Treated Wastewater Characteristics and Efficiency in Madurai City

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International Journal of Civil Engineering and Technology (IJCIET)
Volume 6, Issue 9, Sep 2015, pp. 58-70, Article ID: IJCIET_06_09_006
Available online at
http://www.iaeme.com/IJCIET/issues.asp?JTypeIJCIET&VType=6&IType=9
ISSN Print: 0976-6308 and ISSN Online: 0976-6316
© IAEME Publication
___________________________________________________________________________
GENERATION, CHARACTERISTICS AND
TREATMENT OF MUNICIPAL
WASTEWATER IN MADURAI CITY
Rajendran S.M
Research Scholar, Department of Civil Engineering,
Karpagam University, Coimbatore, TN, India
Dr. Sekaran V
Former Principal, Raja Engineering College, Madurai, TN, India
ABSTRACT
Assessment of characteristics of raw sewage and treated effluent from the
sewage treatment plant (Sequential Batch Reactor), for Madurai city from
January 2014 to December 2014 was studied. The daily average sewage
generation over the year 2014 is 84.46 MLD. The raw sewage BOD was in the
order of 200 mg/L to 300 mg/L and the characteristics indicate its domestic
nature. The Characteristics of treated effluent were well within the Central
Pollution Control Board standards. BOD and COD removal efficiency is more
than 95 % and is also consistent over the study period. Scope for improving
the efficiency of oil and grease still remains.
Key words: Wastewater generation, Characteristics and treatment, Madurai
city.
Cite this Article: Rajendran S.M and Dr. Sekaran. Generation, Characteristics
and Treatment of Municipal Wastewater in Madurai City. International
Journal of Civil Engineering and Technology, 6(9), 2015, pp. 58-70.
http://www.iaeme.com/IJCIET/issues.asp?JTypeIJCIET&VType=6&IType=9
1. INTRODUCTION
1.1 General
Madurai city, known for Tamil language development, is one among the ten
metropolitan cities in Tamil Nadu. Having located at almost in the southern part of the
state, it is the city for education and business. City covers an area of 148.99 square
kilo metre. Climate prevailing is arid to semi arid. Rainfall is occasional. In addition
to urbanization, more and more adjacent areas are merged with the city corporation
limit. The location is given in figure 1.

Generation, Characteristics And Treatment of Municipal Wastewater In Madurai City
Figure 1 Location of Madurai city
The forecast indicates that the population during the year 2044 is more than 30 lakh. It
is almost double the 2011 census population. the present water supply level is more
than 100 LPCD ( litres per capita per day ) and it is planned to increase to 135 LPCD.
Vaigai river is the major source for the city's drinking water demand. Surrounding
area of the city is an agricultural area.
1.2 Wastewater generation calculation
Wastewater quantity generation is generally assumed as 80 % of quantity of water
supplied for drinking purpose. Assuming the per capita rate as 100 litres per head per
day, the quantity of wastewater generation is shown in figure 2.
Figure 2 Wastewater generation in Madurai - present and future
0
50
100
150
200
250
300
350
400
Arithmetic
increase
Incremental
increase
Geometric
increase
Line of best fit
163.2 164.9 169.5 162.8
197.4
219.6
253.6
234.8231.6
294.1
379.4
338.72014 2029 2044
Wastewatergeneration,MLD

Rajendran S.M and Dr. Sekaran
Forecast indicates a wastewater quantity of around 160 MLD and 300 MLD at present
and in 2014 and 2044 respectively. Almost a constant quantity of wastewater can be
expected from the city as the drinking water supply has to be consistent.
1.3 Sewage Treatment Plant (STP)
Madurai city has 2 numbers of sewage treatment plants located one at Avaniyapuran
and the another at Sakkimangalam. The former has 125 Million litres per day (MLD)
capacity and the latter’s capacity is 47.50 MLD totaling to 172.50 MLD. Among
various sewage treatment technologies available ( Oxidation ditch, Activated sludge
process, extended aeration(ASP), Up flow anaerobic sludge blanket (UASB),
fluidized aerobic bio reactor(FAB), moving bed bio reactor (MBBR), sequential batch
reactor (SBR), membrane bio reactor (MBR), waste stabilisation ponds, etc, the
sewage treatment plant of Madurai city employs SBR technology ( otherwise called
as C-Tech basins) with necessary primary treatment unit (screen, grit removal) and
disinfection with sludge handling arrangement due to the following advantages.
Aerial view of the sewage treatment plant at Avaniyapuram is shown in photo 1.
 Less area to install the plant
 Good efficiency in treatment, like reducing BOD, COD, TSS, etc.
 Biological nutrient control for total nitrogen
 No need of secondary treatment.
 Reducing the treatment time.
 Total working in Automation so less manpower.
 Total process take in aerobic method no need of anaerobic no danger.
 Reduced energy consumption
 Biological phosphorus control.
Photo 1 Aerial view of Sewage treatment plant with irrigation tank at Madurai
1.4 sewage farms
Wastewater reuse is not new for the Madurai city corporation. It has two sewage
farms. One is located at Avaniyapuram with an area extend of 385 acres, which is
utilized for both solid waste dumping yard and sewage farm. Guinea grass is grown in
145 acres and the rest is used for solid waste management. Sakkimangalam sewage

farm incorporates 180 acres of land. Photo 2 shows the guinea grass grown in the
farm. Annual revenue earned from the sewage farm on selling fodder is about
Rs.40.00 lakh.
Photo 2 Sewage farm with Guinea grass (fodder crop) at Madurai
After wetting the farm, reclaimed water flows into the nearby irrigation tank and
stored. These tanks are dry in most of the months in a year. they receive flow only
during north-east monsoon i.e during October and November.
2. MATERIALS AND METHODS
Raw sewage and the treated effluent samples were collected daily during January to
December 2014 for testing the pH, temperature, total suspended solids (TSS),
Biological oxygen demand (BOD), chemical oxygen demand (COD), dissolved
oxygen (DO), Oil and grease ( O&G) and were analysed as per the standard methods
for water and wastewater analysis. The efficiency of treatment of each parameter was
determined using the formula given below.
(Value of raw sewage- value of treated effluent)
Efficiency = ------------------------------------------------------------ X 100 (1)
Value of raw sewage
Statistical parameters viz: maximum, minimum, mean and range, were also
determined.
3. RESULTS AND DISCUSSION
The results of daily sewage generation and characteristics of raw sewage with the
treated effluent parameters are presented below.
3.1 Sewage generation
The daily actual sewage generation in Madurai varies from 21.87 MLD to 97.33 MLD
with the range of 84.46 MLD due to varied reasons. The annual sewage generation is
found as 13684 MLD. Though the sewage generation is taken as 80% of water supply,

practically the quantity reaching at STP is found lesser than the calculation based on
the above guideline. The per capita daily water supply is also varying. It is observed
that there is a time lag between the sewage generation at households and reaching the
STP. It infers that some portion of sewage is always in travel. There are some storage
in main pumping station, sub pumping stations and lift stations. Out 365 days, STP
was in operation due power shut down in pumping locations and repair and servicing
etc. In Perambalur underground sewerage scheme (UGSS), the daily sewage
generation is around 2.0 MLD against the calculated daily quantity of 4.20 MLD.
3.2 Characteristics of raw sewage and treated effluent
The mean, maximum, minimum and range value of pH, temperature, DO, TSS, COD,
BOD and oil and grease for the raw sewage and treated effluent from the STP are
given in table 1 and table 2 respectively.
Table 1 Characteristics of Raw sewage during the year 2014
Sl.No Parameter pH
T
(°C)
DO,
mg/L
TSS
mg/L
COD
mg/L
BOD
mg/L
OIL&
GREASE
mg/L
1 Mean 6.8 29.1 0.0 352.0 465.6 228.5 9.3
2 Max 7.28 33 0 421 592 300 12
3 Minimum 6.2 22.5 0 296 392 190 6
4 Range 1.08 10.5 0 125 200 110 6
It is observed that the raw sewage pH is fluctuating from the maximum of 7.28 to
a minimum of 6.2. Almost the raw sewage is acidic. The temperature of sewage is
found to follow the atmospheric temperature. During winter it was 22.5°C with the
highest temperature of 33°C. The dissolved oxygen content was zero in the raw
sewage from January 1 to 31 December 2014. TSS recorded a maximum of 421 mg/L
with the minimum of 296 mg/L. It is inferred that the TSS is less during winter and
rainy season. It may be due to dilution. The COD value in the raw sewage fluctuates
between 300 mg/L and 190 mg/L. The maximum BOD value in raw sewage was
found as 300 mg/L with the lowest value of 190 mg/L. In general, the BOD value in
the domestic sewage shall be in the order of 200 mg/L to 300 mg/L. The raw sewage
characteristics indicate that sewage is of domestic origin only. No industrial effluent
is coming in the sewage. Oil and Grease is present in the level of 6 mg/L to 12 mg/L.
Table 2 Characteristics of treated effluent from STP during the year 2014.
Sl.No Parameter pH
TEMP
(°C)
DO,
mg/L
TSS
mg/L
COD
mg/L
BOD
mg/L
OIL&
GREASE
mg/L
1 Mean 7.44 29.91 3.56 6.13 34.37 6.29 1.04
2 Max 7.9 34 8 10 82 14 2.7
3 Minimum 7.08 25 2.3 3.2 12 4 0.4
4 Range 0.82 9 5.7 6.8 70 10 2.3
It observed from the table 2 that the pH of the treated effluent is above 7.0. The
acidic raw sewage after treatment becomes slightly alkaline. As aerobic treatment
process has been done, gas transfer taking place during treatment process enhances
the pH value of treated effluent. The temperature of effluent after treatment increases
slightly over the raw sewage. It may be the fact that during the digestion of organic

compounds a little bit of temperature is common. Fluctuation is similar as in raw
sewage. The dissolved oxygen level has considerably increased from zero in the raw
sewage to about 2 to 8 mg/L in the treated effluent due aeration process in the
treatment system. TSS in the treated effluent is found in the order of 3 mg/L to 10
mg/L. TSS in the treated effluent is well within the stipulated value set by the
pollution control board, 100 mg/L. Maximum COD value noticed in the treated
effluent is 82 mg/L with the range of 70 mg/L. COD is always less 250 mg/L , the
standard value for the discharge. BOD value in treated effluent is observed in
between 4 mg/L and 14 mg/ with the variation of 10 mg/L. The maximum value set
for the BOD for the discharge is 30 mg/L. Oil and grease value in the treated effluent
records at the average of 1.04 mg/L against the raw sewage mean of 9.3 mg/L. The
oil and grease value can be still brought down if efficient oil and grease mechanism is
employed.
The method adopted in the sewage treatment system is aerobic- sequential batch
reactor. Complete filling, aeration, settling and decanting are done in a basin. Entire
system is operated by automatic control arrangements.
3.3 Mean monthly variation of raw and treated effluent
3.3.1 pH
Monthly mean pH value of raw sewage and treated effluent is presented in figure 3. It
is found that the increase in pH after treatment. A comparison the raw sewage pH in
various cities in India with Madurai in figure 4 and it infers that pH in south Indian
cities ( Bangalore, Madurai, Perambalur) show raw sewage pH value less than 7. It
may be due to food habit and nature of the sewerage system ie either domestic or
combined with industrial effluent.
6.00
6.50
7.00
7.50
8.00
pH
Month, 2014
Figure 3. Monthly mean pH of raw sewage and treated
effluent
Raw sewage

3.3.2 Temperature
Mean monthly variation of temperature of raw sewage and treated effluent during
January to December 2014 is shown in figure 5. It is clear that treated effluent
temperature is higher than the raw sewage temperature for the reason stated
elsewhere. December and January are winter months and hence the temperature of
both raw and treated effluent is the lowest. Summer and pre monsoon months, May to
August, temperature is high in lieu of high atmospheric temperature.
3.3.3 Dissolved oxygen (DO)
Monthly mean value of dissolved oxygen (DO) values in raw sewage and treated
effluent is shown in figure 6 for easy understanding. It shows that the treatment
process certainly increases the DO considerably.
6.2
6.4
6.6
6.8
7
7.2
7.4
7.6
7.8
8
pH
Figure 4. pH of sewage in various cities in India
26
27
28
29
30
31
32
33
TEMP0C
Month, 2014
Figure 5. Monthly mean Temperature of raw sewage and
treated effluent
Raw sewage
Treated effluent

3.3.4 Total Suspended Solids (TSS)
Monthly mean value of TSS of raw sewage and treated effluent with the standard
value stipulated by Pollution Control Board is depicted in figure 7. It infers that
treated effluent has TSS value well below the standard. Figure 8 shows the efficiency
of TSS removal in the STP. Good efficiency is found.
-1
0
1
2
3
4
5
6
7
DO,mg/L
Month, 2014
Figure 6.Monthly mean DO of raw sewage and treated effluent
Raw sewage
Treated effluent
4
54
104
154
204
254
304
354
TSS,mg/L
Month, 2014
Figure 7. Monthly mean TSS value of raw sewage and treated
effluent with CPCB standard
Raw sewage
Treated effluent
CPCB standard

3.3.5 Chemical oxygen demand (COD)
Figure 9 depicts the mean monthly COD value of raw sewage, treated effluent and
standard value for the period January to December 2014. The efficiency of COD
removal in the STP is also presented in figure 10. It is observed that the sequential
batch reactor has high COD removal efficiency. The difference in efficiency over the
months is very marginal and it shows its consistency in removal.
95
96
97
98
99
100
Efficiency,%
Month, 2014
Figure 8. Efficiency of TSS removal in STP
0
50
100
150
200
250
300
350
400
450
500
COD,mg/L
Month, 2014
Figure 9. Monthly mean COD value of raw sewage and
treated effluent
Raw sewage
Treated effluent
CPCB standard

3.3.6 Biological oxygen demand (BOD)
The BOD of raw sewage and the treated effluent over the one year period with the
standard value is presented in figure 11. The figure indicates that the BOD value is
consistently lower than the standard value, 30 mg/L. It is observed from the
efficiency curve (figure 12) that it is above 95%.
90
91
92
93
94
95
96
Efficiency,%
Month, 2014
Figure 10. Efficienct of COD removal in STP
0
50
100
150
200
250
BOD,mg/L
Month, 2014
Figure 11. Monthly mean value BOD of raw sewage and treated
effluent with standard
raw sewage
Treated effluent
Pollution standard

3.3.7 Oil & Grease
Figure 13 and 14 show the value of oil and grease present in the raw sewage and
treated effluent and efficiency. The efficiency of oil and grease removal is in the order
of 85% to 90%. Comparing with the BOD, COD and TSS removal efficiency, oil and
grease removal efficiency is lesser. There is a scope for increasing the same and may
be done.
95
96
97
98
99
100
Efficiency,%
Month, 2014
Figure 12. Efficiency of BOD removal in STP
0
1
2
3
4
5
6
7
8
9
10
11
OIL&GREASE,mg/L
Month, 2014
Figure 13. Monthly mean Oil & Grease value of raw sewage and
treated effluent
Raw sewage
Treated effluent

3.4 Comparison of sewage characteristics
BOD, COD and TSS values in the sewage of various cities in India is shown in figure
15. Variation in the sewage characteristics is observed. BOD value at Bhilai is 21
mg/L. Chandigarh records the highest BOD value at 236 mg/L among the compared
cities. The BOD value at Madurai is 228 mg/L. TSS is lesser than BOD value at
Bhilai and Nasik. In all other places TSS value is found higher than BOD. Generally,
higher BOD (more than 300 mg/L) is observed when industrial effluent is combined
with industrial effluent. Figure 15 infers that all the sewages are domestic in nature.
80
82
84
86
88
90
92
94
96
98
100
Efficiency,%
Month, 2014
Figure 14. Efficiency of Oil and Gas removal in STP
0
100
200
300
400
500
600
700
800
900
Figure 15. Characteristics sewage in various cities in India
BOD
COD
TSS
All values are in
mg/L

4. CONCLUSION
Assessment of sewage generation and results of characteristics analysis of raw sewage
and treated effluent from January to December 2014 results draw the following
conclusions:
 Fluctuation in quantity of sewage generation due to per capita water supply, power
supply position, repair and renewals of machineries,
 The present quantity of sewage generation is about half of the design quantity.
 Sewage generated is of domestic in nature. BOD is in the range 200 mg/L to 300
mg/L.
 Efficiency of BOD and COD removal in sewage treatment plant based on sequential
batch reactor is more than 95%.
 Sewage treatment efficiency is consistent,
 Oil and grease removal efficiency is still to be increased,
 Sewage characteristics vary across the country with respect to food habits.
REFERENCES
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International Journal of Civil Engineering and Technology, 3(2), July-December
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[2] Javier Mateo Sagasta and Prit Salian, Global database on municipal wastewater
production, Collection, treatment, discharge and direct use in agriculture,
Aquastat, FAO. 2012
[3] Tamil Nadu Water Supply and Drainage Board Web site.
[4] Bhamoriya, V, 2002, Wastewater and welfare: Pump Irrigation Economy of Peri-
urban Vadodara, Annual Partner's meet 2002, IWMI-Tata Water Policy Program,
Anand, Gujarat, India.
[5] Gopal, B, et al, 1991, Land Application of Municipal Sewage for Resource
Recovery: the Indian Experience, National Institute of Ecology, New Delhi,
India.
[6] Central Pollution Control Board, 2005, Status of Sewage Treatment in India.
[7] Central Pollution Control Board, Performance evaluation of sewage treatment
plants under NRCD. 2013.
[8] Rajendran, S. M and Dr. Sekaran, V, 2014, Municipal wastewater reuse in arid
regions- scope for irrigation in Madurai city, International journal of Civil
Engineering and Technology, 5(7), PP: 64-80.
[9] D. Jayganesh, Dr. J. Jegan and Dr. P. Mariappan, Impact of Staging Height of
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[10] Er. Devendra Dohare and Er. Parth Bochare, Sequential Batch Reactors: Taking
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