The faecal pollution levels in the Yamuna River, indicative of untreated sewage and significant contamination, reached a record high in September. This came despite some improvement in dissolved oxygen (DO) and biochemical oxygen demand (BOD) levels, attributed to the heavy rainfall in August. However, the rain had little effect on the faecal coliform levels, which soared to 4,900,000 MPN (most probable number)/100 ml.
This figure is 1,959 times the standard of 2,500 units and nearly 9,800 times the desired limit of 500 units. It represents the worst faecal contamination since February 2022, when the level reached 6,300,000 units at the Agra Canal, a key monitoring site on the river.
The Delhi Pollution Control Committee (DPCC) measured the river’s faecal contamination in September, releasing its report last week, based on samples collected earlier that month. The report emerged amid growing concerns over pollution, with certain stretches of the river visibly frothing due to pollutants like surfactants and phosphates, which the DPCC did not specifically test.
Effect of monsoon rains
Although the monsoon season provided some relief by boosting the river’s flow, the increase in dissolved oxygen — a sign of potential life in the river — was limited. BOD and DO are critical indicators, with standards set at no more than 5 mg/l for BOD and no less than 5 mg/l for DO, thresholds crucial for outdoor bathing. While BOD reflects water’s ability to clean itself by consuming oxygen to break down organic matter, faecal coliform signals the presence of untreated sewage.
The DPCC report noted that at Palla, where the river enters the city, the DO was 8 mg/l, BOD was 3 mg/l, and faecal coliform was 1,600 units — within acceptable limits. However, as the river flowed downstream, pollution levels rose. By the time it reached Wazirabad, although DO and faecal coliform remained within standards, BOD exceeded the limit.
At the ISBT bridge, both BOD and faecal coliform breached permissible levels, and by the time the river reached the ITO bridge, all three indicators — DO, BOD, and faecal coliform — were out of range. At ITO, faecal coliform hit 240,000 units, BOD reached 23 units, and DO dropped to 4.1 units.
Rise in faecal coliform
The situation worsened downstream, with faecal coliform spiking to 1,100,000 units at Nizamuddin, 3,500,000 units at Okhla, 1,100,000 units at Agra Canal, and 4,900,000 units at the city’s exit near the confluence of the Shahdara and Tughlakabad drains. Despite these figures, the river still maintained some dissolved oxygen levels past the ISBT bridge, unlike the previous month when they had hit zero.
In August, the highest recorded faecal coliform level was 920,000 units, a sharp rise from July’s 160,000 units. Around 56 per cent of Delhi’s STPs failed to meet water quality standards in August, consistent with the failures in July and June. These plants were unable to meet standards for total suspended solids (TSS), BOD, chemical oxygen demand (COD), and faecal coliform, with treated sewage from STPs often entering the Yamuna or being used for horticulture purposes.
[With agency inputs]
First Published: Oct 08 2024 | 2:27 PM IST
