Yamuna sludge may be behind ammonia spikes: Central pollution board study

Accumulated sludge in the Yamuna bed at Wazirabad may be contributing to ammonia spikes that have caused recent disruptions in Delhi’s water supply, preliminary findings of a Central Pollution Control Board (CPCB) study based on samples collected from the pondage area have shown, government officials said

Accumulated sludge in the Yamuna bed at Wazirabad may be contributing to ammonia spikes that have caused recent disruptions in Delhi’s water supply, preliminary findings of a Central Pollution Control Board (CPCB) study based on samples collected from the pondage area have shown, government officials said.

The concern comes as even the relatively cleaner stretch of the Yamuna between Palla and Wazirabad has recorded deterioration in key water-quality parameters, according to monthly reports of the Delhi Pollution Control Committee. (HT)

The concern comes as even the relatively cleaner stretch of the Yamuna between Palla and Wazirabad has recorded deterioration in key water-quality parameters, according to monthly reports of the Delhi Pollution Control Committee.

The CPCB collected samples from the Wazirabad pondage area during a period of high ammonia levels, and its preliminary findings suggest that accumulated sludge may be one of the factors behind elevated ammonia levels in raw water, officials said. The study was undertaken at the behest of the Upper Yamuna River Board (UYRB), which is examining the causes of recurring ammonia spikes and their impact on Delhi’s water supply.

A senior Delhi Jal Board official said, “There may be accumulation of sludge in the bed of Wazirabad pond, which may be a probable cause for the in-situ generation of ammonia. The CPCB is undertaking a study in this regard and they have collected samples when ammonia levels were high. As per the preliminary findings, it has been found that the accumulated sludge may be one of the reasons for the rise in ammonia level in raw water,” the official said.

Samples collected from several locations upstream of Palla also showed high ammonia levels in water entering the Yamuna through various drains during periods when the city faced disruptions in water supply, officials said.

The Delhi Jal Board can treat ammonia levels of up to 1 ppm, beyond which operations at the Wazirabad and Chandrawal water treatment plants are affected. The DJB is currently commissioning a new plant at Chandrawal, which will increase its ammonia treatment capacity by four to five times.

The findings also come as the DJB prepares to dredge and revive the Wazirabad pondage area up to Ram Ghat. The project, approved by the DJB last month, will involve removing around 387,000 cubic metres of silt, with work expected to begin after mid-September, once the monsoon ends.

But dredging the pondage area may not provide a lasting solution. A one-time de-sludging exercise could be followed by fresh accumulation as nitrogen-rich water continues to flow into the river through drains, a DJB official said. “The long-term situation will improve only when nitrogen levels in the water coming through drains are brought within acceptable limits. The CPCB will study the issue thoroughly and suggest solutions,” the official said.

According to the Delhi Pollution Control Committee’s water-quality report dated August 4, the faecal coliform level at Wazirabad was 3,500 MPN/100ml, against the acceptable limit of 2,500 MPN/100ml or less. Dissolved oxygen was recorded at 3.1 mg/l, below the prescribed level of more than 5 mg/l, while biochemical oxygen demand was recorded at less than 4 mg/l, against the standard of less than 3 mg/l.

The report highlights deterioration in water quality even in the stretch between Palla and Wazirabad, traditionally considered relatively cleaner. Twenty-two drains in Delhi meet the Yamuna between Wazirabad and Okhla, severely affecting water quality downstream.