There has been no significant improvement in the concentration of ammoniacal nitrogen in the Yamuna in Delhi from 2016 to 2020, a study group set up by the Central Pollution Control Board (CPCB) has said.
High ammonia levels in raw water sourced from the Yamuna have often led to disruption in water supply in the capital.
The CPCB monitors the water quality of the Yamuna at 30 locations under the National Water Quality Monitoring Programme (NWMP) in association with state pollution control boards of Uttarakhand, Himachal Pradesh, Haryana and Uttar Pradesh.
Based on the data generated under the NWMP, the study group has concluded that the concentration of ammoniacal nitrogen in the river water increases during the winter season (November to March), mainly in January.
It has also identified Panipat and Sonipat in Haryana as hotspots with respect to high ammoniacal nitrogen levels.
"There is no significant improvement with regard to ammoniacal nitrogen concentration over the five-year period at the monitored locations in Delhi," the report submitted by the study group read.
The Delhi Jal Board lifts raw Yamuna water from the Wazirabad pond for treatment at the Chandrawal and the Wazirabad water treatment plants. The treated water is then supplied to northeast Delhi, west Delhi, north Delhi, central Delhi, south Delhi, Delhi Cantonment and the New Delhi Municipal Council areas.
Operations at the Wazirabad and the Chandrawal WTPs take a hit whenever ammoniacal nitrogen levels in the Yamuna water exceed 0.9 milligram per litre.
"From Yamunotri (Uttarakhand) to downstream of Ranbaxy locations (Himachal Pradesh), the concentration of ammoniacal nitrogen remains constant and is observed in the range of 0.02-0.15 milligram per litre," the report read.
"The increase in the concentration of ammoniacal nitrogen at Panipat and Sonipat in Haryana clearly indicates the impact of drains from these cities meeting the Yamuna," it said.
At Palla, where the river enters Delhi, there has been an increase in the ammoniacal nitrogen levels (up to 4.80 milligram per litre) during all the years.
The concentration increases steeply to 40.7 milligram per litre between Nizamuddin and Okhla.
In Uttar Pradesh, the ammoniacal nitrogen levels vary between 39.90 milligram per litre upstream of Agra and 0.20 milligram per litre downstream of Allahabad.
The study group said the main sources of pollution in the Yamuna before Wazirabad include discharge of untreated or partially treated sewage from Yamunanagar, Jagadhari, Karnal, Panipat and Sonipat in Haryana.
Other sources include fertiliser, dyeing and tannery units in Panipat, Sonepat, Kundli and Karnal industrial area, partially treated effluents from common effluent treatment plants and sewage treatment plants in Panipat, Sonipat and Kundli and unsewered colonies on the outskirts of Delhi.
The study group also said that due to the lean flow in the Yamuna in the winter season, accumulated sludge in the river bed may undergo decomposition amid anaerobic conditions resulting in an increase in the ammoniacal nitrogen levels.
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