Constructed Wetland For Wastewater Treatment and Reuse: A Case Study of Developing Country
Constructed Wetland For Wastewater Treatment and Reuse: A Case Study of Developing Country
Constructed Wetland For Wastewater Treatment and Reuse: A Case Study of Developing Country
1, February 2013
I. INTRODUCTION
Conventional wastewater treatment systems comprising of
energy intensive and mechanized treatment components
require heavy investment and entail high operating costs.
Experience has shown that existing wastewater treatment
systems in most of the developing countries which were built
through funding by international donor agencies failed to
treat wastewater adequately. Reasons for inadequate
treatment include high maintenance costs, lack of local
expertise and poor governance. Compared to conventional
treatment systems, constructed wetlands are low cost, easily
operated and maintained, and have a strong prospective for
application in developing countries. Constructed wetlands
are accepted as a reliable wastewater treatment technology
and represent an appropriate solution for the treatment of
many wastewater types [1].
Comparing with conventional wastewater treatment
Manuscript received December 07, 2012; revised January 28, 2013. This
work was financially supported by NED University of Engineering and
Technology.
A. Mustafa is with the Environmental Engineering Department, NED
University of Engineering and Technology, Karachi-75270, Pakistan (e-mail:
atifm@neduet.edu.pk, atifmenv11@yahoo.com).
DOI: 10.7763/IJESD.2013.V4.296
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International Journal of Environmental Science and Development, Vol. 4, No. 1, February 2013
II. METHODS
A. Experimental Site
The constructed wetland (CW) treatment system is situated
in Karachi, NED University of Engineering & Technology,
at a longitude 25 568 N and latitude 67 06 44 E. The
maximum and minimum temperatures during the study
period were 36 C and 20 C, respectively. NED wastewater
treatment plant (WWTP) treats wastewater from campus and
staff colony. The wastewater contains domestic sewage and
low flows from laboratories of various university
departments. The primary treatment consist of a settling tank,
after that the wastewater is transferred to an aeration tank and
then to a secondary settling tank. The main objective to
construct the wetland at the WWTP site is to evaluate the
performance of simple and low-cost wastewater treatment
technology.
Parameter
Unit
Length
metre
Value
6
Width
metre
1.5
Height
metre
0.6
Surface area
Square metre
days
Flow
Vegetation
4 plants
C. Sampling Methods
For wastewater analysis, grab samples were collected in
plastic bottles previously washed and rinsed with distilled
water. Samples were collected after every two weeks from
the inlet and outlet of the CW. Liquid samples were tested for
pH, total dissolved solids (TDS), total suspended solids
(TSS), 5 days biochemical oxygen demand (BOD5) at 20C,
chemical oxygen demand (COD), ammonia nitrogen (NH4-N)
ortho-phosphate (PO4-P), temperature, dissolved oxygen
(DO), faecal coliforms (FC), total coliforms (TC) using
American Public Health Association standards methods [5].
All samples were analysed in the laboratory of environmental
engineering department.
International Journal of Environmental Science and Development, Vol. 4, No. 1, February 2013
shows that the system has a good buffer capacity and is able
to tolerate organic shock loads. There was a decrease in inlet
and outlet BOD5/COD ratio from 0.55 to 0.27 showing that
organic matter liable to biological degradation was removed
by the CW system. Forty eight percent of effluent BOD
concentrations except for the initial months and some in later
were below the threshold of 30 mg/L as set by US EPA for
wastewater reuse.
TABLE II: WATER QUALITY VARIABLES MEAN (STANDARD DEVIATION) FOR THE CONSTRUCTED WETLAND
S. No.
Variables
Unit
Inlet
Outlet
Reduction (%)
mg/L
16
68.6 23.6
34.0 15.5
50
mg/L
16
122.9 50.7
68.3 20.7
44
mg/L
16
201.4 93.2
45 26.3
78
Ammonia-nitrogen
mg/L
16
19.2 4.8
9.7 4.6
49
Ortho-phosphate
mg/L
16
7.6 1.9
3.7 2.3
52
Total coliforms
Counts/100mL
12
2.1 106
8 103
93
Counts/100mL
12
1.1 10
3 103
98
16
7.8 0.7
7.9 0.4
mg/L
16
1.7 0.6
4.5 1.2
Faecal coliforms
pH
Dissolved oxygen
(a)
Fig. 3. TSS influent and effluent concentrations for the wetland system at
NED University.
(b)
Fig. 2. BOD (a) and COD (b) influent and effluent concentrations for the
wetland system at NED University.
B. Nutrients
The inlet NH4-Nconcentration ranged between 10-29 mg/L
(Fig. 4a) while that of the outlet ranged between 3-18 mg/L
(Fig. 4a) with mean values of 19.2 4.8 mg/L and 9.7 4.6
mg/L at the inlet and outlet, respectively (Table II). A
number of processes transfer compounds from one point to
another in wetlands like ammonification, nitrification,
denitrification, decomposition [2]. Controlling and
decreasing ammonia concentrations is a key consideration in
the design of wetland treatment systems because ammonia is
the principal form of nitrogen in wastewater and has the
potential to degrade the environment.
The reduction in ammonia-nitrogen concentration for this
study was 49%. Reference [6] conducted a study on the
performance of a full-scale constructed wetland system for
sewage treatment in China and found a 40.6% reduction in
International Journal of Environmental Science and Development, Vol. 4, No. 1, February 2013
(b)
pH
mg/L
16 (100)
BOD
mg/L
7 (44)
30
TSS
mg/L
5 (31)
30
CFU/100mL
3 (19)
200
Faecal Coliforms
6-9
Fig. 4. NH4-N (a) and PO4-P (b) influent and effluent concentrations for the
wetland system at NED University.
Results of
this Study
Parameters
Unit
ECw
dS/m
<0.7
0.7-3
>3
1.1
TDS
mg/L
<450
450-2000
>2000
642.8
None
Slight to moderate
Severe
IV. CONCLUSION
The monitoring of horizontal flow constructed wetland
shows that the general performance of the system was good
and it successfully reduced contaminants even under
fluctuating contaminant loading resulting from power
breakdown. The results indicate that if constructed wetlands
are appropriately designed and operated, they could be used
for secondary and tertiary wastewater treatment under local
conditions, successfully. Hence constructed wetlands can be
used in the treatment train to upgrade the existing
malfunctioning wastewater treatment plants, especially in
developing countries. The treated wastewater from these
wetlands can be used for landscape irrigation and also for
other beneficial uses.
C. Indicator Bacteria
The CW reduced both total and faecal coliforms. The
average removals of the analysed indicator bacteria (total
coliforms and faecal coliforms) were in the range 9399%,
showing a high efficiency of the constructed wetland system
in removing the pathogens. The concentrations of total
coliforms and faecal in the constructed wetlands is presented
in Table II. Average concentrations of total coliforms and
faecal coliforms in the influent were 2.1 106counts/100mL
and 1.1 106counts/100mL, respectively. Average effluent
concentrations were 8.0 103 and 3.0 102 for TC and FC,
respectively. Natural treatment technologies have the
potential to reduce pathogen because of natural die-off and
hostile environmental conditions [2].
ACKNOWLEDGMENT
The author wishes to acknowledge the support provided by
Syed Wasiuddin and Mr. Niaz Hussain of Services
Department, NED University of Engineering and
Technology for construction of wetland.
REFERENCES
[1]
[2]
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International Journal of Environmental Science and Development, Vol. 4, No. 1, February 2013
[3]
[4]
[5]
[6]
[7]
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