Best Practices | Centre for Science and Environment


Best Practices

 

Ajay Kumar Garg Engineering College, Ghaziabad

In the Ajay Kumar Garg Engineering College, about 30 cu m of wastewater generated from the girls hostel, canteen and staff quarters is treated by decentralised wastewater treatment system comprising of settlers, upflow anaerobic baffled reactor, planted filters and polishing ponds. This system has been working since 2005. In addition to this, an additive is also used to enhance the treatment process.


Measures taken for treatment

The wastewater generated in the engineering college campus undergoes primary treatment in the settler. In the  settler, the sludge settles down at the bottom and the scum floats at the top. Since the grey water from the canteen carries a high amount of oil and grease, a grease trap is provided before settler. The partially-treated wastewater from all the six settlers undergoes 12 hours of retention before it flows into the next treatment unit, which is the anaerobic reactor. After 24 hours of retention, the wastewater flows to the horizontal planted filter, where  the secondary treatment takes place.

Impact
To assess the performance of the system, samples were taken from the outlets of the settler, baffled reactor and planted filter in 2006. The analysis of the treated effluent shows that BOD and COD removal are 81.3 per cent and 79.9 per cent respectively. The faecal coliform levels reduced from 20 counts per 100 ml to 3 counts, which is  approximately 85% reduction. The nitrate and phosphate removal is 30.2 per cent and 11.1 per cent respectively; this results in a final effluent rich in nutrients. This nutrient-rich treated water is used for irrigation.



Centre for Science and Environment, New Delhi

The wastewater recycling system at CSE has been designed to treat 8000 litres per day based on the assumption that at any given moment at least 100 persons would be ocupying the premises. The components involved in treatment are a settler, a baffled reactor and planted filter. The treated wastewater is stored in an underground sump. This water is used for irrigation, gardening and landscaping.

Measures taken for treatment

Grey water from the canteen passes through a grease trap to separate the scum. After this, the water goes into the settler for primary treatment. The black water from toilets is taken separately in another settler from where it goes to anaerobic baffled reactor for secondary treatment. The outlet from the baffled reactor after 24 hrs of retention time is mixed with the outlet of the grey water settler. The combined grey and black water then goes into the horizontal planted filter for further treatment. Final treated water is stored in an underground tank of 10 cum capacity from where it is pumped out to meet the irrigation and horticulture requirements of the building.

Impact
The area has huge water scarcity and the ground water table is at depth of 70m. About 8 KL of wastewater is treated and reused. All the water requirement for horticulture and gardening is met by the treated wastewater. The efficiency of the system is 90% in terms of BOD removal.  


Mughal Sheraton Hotel, Agra

In the Mughal Sheraton Hotel, Agra, wastewater is treated using Soil Biotechnology (SBT) system of 400 kld capacity, which was implemented by Enhanced Wapp System, Delhi. The project was completed in July 2004. The hotel dismantled the conventional sewage treatment plant and implemented SBT technology at a cost of Rs 36 lakh, including the dismantling cost. Certain components of the old system, like the collection well and pumps, were utilised for the SBT.

Measures taken to treat wastewater

In this project, wastewater from the kitchen and laundry is treated using SBT. All the waste is collected in the storage tank. The collected wastewater is then sprayed on the top of the soil through perforated PVC pipes. The bed consists of specially cultured soil media, made up of a layer of stone ballast, pebbles and sand. The filtered wastewater, after passing through the soil bed, is collected in the furrows provided between the layers of soil. This water in the furrows is drained in a collection well after passing through the soil bed repeatedly, until the desired quality is obtained. The treated water is finally collected in a well.

Impact
Around 400 kld of wastewater is treated onsite and reused locally for irrigation purposes thereby saving a considerable amount of fresh water.


Ravindranagar, Ujjain, Madhya Pradesh

At Ravindranagar in Ujjain, about 13 to 14 cu m of wastewater generated from 400 households is treated using Root Zone System. The system was set up in 1997 at a cost of Rs 54,000.

Measures taken for treatment
The sewage generated from the colony is collected in an open drain, which runs adjacent to the road. The light material which can float like plastic, is removed in the pre-treatment process, when the sewage passes through a layer of boulders in the pre- treatment tank. The pre-treated wastewater is then evenly distributed over the reed bed through a perforated PVC pipe fixed at the beginning of the bed. The treated water is collected at the other end of the reed bed in a collection chamber from where it is diverted to a pond for recharging the ground water.

Impact
Within the first year of its operation, the root zone system achieves a removal efficiency of 78% of ammonia and TSS, 58-68% removal of phosphorous, BOD and TKN in the aerobic rootzone gravel with an enhanced 34% DO in the effluent.


Shri Ram School, Vasant Vihar, New Delhi

In the Shri Ram School, about 3 to 4 cu m of grey water from the canteen is recycled using the upflow anaerobic baffled reactor and planted filter. This system has been working since 2006 and was installed in the school at a cost of Rs 33,000. In addition to this,  an additive to enhance the treatment process.

Measures taken for treatment
The wastewater from the canteen contains a high amount of oil  and grease. To prevent this from entering the reactor, a grease trap is installed. The grease trap consists of a plastic “T” bend pipe, which diverts clear wastewater from the floating layer of oil and grease to the next treatment unit – the anaerobic reactor. The accumulated grease deposit is then scooped out once a month and disposed off .The grease-free wastewater from the grease trap then flows into the underground anaerobic chamber.  As the wastewater in the collection chamber reaches a particular level, an automatic pump starts pumping the wastewater to the next treatment unit, namely, the planted filter.

Impact   
An analysis of the lab report shows that BOD and COD have reduced by 74.1 per cent and 68.7 per cent, respectively. Nitrate content removal is as high as 90.8 per cent through the planted filter. The incoming phosphate level is as high as 225.7 mg/l, but is reduced to 154.4 mg/l in the final treated effluent. Since the water is used for irrigation, it acts as a valuable source of nutrients for the plants.


Horizontal Flow Constructed Wetland (HFCW) at Pradeep Sachdeva Design Associates Office, New Delhi

At PSDA office, Horizontal Flow Constructed Wetland has been adopted to treat about 2KLD of wastewater coming from toilets.The total cost of construction of the plant is Rs 85,000.

Measures taken for treatment
Primary treatment takes place in the settler/septic tank, where the sludge settles down and scum floats to the top and the clear liquid flows to the collection chamber. From this chamber, water is pumped using a small manually operated pump to the root zone treatment system for secondary level treatment. The root system treats the wastewater by injecting oxygen to the water which flows in the  gravel bed and removes nitrates and phosphates during the process . The final treated wastewater is collected in the storage tank.

Impact

The treated wastewater is used for horticultural purposes thereby reducing groundwater extraction.

 

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