Heavy metals make surface water poisonous
World Water Day today
FAISAL MAHMUD
With the groundwater table depleting because of excessive water withdrawal, the Water Authority has long been planning to increase its usage of surface water and supply the same to the households of Dhaka. While tanneries and other industries recklessly discharge harmful heavy metals including chromium, lead, cadmium and mercury in the rivers surrounding Dhaka, none of the existing water treatment plants are equipped to neutralize these heavy metals.
The presence of those heavy metals in the water may cause serious kidney, liver, lung, stomach diseases and even cancer among consumers, fear experts. Sources from the Dhaka Water Supply Authority (Wasa) said the water authority does not test any parameters of heavy metals that are harmful to human health as per provisions for treating the heavy metals were not put in the surface water treatment plants (SWTP) during the first phase of the plants installation in the early 90s.
The intake point of the existing SWTPs are located in the middle of the highly polluted river, whose shore are dotted with several industries without effluent treatment plants (ETP), discharging toxic elements including heavy metals in the river.
The intake point of the Saidabad SWTP is located at Sharulia, Demra and 500 meters upstream, the Balu River falls into Shitalkkhya River. During the dry season, as the water level falls, the conventional SWTP could barely treat the water with the ongoing pollution in both rivers, Wasa sources said.
The Saidabad SWTP supplies 22.5 million litres of treated water each day to the capitals north-south pipeline that runs from Postogola Bridge to Farm Gate, and to the east-west pipeline which supplies water to the vast area from Goran through Old Dhaka to Dhanmondi. The sources also said that the intake point of the Chandnighat SWTP is located near the Central Jail and that particular plant uses pitch black, highly polluted and untreatable water from the virtually dead Buriganga River.
The Chandnighat plant supplies 3.9 million litres of treated water mainly in localities including Armanitola, Lalbagh, Hazaribagh and surrounding areas.
Talking to The Independent, an official with the Wasa said the water authority could check only a few parameters such as Ph, Turbidity, Free Chlorine, Conductivity, TDS, Dissolved Oxygen, Faecal Coliform and Ammonia in its SWTPs. But for treating heavy metals in the surface water, the official said, the traditional SWTP needs to upgrade the system. Admitting the presence of heavy metal in the treated water, the Wasa official said the government still doesnt take any steps to dislocate the industries without ETP from the shores.
Taqsim A Khan, Managing Director of Dhaka Wasa, informed of the presence of a heavy metal detector in the Siadabad SWTP, used to test the water for heavy metals every 15 days. Our water treatment plant treats the water and the level of heavy metal is still in an expected range, he said, adding that Wasa wouldnt have supplied the water if it found excessive amounts of heavy metal in the water. He feared that if an attempt isnt made to stop discharge of heavy metal pollutants from industries, then the water would not be treatable in the near future. Meanwhile, a study of the Water Resource Engineering Department of BUET said the dumped effluents by industries located on the shores of river Buriganga, Balu and Shitalakkhya deplete the oxygen in the water bodies to a point when no living creature may survive in the water.
