How spike in ammonia levels in Yamuna affected Delhi water supply?

Water supply was affected in parts of Delhi due to an “abnormal” increase in ammonia levels in raw water discharged into the Yamuna by Haryana

It is said that ammonia levels in the river, flowing into Delhi from Haryana, had reached nearly 3 parts per million (ppm) which is almost six times above the acceptable limit of 0.5ppm

The water shortage in parts of North-West, West, and South Delhi was caused after two water treatment plants had to be shut. The Sonia Vihar and Bhagirathi water treatment plants were adversely impacted due to the spike in the levels of ammonia (pollutants) in the water.

According to Indian Express, Delhi Jal Board has the capacity to treat 0.9 ppm of ammonia in the raw water at nine water treatment plants. If the concentration is higher than this, then raw water is either diluted with fresh water from the Upper Ganga Canal or from the Munak Canal

The report further states that The Upper Ganga canal closes every year in October-November for 15 days to a month for maintenance. This year it has been shut since October 15, but until Friday was providing about 100-150 MGD of water to the two plants

As the ammonia levels spiked on Thursday, the Sonia Vihar and Bhagirathi plants had to be shut until Yamuna water was diluted with Ganga water. They resumed functioning a few hours later with reduced treatment capacity.

Later, around 1 am on Saturday, the low amount of water being supplied through the Ganga canal was reduced further. The share of water being taken from the Yamuna was then increased at the two plants to meet the shortfall from Ganga. However, at this time there was another sudden spike in the ammonia levels, due to which, the two plants reduced their production capacity by 50% on Saturday morning.