In Dhaka, only 20% of houses are connected to the sewerage system that flows to the lone Pagla Sewage Treatment Plant in Pagla (Southern part of Dhaka city), while the rest of the 80% of houses are dependent on septic tanks. But the illegal connection of septic tanks with the sewerage system is causing damage to us all.
Septic tank is a scientific solution, but a defective septic tank is dangerous. If a septic tank cannot discharge faecal sludge properly, it is of no use; rather it will harm us all. It requires a retention period of 48 hours for the sludge to settle.
Due to the increasing density of population and people not following city corporation's regulations and the dimensions of the Bangladesh National Building Code, the rate of generation and accumulation of faecal sludge is becoming faster than the rate of decomposition. So, the septic tank is getting filled earlier. If the faecal sludge is kept in the tank in an anaerobic condition, it takes 1.5 to 2 years to get properly decomposed and become safe for disposal.
Faulty design of septic tanks (having one compartment instead of 2-3) is a great problem. Besides, a scarce and inefficient sewerage system is illegally connected to the septic tanks, a fact unofficially known to all. The toxic elements in the faecal sludge are getting mixed with the storm drainage system and polluting surface water and drinking water, spreading many water-borne diseases and damaging the environment severely.
In and around Dhaka, there are more than 1200 hotspots where wastes are being dumped illegally into water bodies. Regulators, whistleblowers and watchdogs should remain vigilant against such activities.
If people followed and maintained the prescriptions of the building code, there would be fewer problems. Currently there is no surveillance over the direct connection of septic tanks with the sewerage system. The process of cutting off the connections should be gradual and step-wise, keeping alternate solutions at hand. People need to be prepared before getting disconnected. Otherwise, they might seriously pollute their surroundings.
Septic tanks' overflowing sludge is being emptied into drains. This practice is causing the same problem. What we need to do is to find an alternative solution. The accumulated faecal sludge must be periodically removed, which is commonly done with a vacuum truck. We have already adopted this system for several cities of Bangladesh including Kushtia city.
Besides, DPHE has completed several projects and we are proposing another project in the Pagla catchment area located at the southern part of Dhaka with DPHE, funded by the World Bank. Baffle Reactors with filtration system are proposed in these densely populated areas, which is an elongated version of the septic tanks. It contains many compartments, anaerobic filters and retention tanks for systematically treating the sludge and cleaning the water.
The septic tanks (with proper collection and treatment system) compared to central sewerage system are less expensive, is common in Asian cities like Bangkok and Manila. This decentralized system can be implemented in a congested area like old Dhaka and slum areas. In slums and congested older part of Dhaka city, there are little space for laying pipes for central sewerage system. The Decentralised, community-level wastewater treatment technology called the Decentralized Waste Water Treatment System (DEWATS) for clusters of households and communities can be a solution. A combination of solutions can be taken into account phase-wise for future Dhaka. One solution is not just enough.
We don't have a magic bullet at hand to shoot out the problem. Though the government and DPHE have taken many projects to mitigate the issue, it will take time. But what will happen in the interim? We must find alternative and decentralised solutions. We have to revise the existing defective designs of septic tanks at houses with introduction of proper maintenance.
You cannot cut your head if you have a bad headache. Decentralised approach and phase-wise solution are two key themes in addressing public service. Without giving an alternate solution, more sludge will amass and overflow even on to roads. Rivers will be filled up and the situation will get worse. You must have proper logistics with short, medium and long-term plans.
Ward, zone and community-based initiatives may work. Many private investors are waiting to invest in the sector. It can also be implemented through PPP. If the city corporations/government/ municipality settle on service fees, people will pay and take services. Human excrete or sludge is a resource; it can produce fertiliser and compost.
City corporations/municipalities/local governments have many roles to play in this regard. They can encourage private sectors to compete in managing the septic tanks and sewerage system with innovative ideas and implementation. There is a business angle associated with it.
We worked with the Department of Environment where private sectors are encouraged to properly collect, transport and treat these health care waste against a service fees; septic tanks and sewerage system problems can follow the same path. We call it DEWATS (Decentralised Wastewater Treatment System). This is one of the solutions. You can envision a 100% technologically sound, modern and smart city if you have that ability to afford it. Why not? But there is a big difference regarding the expenses.
Someone has to take the faecal sludge away. Otherwise, there will be odour pollution and serious environmental degradation. You can even make an effective online system to take the sludge away from houses. Private sector companies with vacuum trucks can take those away from home in exchange for online-based service payment. The initiation of these services will make the service more effective.
Pagla Sewage Treatment Plant in southern part of Dhaka is established in a 110.5 hector land with huge land which is not being used efficiently. Collected faecal sludge can be treated within this plant, the solid part faecal sludge can be converted into compost and wastewater can be treated.
Initially, you can get benefitted by punishing people, but in the end, everybody will be losers, if the decision to cut the connection is implemented. The alternative solution must be innovative and eco-friendly. You cannot punish the taxpayer citizens, without proper alternatives.
Rivers are dying, if you examine the water sample from the Buriganga, you will find the least level of oxygen and the worst type of pathogens there. To save rivers, environment and humans, you have to take up phase-wise, decentralised and innovative solutions to address the dire issue.
We cannot further treat water from the rivers circling Dhaka. In future, this city may require water to be collected from far away rivers for treatment. A major part of the groundwater is being extracted in Dhaka, which may cause land subsidence. We also have uncontrolled landfills which generate leachate water from the waste. If not properly managed, leachate water can pollute the underground water, it will be very costly and difficult to treat this water.
Both the mayors are struggling with thousands of problems of the city every day. Honestly speaking, the reality is that citizens also have the rights to get the best service and at the same time have responsibilities to overcome these problems. Mayors of this city need the right policy guidelines, technical know-how, manpower, resource and study to overcome this problem. Decisions should be taken sitting with experts, researchers, and communities, WASA, DPHE, DOE (Department of Environment) and other concerned stakeholders.
Abu Hasnat Md. Maqsood Sinha is Co-founder of Waste Concern