Water quality of six major rivers flowing around Dhaka gets polluted, particularly in the dry season, to the extent that it cannot be treated for drinking, experts say.
However, the quality slightly improves during the monsoon, they observe.
None of the rivers was found to have “blue” category water suitable for drinking after disinfection as evident from the water quality analysis, said Prof Amir H Khan, chief scientist of Plasma Plus laboratory.
He was speaking at a seminar on “Pollution Profile of Major Rivers around Dhaka” organised jointly by Plasma Plus, a private scientific research laboratory, and Brotee, a non-government organisation, at Cirdap Auditorium in the capital yesterday.
On behalf of Dhaka Wasa, Plasma Plus conducted a study on the pollution profile of the six rivers -- the Buriganga, the Turag, the Balu, the Shitalakkhya, the Dhaleshwari and the Bangshi -- from April to December last year. The study was funded by the World Bank.
The deteriorating water quality of the Buriganga has been a major concern and that five more rivers around the capital are also in appalling state is worrying.
In the study, water quality of the rivers was classified into five groups -- blue, green, yellow, brown, and red. They represent what the water is suitable for -- drinking water supply, agriculture, fisheries, industrial use, and recreational purpose.
Prof Amir said most rivers they studied were of “yellow” category, meaning they are suitable only for recreation, pisciculture, and livestock. Besides, water belonging to “green” category, suitable for aquaculture, was rare.
Citing the findings of the study, he said water of the six rivers was contaminated with organic micro pollutants and non-degradable heavy metals, making it “undrinkable”.
Surface water is extremely precious, as the ground water is depleting consistently, Prof Amir said, adding, “So, we cannot afford the luxury of polluting it anymore.”
Presently, less than a quarter of Dhaka's daily demand for 25 million litres of water is met from surface water sources, he said.
But the Sayedabad Water Treatment Plant is in trouble since it has to treat water of the Shitalakkhya that has excessive ammonia, the professor said, adding that excessive use of nitrogen and phosphate fertiliser was polluting the surface water.
Organic contaminants, pesticides and heavy metals from industrial and domestic solid and liquid waste cannot be treated with traditional chlorination and disinfection processes, he said.
Prof Amir said dissolved oxygen level, an indicator of river health and aquatic life, goes below three parts per million (ppm) in the river water during the dry season, which should never happen as per US regulations.
“The sustainable development goals cannot be achieved without conserving water resources.”
Echoing Prof Amir, Alamgir Hossain, head of central laboratory of Dhaka Wasa, said the river water is hardly treatable.
Syeda Rizwana Hasan, chief executive of Bangladesh Environmental Lawyers Association (Bela), said “chronic failure of governance” could be seen as the reason for the destruction of water resources and the environment.
She alleged that saving the rivers was never a priority of the government.
Water Resources Minister Anisul Islam Mahmud said, “To me, this finding is new, and also alarming that the water of the rivers is not treatable.”
It is extremely vital to stop river pollution now, he noted.
The minister said a river must have an identifiable demarcation and the flow of quality water. Any structure encroaching on the rivers must be demolished, irrespective of who installed it, he added.
“The grabbers then will not dare to encroach on the rivers.”
Bangladesh Poribesh Andolon (Bapa) General Secretary MA Matin and former BARC executive chairman Zahurul Karim, among others, also spoke.