Faecal matter in Dwarka rainwater pits, says Delhi pollution panel
DPCC said it tested water samples from pits in 103 out of the 180 societies in Dwarka where high ammoniacal nitrogen levels were previously found
The Delhi Pollution Control Committee (DPCC) has found faecal coliform in rainwater harvesting pits (RWH) in 103 housing societies in Dwarka, indicating that sewage was either mixing with rainwater or directly entering the pits, leading to groundwater contamination in the south-west Delhi neighbourhood, officials said on Wednesday. A previous study had found high ammoniacal nitrogen levels in the water samples taken from the same housing societies, with DPCC flagging the problem of ill-maintenance and poor design of these pits as the reason behind the problem.
DPCC, in a report dated May 14, said it tested water samples from RWH pits in 103 out of the 180 societies in Dwarka where high ammoniacal nitrogen levels were previously found. Samples could not be collected from the remaining pits because water had either dried up or the pits were locked, officials said.
“According to the analysis report, faecal coliform has been detected in all the 103 samples. According to drinking water standards prescribed in IS 10500:2021, faecal coliform should not be detectable at all in a 100ml sample,” said the report, which has been submitted to the National Green Tribunal.
Groundwater contamination in Dwarka
Since February last year, NGT has been hearing a plea from a Dwarka resident who said that rainwater harvesting pits in the sub-city were contaminating the groundwater. In May last year, a joint inspection by an NGT-appointed expert committee, which included members from DPCC and the Delhi Jal Board (DJB), took samples from RWH pits in 235 societies in Dwarka and found high ammoniacal nitrogen and high total dissolved solids in 180 societies.
NGT then sought details from the Delhi government on the source of the ammoniacal nitrogen.
The latest report said, “The presence of ammoniacal nitrogen in rainwater harvesting pits water can be attributed to various sources such as decomposition of organic matter in the soil and contamination from nearby sources such as animal waste or sewage. Ammoniacal nitrogen is found in soil and water, and its presence in rainwater harvesting pits can indicate anthropogenic influences.”
The report added that all ammoniacal nitrogen samples were collected during the dry season and that this was not run-off rainwater, but instead likely to be coming off either directly from pipes bringing sewage or as run-off from pipes carrying wastewater that eventually found its way to a recharge pit in a housing society or house.
“The water available in these RWH pits cannot be pure rainwater but waste water from human activities seems to be intermixed through the drainage network of the societies. Prime facie, the mixing of sewage into these pits is violative of the sewerage scheme and the water supply scheme sanctioned by DJB to the societies,” DPCC said and sought further directions from NGT on the matter.
DPCC and DJB did not respond to requests for comment.
Rejimon CK, a resident of Nav Sansad Vihar CGHS in Sector 22, Dwarka, said all RWHs in the neighbourhood were approved and designed by DJB. “The sewage drains are directly going underground and so if the contamination is happening underground, then the question is how this is happening and why the pits were created near sewage pipelines. DJB should look at these pits, their design and help societies find a solution,” he said.
Shashank Shekhar, assistant professor, department of geology at the Delhi University, said both ammoniacal nitrogen and faecal coliform were indicative of human waste or sewage entering the water. “This indicates either directly or indirectly, sewage and wastewater are flowing through pipes and entering these pits. In some cases, the pipes may have been directly connected to the pits. High ammonia in water leads to the formation of chloramine, which is toxic for the human body,” he added.
The Delhi government made RWH systems mandatory in 2012 and according to law, non-compliance can attract a penalty of 1.5 times the water bill amount. A 10% rebate is given on the water bill if an RWH system is installed. It is also mandatory for government buildings in Delhi to have RWH, however, maintenance of these structures has long been a problem.
DJB In March this year issued an order asking water consumers to ensure that run-off of wastewater from balconies and parking spaces does not contaminate the groundwater through rainwater harvesting pits, saying that failure to do so may lead to withdrawal of the rebate provided to users.
“Only rooftop rainwater can be connected to the rainwater harvesting system. All other wastewater from the balcony washing and paved parking areas, where vehicular movement takes place, should be separated from the rainwater harvesting system,” DJB had said.