According to a report by the environment department, the pollutant load in the Yamuna river has significantly increased over the previous five years, despite the Delhi government’s pledge to clean the river to bathing levels by 2025.
According to the survey, every area where water samples were taken for testing in the national capital had an increase in the annual average level of biological oxygen demand (BOD), with the exception of Palla.
BOD is a crucial factor in determining the quality of the water since it measures how much oxygen aerobic microorganisms need to break down organic matter in a water body . BOD concentrations of fewer than 3 mg/l are regarded as favourable.
There was no immediate reaction available from the environment department.
The Delhi Pollution Control Committee (DPCC) collects river water samples at Palla, where the Yamuna enters Delhi; Wazirabad, ISBT bridge, ITO bridge, Nizamuddin bridge, Agra Canal at Okhla Barrage, Okhla Barrage and Asgarpur.
The DPCC data showed while there has been no major change in the annual average BOD level at Palla over the last five years (from 2017 to 2022), it has increased from around 3 mg/l to around 9 mg/l at Wazirabad.
The BOD level has risen from around 30 mg/l to 50 mg/l at the ISBT bridge and from 22 mg/l to 55 mg/l at the ITO bridge during the period.
Similarly, the BOD level worsened from 23 mg/l to around 60 mg/l at Nizamuddin bridge, from 26 mg/l to 63 mg/l at Agra Canal at Okhla Barrage, from 26 mg/l to 69 mg/l at Okhla Barrage and from around 30 mg/l to 73 mg/l at Asgarpur, the data showed.
The Yamuna river can be considered fit for bathing if BOD is less than 3 milligram per litre and dissolved oxygen (DO) is greater than 5 milligram per litre.
Dissolved oxygen (DO) is the amount of oxygen available to living aquatic organisms. Aquatic life is put under stress if DO levels in the water drop below 5 mg/l.
Twenty-two drains carrying domestic wastewater and industrial effluent fall into the Yamuna between Wazirabad and Okhla. Though the 22-km stretch is less than two per cent of the river length, it accounts for about 80 per cent of the pollution in the river.
Though a minimum environmental flow is required to clean the river to bathing standards, treating all the domestic wastewater and industrial effluent and further cleaning it using in-situ techniques can help reduce pollutant load significantly, according to eminent environmentalist Manoj Mishra.
In-situ bioremediation techniques involve treatment at the site using aquatic plants or microbial remediation methods. Such systems take less time to become operational, are easy to operate, and require less energy as compared to conventional treatment technologies.
Some common in-situ treatment systems are microbial bioremediation, phytoremediation, constructed wetland system and root zone treatment. Adequate space and appropriate flow are general requirements for adoption of these technologies.
(Headline and initial paragraphs has been edited by CS team)