The Buriganga has been Dhaka’s lifeline for more than a thousand years, as a source of livelihood and a means of transportation for its residents. But in return, people have repaid the old river with incessant pollution, robbing it of it’s own life.
As Dhaka expanded and its population increased by leaps and bounds, aquatic species in other rivers around the capital – Turag, Shitalakkhya, Balu and Bangshi – have declined in great numbers because of severe pollution.
None of these rivers today contain the minimum level of dissolved oxygen (DO) required for life forms to survive.
The Department of Environment (DoE) conducted a three-month study between January and March this year, on the levels of DO in these rivers. The study’s findings are alarming.
The chemical analysis of various samples collected from these rivers show that in January, the levels of DO in Buriganga, Turag and Bangshi were 0.38, 0.59 and 0.0 milligram per litre respectively.
According to the Environment Protection Act (Amendment) 2010, the minimum required level DO for any water body to sustain aquatic species including fishes and others is 5 mg/l. The standard is minimum 6 mg/l for water being eligible for treatment as drinking water.
Environmentalist Dr Ahsan Uddin Ahmed says such a meagre amount of DO in water poses severe threats to biodiversity and hydro-ecology.
The figures remained almost the same over the following two months.
Experts say both the people and government neglect are to be blamed for the severe degradation.
Professor Mujibur Rahman of Bangladesh University of Engineering and Technology (Buet) said an indiscriminate dumping of industrial and human waste has put the rivers in and around the capital in a coma.
He also said the government should shift the tannery industry from the capital’s Hazaribagh area as soon as possible. The chemical waste from the tanneries is a major polluter of these rivers.
The DoE study found that the level of DO at the Hazaribagh point of Buriganga was 1.06, 0.50 and 1.0 mg/l in January, February and March respectively.
In addition, the Bio-Chemical Oxygen Demand (BOD) is also very high in these waters.
BOD is the amount of dissolved oxygen needed by aerobic biological organisms in a body to work. It is an indication of the organic quality of water, which determines whether the water is treatable or not. The lower the BOD, the healthier the water.
The DoE standard for river water BOD is not more than 2mg/l.
According to Dhaka Water Supply and Sewage Authority (Wasa), around 22% of Dhaka’s total demand for water is met by treating the water in these rivers.
In January 2013, the lowest BOD of 3 mg/l was found at the Pagla and Kamrangirchar points of Buriganga. At the Tongi Bridge point of river Turag, the amount was a staggering 65 mg/l.
Bangladesh Poribesh Andolon (Bapa) Joint Secretary Iqbal Habib said the situation would only worsen if the government failed to compel industry owners to set up effluent treatment plants (ETP) in their factories. Most factories in Dhaka release untreated liquid wastes into these rivers, he pointed out.
The government owned factories are also responsible because none of them have ETPs either, Habib added.
He claimed that most of the factories in the state-owned Export Processing Zone at Savar, near Dhaka, do not have ETPs and their wastes have badly damaged the biodiversity of the Bangshi River nearby.
Due to excessive BOD in the Buriganga, authorities at the capital’s Sayedabad Water Treatment Plant have been forced to increase their use of chlorine everyday, Iqbal said.
Nearly a decade ago, the government declared Buriganga, Turag, Shitalaksha and Balu as Ecological Critical Areas (ECA) under the ECA Act 1999.
The Environment Protection Act obliges the government to take immediate action and conserve an area declared as an ECA.
Md Alamgir, Director (Enforcement) of the DoE, told the Dhaka Tribune that the department plans to launch a comprehensive enforcement drive and strictly implement the act by penalizing factories that are found in violation.