Journal of Community Based Environmental Engineering and Management, 2023, Vol. 7, No.

1: 11-16

THE USE OF A STATIC MIXER FOR THE COAGULATION UNIT IN

THE DUREN SERIBU II WATER TREATMENT PLANT

Sheryline Putri Chandra Sari, Riana Ayu Kusumadewi, Winarni*

Environmental Engineering Department, Universitas Trisakti, Indonesia

Abstract

In the drinking water treatment plant involves a significant component i.e., coagulation, which distributed
coagulants vastly and equally through rapid stirring for destabilizing colloids and suspended particles in
the raw water. In water treatment plants, coagulation units are often classified into mechanical and
hydraulic coagulation. This study aimed to discover the use of and in-line static mixers as coagulation in
designing the Duren Seribu II Drinking Water Treatment Plant (WTP). The design criteria for coagulation
unit in Duren Seribu II WTP was determined by comparing several data obtained from literature studies
and evaluation of the existing conditions of Duren Seribu I WTP. Duren Seribu I WTP was evaluated by
direct measurement in the field. From the results of data analysis, the design criteria appropriate for Duren
Seribu II WTP, the G value is 2078.07 sec-1, the detention time (td) is 4 sec, and the G.td value is
8352.19.

Keywords: coagulation, drinking water, Duren Seribu II WTP, water treatment plant

Introduction1 City that met the Indonesian standard drinking

Along with the population growth in Depok water quality requirements according to the
City, it will increase the water demand therefore Regulation of the Minister of Health Republic of
the development of drinking water services are Indonesia Number 492 of 2010.
necessary. A way to conform the increasing On the time being, a 100 L/sec WTP named
water demands is developing a water treatment Duren Seribu I is operated to fullfil the existing
plant (Reynold & Richard, 1996). Based on water demand. It is located at Sawangan Elok
RISPAM or Master Plan for Drinking Water Street Number 10, Duren Seribu, Bojongsari,
Supply for Depok City, it is planned to develop Depok. Consider the existing WTP withdrawn
Duren Seribu II WTP with capacity of 150 L/sec its raw water from Angke River which will be
that uses Angke River as raw water source to used as raw water resources for the new WTP,
increase the service coverage of Depok City therefore the Duren Seribu I WTP is used as a
(RISPAM Kota Depok, 2020). The WTP is reference for design the new Duren Seribu II
planned to be built in Bojongsari District, Depok WTP. The existing Duren Seribu I WTP is a
conventional water treatment plant consists of
*)
Corresponding Author:
coagulation, flocculation, sedimentation, rapid
E-mail: winarni@trisakti.ac.id sand filtratrion, and disinfection units. It uses in-
line static mixer as coagulation unit.
Received: 20 February 2023
Revised : 7 March 2023 The coagulation unit is a significant component
Accepted: 30 March 2023 in drinking water treatment, as mixing
DOI: 10.23969/jcbeem.v7i1.7260

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The Use of A Static Mixer for The Coagulation Unit in The Duren Seribu II Water Treatment Plant

coagulants is dispersing coagulant uniformly Table 1. Design Criteria Coagulation In-Line

throughout the basin and allowing contact Static Mixer
between the colloids particles and coagulant for Parameter Design Criteria Source
destabilizing colloids particles in raw water
Detention Time (td) 1-5 sec (Davis,2010)
(Kawamura, 1991). By the time the water leaves
this unit, the coagulation process has progressed Velocity Gradient (G) >750 sec-1 (Davis,2010)
sufficiently to form microfloc. G.td Value 600-10.000 (Davis,2010)

Various types of coagulation units may be In general, hydraulic coagulation depend on the
generally classified as (i) mechanical head differential that provides hydraulic
coagulation uses mechanical equipment as turbulence to achieve the desired velocity
impeller and turbine mixers, paddle mixers, by gradient. Static mixers are principally identified
a motor with the help of electricity (Reynold & by their lack of moving parts. Typical examples
Richard, 1996), and (ii) hydraulic coagulation include in-line static mixer, which is a type of
with gravity force as hydraulic jump, and in-line rapid mixing which occurs in a standard pipe
static mixers (Qasim, 2000). The degree of diameter that equipped with plates/elements that
mixing is based on the power imparted to the causing sudden changes in the velocity patterns
water that measure as velocity gradient, as well as momentum reversals. It can break up
considering that more input power creates the flow and increasing turbulence.
greater turbulence, and greater turbulence lead to The advantage of using an in-line static mixer is
better mixing. that there are no moving parts, and no external
energy sources are needed. Thus, mixing using
G= (1) an in-line static mixer is quite effective and the
coagulation of an in-line static mixer does not
Where G is velocity gradient (sec-1), P is mixing
require a large area (Davis, 2010). The in-line
power (watt), V is volume (m3), µis dynamic static mixer is the most compact method and is
viscocity (kg/m.s). As shown in the Equation increasing in popularity. It is found that in-line
(1), the value of G depends on the power input, static mixer is used in 65 L/sec Sindang Pasekan
the fluid viscocity, and the basin volume. The water treatment plant (Arief et al., 2020) and
velocity gradient also related to the shear forces 290 L/sec Kaligarang III water treatment plant
in the water; thus, larger velocity gradients (Lestari et al., 2019).
produce appreciable shear forces. G value in-line
The power consumed by static-mixing devices
static mixer are shown in Table 1.
can be computed using the following equation.
The degree of mixing completion is dependent P = Q × hL × ρ (2)
on the velocity gradient and the value of G.td, Where P is mixing power (watt), Q is flow rate
whereas td is the detention time. The magnitude (m3/sec), hL headloss (m), ρ is water density
of the dimensionless parameter G.td is related to (kN/m3).
the vigorous of the mixing during coagulation
Headloss dissipated as liquid passes through in-
(mixing intensity) (Gabrielle et al., 2021). G.td
line static mixer can be calculated according to
value has a range of 600-10.000 (Davis, 2010).
the graph that determining pipe diameter and
head loss per element, as shown in Figure 1.
Mixing ratio of 1.5 is usually used in the design.
(Davis, 2010).

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 Journal of Community Based Environmental Engineering and Management, 2023, Vol. 7, No. 1: 11-16

design of coagulation unit of Duren Seribu

II WTP, i.e:
- Guidelines for water treatment pant
design,
- The condition of the planning area,
- Related researchs in the area of mixing
and coagulation.
c. Design of coagulation unit, as follows:
- Jartest analysis to select the proper
coagulant and determine its doses.
- Evaluate and select the value of velocity
gradient (G), time detention (td), and G.td.
- Spesify pipe diameter from intake to
Figure 1. The Graph of Determining Pipe flocculation unit that fullfil the velocity
Diameters and Headloss per Element. requirement.
- Calculation of the headloss occurs in the
hL = Total of elements × hL per element (3)
in-line static mixer using graph developed
The pipe length (L) of in-line static mixer can be by Davis (2010) as shown in Figure 1.
obtain as follows. - Calculate the required length of in-line
L = Total of elements x mixing ratio x pipe static mixer using equation (4).
diameter (4) Results and Discussion
Existing Coagulation at Duren Seribu I WTP.
Research Methodology In designing a WTP, it is necessary to reference
The design of the coagulation unit for Duren an existing WTP for estimating (i) the water
Seribu II WTP consists of several stages: treatment unit that can be used, (ii) the water
a. Evaluation the performance of in-line static treatment process can be operated optimally, to
mixer which is used in the existing Duren produce water that meets the quality of drinking
Seribu I WTP, as follows: water. The evaluation performance of the
Data collection: coagulation unit carried out at Duren Seribu I
- Inventory of pipeline from intake to WTP with a design capacity of 250 L/sec. The
flocculation unit (length and diameter). schematic of coagulation unit Duren Seribu I
- Measure the pumping head in the intake. WTP can be seen in Figure 2.
- Measure the pressure as shown in the
manometer inserted after the static mixer.
Performance evaluation:
- Calculate headloss occuring in the static
mixer using the head differential between
pumps and manometer.
- Evaluate mixing power (P), velocity
gradient (G), and G.td value.
b. Literature review,
The literature review was conducted to
Figure 2. Schematic of Coagulation Unit of
provide such a useful information in the
Duren Seribu I WTP.

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The Use of A Static Mixer for The Coagulation Unit in The Duren Seribu II Water Treatment Plant

The type of coagulation used by the Duren coagulation unit in the new Duren Seribu II
Seribu I WTP is in-line static mixer, where this WTP.
system does not use a machine, but uses a plate
Design of Coagulation Unit at Duren Seribu II
that causes mixing power. The coagulant used
WTP.
by the Duren Seribu I WTP is aluminum sulfate
The schematic of coagulation unit Duren Seribu
with a dose of 30.68 mg/L. Aluminum sulfate
II WTP can be seen in Figure 3, where the 400
coagulant that has been diluted will be injected
mm diameter with 17.95 m pipe length transmit
to the coagulation unit using a dosing pump.
water from intake to flocculation unit. The in-
The coagulation in-line static mixer at Duren line static mixer has a diameter of 400 mm and
Seribu I WTP has a diameter of 400 mm and a length of 5 m.
pipe length of 8 m. The head of pump at the
intake is 30.8 m, and the manometer
measurement is 24 m. Thus, the headloss value
obtained on the static mixer pipe is 6.77 m or
equivalent to 0.677 bar.
The volume in the in-line static mixer is 1 m3
with a discharge at the time of observation of 50 Figure 3. Schematic of Coagulation Unit Duren
L/sec which is less than design capacity of 250 Seribu II WTP.
L/sec. This existing operational condition gives
detention time (td) value of 20.10 second. The Calculation the in-line static mixer dimensions
mixing power (P) can be estimated using water starts with calculating the headloss value. Based
density value of 996.81 kg/m3 and headloss of on the graph of the pressure drop for pipe
6.77 m as mentioned above, resulted the mixing diameters between 150 mm to 700 mm (used
power of 3324.32 Nm/sec. Then, it followed by 400 mm), discharge of 540 m3/h, resulting in
resulted the value of G (velocity gradient) = headloss value of each element is 2 kPa = 1.02
1944.94 sec-1 and G.td = 39,086. The detention m, as shown in Figure 4.
time (td) and G.td value obtained have not met
the design criteria of Davis (2010).
In spite of that, the quality of the water produced
based on tubidity parameter found in the
reservoir of Duren Seribu I WTP is 0.74 NTU. It
shows that the existing WTP has fulfilled the
drinking water standard according to the
Minister of Health Republic of Indonesia
Number 492 of 2010 based on turbidity
parameter below 5 NTU. In the existing
conditions, the td and G.td values in coagulation
do not conform the design criteria. However, it Figure 4. The Pipe Diameters and Headloss
does not cause problems during operation per Element for Q 150 L/sec or 540 m3/h
because the flocs that were formed are quite
large and dense. Accordingly, the in-line static Total headloss (hL)
mixer of Duren Seribu I WTP is adopted as hL = Total of element × hL per element
= 8 × 2 kPa

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 Journal of Community Based Environmental Engineering and Management, 2023, Vol. 7, No. 1: 11-16

= 16 kPa = 1.63 m WTP. The jartest experiment with Al2O3 content

The lenght of static mixer (L) of 17% results an optimum dose of 15 mg/L
L = 8 × 1.5 × 0.40 m which is twice the average dose of the existing
=5m Duren Seribu I WTP i.e 30.68 mg/L of
Volume static mixer (V) aluminum sulfate that contain 5% of Al2O3.
V = π D² L

= × 3.14 × (0.4 m)² × 5 m = 0.60 m3

Detention time (td)
td = = 4 sec
Figure 5. Coagulation Plan Design
The detention time (td) obtained meets the
design criteria of Davis, 2010 and several Based on the existing Duren Seribu I experience
researchs related to the coagulation in the pipe, above, an average dosages of 30.68 mg/L
i.e 5.4 sec is found in Sindang Pasekan WTP aluminum sulfat (5% Al2O3) will be added to the
(Arief et al., 2020), and 5.2 sec is used in new Duren Seribu II WTP.
Kaligarang III WTP (Lestari et al., 2019).
Conclusions
Mixing power (P) imparted in this static mixer is Based on the Duren Seribu I WTP performance
calculated using equation (2) above: evaluation, it can be concluded that several
P = 0.15 m³/sec × 1.63 m × 9987 kN/m3 design parameters do not meet the design criteria
= 2442 kW standard such as the detention time (td) and G.td
value in the coagulation in-line static mixer.
The velocity gradient (G) resulted can be Nonetheless, the production water has fulfilled
calculated using equation (1), i.e.: as the quality of drinking water standard
G = according to the Regulation of the Minister of
Health Republic of Indonesia Number 492 of
= 2078.07 sec-1 2010. Therefore, the evaluation of existing
parameters in Duren Seribu I WTP can be used
G.td value = 2078.07 /sec × 4 sec as a reference for planning a new water
= 8352.19 treatment plant Duren Seribu II.
The resulted velocity gradient is within the References
range of the existing Duren Seribu I WTP i.e. Arief I., Tazkiaturrizki, and Winarni. (2020).
1944.94 sec-1 and 3183.09 sec-1 is found in Performance Evaluation of Sindang
Solear WTP (Ramdhan et al., 2019). Pasekan Water Treatment Plant.
G.td value obtained has met the design criteria International Journal of Scientific &
of Davis, 2010 with a range of 600-10000 and Technology Research, 9(3), 1385-1389.
similar to Cipageran WTP that resulted 6746.6 Davis, M. L., (2010). Water and Wastewater
as its G.td value (Sani et al., 2019). Engineering. McGraw-Hill, Inc. Facilities
(2nd ed.). John Wiley & Sons, Inc.
The proposed design of coagulation unit Duren
Gabrielle H., Kusumadewi, R. A., and
Seribu II WTP can be seen in Figure 5.
Ratnaningsih. (2021). Optimisation of
Coagulant to be used is aluminum sulfate that Degreemont Water Treatment Package on
consistent with the existing Duren Seribu I Kedung Halang Water Treatment Plant,

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The Use of A Static Mixer for The Coagulation Unit in The Duren Seribu II Water Treatment Plant

Bogor, West Java. IOP Conference Reynold & Richard. (1996). Unit Operation and
Series: Earth and Environmental Science Processes in Environmental Engineering.
894. Boston.
Kawamura, S. (1991). Integrated Design of
Reynolds, T. D. (1982). Unit Operation and
Water Treatment Facilities. New York:
Processes in Environmental Engineering.
John Willey & Sons, Inc.
California: Brook/Cole Engineering
Lestari, S. A., Tazkiaturrizki, and Winarni.
Division.
(2019). Evaluasi Ipa Kaligarang III
RISPAM (Rencana Induk Penyediaan Air
sebagai Dasar Penentuan Kriteria Desain
Minum) Kota Depok. (2020). Penysunan
Ipa Pudakpayung di Kota Semarang.
Review Rencana Induk Sistem Penyediaan
Seminar Nasional Cendekiawan ke 5
Air Minum (RISPAM) Kota Depok.
Tahun 2019.
Depok: Badan Perencanaan Pembangunan
Peraturan Kesehatan Republik Indonesia
Derah (BAPPEDA) Kota Depok.
492/MENKES/PER/IV/2010. (2010).
Sani, I. K., Kusumadewi, R. A., and Winarni.
Persyaratan Kualitas Air Minum.
(2019). The Use Of Multi-Criteria
Qasim, S. R., & Motley, G. Z. (2000). Water
Analysis in Selecting Water Treatment
Works Engineering: Planning, Design,
Units in Sadu Water Treatment Plant,
and Operation. Prentice-Hall, Inc.
Bandung District, West Java Province,
Ramdhan, F., Siami, L., and Winarni. (2019).
Indonesia. Journal of Community Based
Optimalisasi Instalasi Pengolahan Air
Minum Solear, PDAM Tirta Kerta Environmental Engineering and
Raharja -Kabupaten Tangerang. Seminar Managemen,. 3(2).
Nasional Pembangunan Wilayah dan
Kota Berkelanjutan.

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