Ahead of Chhath Puja, environmentalists blamed the Delhi government for "not taking adequate action" to make the Yamuna pollution free as toxic foam covered sections of the river near Kalindi Kunj on Thursday.

Chhath Puja, which involves the offering of 'arghya' to the Sun god by fasting women in knee-deep water, will be celebrated on October 30 and 31. Delhi Lieutenant Governor Vinai Kumar Saxena has given his nod to hold Chhath Puja at designated ghats on the Yamuna and urged Chief Minister Arvind Kejriwal to ensure clean ghats and water for devotees, sources in his office said on Wednesday.

Environmentalist Vimlendu Jha said lack of political intent, zero urgency in cleaning the Yamuna and minimal action on the ground were behind the frequent foaming of the river.

"Environmental governance doesn't seem to be a priority for the Delhi government. The unfortunate part is that there is a lack of political intent, zero urgency in cleaning the Yamuna and minimal action on the ground, leading to frequent foaming and frothing of the river," Jha told PTI.

He also cited lack of minimum flow in the river as a major reason behind the pollution every year.

"Delhi empties more than 3,500 million litres of municipal sewage in the river and, despite tall claims, over 50 per cent of the sewage is either untreated or not adequately treated, and flows directly into the Yamuna.

"Lack of minimum flow in the river is another major cause of the Yamuna's pollution," he said.

When asked about what actions the government had taken to remove the toxic foam, Delhi Environment Minister Gopal Rai said cleaning of the river had started.

Environmentalist Jha further said the Delhi government needed to treat every drip of sewage before emptying it into the river.

"Some of the critical tasks the government needs to undertake to keep the river clean and the citizens of Delhi safe are ensuring every drip of sewage is treated before emptying the drains into the river, adequate flow of water in the Yamuna and a comprehensive common effluent treatment plan and management," he said.

Bhavreen Kandhari, another environmentalist, alleged that toxic foam covered sections of the river every year due to negligence and absence of real action on the ground.

"On the Yamuna and Hindon edges, scores of farmhouses and industries are discharging pollutants into the river. There are about 92 drains that open directly into Yamuna, out of which 62 are untapped. Therefore, due to negligence and lack of real action on the ground, there is toxic foam in the Yamuna every year," Kandhari said.

Several citizens pointed out the violations but there are no officials on the ground to carry out a survey, she alleged.

"Many citizens are pointing out the violations in the form of complaints but why are the officials not on the ground to survey the situation? We can save the river only if the government has the true intent to work on the sources of pollution," she said.