Updated: July 31, 2020 1:25:11 pm
For the second time in a week, the Delhi Jal Board (DJB) on Monday had to reduce water production capacity by 25 per cent after high levels of ammonia were detected in the Yamuna river. Raghav Chadha, the vice-chairman of the DJB, said the concentration of the pollutant was high in raw water released from Haryana, due to which supply was affected in parts of the city. The situation was brought under control later in the day.
The level of ammonia in raw water on Monday morning was 1.8 parts per million (ppm). This was significantly less than 3 ppm recorded on Friday.
The acceptable maximum limit of ammonia in drinking water, as per the Bureau of Indian Standards, is 0.5 ppm. The DJB presently has the capacity to treat approximately 0.9 ppm.
What is ammonia and what are its effects?
Ammonia is a colourless gas and is used as an industrial chemical in the production of fertilisers, plastics, synthetic fibres, dyes and other products. Ammonia occurs naturally in the environment from the breakdown of organic waste matter, and may also find its way to ground and surface water sources through industrial effluents or through contamination by sewage.
If the concentration of ammonia in water is above 1 ppm it is toxic to fishes. In humans, long term ingestion of water having ammonia levels of 1 ppm or above may cause damage to internal organs.
How does it enter the Yamuna?
The most likely source is believed to be effluents from dye units, distilleries and other factories in Panipat and Sonepat districts in Haryana, and also sewage from some unsewered colonies in this stretch of the river.
Water used from the Yamuna for supply to the city is taken before the Wazirabad barrage. Officials of the Delhi Pollution Control Committee (DPCC) claim discharge from industries in Delhi begins after this point.
On Monday, a DJB official pointed to high concentration of pollutants being carried by Drains 8 and 4, which bring potable raw Yamuna water to Delhi from Haryana. Drain 8 is also infamous for running alongside another drain carrying industrial waste and sewage in certain stretches of Sonepat district. In some areas here, sandbags are used to prevent the two drains from mixing. However, on days of heavy rain, both the drains overflow, according to residents in the area and experts from the South Asia Network on Dams, Rivers and People (SANDRP).
How is it treated?
The DJB at present does not have any specific technology to treat ammonia. The only solution it adapts is to reduce production at three water treatment plants — Wazirabad, Chandrawal and Okhla — which are largely affected by the pollutant.
In addition to this, the board mixes raw water that carries high concentration of ammonia with fresh supply from Munak canal, which brings Yamuna water from Munak area in Haryana to Delhi. The amount of chlorine added to disinfect raw water is also increased when high levels of ammonia are detected.
With the completion of a new unit of the Chandrawal water treatment plant by 2022, fitted with advanced technologies and filters, the DJB expects it can treat ammonia levels up to 4 ppm.
What is the long-term solution to the problem?
Stringent implementation of guidelines against dumping harmful waste into the river, and making sure untreated sewage does not enter the water are two things pollution control bodies are expected to do. However, neither Haryana nor Delhi have been able to ensure the same.
But, a more organic method agreed upon by environmentalists and experts is to maintain a sustainable minimum flow, called the ecological flow. This is the minimum amount of water that should flow throughout the river at all times to sustain underwater and estuarine ecosystems and human livelihoods, and for self regulation. It is, however, a sore point between the two state governments. With Delhi dependent on Haryana for up to 70 per cent of its water needs, it has approached the courts several times over the past decade to get what it calls an equitable share of water. Haryana, with a large number of people involved in agriculture, has water paucity issues of its own. Both states have argued over maintaining 10 cumecs (cubic meter per second) flow in the Yamuna at all times.
The lack of a minimum ecological flow also means accumulation of other pollutants. After water is extracted from the river for treatment in North East Delhi, what flows is mostly untreated sewage and refuse from homes, run off from storm water drains and effluents from unregulated industry.
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