To demonstrate the use of wastewater in agriculture, the Indian Agricultural Research Institute (IARI) is constructing a wetland in its Delhi campus. Spread over 1.42 hectares, the wetland is capable of holding and treating two million litres of sewage a day from the Krishi Kunj Colony adjoining IARI's campus. The institute plans to use the treated sewage in its farms to grow crops.
Developed by IARI's Water Technology Centre (IWTC) at a cost of Rs 1.4 crore, the wetland consists of one holding tank and three treatment tanks. IWTC's project director Ravinder Kaur says the institute had wasteland in a corner with the remnants of an old pond, sumps and pumps. The tanks were developed from these detritus.
Sewage from the Krishi Kunj Colony is first let into one sump where any lumps or larger pieces settle down to the bottom. The wastewater is then pumped into the second sump for further sedimentation. These sumps are cleaned periodically. From here it goes to a grit chamber filled with broken pieces of bricks and then to the tanks of the wetland. The effluent entering the tanks are now clear of any large floating pieces that could clog inlet pipes. The wastewater is stored in these treatment tanks for 2.2 days. Each treatment tank is layered with 60 cm thick layer of stones, on which different species of plants such as phragmites, typha and acorus are planted. These aquatic plants grow by absorbing micronutrients (nitrates, phosphates, heavy metals, potassium and sulphate) from the sewage and thereby disinfecting the wastewater. Water flow into these tanks is regulated so that its level does not rise beyond the gravel layer. This prevents mosquitoes from breeding.
Sewage treatment wetland in making | Down To Earth