn. A-9.
Eqn. (A-11) is oriented on the consideration of
The specification should always be with refer- precipitation of constant intensity and the appli-
ence to a specified precipitation event (amount cation of flow time procedures for the calcula-
of rain hP and duration D) or an appropriate tion of maximum discharges in dimension-
range of values. ing in accordance with Eqn. (A-12).
hP,eff = hP ⋅ ψm or
Qmax = AC,s ⋅ rD,n ⋅ ψs (A-12)
VPR = 10 · hP ⋅ ψm ⋅ AC,s (A-9)
with Qmax – calculated maximum discharge in l/s
with
rD,n – rainfall intensity (block rain) for the du-
hP – amount [height] of precipitation in mm
ration D and frequency n in l/(s⋅ha)
hP,eff – discharge effective precipitation [rain] in mm
VPR – precipitation runoff volume in m3
The specification of peak runoff discharge coef-
AC,s – catchment area with sewers in ha
ficients for the dimensioning should always be
with reference to a certain rainfall intensity or an
In the same way ψm can be determined via Eqn.
appropriate range of values.
(A-9) as result of a measurement of the
amounts of precipitation and runoff for a clearly
The peak runoff coefficient ψs can be identified
defined area AC,s.
via Eqn. (A-11) as result of a runoff modelling.
Through the employment of time-variable pre-
As calculation result of the runoff modelling
cipitation (for example model rainfall) and
ψm in accordance with Eqn. (A-10) is deter-
statements on loss (initial losses, long-term
mined as
losses) using Eqn. (A-11) both the significantly
reduced as well as essentially increased coeffi-
ψm = VPR / (10 · hP ⋅ AC,s) (A-10)
cients of maximum discharge in comparison
with the standard values in literature can result.
The amount of precipitation hN specified in the
While discharge models reflect the surface run-
calculation and the calculated loss hL,i can refer
off for rainfall events of “arbitrary” magnitude
to a limited, individual event or a defined period
(for example return times Tn = 0.5 years to Tn =
of time, e.g. one year, or can represent the
50 years), the coefficients of maximum dis-
long-term mean.
charge named in literature are derived and can
be used in regulation for a narrowly limited
• Peak runoff coefficient ψs [-]
range of rainfall intensities (for example refer-
Quotient from the peak runoff rate qmax and as-
ence rainfall intensity r15,n).
sociated maximum rainfall intensity rmax, in the
first instance for flow time procedures and block
• Runoff coefficient ψA128 [-]
rain.
application-related runoff coefficient in accor-
dance with ATV Standard ATV-A 128E (1992)
The peak runoff coefficient ψs (previously also
and/or Advisory Leaflet ATV-DVWK-M 177
runoff coefficient during storm peak) refers to an
(2001) [not available in English] for the determi-
individual rainfall event (e.g. dimensioning rain-
nation of the calculation value Aimp,A128 from the
fall) and is adopted in the sewer network calcu-
size of the paved surface area AC,p.
lation in accordance with ATV Standard ATV-A
118E (1999) together with flow time procedures

34 April 2003
 ATV-DVWK-A 198E

In the context of ATV-A 128E (1992) and ATV- [with

DVWK-M 177 (2001) the runoff coefficient ψA128 hL,perc loss due to percolation
corresponds with the ratio value between the hP amount of precipitation
calculation value Aimp,A128 and the paved surface hL,W+M loss due to wetting (W) and suppres-
area AC,p sion storage (M) effects]
ψA128 = Aimp,A128 / AC,p or Aimp,A128 = AC,p ⋅ ψA128
From long-term simulation, coefficients of dis-
(A-13)
charge ψA128 significantly smaller than identified
and at the same time serves for the valuation of in Advisory Leaflet ATV-DVWK-M 177 (2001)
the contribution of pervious paved areas to the can result through the involvement of all rainfall
runoff. With limitation to the paved surfaces it events in the annual period.
describes the part of the surface which, in the
annual mean, after covering wetting and filling
of hollows, contributes entirely to the runoff. A 1.4 Numerical example for surfaces
and surface parameters
The runoff coefficient ψA128 thus serves for
the valuation of the flow reducing effect of AC 120 ha
impervious or pervious paved areas in the AC,p 100 ha
catchment related to the problem in ATV-A AC,np 20 ha (AC,np = AC – AC,s)
128E “Dimensioning of Stormwater Overflow AC,s,p 40 ha
Facilities”. Its magnitude is influenced by the AC,s,np 60 ha (AC,s,np = AC,s – AC,s,p)
type of surface pavement and, possibly, through γC,s = AC,s,p / AC,s = 40 / 100 = 0.40
the type of soil and the covering of vegetation.
Impermeably paved sub-surfaces (roofs, asphalt Using the value calculated in Table A-1 ψA128 =
roads etc.), by definition, have a coefficient of 0.83 one obtains:
discharge ψA128= 1.0. Permeable surface pave-
Aimp,A128 = AC,s,p ⋅ ψA128 = 40 ⋅ 0.83 = 33.2 ha
ments are evaluated according to their effec-
tiveness with the relevant rainfall event with co-
Table A-1: Example for the determination of the
efficients of discharge ψA128 < 1.0. Thus, in the
runoff coefficient ψA128 (various sub-
difference to 1.0 the coefficient of discharge
surfaces of a residential area as-
ψA128 quantifies the flow reducing effect of the
sumed as examples and ψA128,i - val-
percolation whereby, with the application ATV-A
ues in accordance with ATV-DVWK-
128E, relief-relevant precipitation events are in
M 177 (2001))
the foreground. Paved areas, which can be veri-
fied as not being connected to the drainage sys-
Type of surface Surface frac- ψA128,i AC,s,p·ψA128,i
tem, are valuated as ψA128 = 0.0.
tion [-] [-]
AC,s,p[%]
Advisory Leaflet ATV-DVWK-M 177 (2001), for
Roof surfaces 30 (0.30) 1.00 0.3
selected types of surface, contains different Roads, asphalt 25 (0.25) 1.00 0.25
runoff coefficients ψA128 for application in the Parking areas and 20 (0.20) 0.85 0.17
design process in accordance with ATV-A places, courtyards,
128E (1992). With this a detailed determination continuous pave-
of the calculated quantity Aimp,A128 according to ment
Eqn. A-6 can take place (see numerical exam- Parking areas, 10 (0.10) 0.75 0.075
ple below). courtyards, jointed
pavement
For the identification of the coefficient of dis- Grassed ballast 5 (0.05) 0.60 0.03
charges ψA128 in flow models - referred to indi- Non-connected 10 (0.10) 0.00 0
vidual surfaces or the (sub-) catchment area paved surfaces

under consideration - the employment of the ψA128 0.825 ≈

0.83
definition equation (A-14) is recommended.
ψA128 = 1 – (hL,perc / (hP – hL,W+M) ) (A-14)

April 2003 35
ATV-DVWK-A 198E

A. 1.5 Catchment area related values planned areas the population density, for exam-
ple from existing development plans, is
• Concentration [flow] time tf [min] adopted. With this the respective reference sur-
Time, which the relevant stormwater runoff re- face area is to be observed.
quires from the catchment area to a determined
point of the drainage system. • Industrial wastewater discharge rate qInd
[l/(s⋅ha)]
The concentration time is an auxiliary value for Industrial wastewater flow QInd referred to the
the characterisation of the flow behaviour with catchment area AC,Ind of the commercial or in-
rainfall. It is determined for existing sewer sys- dustrial area under consideration.
tems via the maximum flow rate with dimension-
ing rainfall and the lengths of the individual With the planning of commercial and industrial
sewers and channels. With new planning, as an areas the quantity qInd can be selected from
approximation, one assumes the flow velocity empirical values. If the calculation refers to ex-
with complete filling of the selected profile. With isting areas the industrial wastewater discharge
extreme dissimilar flows and at confluences, per unit area can be calculated from the flow
branches and special structures which effect a QInd and the associated area. It should be given
marked change of the discharge wave through related to the surface area of the commercial or
throttling, storage and/or reduction (flattening, industrial area AC,Ind,s which has sewers.
extension), special considerations are to be
made depending on the problem. • Infiltration water discharge rate qInf [l/(s⋅ha)]
Infiltration water flow QInf (with dry weather) re-
• Surface ground slope IG [%] lated to the catchment area with drainage sys-
Gradient of an area, details are in % and is fre- tem AC,s under consideration.
quently allocated to slope groups (Table A-2).
With new planning of residential and commer-
Table A-2: Slope groups SG of the ground cial/industrial areas the infiltration water dis-
slope IG (e.g. in accordance with charge qInf is used for the estimation of the an-
ATV-A 128, 1992) ticipated amount of the infiltration water flow.
With the consideration of existing areas it can
Slope Group SG Ground slope IG be determined from the infiltration water flow
1 ≤1% QIW and the associated surface. For reasons of
2 1%-4% comparability it should always be related to the
3 4 % - 10 % area with sewers AC,s.
4 > 10 %
• Stormwater discharge rate in sanitary [sew-
The mean ground slope characterises the gra- age] sewers qR,Sep [l/(s⋅ha)]
dient conditions in the respective catchment Unavoidable stormwater runoff QR,Sep in sanitary
area independent of the prevailing flow direction sewers from areas served by separate sewer
in the sewers. system related to the associated drainage area
AC,s.

A2 Surface reference parameters • Throttle discharge rate qThr [l/(s⋅ha)]

Throttle flow QThr from stormwater overflows
• Population density PD [I/ha] and stormwater tanks referred to the associated
Quotient from the number of inhabitants (I) and catchment area.
the area of the catchment.
The reference catchment area, depending on
With the consideration of existing areas the the scope and problem, can be differentiated;
population density can be calculated from the e.g. direct catchment area or overall area with
number of inhabitants and the associated sur- sewers upstream. For clarification additional in-
face, whereby this is often related to the surface dices can be employed, e.g. qThr,s = QThr / AC,s.
area with sewers AC,s (PD = I / AC,s). With

36 April 2003
 ATV-DVWK-A 198E

• Rainfall fraction of the throttle discharge rate • Stormwater discharge rate qR [l/(s·ha)]
qThr,R [l/(s⋅ha)] Stormwater flow of an area related to an asso-
Rainfall fraction in the throttle flow QThr,R from ciated surface area AC.
stormwater overflows and stormwater tanks re-
lated to the surface of the associated catchment • Stormwater discharge rate in accordance
areas. with ATV-A 128E (1992) qr [l/(s·ha)]
In ATV-A 128E (1992) the stormwater discharge
In combined sewer systems the separate identi- rate (using the symbol qr) is to be seen as an-
fication of the rainfall fraction often takes place nual mean value in the throttle flow of a storm-
in the throttle flow of a monitoring facility (comp. water overflow tank or sewer with storage ca-
qR). The reference catchment area, depending pacity. It derives from the fraction of the
on the scope and problem, can be differenti- stormwater runoff in the throttle flow Qr with re-
ated; e.g. direct catchment area or overall area gard to the impermeable surface Aimp,A128 (qr =
with sewers upstream of the monitoring facility. Qr / Aimp,A128) and thus represents an application-
related quantity.

April 2003 37
ATV-DVWK-A 198E

Appendix B 1:
Summary of flow values from the English translations
of respective ATV-DVWK Standards

In the following summary only those flow values the throttle flow from retention facilities, have
have been incorporated which are required as ini- therefore not been listed. This is also the reason
tial quantities. Values which are derived from cal- why a series of standards which, for example, are
culations in the standards such as, for example, directed at hydraulic calculations, are not listed.
[Translator’s note: here only the English versions of the symbols are compared. For a comparison of the German symbols please refer
to Appendix B2 below.]

Symbol
Unit Definition/Explanation A 198E
Old A 198E
ATV-A 118E (1999): Hydraulic Dimensioning and Verification of Drainage Systems
Qiw QInf,aM l/s Infiltration water as annual mean
Qc QInd,h,max l/s Max. hourly commercial resp. industrial wastewater flow
Qd QD,h,max l/s Max. hourly domestic wastewater flow
Qs QR,h,max l/s Max. hourly stormwater runoff
Qs,S QR,Sep,h,max l/s Max. hourly unavoidable stormwater runoff in sanitary sewers from areas with
separate sewer system
Qdw QDW,h,max l/s Max. hourly dry weather flow
ATV-A 126E (1993): Principles for the Wastewater Treatment in Sewage Treatment Plants according to the Activated
Sludge Process with Joint Sludge Stabilisation with Connection Values between 500 and 5000 Total Number of In-
habitants and Population equivalents
Qi QInf,aM m³/h Infiltration water flow as annual mean
Qd24 QD,2h,max m³/h Max. hourly domestic wastewater flow as 2-hourly mean
QC QInd,2h,max m³/h Max. hourly commercial resp. industrial wastewater flow as 2-hourly mean
QI QInd,2h,max m³/h As above (QC and Qi are no longer differentiated, instead QInd)
Qcs QComb m³/h Combined wastewater flow to the wastewater treatment plant
Qr QR,Sep m³/h Unavoidable stormwater runoff in sanitary sewers from areas with separate
sewer system
QDI QWW,2h,max m³/h Max. wastewater flow as 2-hourly mean
Qdw QDW,2h,max m³/h Max. dry weather flow as 2-hourly mean
Q Qd m³/d Daily sewage flow
ATV-A 128E (1992): Standards for the Dimensioning and Design of Stormwater Structures in Combined Sewers
Qiw24 QInf,aM l/s Infiltration water flow as annual mean
Qd24 QD,aM l/s Max. hourly domestic wastewater flow as annual mean
Qc24 QInd,aM l/s Max. hourly commercial resp. industrial wastewater flow as annual mean
Qi24 QInd,aM l/s As above (QC and Qi are no longer differentiated, instead QG)
Qcw QComb l/s Combined wastewater flow to the wastewater treatment plant
QrS24 QR,Sep l/s Unavoidable stormwater runoff in sanitary sewers from areas with separate
sewer system
Qw24 QWW,aM l/s Wastewater flow as annual mean
QwST24 QWW,Sep,aM l/s Wastewater flow from areas with separate sewer system as annual mean
Qdw24 QDW,aM l/s Dry weather flow as annual mean
Qdwx QDW,h,max l/s Max. hourly dry weather flow
ATV-DVWK-A 131E (2000): Dimensioning of Single-Stage Activated Sludge Plants
QWW,h QCW m³/h Combined wastewater flow to the wastewater treatment plant
QDW,d QDW,d,aM m³/d Daily dry weather flow as annual mean
QDW,h QDW,2h,max m³/h Max. dry weather flow as 2-hourly mean
ATV-DVWK-A 281E (2001): Dimensioning of Trickling Filters and Rotating Biological Contactors
[Translator’s note: This Standard was translated after A198 and therefore the symbols in English are standardised]
QCW QComb m³/h Combined wastewater flow to the wastewater treatment plant
QDW,d,aM QDW,d,aM m³/d Daily dry weather flow as annual mean
QDW,2h,max QDW,2h,max m³/h Max. dry weather flow as 2-hourly mean

38 April 2003
 ATV-DVWK-A 198E

Appendix B 2:
Summary of flow values from the original German
ATV-DVWK Standards

In the following summary only those flow values the throttle flow from retention facilities, have
have been incorporated which are required as ini- therefore not been listed. This is also the reason
tial quantities. Values which are derived from cal- why a series of standards which, for example, are
culations in the standards such as, for example, directed at hydraulic calculations, are not listed.

Symbol
Unit Definition/Explanation A 198E
Old A 198
ATV-A 118 (1999): Hydraulic Dimensioning and Verification of Drainage Systems
Qf QF,aM l/s Infiltration water as annual mean
Qg QG,h,max l/s Max. hourly commercial resp. industrial wastewater flow
Qh QH,h,max l/s Max. hourly domestic wastewater flow
Qr QR,h,max l/s Max. hourly stormwater runoff
Qr,T QR,Tr,h,max l/s Max. hourly unavoidable stormwater runoff in sanitary sewers from areas with
separate sewer system
Qt QT,h,max l/s Max. hourly dry weather flow
ATV-A 126 (1993): Principles for the Wastewater Treatment in Sewage Treatment Plants according to the Activated
Sludge Process with Joint Sludge Stabilisation with Connection Values between 500 and 5000 Total Number of In-
habitants and Population equivalents
Qf QF,aM m³/h Infiltration water flow as annual mean
Qh QH,2h,max m³/h Max. hourly domestic wastewater flow as 2-hourly mean
Qg QG,2h,max m³/h Max. hourly commercial resp. industrial wastewater flow as 2-hourly mean
Qi QG,2h,max m³/h As above (QC and Qi are no longer differentiated, instead QInd)
Qmz QM m³/h Combined wastewater flow to the wastewater treatment plant
Qr QR,Tr m³/h Unavoidable stormwater runoff in sanitary sewers from areas with separate
sewer system
Qs QS,2h,max m³/h Max. wastewater flow as 2-hourly mean
Qt QT,2h,max m³/h Max. dry weather flow as 2-hourly mean
Q Qd m³/d Daily sewage flow
ATV-A 128 (1992): Standards for the Dimensioning and Design of Stormwater Structures in Combined Sewers
Qf24 QF,aM l/s Infiltration water flow as annual mean
Qh24 QH,aM l/s Max. hourly domestic wastewater flow as annual mean
Qg24 QG,aM l/s Max. hourly commercial resp. industrial wastewater flow as annual mean
Qi24 QG,aM l/s As above (QC and Qi are no longer differentiated, instead QG)
Qm QM l/s Combined wastewater flow to the wastewater treatment plant
QrT24 QR,Tr l/s Unavoidable stormwater runoff in sanitary sewers from areas with separate
sewer system
Qs24 QS,aM l/s Wastewater flow as annual mean
QsT24 QS,Tr,aM l/s Wastewater flow from areas with separate sewer system as annual mean
Qt24 QT,aM l/s Dry weather flow as annual mean
Qtx QT,h,max l/s Max. hourly dry weather flow
ATV-DVWK-A 131 (2000): Dimensioning of Single-Stage Activated Sludge Plants
Qm QM m³/h Combined wastewater flow to the wastewater treatment plant
Qd QT,d,aM m³/d Daily dry weather flow as annual mean
Qth QT,2h,max m³/h Max. dry weather flow as 2-hourly mean
ATV-DVWK-A 281E (2001): Dimensioning of Trickling Filters and Rotating Biological Contactors
Qm QM m³/h Combined wastewater flow to the wastewater treatment plant
Qd QT,d,aM m³/d Daily dry weather flow as annual mean
Qt QT,2h,max m³/h Max. dry weather flow as 2-hourly mean

April 2003 39
ATV-DVWK-A 198E

Appendix C:
Example for the evaluation of measured values
C1 Flows

C 1.1 Summary of measured values

As a rule the evaluation takes place with the aid of a table with data and some calculations are shown
a tabular calculation programme. The scheme with as examples in Table C-1.

Table C-1: Summary of flow data

Dry weather flow(QDW,d)

max. hourly DW flow

min. hourly DW flow

QDW,h,max/QDW,d

QDW,h,min/QDW,d
(QDW,h,max)

(QDW,h,min)
Flow (Qd)
Weekday

Weather
Date

m3/d m3/d l/s l/s - -

1 2 3 4 5 6 7 8 9
1.1. Fr DW 24077 24077 348 210 1.25 0.76
2.1. Sa 35041

24.5. Mo DW 15845 15845 260 105 1.42 0.57

25.5. Tu DW 17156 17256 263 111 1.32 0.56

31.12 Fr 43502
Mean (aM) 30579 16820 259 112 1.35 0.55

The following on the contents of the columns Column 5, Dry weather (DW) flow:
should be noted: for dry weather days (see Col. 3) taken over from
Column 4.
Column 3, Weather:
In the wastewater treatment plant the weather Columns 6 and 7:
code recommended in the logbook [8] can be used maximum and minimum hourly flow (QDW,h,max and
as the basis: 1-dry; 2-frost; 3-rain; 4-thunder; 5- QDW,h,min). For dry weather days (see Col. 3) de-
snow melt; 6-snowfall; 7-rainfall follow-up. Accord- termined from (digital) records.
ing to this, only days with 1 or 2 are dry weather
days. At the same time there are [German] Federal Columns 8 and 9:
State regulations, for example in North Rhine ratio values from Columns 6 and 7 for the mean
Westphalia, it counts as a dry weather day if, on dry weather flow (QDW,d in l/s) each day.
the day considered or the day before N ≤ 1 mm/d.
In Column 3 one can limit this to the designation For Columns 4 to 9 the annual means have been
dry weather days (“DW“). formed in the last line.

Column 4, Flow:
Taken over from the logbook or determined from
digital records.

40 April 2003
 ATV-DVWK-A 198E

C 1.2 Daily flows C 1.3 Determination of the dry weather

flow
As overview of the daily sewage flow as well as for
plausibility check the graphical presentation is The annual mean of the dry weather flow is calcu-
practical using the data from Table C-1. lated as mean of the values in Column 5 of Table
C-1. The dry weather flows in Fig. C-3 show a
Q [1000 m³/d] Daily flow, all days trend similar to the smallest daily flows in Fig. C-1.
d
Freak values can not be identified in the time se-
100
ries of the dry weather flow.
80
From Column 5 of Table C-1, for this example a
60 dry weather flow of QDW,d,aM = 16,820 m3/d corre-
sponding with QDW,aM = 195 l/s results, which is
40 confirmed optically by Fig. C-3. Typical dry weather
conditions with approximately constant infiltration
20 water flow predominate in 1999 from 01 July to 31
October. In this period the mean with QDW,d,pM =
0 13,565 m³/d is significantly lower than the annual
J F M A M J J A S O N D
mean.
Fig. C-1: Time series of the daily flow in 1999

Q [1000 m³/d] Daily flow, dry weather days

Q [1000 m³/d] Daily flow, all days T,d
d
100
100
Annual mean
80 16,820 m³/d
80 70 DW days

60
60
01 July to 31 Okt.
40 Mean 13,565 m³/d
40
20
20
0
0 J F M A M J J A S O N D
J F M A M J J A S O N D
Fig. C-2: Time series of the daily flow in 1997, Fig. C-3: Time series of the flow on dry
1998 and1999 weather days in 1999

Fig. C-1 shows that, in the months January to May The dry weather flow can, in accordance with
and November/December 1999, there are many Chap. 4.2.2.1, Para 4, also be determined inde-
days with high flows. The minimum flow values in- pendently from the weather conditions. This is
dicate a seasonal variation; they are higher in the demonstrated for 1999. For this the lowest daily
winter months than, for example, in summer. From flow for each day of the preceding 10 days, of the
precipitation records it can be seen that in the day considered and the following 10 days (sliding
months of January to May and Novem- 21-day value) is sought. The polygon resulting
ber/December it rained a great deal. These rainfall from this is shown by the continuous line in Fig. C-
periods have evidently caused a seasonal variation 4.
of the infiltration water flow. The flows of the three
years 1997 to 1999 (Fig. C-2) show clearly that the All flows which lie by up to 20% above the polygon
course of the flow can also be different. are considered as dry weather flows, see Fig. C-5.

April 2003 41
ATV-DVWK-A 198E

Q [1000 m³/d] Daily flow, all days Frequency of undercutting [%]

d 100
+ f lo w f r o m
100 90 d ry w e a th e r d a y s
80 ( 7 0 v a lu e s )
80 70
60
60 F lo w f r o m
50
c a lc u la t e d
40 d ry w e a th e r d a y s
40 (1 4 1 v a lu e s )
30
20 20
1 9 99
10
0 0
J F M A M J J A S O N D 0 10 20 30 40
[1 0 0 0 m ³/d ]
,
Fig. C-4: Polygon of the lowest flows in 21-day T
QDW,d [1000 k
m³/d] tt b fflow
dry weather l
intervals (1999)

Q [1000 m³/d] flow, calculated DW days Fig. C-6: Frequency of the undercutting of the
d flow on dry weather days and those
100 calculated as dry weather days of
Annual mean 1999
80 17,790 m³/d
141 DW days

60 C 1.4 Determination of the wastewater

01 Jul to 31 Oct. flow as annual mean
40 Mean 13,710 m³/d

There are 75,400 inhabitants living within the

20 catchment area of the wastewater treatment plant
involved in the measurement. The responsible wa-
0
J F M A M J J A S O N D ter supply company gives the mean water con-
sumption incl. small commercial consumers, as
Fig. C-5: Time series of flows from calculated 150 l/(I·d). Larger industrial and commercial busi-
dry weather days in 1999 nesses drew together an annual amount of
418,000 m³ they, however, discharged only
The annual mean of the dry weather flows defined 391,000 m³ into the sewer network. With this one
using weather records and the calculated dry obtains the annual mean of the wastewater flow as
weather flows differ only very slightly, even the
summer means are practically equal. The useful-
75,400 ⋅ 150 391,000 3
ness of this procedure is also confirmed by the QWW ,d ,aM = + = 12,380 m /d
1,000 365
very great similarity of the frequency of undercut-
ting of the dry weather flows, comp. Fig. C-6.
respectively QWW,aM = 143 l/s

The daily water consumption shows no marked

seasonal variation.

42 April 2003
 ATV-DVWK-A 198E

C 1.5 Determination of the infiltration C 1.6 Determination of the maximum and

water flow minimum dry weather flow
The daily maximum, mean and minimum hourly
Measurements of the infiltration water flow are not
flows show a similar seasonal variation as for the
available. Therefore the infiltration water flow is
daily dry weather flows (comp. Fig. C-7). The fol-
calculated as the difference between the dry
lowing monthly means have been calculated:
weather sewage flow and the wastewater flow.
Here, as an example, the infiltration water flow for March: Maximum QDW,h,max,mM = 370 l/s
1999 is determined on the basis of weather data September: Minimum QDW,h,min,mM = 80 l/s
(Fig. C-3) and using calculated dry weather days
Due to the almost constant infiltration water flow
(Fig. C-5) in Table C-2. Using the calculated dry the mean of the maximum hourly flows of the
weather days one obtains higher mean dry summer is of interest, it is QDW,h,max,pM = 225 l/s.
weather and infiltration water flows than with the
flows derived from weather data because many In Table C-1 the ratio values QDW,h,max/QDW,d and
high flow values in the period January to March are QDW,h,min/QDW,d have been formed, whose time se-
not recorded as dry weather days. ries is shown in Fig. C-8. As a result of the, for ex-
ample, in March high fraction of infiltration water in
Table C-2: Determination of the infiltration the dry weather flow the ratio value with
water flow in 1999 QDW,h,max/QDW,d = 1.25 is significantly lower than, for
example, in August/September with
Designation Unit QD,d in ac- QDW,d from
cordance calculated
with weather dry weather QDW,h,max/QDW,d = 1.45.
data days
QDW,d,aM m3/d 16,820 17,790
QT,h
DW,h or Q
bzw. QDW,d
T,d [l/s]
[l/s]
QDW,aM l/s 195 206
QWW,aM l/s 143 143 500
QInf,aM l/s 52 63
QInf,aM/QDW,aM % 27 31
400
QDW,h,max
From the three year series investigated 1999
shows the highest monthly mean of the daily dry 300

weather flow. According to Fig. C-5 these occur in

the months January to March with ca. 200 QDW,d

QDW,d,mM,max = 30,000 m3/d corresponding with = QQ

DW,h,min
DW,h,min
100
347 l/s. In Fig. C-3 also (according to weather
data) one finds individual values of QDW,d ≅ 30,000
0
m3/d. Under the premise of the constant wastewa- J F M A M J J A S O N D
ter flow of QDW,aM = 143 l/s there results the maxi- Fig. C-7: Maximum, mean and minimum hourly
mum monthly mean of the infiltration water of: dry weather flows in 1999

QInf,mM,max = 347 - 143 = 204 l/s

QQDW,h,max or Q
/Q DW,dbzw.
T,h,max T,d T,h,min /QT,d
QDW,h,min/Q [-] [-]
DW,d
The maximum monthly mean of the infiltration wa- 2.0
ter is thus 204/52 = 4-times (QDW,d according to QDW,h,max /QDW,d
weather data) or 204/63 = 3.2-times (QDW,d of cal- 1.5
culated dry weather days) of the annual mean. In
summer the dry weather flows with, on average, 1.0
QDW,d = 13,565 m3/d or 13,710 m3/d corresponding
with ≅ 157 l/s are the least both according to
0.5
weather data and for calculated dry weather days. QDW,h,min/QDW,d
The minimum infiltration water flow of this period
0.0
then results as: J F M A M J J A S O N D

QInf,pM,min = 157 - 143 = 14 l/s Fig. C-8: Ratio values QDW,h,max/QDW,d and
QDW,h,min/QDW,d in 1999

April 2003 43
ATV-DVWK-A 198E

C 1.7 Maximum and minimum wastewater with fWW,QComb = 3.5:

flow QComb = 143 ⋅ 3.5 + 52 = 500 + 52 = 552 l/s

For the summer the maximum hourly dry weather

flow has been determined in Chap. C 1.6 as with fWW,QComb = 6.5:
QDW,h,max,pM = 225 l/s. The infiltration water flow is
QInf,min,pM = 14 l/s (Chap. C 1.5). Thus the maxi- QComb = 143 ⋅ 6.5 + 52 = 930 + 52 = 982 l/s
mum hourly wastewater flow for the summer is:
QWW,h,max,pM = 225 - 14 = 211 l/s According to Fig. C-7 the maximum hourly dry
weather flows in the wet weather periods are
The ratio of the maximum wastewater flow and QDW,h,max ≅ 400 l/s. If one calculates with QComb =
daily average is 551 l/s, then in the daytime hours the emptying of
a stormwater reservoir would be very slow. There-
QWW,h,max,pM /QWW,aM = 211 / 143 = 1.48 fore, for the combined wastewater flow, a value be-
tween QComb = 700 and 900 l/s should be selected.
The divisor xQmax, according to Eqn. 7, results as
follows: If, for example, the secondary settling tanks of the
24 wastewater treatment plant have reserves, one
xQ max = ≈ 16.2 can apply the higher combined sewage flow in or-
1.48
der to save volume for combined sewage reser-
voirs and to further relieve the receiving water.
This value, in comparison with Fig. 2, appears
plausible. With a forecast mean wastewater flow
According to the previously usual approach the fol-
one can determine the maximum and minimum
lowing would have resulted: the 85-Percentile
wastewater flows either with the aid of the ratio
value of the daily wastewater flow is applied as
value or the divisor.
1.25·QDW,aM. The peak flow is then calculated using
the divisor xQmax = 16.2, according to Chap. C 1.7.
The peak flow then results as
C 1.8 Determination of the combined
wastewater flow QWW,max,85 = 1.25 · 143 · (24/16.2) = 265 l/s

Using the following initial data, calculated above, The infiltration water flow is the applied as above
an estimate of the combined wastewater flow is to with 52 l/s.
be undertaken:
Q Comb = 2 ⋅ Q WW + Q Inf = 2 ⋅ 265 + 52 =
l/s
QWW,aM = 143 l/s 530 + 52 = 582
QInf,aM = 52 l/s
QInf,mM,max = 204 l/s The value for QComb calculated according to the
previous approach lies nearer to the smallest value
Connected inhabitants and total numbers of inhabi- according to the new approach. The emptying of
tants and population equivalents: ca. 75,000 I. the storage facility in wet weather periods would
have taken place also appropriately slowly (see
According to Fig. 1 the factor for this population above). If one were to calculate using QInf,mM,max =
can be assumed as being between fWW,QCW = 3.5 204 l/s instead of QInf,aM = 52 l/s, one would enter
and 6.5. The maximum monthly mean of the infil- the more convenient range of QComb = 700 to 900
tration water flow is higher than two-times the an- l/s.
nual mean. According to Chap. 4.2.2.6 a higher
value than the annual mean can be applied for the
infiltration water flow. Initially, however, QComb is
calculated using the annual mean of the infiltration
water flow:

44 April 2003
 ATV-DVWK-A 198E

C2 Loads and concentrations year should be evaluated. As here all concentra-

tions and load values refer to the inflow to the bio-
C 2.1 Summary of measured values logical stage, the index INB is left out for the sake
of simplicity.
Table C-2 shows, as an example, a listing of
measured values as well as the determination of
loads and ratio values. A period of at least one

Table C-2: Summary of the measured values, the calculated COD loads and the
ratio values of the master parameter COD

Inflows Concentrations
Wastewater temperature (T)

Phosphorus, homog. (CP)

Ammonia nitrogen (SNH4)
Weather (give DW only)

suspended solids (XSS)

Nitrate nitrogen (SNO3)

BOD5, homog. (CBOD)
COD, homog. (CCOD)

COD, filtered (SCOD)

TKN homog. (CTKN)

DW-days (QDW,d)

Alkalinity (SAlk)
All days (Qd)
Weekday
Date

°C m3/d m3/d mg/l mg/l mg/l mg/l mg/l mg/l mg/l mg/l mmol/l
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
1.1. Fr
2.1. Sa
3.1. So
4.1. Mo

31.12. Fr
Mean

Sludge liquor [SL] COD loads Ratio values

2-weekly mean
Weekly mean

CBOD/CCOD
SCOD/CCOD

CTKN/CCOD

SNH4/CCOD
Bd,COD,2WM
Weekday

SAlk/CCOD
Bd,COD,WM

XSS/CCOD

CP/CCOD
SNH4,SL

Bd,COD
Date

Qd,SL

Start

End

m3/d mg/l h h kg/d kg/d kg/d - - - - - - -

1 2 16 17 18 19 20 21 22 23 20 24 25 26 27 28
1.1. Fr
2.1. Sa
3.1. So
4.1. Mo

31.12. Fr
Mean

April 2003 45
ATV-DVWK-A 198E

The following is to be noted for the individual col- Columns 23 to 28, Ratio values:
umns: The ratios of the concentrations from Cols. 8 to 15
to the concentration of the master parameter COD
Column 3, Weather code: (Col. 7) are entered.
It is sufficient to designate the dry weather days,
comp. also Chap. C 1.1. In the last line the mean value is formed from a se-
ries of columns, some of which are only informa-
Column 4, Wastewater temperature: tive others are used for further calculations.
The temperature is measured in the outlet of the
biological reactor. If there is still no wastewater Not listed in Table C-2 are the BOD5 and COD
treatment plant available, the sewage temperature loads in the inflow to the wastewater treatment
can be used. plant with dry weather which are possibly required
for the determination of the design capacity and/or
Column 5, Inflow on all days: for the dimensioning of combined sewer overflows,
Transferred from the logbook or Table C-1, Col. 4. (comp. Chap. 3.3.3.1 and 3.3.3.2) as well as the
Sludge Volume Index of existing facilities.
Column 6, Inflow on dry weather days:
Transferred Column 5 together with Column 3.
C 2.2 Planning of sampling
Columns 7 to 15, Concentrations:
Measured values are entered. Fundamentally there are two possibilities:
1. Consolidation of routine sampling with the aim
Columns 16 to19, Sludge liquor [SL] discharge:
of carrying out dimensioning on the basis of
To be recorded are: the daily volumes of sludge
loads undercut on 85% of the days. It is suffi-
liquor (Col 16); the ammonia nitrogen concentra-
cient for this if, during a year, at least one
tion (Col.17) is not necessary each day; the start
sampling takes place per week. The determi-
and end of the discharge (Cols. 18 and 19). If con-
nation of the relevant loads on the basis of
siderable volumes of faecal sludge or other sludge
the 85-percentile value is necessary for the
as well as filter washing water are to be dis-
dimensioning of trickling filters and rotating
charged, appropriate columns should be added for
biological contactors in accordance with ATV-
these. Essential are the daily volume and start and
DVWK-A 281E (2001). For the dimensioning
end of the discharge. These entries are valuable,
of activated sludge plants this should take
in particular on days with investigations of the peak
place in accordance with ATV-DVWK-A 131E
factor as irregularities can be identified.
(2000) for small plants or in special cases
only.
Columns 20 to 22, COD loads:
2. Consolidation of the sampling in certain peri-
First the daily loads are formed as product of the
ods with the aim of forming weekly means for
values of Columns 5 and 7 (divided by 1000)
the loads. This is to be the standard case for
(Col. 20). Columns 21 and 22 are necessary for
the dimensioning of activated sludge plants in
the dimensioning of activated sludge plants only, if
accordance with ATV-DVWK-A 131E (2000).
the dimensioning is to take place in accordance
with 2- or 4-weekly means. If at least four loads
For the following example, a sampling for the
have been calculated per calendar week, the
weekly mean for the dimensioning of activated
weekly mean is entered in Column 21, respectively
sludge plants is demonstrated. The sampling for
on Sunday (end of the week) and in Column 22, for
this is planned on the basis of the seasonal varia-
example, the 2-weekly means, which are the mean
tion of the COD loads, the ratios of the important
of respectively two consecutive weekly loads
parameters to the COD as well as the time series
(“Sunday values” from Column 21).
of the temperature of the previous years.

46 April 2003
 ATV-DVWK-A 198E

Both the COD loads as well as the ratio values [of with daily sampling are marked by dashes. For this
previous years] indicate no marked seasonal varia- the weekly means are presented in Fig. C-11.
tion. In the meanwhile no seasonal operating in-
dustrial and/or commercial firms have been estab- B [1000 kg/d] COD load to biol. stage
d,COD
lished. Sampling can therefore be oriented to the
20
wastewater temperature. 18
16
In order to exclude coincidences the time series of 14
the 2-weekly mean of the temperature of the previ- 12
ous three years is considered, Fig. C-9. One can 10
form sliding 14-day means, as in Fig. C-9, or 8
means from two calendar weeks. The content of 6
information is the same with both representations. 4
2
0
For the dimensioning of an activated sludge plant J F M A M J J A S O N D
the following periods are selected in which the
Fig. C-10: Time series of COD loads in 1999
sampling is so consolidated that weekly means
can be formed:
B [1000 kg/d] weekly mean COD load
– 25. 1 to 26. 3 as period for the dimensioning d,COD,wM
temperature and the lowest temperature. 20
– 23. 8. to 1. 10. as period for the highest tem- 18
perature (July and August inappropriate due to 16
holidays). 14
12
Alternatively in Chap. C 2.4 the determination of 10
the relevant COD load as 85% value is demon- 8
strated. 6
4
Temperature in the aeration tank [°C] 2
0
20 J F M A M J J A S O N D
18
16 Fig. C-11: Weekly mean of the COD loads from
14 1999
12
10 B [1000 kg/d] 2-weekly mean COD load
d,COD,2wM
8
6 20
4 18
2 16
0 14
J F M A M J J A S O N D
12
Fig. C-9: Time series of the temperature from 10
three years (sliding 2-weekly mean) 8
6
4
2
C 2.3 Determination of the relevant COD 0
load on the basis of weekly means J F M A M J J A S O N D

Fig. C-12: Two-weekly mean of the COD loads

At this wastewater treatment plant the inflow to the
from 1999 (overlapping)
biological stage is sampled once a week on differ-
ent week days. In the periods given in Chap. C 2.2
For the dimensioning of an activated sludge plant
a daily sampling took place with the exception of
2-weekly means of the COD loads form the basis.
Sundays. Fig. C-10 shows the result. The periods

April 2003 47
ATV-DVWK-A 198E

In order to find the maximum 2-weekly means, C 2.4 Determination of the relevant COD
means from respectively consecutive weeks are load as 85 % value
formed. As each week can lie once as first and
once as second in a 2-weekly interval, one obtains, The determination of the relevant COD load as
for example, for a 10 week period, nine 2-weekly 85% value is necessary for the dimensioning of
means, comp. Fig. C-12. trickling filters and rotating biological contactors,
for activated sludge plants it should only serve in
The highest 2-weekly mean lies in September with special cases, for example if the consolidation of
Bd,COD = 7,500 kg/d. In February/March one can the sampling is out of proportion to the usage.
reckon with Bd,COD = 6,700 kg/d. Additions are to
be made (comp. Chap. 5) for growth in population In 1998 a sampling took place weekly on differing
or connection of further residential developments days. Through this some 50 load values are avail-
and industrial/commercial firms. able. A seasonal variation of the COD loads and in
particular the ratio values CTKN/CCOD was not identi-
The plotting of the COD loads over the flows fiable. The value achieved or undercut on 85% of
shows at a glance the dependencies and the the days is Bd,COD = 7,500 kg/d, comp. Fig. C-14. It
widths of scatter of the flows, of the loads and of is purely coincidental that here the 85% value of
the concentrations, Fig. C-13. Here it is apparent, the COD load from 1998 is practically the same as
for example, that with increased combined waste- the relevant load of Summer 1999, derived from
water flows, the loads remain almost constant and the 2-weekly means.
the concentrations reduce accordingly. One can
also easily identify the “cloud” of the flows of dry
Frequency of undercutting [%]
weather days with Qd = 13,000 and 18,000 m³/d
100
and the associated loads of Bd,COD = 5,000 and
90
7,000 kg/d, whereby concentrations of CCOD = 300
80
to 500 mg/l appear. It is to be noted that, due to
the lower sampling frequency in summer, many 70
values with higher concentrations and flows below 60
13,000 m3/d are missing in the plot. 50
40
B [1000 kg/d] daily COD load 30
d,COD
15 20
500 300 200 10
0
0 5 10 15
10 B [1000 kg/d] daily COD load
d,COD
100
Fig. C-14: Undercutting frequency of COD
loads for 1998
5
Parameter
C [mg/l]
C 2.5 Ratio values of important
COD
parameters
0
0 20 40 60 80 100 As a rule, all important parameters were deter-
Q [1000 m³/d] daily sewage flow mined with the weekly sampling. This was main-
d
tained in the phases with daily sampling. Here, for
example, TKN/COD, P/COD and BOD5/COD were
considered.
Fig. C-13: Plot of the daily flows and COD
loads (1999)
The ratios CTKN/CCOD appear to be subject to a cer-
tain seasonal variation, Fig. C-15. In the period
February/March the ratio was, as a mean,

48 April 2003
 ATV-DVWK-A 198E

CTKN/CCOD = 0.22, while in September the mean

C /C [-]
was CTKN/CCOD = 0.17. BOD COD
0,8
Mean 0,40 kg/kg
Rather constant with only a slight scatter CP/CCOD
0,6
= 0.017 as a mean in February/March and CP/CCOD
= 0.016 in September is found, Fig. C-16.
0,4
C /C [-]
TKN COD
0,4 0,2

0,3 0
J F M A M J J A S O N D
Fig. C-17: Time series of the ratio CBOD/CCOD
0,2

0,1 C 2.6 Determination of the concentrations

In accordance with Chap. 4.3.1.5 the relevant

0
J F M A M J J A S O N D loads and concentrations are to be determined for
at least three different temperatures. The dimen-
Fig. C-15: Time series of the ratio CTKN/CCOD sioning temperature is specified as TDim = 12 °C.
The lowest temperature is T2wM,min = 8 °C and the
C /C [-] highest T2wM,max = 21 °C, comp. Fig. C-9.
P COD
0,04
To the COD loads presented in Figs. C-10 to 12
belong the flows shown in Fig. C-1. Initial figures
0,03
for the calculation of the relevant concentration of
the COD are respectively the COD loads of
0,02 Bd,COD = 6,700 and 7,500 kg/d determined in Chap.
C 2.3. Dividing by the appropriate flow gives the
0,01 relevant concentration.

The dry weather flow in February/March 1999,

0
J F M A M J J A S O N D caused by high rainfalls, is Qd ~ 25,000 m3/d. With
less rainfalls, flows of Qd ~ 17,000 m3/d were
Fig. C-16: Time series of the ratio CP/CCOD measured in other years, therefore, for the winter
calculation was carried out using Qd,conc = 17,000
The ratio values CBOD/CCOD show the largest scat- m3/d. In Summer one can calculate using
ter (Fig. C-17). The scatter is a sign for the possi- Qd,conc = 13,000 m3/d, comp. Fig. C-2.
ble proneness to error of the BOD5 determination.
This is, therefore, a reason in future to carry out The results in Table C-3 show, that this wastewa-
dimensioning on the basis of the COD. A seasonal ter, in comparison with normal domestic wastewa-
variation of the ratio BOD5/COD is also not identifi- ter, contains higher nitrogen loads. These are
able here. caused by an industrial discharger.

April 2003 49
ATV-DVWK-A 198E

Table C-3: Derivation and summary of selected dimensioning values

Designation Unit Dimensioning temperature Lowest temperature Highest temperature

T °C 12 8 21
Bd,2wM,max kg/d 6,700 6,700 7,500
Qd,conc m3/d 17,000 17,000 13,000
CCOD mg/l 394 394 577
CTKN/CCOD - 0.22 0.22 0.17
CP/CCOD - 0.017 0.017 0.017
CBOD/CCOD - 0.4 0.4 0.4
CTKN mg/l 87 87 98
CP mg/l 6.7 6.7 9.8
CBOD mg/l 158 158 231

CTKN in mg/l and Bd,TKN in kg/h are listed in Col-

C 2.7 Determination of the peak factor for umn 7. The highest value from Columns 4 to 6 is
the nitrogen loading transferred into Column 8 and the ratio value
B2h,TKN/Bd,TKN is formed in Column 9. The mean
In a plant it is known that the maximum 2-hourly values are calculated in the last line. Sampling
load of nitrogen B2h,TKN in kg/h with dry weather al- should be for at least 14 days. If a seasonal varia-
ways occurs between 10 h and 16 h. Some meas- tion for CTKN/CCOD is observed, then in the corre-
ured values are listed in Table C-3 as an example. sponding periods of sampling should be twice in a
minimum of 14 days.
As far as possible only dry weather days should be
included for the evaluation. In columns 4 to 6, for With this procedure, with three additional analyses
each day one below the other are the flows QDW,2h daily in addition to the in any case analysed daily
in m³/h, the concentrations CTKN,2h in mg/l from 2- composite sample one has sufficient information.
hourly composite samples and the loads as 2- What is required is the mean of the ratio as peak
hourly mean B2h,TKN in kg/h. The values for the factor, inter alia for the calculation of the oxygen
daily average corresponding with QDW,d in m3/h, consumption of activated sludge plants, here fN =
1.77.

Table C-4: Example for the determination of the peak factor for the nitrogen load

Max. 2-h load/

24-h mean

24-h mean
Parameter

Maximum
12 - 14 hr
10 - 12 h

14 - 16 h

2-h load
Date

Unit

1 2 3 4 5 6 7 8 9
3
10.2. QDW,2h (QDW,d) m /h 789 957 896 623
Wed CTKN mg/l 67 58 61 54
B2h,TKN (Bd,TKN) kg/h 52.9 55.5 54.7 33.6 55.5 1.65
3
4.3. QT,2h (QT,d) m /h 870 1023 977 678
Thur CTKN mg/l 65 61 58 51
B2h,TKN (Bd,TKN) kg/h 56.6 62.4 56.7 34.6 62.4 1.80
3
QT,2h (QT,d) m /h
CTKN mg/l
B2h,TKN (Bd,TKN) kg/h
Mean 59.3 1.77

50 April 2003