Treated sewer water may recharge groundwater

NEW DELHI: The ravines and ditches in Bhati Mines might lend themselves to a new groundwater recharge experiment.

NEW DELHI: The ravines and ditches in Bhati Mines might lend themselves to a new groundwater recharge experiment.

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The Delhi Jal Board (DJB) is looking into sending treated sewer water from the Okhla sewage treatment plant to the ditches to make perennial ponds. These ponds will recharge ground water, which is fast depleting in south Delhi.

Environmentalists working in the field of water have advocated using wastewater and excess water for groundwater recharge for a long time.

If approved, this will be the second such project after Palla.

At Palla in northwest Delhi, the water utility has dug wells where excess water from Yamuna, especially during monsoon months, can recharge groundwater.

“At first we were thinking of making sure monsoon rains feed the ditches and ravines in the area but that would not have been a perennial source,” said DJB CEO, Keshav Chandra.

“Our sewage treatment plant in Okhla treats waste water and its final biological oxygen demand is 10, which is reasonable. Another big advantage is that the plant is just 7-8 kilometres away from Bhati Mines area and transporting treated water will not be an issue,” he said.

Biological oxygen demand (BOD) indicates the quality of water. The lower the BOD, the better it is.

A preliminary study for the project has already been completed by a specialised agency and a detailed study is underway. The preliminary study was encouraging about the prospects of the project. Work on the project might begin in four to five months.

The water utility is also looking at a project in Najafgarh wherein water from aquifers will be treated and used for supply.

“In this case, however, the water in the aquifers is brackish and we will have to set up desalination plants to treat it. We are looking into the possibility of starting a project there but the desalination plant comes with its own problems as it produces unusable wastewater – brine – that is very difficult to dispose of. We will have to thoroughly check the feasibility of that project,” Chandra said.

Desalination plants can be described as large-scale reverse osmosis (RO) water purifiers that we use in homes. The wastewater released is full of concentrated minerals and heavy metals and can be an environmental threat.