The project titled "Problem Analysis and Portfolio of Solutions" will be submitted to the environment ministry this month sources said.

DoE officials said the project would take about 20 years to complete at a cost of up to Tk 10 billion.

Rivers surrounding the city, including Buriganga, Shitalakhya, Turag and Balu, are severely affected by encroachment, waste dumping and other polluting agents. It is also becoming harder to meet the increasing demand for water.

"The proposal is designed not only to save these rivers but to deal with all water-related problems city dwellers are facing now and which will increase with the population growing," a DoE high official said.

The project proposal includes as many alternative solutions as possible, apart from technical analysis of the problems.

Assurance of adequate and safe drinking and cooking water took centre stage in the proposal that suggested a strategic shift from ground water to surface water supply and rainwater storing.

It also suggested moving the intake of 9,00,000-m3 water a day by Sayedabad water treatment plant from the Shitalakhya to Meghna.

Improving the quality of polluted water and introducing appropriate waste disposal methods in residences, markets, small businesses and factories also features in the proposal.

It suggested banning the use of phosphate-based detergents in laundry, as phosphate pollutes water, creating algae in it. The disposal of solvents and thinners and other liquid hazardous materials such as corrosive cleaners, pesticides, herbicides, petrol, other fuels, paint in the discharge water lines and drains should be banned, the proposal says.

It also recommended installation of grease traps on grey (polluted) water discharge lines and drains from kitchen sinks and bathrooms in homes and business centres with regular maintenance.

The proposal says at least 80 percent of the sewage produced by 10 million people in Dhaka goes to the river system untreated. Almost all of the 7,000 industries in Dhaka and its environs dispose of their waste directly to drainage ditches, canals and the rivers without treatment. Tanneries in Hazaribagh are creating a severe toxic hazard to river users.

Construction of secondary sewage treatment plants at Dhaka North West, Dhaka North East and Tongi is essential to tackle the situation, the proposal says.

It also recommended construction of primary sewage treatment plants for Narayanganj and Savar and eventually turn them into secondary treatment plants.

The proposal also suggested banning hanging and pit latrines and underscored proper installation and maintenance of dry composting toilets in public places.