A futile exercise
At present, Delhi treats the same wastewater at multiple plants because treated water gets mixed with wastewater in drains
Delhi sewerage network is divided into six zones. The Shahdara drainage zone has three sewage treatment plants (STPs) at Sonia Vihar, Yamuna Vihar and Kondli. The Yamuna Vihar STP draws wastewater for treatment from a nearby drain. After treatment, the effluents are discharged back into the same drain downstream of the intake point (see map). As the drain travels towards the Yamuna river, more untreated waste is added to it. This happens because the Yamuna Vihar area is only partially sewered and the STP is operating at just 58 per cent of its 90 million litres of water per day (MLD)capacity, according to the Delhi Jal Board (DJB).
As a result, another treatment plant at Kondli intercepts this wastewater and treats it all over again. This re-treated waste is once again diverted into an open drain. This drain collects more wastewater from unsewered colonies of Delhi and Noida before it meets the river. The end result is that the output of the two STPs is completely negated. Kondli area is mostly sewered and has three treatment plants with a combined capacity of 450 MLD (40.5 MLD of this is under construction).
Under the Sewerage Master Plan for Delhi 2031, the DJB plans to divide the Shahdara drainage zone into three smaller sub-drainage zones: Sonia Vihar, Yamuna Vihar and Kondli. It also plans to set up a new treatment plant at Yamuna Vihar, which will have a capacity of 112.5 MLD. DJB is in the process of making interceptor sewers that will check all wastewater sub-drains from mixing with the main Shahdara link drain that carries treated water to the Yamuna. Meanwhile, the Wazirabad Trunk Sewer, laid under the Yamuna Action Plan-II, will be used to bring most of the sewage to the Yamuna Vihar treatment plant.
BUT PROBLEM PERSISTS
The plan assumes that there will be no outfall from the treatment plants into the drain, which is unlikely. The plan is overambitious about the running capacities of the old and new treatment plants. It also does not explain how the new plant at Yamuna Vihar will run at full capacity or how the old plant will be upgraded to run at full capacity. The plan also underestimates the actual wastewater generated as it does not include the discharge on account of groundwater extracted in the area.