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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

253.6 234.8 231.6

294.1

379.4

338.7 2014 2029 2044

Wa

ste

wa

ter

gen

era

tio

n, M

LD

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

TEM

P 0 C

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

Effi

cien

cy, %

Month, 2014

Figure 8. Efficiency of TSS removal in STP

0

50

100

150

200

250

300

350

400

450

500

CO

D, m

g/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

Effi

cien

cy, %

Month, 2014

Figure 10. Efficienct of COD removal in STP

0

50

100

150

200

250

BO

D, m

g/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

Effi

cien

cy, %

Month, 2014

Figure 12. Efficiency of BOD removal in STP

0

1

2

3

4

5

6

7

8

9

10

11

OIL

& G

REA

SE,m

g/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

Effi

cien

cy,%

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.

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