In his speech after the Budget session, Delhi Chief Minister Arvind Kejriwal said that “not enough water from Sewage Treatment Plants (STPs) was being reused”, and a lot of it was “only being released into the Yamuna”. Reports on tests conducted by the Delhi Pollution Control Committee (DPCC), however, show that of the 22 STPS, where water quality tests were carried out, eight failed to meet the standards. The two parameters where the STPs failed to hit the mark was Biological Oxygen Demand (BOD) and Total Suspended Solids.
BOD is the amount of dissolved oxygen needed for organisms to break down organic matter in water. The higher the BOD, the more polluted the water. In a river, the acceptable BOD is 3. In water treated at STPs, it is 30. Across the world, water treated at STPs is used for horticulture purposes or as a coolant in industries. Kejriwal, in March, had said, “Many countries in the world are utilising each drop of water coming from sewage treatment plants, as its saves potable water for drinking. We produce around 450 MGD (million gallons daily) of water at these treatment plants, but only 89 MGD is being used.”
Dinesh Mohaniya, Delhi Jal Board (DJB) vice-chairperson, said he was not aware of the problem. A senior DJB official, however, said that several STPs have not been working as desired for a long time now, and DPCC reports have flagged this issue several times. “In some cases, we miss the mark by a bit, but there are a few STPs where the difference between ideal standards and present standards is big. The team is working on improving these aspects,” the official said.
The Delhi government, for now, is planning to focus on smaller STPs instead of creating a network of pipes to carry sewage to a big STP far away from a colony. The idea is to treat sewage of an area at a small plant locally, and use the treated water within the area for toilets, horticulture and rejuvenating water bodies. Six pilot projects, which aimed to do the same, were announced three years ago in 2015 — but they haven’t taken off yet.