What the fear of pollution could not do, the pandemic has done in Calcutta.

A Durga idol was immersed in the pandal following the most environment-friendly “wash and melt” model and in the process spared the Hooghly of pollution.

This year, Tridhara in south Calcutta club followed the “wash and melt” model. All the idols were washed and melted by spraying water from multiple water jets after positioning them within a makeshift 400sq ft water body adjacent to the pandal.

Once the immersion of an idol got over — the outer clay and colour got washed off and the inner frame became partially visible — the same water, about 25,000 litres, was recycled to wash and melt the next idol.

Once the process was completed for all the idols, the frames were taken to the Dhapa dumping ground just like the other idols immersed in the Hooghly are carried there after being taken out of the water.

The “immersion” at Tridhara took close to 2 hours.

“We have various restrictions because of the pandemic and risks associated with the conventional immersion in the Hooghly; so, we decided to follow this unique method,” Debasish Kumar of Tridhara, who is in charge of the Calcutta Municipal Corporation’s immersion proceedings, said. “We could cut down on cost as well as manpower in this process.”

He said the club had followed the practice of clubs in Naihati. It is up to the other clubs in the city to decide if idols will be immersed this way, he said.

The Telegraph had earlier reported about clubs in Naihati and adjacent Bhatpara, where Kali Puja is the bigger festival, going for such immersions. Water jets are used to melt idols there after a “darpan visarjan”, in which water from the Ganga is symbolically poured over the reflection of the goddess in a mirror.

“Once darpan bisarjan is completed, the immersion is formally complete,” former Sanskrit College teacher Himangsu Pandit, who heads the team that publishes the almanac Bisudhha Siddhanta Panjika, told The Telegraph.

Both the regulators and activists hailed the Tridhara move.

“It’s a good environment-friendly initiative and we will be happy to support it if the Calcutta Municipal Corporation wants to expand the model in future,” Kalyan Rudra, chairman of the West Bengal Pollution Control Board, said on Monday.

“A new and extremely worthwhile initiative,” environment activist Subhas Datta said. “Immersion pollutes our rivers and water bodies.”

Immersion directives have been passed earlier based on Datta’s petition in court.

Various studies have shown that the level of pollution, particularly that of highly toxic heavy metals, increases significantly because of the immersion of thousands of idols in the Hooghly.

The National Mission for Clean Ganga, a central government agency, and the National Green Tribunal have been pushing for immersions to be stopped on open stretches of the river since 2018.

“We have set up dedicated and barricaded portions in water bodies in Lake Town, Debi Ghat and Dumdum Tank No. 2, following the National Mission for Clean Ganga guidelines, to ensure environment-friendly immersion,” pollution board chairman Rudra said. “The base of water bodies has been lined with synthetic cover so to arrest the diffused pollutants. If the model works, we will think of expanding it in future.”

The Tridhara or the pollution board’s initiatives are standalone ventures, environment activist Krishnajyoti Goswami said. “Unless these become the rule rather than an exception, we will not be able to save the Ganga.”