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ABSTRACT: | up | previous | next | last |
The physico-chemical analysis of various parameters in Bellandur tank exhibited considerably high values, revealing the lake unfit for human consumption. Residential, industrial and commercial activities in the catchment have been recognized as the source of pollution and their individual roles have been estimated. Suitable and feasible environmental strategies, for the restoration and management of the tank, have also been suggested.
INTRODUCTION: | up | previous | next | last |
The continuous migration of people from rural areas and smaller towns to metropolitan and megacities, in search of employment, educational facilities, commercial and trade opportunities and good infrastructure has resulted in rapid urbanization. Though urbanization helps in the growth process to a large extent, the clear deterioration in the physical environment and quality of life in urban areas always overshadows this positive aspect. For better and healthy living, safe drinking water supply and hygienic sanitation are a must. However, due to the ever-increasing population, it is becoming extremely difficult to cope with the demand for these basic amenities (Abbasi, S.A., 1997). Almost all the cities at present are facing severe problems of managing wastewater. Formerly designed wastewater management systems are incapable and inefficient in the present scenario. Thus, wastewater gets discharged into natural water bodies indiscriminately, deteriorating the quality of surface and groundwater day by day (Carpenter et. al., 1996).
The increasing population is posing a great threat to the ecology and well being of the aquatic ecosystem, especially lakes. Bellandur tank is under serious threat due to damaging land use practices in its catchment. The tank, choking with weeds, silting up, and encroached from all sides, is shrinking in size, with deterioration in its quality and loss of its rich and varied faunal, floral, and other resources. Many precious wetlands have either gone extinct or are in the throes of death.
LITERATURE SURVEY: | up | previous | next | last |
It is evident that over the last four decades, the quality of the watercourses has undergone a drastic deterioration that can be linked to industrial and demographic transformation. Analysis of the quality of surface water in Parma Valley of Italy over three decades (1951 - 1981) show that, there was a 360 % increase in the pollution load by human activities with much of the increase occurring between 1961 and 1971. This was due to wastewater from four sources - domestic, industrial, commercial and agricultural activities. (In this catchment, agricultural activity can be hardly seen and only the first three are significant). De, et al (1991) in their study of Calcutta Metropolitan city have shown that the Hoogly river is polluted severely by domestic waste (52 m. gallons per day) as well as industrial waste (100 m. gallons per day). In addition, there are discharges with pathogens from Tolly's Nullah, and shipping wastes of Calcutta Port. A large part of Kidderpore and garden reach sewerage system carry toxic and heavy metal discharge of industrial origin. The unscientific method of dumping garbage by filling swamps and marsh lands has also affected the ground water of Calcutta. The concern over the problem is not a new one. Rai et al (1993) studied pollution of Nainital Lake and the results showed that the lake was unfit for any purpose. They identified factors such as human settlement in catchment area, tourism and other recreational activities, which deter the quality of the lake.
Analysis of chemical and fisheries data from the Willow Brook, Northamptonshire, UK, a stream polluted mainly by ammonia and zinc, and found it without fish for over a 3-year period. High bacterial population and BOD values in the Varuna river, could be attributed to the discharge of untreated wastewater and industrial effluents into the river at Varanasi (Joshi, G and Adoni, A.D, 1993).
OBJECTIVES: | up | previous | next | last |
The objectives of the present study are:
STUDY AREA | up | previous | next | last |
METHODOLOGY: | up | previous | next | last |
COLLECTION OF SECONDARY DATA FROM GOVERNMENT AGENCIES | up | previous | next | last |
COLLECTION OF PRIMARY DATA | up | previous | next | last |
Primary data relating to industries, hospitals and major vehicular service centers were collected through a sample questionnaire survey. The questionnaire data was generalized to estimate the total wastewater generation by all these activities in the area.
DEVELOPMENT OF METHODOLOGY FOR SAMPLING SURVEY | up | previous | next | last |
A stratified sampling methodology has been developed for the present study. Industries with more than 100,000 rupees investment were selected for the industrial survey. Based on the distribution of the industries, several clusters were identified. Each cluster was classified into several categories considering the type of production. Under each category, survey was conducted so as to cover at least 20 % of the total industries. Also the selected industries were distributed equally over the total range of investments under each category. The methodology was extended to hospitals in the catchment. About 40 % of the hospitals were surveyed randomly all over the catchment (the capacity ranging from 8 to 1000 beds). The wastewater contribution by the hospitals in total has been estimated by generalisation of the data obtained. As the data regarding the total number of vehicular service stations and their location could not be obtained from any of the authorized organizations, the sampling methodology has been slightly modified. Here, two sampling stations having one sq. km of individual area were chosen. One is located at the periphery of the city and the other is located at the densely populated central part of the city. All the service stations coming under the sampling area were surveyed and finally averaged.
DOMESTIC WASTEWATER ESTIMATION | up | previous | next | last |
The population data of 1991 census, obtained from the Census Department was used to estimate the present and extrapolate the future population. With this population data, total domestic wastewater generation was estimated. The per capita water consumption has been considered based upon detailed literature survey and discussions with the concerned authorities. The quantity of wastewater generation has been projected for the future 20 years with the corresponding increase in population.
QUALITATIVE ANALYSIS | up | previous | next | last |
A complete analysis of the wastewater sample was done to check the pollution load qualitatively, and to verify, whether they meet the wastewater parameter limits prescribed by statutory boards before discharging the same into fresh water bodies. For this purpose, the grab samples were collected from various points and were subjected to analysis.
SAMPLING METHODOLOGY | up | previous | next | last |
Water samples were collected gently in two litre black-polythene cans. The pH, temperature, dissolved oxygen, free carbon dioxide and total alkalinity were determined in the field. For other analysis, the samples were preserved by adding a few drops of chloroform, taken to the laboratory and stored in a refrigerator for further analysis.
RESULTS AND DISCUSSIONS: METEOROLOGICAL PARAMETERS |
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The rainfall data is available for the last 100 to 110 years. Rainfall varies from 725.5 mm to 844.8 mm. The district receives 51 % of the total annual rainfall in the southwest monsoon period, i.e. June to September. The average annual rainfall in the catchment was 859 mm in 1999. April is usually the hottest month with the mean daily maximum and minimum temperature of 33.4o C and 21.2o C respectively. December is generally the coolest month with the mean daily maximum and minimum temperature of 25o C and 15.3o C respectively. The temperature drops down to 8o C during January nights. Relative humidity is high from June to October (80 to 85 %). Thereafter, it decreases and from February to April becomes 25 to 35%. The relative humidity in the morning is higher than in the evening, giving rise to the formation of fog.
WASTEWATER ESTIMATION FOR THE INDUSTRIAL CLUSTERS | up | previous | next | last |
The growth pattern of the industries formed three clusters in the region. All the three clusters are located at the periphery of the city. The urban encroachment has affected these industrial clusters, giving rise to mixed land use pattern. The area around Koramangala and HAL forms cluster I, the area along Bannerghatta road forms cluster II and the area around Hosur road forms cluster III.
Cluster I: Out of 42 identified industries in this cluster, 21 were subjected to sampling. Most of the industries were found to be wet processing, discharging 121,073.7 L/day of wastewater to the catchment (Table1).
TABLE 1: DETAILS OF INDUSTRIAL SAMPLING IN CLUSTER I. | up | previous | next | last |
Sl No. |
Type of Industries |
Total No of Industries |
No. of Industries Surveyed |
Percentage of Sampling |
Wastewater Discharge for the Sampled Industries (L/day) |
Estimation of Total flow (L/day) |
1 |
Engineering |
13 |
5 |
38.46 |
8090 |
21067.7 |
2 |
Rubber |
1 |
1 |
100 |
480 |
480 |
3 |
Textile |
1 |
1 |
100 |
4500 |
4500 |
4 |
Bricks/Granites |
2 |
1 |
50 |
80 |
160 |
5 |
Dyeing |
1 |
1 |
100 |
4160 |
4160 |
6 |
Miscellaneous |
24 |
9 |
37.5 |
34015 |
90,706 |
Total |
42 |
21 |
121073.7 |
Cluster II: Out of 72 industries identified in this cluster, 22 were selected for the survey. Engineering industries are more in number. The total wastewater contribution is found to be 45,444 L/day (Table 2).
TABLE 2: DETAILS OF INDUSTRIAL SAMPLING IN CLUSTER II | up | previous | next | last |
Sl No. |
Type of Industries |
Total No of Industries |
No. of Industries Surveyed |
Percentage of Sampling |
Wastewater Discharge for the Sampled Industries (L/day) |
Estimation of Total flow (L/day) |
1 |
Engineering |
13 |
4 |
30.7 |
2260 |
7362 |
2 |
Rubber/Plastic |
1 |
1 |
100 |
160 |
160 |
3 |
Textile |
6 |
3 |
50 |
4200 |
8400 |
4 |
Electronic/ Electrical |
5 |
2 |
40 |
750 |
1875 |
5 |
Bricks/Granites |
4 |
2 |
50 |
440 |
880 |
6 |
Chemical |
2 |
1 |
50 |
1000 |
2000 |
7 |
Miscellaneous |
41 |
10 |
24 |
5944 |
24767 |
Total |
72 |
23 |
45444 |
Cluster III: In Cluster III, 42 industries were identified, out of which 17 were selected for the sample survey. Industries along the Bannerghatta road come under this cluster. In this cluster also, engineering industries are more in number. The total wastewater generation in this cluster is found to be 24,938 L/day (Table 3).
TABLE 3: DETAILS OF INDUSTRIAL SAMPLING IN CLUSTER III | up | previous | next | last |
Sl No. |
Type of Industries |
Total No of Industries |
No. of Industries Surveyed |
Percentage of Sampling |
Wastewater Discharge for the Sampled Industries (L/day) |
Estimation of Total flow (L/day) |
1 |
Engineering |
11 |
3 |
27.2 |
1930 |
7096 |
2 |
Rubber/Plastic |
6 |
2 |
33.3 |
400 |
1212 |
3 |
Textile |
3 |
2 |
66.6 |
3700 |
5555 |
4 |
Bricks/Granites |
1 |
1 |
100 |
1500 |
1500 |
5 |
Dyeing |
1 |
1 |
100 |
1600 |
1600 |
6 |
Miscellaneous |
20 |
8 |
40 |
3190 |
7975 |
Total |
42 |
17 |
24938 |
All the three industrial clusters, in total, contribute 191,455.7 litres of wastewater everyday to the catchment.
DEMOGRAPHIC STUDIES | up | previous | next | last |
Population data for the last 6 decades was collected from the Census Books and the growth pattern have been analyzed. With this growth pattern the present (2001) and future population for the year 2011 is estimated (Table 4).
TABLE 4: POPULATION GROWTH IN THE LAST FEW DECADES AND FUTURE ESTIMATION | up | previous | next | last |
Year |
Population |
Density (persons/km) |
1941 |
99,322 |
671 |
1951 |
141,222 |
954 |
1961 |
243,225 |
1643 |
1971 |
487,493 |
3293 |
1981 |
867,375 |
5860 |
1991 |
13,23,124 |
8940 |
2001 |
23,89,694 |
16146 |
2011 |
43,16,026 |
29162 |
Using Geometrical Increase Method, the population in the catchment is estimated for the years 2001 and 2011 (Fig 1). For the year 2001, it is found to be 23,89,694 and it becomes 43,16,026 by 2011. Data compiled from various literatures show the per capita water consumption for purely domestic purposes as about 135 litres per day. The literatures also show that 80 % of the total water consumption becomes wastewater. Thus, considering all these aspects, the present wastewater contribution by domestic activity is estimated to be 2,58,087 m3/day. In 10 years the quantity will increase to 4,66,130 m3/day. Thus, a significant amount of wastewater is being generated in the region and it has become a major concern to collect, transport, treat and discharge.
FIGURE-1: POPULATION GROWTH PATTERN OF THE REGION | up | previous | next | last |
COMMERCIAL ACTIVITIES IN THE CATCHMENT Estimation of wastewater generated by hospitaLS: |
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There are totally 65 hospitals identified in the region, of which 32 were sampled and the data generalized to get the total wastewater contribution by hospitals (Table 5).
TABLE 5: DETAILS OF SAMPLE SURVEY CONDUCTED FOR HOSPITALS IN THE REGION | up | previous | next | last |
Bed Range |
Number of Hospitals |
Number of Sampled Hospitals |
Percentage of Sampled Hospitals |
Obtained Quantity by Sampling (L/day) |
Estimated Total Quantity (L/day) |
1 – 50 |
41 |
18 |
43.9 |
378900 |
863098 |
51 – 500 |
18 |
9 |
50 |
181000 |
362000 |
501 – 1000 |
6 |
6 |
100 |
332000 |
332000 |
Total |
1557098 |
The above results show that the major contribution among these three categories is by small hospitals.
Estimation of wastewater generated by vehicular service centres: | up | previous | next | last |
Sampling survey reveals the number of service centers per square kilometer of the area as 5 and the daily discharge of wastewater by them as 9632.25 liters. From the sampling survey, it can be estimated that the catchment contains 740 service stations, and they discharge 14,25,573 liters of wastewater everyday (Table 6).
TABLE 6: DETAILS OF SAMPLE SURVEY CONDUCTED FOR VEHICULAR SERVICE CENTRES | up | previous | next | last |
Sample Station |
No of Service Stations |
Wastewater Generation (L/day) |
1 |
7 |
10,592.5 |
2 |
3 |
8,672.0 |
Average |
5 |
9,632.25 |
Total Wastewater Contribution: | up | previous | next | last |
The total wastewater generation in the catchment is found to be 2,61,274.17 m3/day. The individual contribution by residential sector is found to be 98 % of the total wastewater and as the population increases at such a fast rate, there will be tremendous increase in wastewater generation in the coming years (Table 7).
TABLE 7: INDIVIDUAL AND TOTAL WASTEWATER GENERATION IN THE REGION | up | previous | next | last |
Sl. No. |
Type of Activity |
Individual Contribution in m3/day |
Percentage Contribution |
|
1 |
Industrial |
191.50 |
0.073 |
|
2 |
Residential |
258100.00 |
98.00 |
|
3 |
Commercial |
Hospitals |
1557.10 |
0.595 |
Service Centres |
1425.57 |
0.55 |
||
Total |
261274.2 |
Treatment facility: | up | previous | next | last |
On the northwestern side of Bellandur tank, the Koramangala and Challaghatta valley sewage treatment plant is situated. The designed capacity of the plant is 163,000 m3/day of wastewater. But currently it is treating only 100,000 m3/day. The incapability of the network of pipes to transport the generated wastewater is one of the main reasons for less flow in to the sewage treatment plant (STP). The remaining 161,274.17 m3/day of wastewater requires complete treatment. At present, this wastewater is directly entering various tanks in the catchment, polluting them.
Bellandur tank is a rainfed tank. The central stream joins the tank from the northwestern part. Before the confluence of the central stream, it joins with the western stream and finally flows as one and joins the tank. Though the actual area of the tank is about 328.87 hectares, the growth of weeds, siltation and slush formation have reduced it to 154.34 hectares (Table 8). For the last few decades, treated, partially treated and untreated wastewater has been discharged to this tank. The Minor Irrigation Department is using the water of this tank for irrigating agricultural lands, coconut trees, etc. Many episodes of diseases in coconut trees have been reported due to this contaminated water.
TABLE 8: GEOGRAPHICAL FEATURES OF BELLANDUR TANK | up | previous | next | last |
Parameter |
Value |
Longitude |
13o00´ north – 12o 50´ south |
Latitude |
77o35´ west – 77o 45´ east |
Annual Rainfall in the catchment |
859 mm |
Maximum Temperature (oC) |
35 in April |
Minimum Temperature (oC) |
14 in January |
Surface Area (ha) |
328.87 |
Area engulfed with slush and weed (ha) |
174.33 |
Catchment Area (ha) |
8,868.83 |
Area irrigated by the tank (ha) |
10,271.15 |
Human Population in the catchment (1991 Census) |
13,23,124 |
Qualitative Analysis: | up | previous | next | last |
Maximum values of BOD and COD may be attributed to the heavy input of variety of nutrients such as sulphates and phosphorous to the tank, creating a favorable environment for microbial activity. Hazardous substances such as cyanide were not detected, which is an indication of the absence of hazardous industrial discharge. The alkalinity at the outfall is an indication of prevailing concentration of the parameter (Table 9). The high values of sewage at the inflow are a clear indication of the pollution of the tank.
TABLE 9: TEST RESULT OF SAMPLES OF DRY WEATHER FLOW INTO BELLANDUR TANK | up | previous | next | last |
Sl No. |
Parameters |
Sample at the central stream inlet |
Sample at the eastern stream inlet |
Sample at the outfall of the tank |
1 |
Temperature |
28o C |
28o C |
28o C |
2 |
Colour |
Black |
Brownish |
Light black |
3 |
Odour |
Pungent |
Pungent |
Pungent |
4 |
pH |
7.3 |
9.4 |
7.1 |
5 |
Alkalinity (mg/L) |
362.00 |
348.00 |
230.00 |
6 |
Total Dissolved Solids (mg/L) |
420.00 |
498.00 |
418.00 |
7 |
Total Phosphorous as phosphates (mg/L) |
2.10 |
1.80 |
0.6 |
8 |
COD (mg/L) |
396.00 |
456.00 |
122.00 |
9 |
BOD3 (mg/L) |
278.00 |
294.00 |
84.00 |
10 |
Nitrates (mg/L) |
0.387 |
0.347 |
0.124 |
11 |
Sulphates (mg/L) |
62.00 |
68.00 |
49.00 |
12 |
Cyanide |
ND |
ND |
ND |
13 |
Lead |
ND |
ND |
ND |
RECOMMENDATIONS AND CONCLUSIONS: | up | previous | next | last |
It is a highly complex task to bring out a feasible and environmentally sustainable solution to restore the original quality of the tank and the streams.
REFERENCES: | up | previous | next | last |
Address: | up | previous |
1.) Centre for Ecological Sciences,
Indian Institute of Science,
Bangalore,
560 012,
India
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