Dhaka's inadequate and age-old sewage management system is taking a huge toll on the environment as wastes often end up in rivers, severely polluting them.
A city of around 1.5 crore people, Dhaka generates approximately 20 lakh cubic metres of wastewater every day. Pagla sewage treatment plant, which is the city's only sewage treatment facility, has the capacity of treating 1.2 lakh cubic metres of waste per day.
However, only one-third of the plant's capacity can be utilised because of its decades-old pipelines that do not function properly.
Pagla treatment plant has around 530 kilometres of sewerage networks with 26 sewage lift stations that have been renovated in phases to keep up with the expansion of the city. Dhaka Water Supply and Sewerage Authority (WASA) officials said only around 20 percent area of the city has come under the sewerage network of Pagla plant in Narayanganj.
Waste management experts said around 70 percent of wastewater is one way or another being thrown into rivers, including Buriganga, Balu and Turag, resulting in environmental degradation.
Citing a 2014 World Bank survey, Dr Md Mujibur Rahman, professor of civil engineering at Bangladesh University of Engineering and Technology, told The Business Standard that wastewater of only two percent of the city's population is properly disposed of after treatment.
"Untreated wastewater produced by the remaining 98 percent of the population is going to wetlands and rivers, seriously polluting the environment," he said.
Domestically produced wastewater often carries human waste or faecal sludge. Experts said Bangladesh mainly follows two faecal sludge management methods. One is off-site method which consists of sewage pipe network with a central treatment plant and the other is on-site method. The on-site method involves setting up a septic tank with a building or constructing a soak pit.
Eighty percent of Dhaka city area has either septic tanks or soak pits. Building owners set up septic tanks or soak pits, and they are supposed to manage the sewage on their own.
However, many people connect septic tanks to storm drains in order to save cleaning costs. Thus, the faecal sludge is ending up in rivers through storm drains.
Abu Hasnat Md Maqsood Sinha, executive director of research organisation Waste Concern, told The Business Standard that 80 percent of fecal sludge is directly or indirectly going to rivers in and around the city.
"Even though 20 percent of the city people are connected to Pagla treatment plant's sewage network, half of that sewage cannot go to the plant for faulty pipelines.
"On average, one produces 1.5 kg excreta per day – 20 percent solid and 80 percent urine. If Dhaka has 1.5 crore people then the amount of human excreta generated every day stands at 22,500 tonnes.
"As part of proper waste management, first we need to stop cleaning septic tanks manually by cleaners. Cleaners often dump the faecal sludge from septic tanks in storm drains. Septic tanks need to be cleared by vacuum truck and the waste then needs to be treated properly," he explained.
"The second problem is that the correct design was not followed when most of the septic tanks were built. Many septic tanks are smaller than the required size and some were connected to storm drains in secret," he added.
Terming Dhaka's sewerage system totally dysfunctional, Professor Mujibur said the whole Dhaka city should be brought under sewerage network as soon as possible.
"If we fail to do that, we will definitely fail to fulfill one of the 16 sustainable development goals," he said.
He said sewerage system is the appropriate system for Dhaka because it is very difficult to construct septic tanks in such a densely populated city.
"As constructing a sewerage system is expensive, it is often not prioritised by the government. As a result, the sewerage system has not yet developed in the city," said Mujibur.
He said the Dhaka WASA authorities have begun working on sewage treatment plants after ignoring their importance for a long time.
"However, they are not expanding the sewage networks. If the government wants to bring the whole city under sanitation facilities rapidly, it will have to go for a combination of on-site and off-site methods.
"Initiatives taken by the Dhaka WASA are not adequate. Even though they formulated a masterplan for sewage disposal in 2014, nothing much has been done to implement it," added the expert.
Dhaka WASA's masterplan included constructing 11 sewage treatment plants in different areas, including Dasherkandi, Rayer Bazar, Mirpur and Uttara, along with pipelines and other relevant structures.
Construction of Dasherkandi treatment plant began in March 2017. It has a capacity of treating five lakh cubic metres of sewage daily. Located in Khilgaon, five kilometres from Rampura bridge, the plant will treat sewage produced in Niketon, Baridhara and West Badda areas.
Dhaka WASA Managing Director Taqsem A Khan told The Business Standard that 46 percent of construction had already been completed and the remaining work was expected to be finished by December this year.
"I believe we will be able to open the plant on time," said Taqsem.
He said he was not aware of dumping of faecal sludge in storm drains.
"Even if someone does it, it is not right," he said.
Taqsem said the whole city would be brought under sewerage network by 2030 as per the masterplan. "But it can happen much earlier in 2025."