The Central Pollution Control Board said accumulated sludge and drain water cause ammonia spikes in the Yamuna. This pollution often disrupts Delhi’s water supply. The board noted, "The CPCB said that due to this, one-time de-sludging of the pond will not be effective." Officials now seek better nitrogen control.
Accumulated sludge on the Yamuna riverbed and polluted water from drains upstream are contributing to frequent spikes in ammonia levels in the river, which often lead to disruption in Delhi's water supply, the Central Pollution Control Board (CPCB) has found.
Even the relatively cleaner stretch of the Yamuna between Palla and Wazirabad in Delhi has had deteriorating water quality, with the CPCB identifying sludge accumulation and nitrogen-rich wastewater entering the river as key factors behind the recurring problem.
In a report submitted to the Upper Yamuna River Board (UYRB), the CPCB said the water holding pondage area from which the Wazirabad and Chandrawal water treatment plant draws raw water could be generating ammonia because of excessive silt and sludge accumulation.
The pollution watchdog cautioned that dredging the reservoir alone would not resolve the problem. It said the situation would improve only when nitrogen levels in water discharged into the Yamuna through drains are brought within acceptable limits.
HT reported on August 12 that the UYRB asked the CPCB to study the sludge factor behind the disruption in the water supply due to a spike in ammonia levels.
A government official said the study found that high levels of ammonia in water coming from drains and the accumulated sludge are both the reasons for the rise in ammonia level in raw water. "The CPCB said that due to this, one-time de-sludging of the pond will not be effective, as the sludge carried by water containing high levels of nitrogen will again get deposited in the pond and will restore the problem."
The CPCB has said that the situation will improve only when nitrogen levels in water coming from drains are brought within acceptable limits.
The raw water from Yamuna feeds the treatment plants in Wazirabad and Chandrawal, which supply water to the Central, North and Old Delhi areas.
A rise in ammonia levels, which are indicative of high industrial pollutant levels, leads to disruption in the water supply.
Periodic spikes in ammonia levels have been a long-standing point of dispute between Delhi and Haryana.
The Delhi Jal Board (DJB) argues that the industrial pollutants, such as dyes, chlorides and ammonia-based chemicals, flow from the Panipat industrial drain.
Besides Panipat, DJB regularly cites the intermixing of industrial waste in Sonipat, where two canals carrying freshwater and industrial water run parallel to each other, separated by a sand wall of a few inches.
In its submission to the UYRB, Haryana informed the CPCB that multiple steps are being taken to reduce pollution loads in drains ending up in Yamuna, including construction of a Sewage Treatment Plant. "The programme is being strictly monitored by the Union Home Ministry," Haryana said in its submission.
Wazirabad pondage, a primary holding area formed by the Wazirabad barrage, spans approximately 250,000 square meters and has a depth of about 8.20 feet (2.5 metres). It is so heavily laden with sludge that its water storage capacity has been significantly reduced. Its effective depth is now barely one to 1.5 metres.
Water entering the Yamuna from drains contains high levels of nitrogen, specifically in the form of nitrates and nitrites, which leads to ammonia formation. This nitrogen dissolves into the accumulated sludge, causing continuous ammonia generation.
This year, the DJB announced that dredging of the pondage area near Wazirabad barrage will be carried out after monsoon.
The UYRB has suggested that once the pollution load of drains is within acceptable limits, DJB may consider one-time de-sludging of the river bed.
A second official said CPCB has advised Delhi that a one-time desilting of the reservoir will not solve the problem. "This is because, following the removal of the sludge, water from the drains will continue to flow into the Yamuna, and the silt carried by this drain water will inevitably accumulate in the reservoir once again," the official said. "The silt in the drains is likely to have a very high nitrogen content, which will, in turn, generate ammonia."