A survey of Jharkhand State Pollution Control Board (JSPCB) conducted by its Afityapur-based regional office on river health before and after Durga Puja immersion this year revealed slight changes in two twin lifeline rivets – Subarnarekha and Kharkai.

The survey report reflected before-and-after changes in dissolved oxygen (DO) level, biological oxygen demand (BOD), chemical oxygen demand (COD), pH scale, total dissolved solids (TDS) and turbidity.

The findings revealed low depletion of dissolved oxygen (DO) after immersions owing to toxins and chemical dyes. Tests showed water at both rivers had over 5 mg/litre of DO two days before immersion, and 4.5 mg /litre post immersion.

The pollution control board had identified eight spots in Subarnarekha and Kharkai from where water samples were collected before and after immersions. The immersion of idols took place on October 26.

However, tests concentrated at two places, Subarnarekha ghat at Sakchi near Jai Prakash Narayan Setu and Kharkai ghat under Adityapur bridge.

Subarnarekha ghat saw around 80 immersions this year, much less as compared to last year's 150. This is because of the ongoing pandemic.

The Kharkai ghat saw less than 50 immersions as compared to last year's 80.

Last year, a similar survey had found 6.5mg/litre of DO before immersion and 5mg/litre afterwards.

The BOD at Kharkai ghat increased from 5 mg/litre to 6 mg/litre and COD from 14mg/litre to 20mg/litre.

At Subarnarekha ghat, both BOD and COD levels witnessed a slight rise post-immersion. The BOD levels, which were around 6mg/litre before immersion, increased to 6.9mg/litre. Again, the COD count, which was 11.5mg/litre before, went up to 14mg/litre after immersion.

The TDS level in the sample from river Kharkai was around 190mg/litre but it rose to 198mg/litre post-immersion.

The Subarnarekha sample, likewise, showed 200/litre before immersions and around 210mg/litre afterward.

The concentration of heavy metals like copper and zinc at Subarnarekha and Kharkai saw a marginal rise, the findings revealed.

Samples from both rivers reflected slight alkalinity and a small increase in turbidity after immersions.

A JSPCB official who was part of the survey team said, “This year was different. Because of the pandemic and the government guidelines, the size of idols was reduced to 4-5 ft. The immersion count in bigger ghats had reduced. Moreover, artisans who made idols also avoided toxic paints, which increase various parameters beyond prescribed limits and thus causing water pollution.”

He went on to say that last year rain has been a savior. “Last year continuous rain after immersions helped in washing away a bulk of pollutants and recharging water at both rivers,” said the state pollution control board official.