India, Nov. 12 -- Ammonia levels in the Yamuna at Wazirabad have climbed to 1.5-2 parts per million (ppm), above the 0.9 ppm threshold beyond which Delhi's water supply operations begin to be affected.

The spike has once again exposed the vulnerability of the capital's drinking water supply to pollution entering the river upstream, even as the water body continues to deteriorate dramatically after entering the city.

Ammonia is a nitrogen-based compound that enters water bodies primarily through untreated sewage, industrial effluents and agricultural runoff. High concentrations indicate pollutants and make the water more difficult to treat for drinking.

Delhi Jal Board (DJB) officials say the treatment plants can handle ammoniacal nitro...