The North 24-Parganas district administration on Tuesday morning started the cleansing of the Ichhamati river following the pollution of water during immersion of idols on Dashami.

The authorities of Basirhat and Taki municipalities launched the cleaning drive with workers fishing out wooden structures of the idols and other puja materials. Municipal authorities have said the paint on the idols leads to chemical pollution of the river and it affects fish and other aquatic lives. The cleaning was undertaken immediately after the immersion to reduce adverse impact on the aquatic lives, an official said.

“Since we were not in a position to stop immersions in the Ichhamati, which is the lifeline of the area, we decided to remove the waste as fast as possible. The crowd was less compared to other years because of restrictions imposed by Calcutta High Court. This helped us begin cleaning the river from the early hours of Tuesday,” said Basirhat municipality chairman Tapan Sarkar.

Nature activists have welcomed the alacrity shown by the administration, but at the same time demanded a complete ban on immersion in the river in compliance with the directives issued by the Centre last year that disallowed immersions in the Ganga and its tributaries.

They demanded setting up temporary water tanks at designated locations for immersion of idols and discourage immersion in the river in the name of tradition.

Since Monday afternoon, most of the 1,096 community puja committees in the Basirhat subdivision immersed idols in the Ichhamati. In Taki, till Monday evening, 75 idols were immersed under the supervision of the BSF and police.

Attempts were made to clean the Ichhamati in Hansnabad, Hingalganj, Swarupnagar, Baduria, Haroa and Nazat also. “We remove waste every year, but we began the job early this year so that people also become aware of the problem,” Sarkar added.

The idols are usually made using clay and plaster of Paris. The chemical contents of the paints are toxic and pollutes water when it dissolves in the river. “Plaster of Paris contains calcium sulfate hemihydrate that takes a long time to dissolve in the river water,” said Tanmay Sanyal, an expert in limnology and fisheries who teaches at the Krishnagar Government College.

“At the same time, it reduces dissolved oxygen (DO) level in the water, causing harm to fish and other aquatic lives. The paints also contain various carcinogenic heavy metals like chromium, cobalt, lead among others that directly affects the quality of water.

“Even researches indicate that flower which is a bio-degradable cause pollution because chemical fertilisers and pesticides are used to grow them. Such metals and chemicals change the chemical parameters of water affecting the bio-diversity creating food crisis for fish,” Sanyal said.

President of Paschim Banga Vigyan Mancha's Basirhat zonal committee Ranjit Mukherjee said: “It is a welcome move but much cannot be achieved until the administration bans immersion in the river and makes an alternative arrangement for the purpose.”