New Delhi: The Yamuna experienced its highest pollution levels this Nov since Dec 2020. While this continued a pattern seen in previous Novembers, the faecal pollution, which worsened throughout the year, was the highest in four years.
The monthly analysis by Delhi Pollution Control Committee (DPCC) revealed that faecal coliform or E. coli count reached 79,00,000 MPN/100ml (most probable number per 100ml), compared to 3,20,000 in 2023 and 6,80,000 in 2021. Although the peak faecal levels in Oct matched Nov’s, biochemical oxygen demand (BOD) deteriorated in Nov, indicating increased pollution compared to Oct. The faecal coliform level reached 1,20,00,00,000 MPN/100ml in Dec 2020.
For the river water to be considered healthy, faecal levels, which indicate the presence of untreated sewage and excreta, should not exceed 2,500 units, with an ideal limit of 500 units.
Since Sept, several stretches of the river experienced heavy frothing, a visible proof of pollution when mixed pollutants like surfactants and phosphates are churned. Other parameters like dissolved oxygen (DO) and BOD levels were also not any better. While DO depicts the presence of life in a waterbody, BOD, the amount of oxygen required for water to treat organic matter in it, indicates the capacity of water to clean itself.
According to the DPCC report, during the river’s entry into the city at Palla, the DO level was 6.1mg/l, BOD was 3mg/l, and the faecal level was 1,100 units—all within the standards. However, by the time the Yamuna reached the ISBT bridge, the contamination spiked with DO becoming nil, BOD a whopping 47 units, and the faecal levels 490,000 units. As the river traversed further, the pollution load increased. As per standards, BOD must not exceed 5mg/l, and DO must not go below 5mg/l, which is standard for outdoor bathing.
Earlier this year, due to the surplus monsoon that retreated only by Oct 2, the Yamuna had a good flow with additional water from the upstream. However, while the surplus water improved the status of DO, other pollutants spiked.
“Unless there is 100% sewage treatment in Delhi, the Yamuna will remain polluted. The majority of pollution in the river comes from Delhi due to its many drains where sewage is not treated completely. So obviously, the untreated sewage would contaminate the river,” said SK Sarkar, distinguished fellow at TERI and former secretary of Union water resources ministry.
“Although Delhi Jal Board (DJB) does treat sewage, a lot of it goes untreated. Ideally, contamination must be treated at the source. The river originates very clean and remains so to a great extent until Hathni Kund because not much untreated waste goes into it. There is a need for more rigorous monitoring of pollution in the river, and it must be broadly publicised. 100% treatment is a must,” he added.
According to a DJB submission to National Green Tribunal in Nov, Delhi’s estimated sewage generation is 792 million gallons per day (MGD), of which around 650MGD is treated while the installed capacity is 712. However, out of the 38 active monitoring stations, many don’t meet the standards. DJB stated that most of its STPs would be ready to treat the entire sewage up to the standard by March 2026.