Aged sewer system worsens Colombo’s wastage disposal issue

The Colombo sewer system is in serious need of a renovation;. pipe failures, leaks, and blockages are becoming increasingly common as the system ages and Colombo’s population continues growing. It is not unusual that the sewers get clogged to the point that water has nowhere to go but up onto the street.

The major reason for these shortcomings is the sewer’s age. Construction on the Colombo Municipal Council (CMC) area sewage system was started all the way back in 1906. The original system was supplemented by the construction of another sewer scheme in Dehiwala, the Mt. Lavinia Municipal council area, and the Kollonawa Urban Council area that was built between 1983 and 1987.

Fully aware that the system needs an upgrade, the Ministry of Local Councils and Provincial Government, using a 116 million dollar loan from the Asian Development Bank, has begun the Greater Colombo Wastewater Management Project, an extensive venture aimed at improving the condition of the city’s sewers.

“We are currently working on many projects, including using CCTV cameras to spot deficiencies in the existing pipes and fixing those, while also repairing the pump stations that make the wastewater flow through the system,”CMC Director of Drainage M. Saleem said. He did note, however, that some delays have been there in repairing the pipes.

Pump stations are used to both propel wastewater through conventional gravity sewers, as well as to propel the water to higher elevations when necessary. Without functioning pumps, sewage flow can cease.

While there have been troubles with the pipes and pump stations, another issue is the lack of coverage: only about 500,000 people in the Colombo area, and between 1.9-2.6 percent of Sri Lanka’s population overall, live on land with access to traditional sewers. The current project involves mostly rehabilitating the existing sewers, and there are only limited plans to expand the network within Colombo. The small coverage zone also increases flood risks in the city.

Because the population has limited access to sewers, many people do not have an easy, efficient, and safe method to dispose of their waste.

Many people in the Colombo suburbs use septic tanks, or underground containers in which sewage collects and decomposes, that must be emptied. Usually, a truck equipped with a special hose will extract the waste from the tanks, but without nearby wastewater treatment plants, the driver must figure out a way to dispose of the sewage.

Common problem

“After you call the truck service and they take the sludge out, many of the service providers, not only in Sri Lanka, have a common problem. Where to dump it? They do not have treatment plants. Around Colombo, they mostly dump the sludge into the sewers. They drive to sewer manholes, then they dump it there,” Theme Leader on water quality, health and environment at the International Water Management Institute (IWMI) Dr. Pay Drechsel said.

“This can cause problems because the sewer system is designed so that it needs a certain flow rate, and that’s why there needs to be water in there. If they dump in a lot of very dense fecal sludge, dense because the settled sludge often sits for years in household septic tanks, it can make it more difficult for the sewers to flow properly,” he continued.

Communities that cannot or do not dump their waste in manholes often dispose of it in convenient, if improper locations.

“Oftentimes shortcuts are taken, and the shortcuts are depositing the material in the next forest, landfill, or farm field. This is a significant environmental problem,” Drechsel noted.

Indeed, traces of fecal sludge, or liquids and solids pumped from septic tanks, are appearing in the Western Province’s water networks.

“We have a lot of direct disposal into waterways, and this material is getting into wetlands, canals, and rivers in Colombo’s suburbs, both north and south,” environmental engineer Dr. Missaka Hettiarachchi said, He added that rivers are not immune to the influx of bacteria, as improperly disposed waste easily makes its way into ground and surface water.

“Generally, the best option is to put the material in a solid waste dump,” he continued. This can be difficult, however, as landfills like these are somewhat rare in the Western Province.

While the sewage system’s difficulties, most notably its leaks, blockages, and lack of coverage, cause some degree of trouble, perhaps a bigger issue lies in the fact that Colombo does not treat the sewage that it produces.

Instead of processing the effluent, the city sends it into large pipes, known as outfalls, which then release the wastewater directly into the ocean.

“The untreated wastewater is channeled through two outfalls that each go about two kilometers out to sea. These are off the coast of Wellawatta and Modara, respectively,” Resource Recovery and Reuse Expert at IWMI Dr. Sudarshana Fernando.

Though this might seem surprising, this method of ejecting raw sewage is technically accepted within the international community.

“There is no issue with the outfalls. They are in line with environmental standards,” National Water Supply and Drainage Board former General Manager K.L.L. Premanath said.

Researcher on septage management and reuse at IWMI Nilanthi Jayathilake provided a slightly different interpretation of the proper environmental standards:

“Sea outfalls can be considered a proper disposal method provided that there is proper treatment before the wastewater is pumped into the sea.”

Several other experts expressed dismay about the state of Colombo’s sewage treatment, or lack thereof, and argued that untreated effluent is causing environmental problems along the coast and in the sea itself.

Sewage is generally treated through chemical, biological, and physical processes to remove harmful contaminants not only from human waste, but also from industrial activities. When raw sewage is pumped into the sea, it leads to several problems, such as the spread of bacteria, eutrophication, and in some instances, the release of heavy metal contaminants.

Sea Outfalls

One of the major risks that comes with pumping raw sewage into the sea is the proliferation of harmful bacteria like E. coli. Human waste often contains these usually harmless bacteria, but pathogenic strains can cause gastroenteritis and urinary tract infections as well as other severe ailments. Despite being two kilometers away from shore, E. coli bacteria could be carried back towards land.

“There is certainly the risk of high concentrations of E. coli in the water around the outfalls. The outfalls are far enough to be out of sight but not out of the zone of impact,” marine biologist and diver Nishan Perera said.

“Depending on the direction and strength of the currents, these bacteria could make their way back to shore, since they can exist in the water for a while,” he continued.

E. coli can adversely affect human health, usually causing diarrhea, and experts are concerned that high levels of E. coli could be present in tourist areas such as the Mt. Lavinia and Dehiwala beaches.

There are also concerns that the polluted water can have deleterious affects on marine life, as fish are liable to contract parasites in these environments, according to Perera.

Another issue is that of algal blooms and concomitant eutrophication, or the depletion of oxygen in a marine environment. Because human waste has large amounts of nutrients such as phosphorous and nitrates, it can cause algal blooms that block light from entering the sea and use up the water’s oxygen.

Eutrophication can lead to dead zones where not much marine life can survive, but Sri Lanka’s case is not so severe, as the ocean’s huge water volume dilutes the nutrients. However, sensitive corals are being negatively affected.

“The nutrient-rich environment, coupled with the overfishing of animals that eat algae, has allowed algal blooms to become more frequent. This, in turn, has negatively affected coral reefs,” Perera said.

“The reefs off the coast of Dehiwala and Mt. Lavinia are being degraded, which is also causing the biodiversity of the waters to decrease,” he continued.

Experts also expressed alarm about nutrients that can be used by humans escaping into the water.

“From an agricultural perspective, we see lots of valuable resources being wasted. Huge amounts of nutrients, including phosphorous, a finite resource, are being pumped out into the sea. Waste treatment can reclaim these nutrients and transform them into fertilisers,” Drechsel said.

Yet another problem is the high concentration of plastic in the ocean. While much of this can be blamed on garbage blowing into rivers, canals, and the ocean itself, there is plastic ejected through the outfalls.

Sewers collect all sorts of detritus, and, though there are screens in the system, a lot of plastic still gets through.

“I have dived at the outfall, and I saw lots of plastic bags and other inorganic rubbish. This worsens after it rains,” Perera said.

Despite these troubles, help does appear to be on the way. The CMC, as well as the Local Councils Ministry and the Provincial Government, have pledged to remedy the lack of sewage treatment plants in the Colombo area.

“We have funding from the ADB to build wastewater treatment plants in Modara and Wellawatta. After these are built, treated sewage will be expelled from the outfalls. They should be up and running within five years,” said Premanath.

As the sewers are rehabilitated and treatment plants are built in Colombo, the focus then shifts to sewage problems in the rest of the country.

Much of the government’s sewage policy focuses on the Colombo sewage system, but it serves under 3 percent of the population.

“Ninety seven percent of the island’s wastewater is handled in different ways. Unfortunately, this gets little policy attention,” said Drechsel.