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Kotte waters’ dirty secrets: Study reveals shocking levels of contamination
At least six tons of bio solids and 18,000 cubic metres of untreated or partially treated wastewater are discharged continuously into the ground every day in the Sri Jayawardenepura Kotte area, an environmental impact assessment (EIA) has revealed.
Sanitation facilities in the region are mainly on-site in the form of septic tanks combined with soakage pits or pit latrines. It is through these that the bio solids enter the ground. But the EIA survey team also observed that in certain low-income premises at Obeyeskerepura in Rajagiriya, black water from toilet pits were released into water sources.
Most areas are low-lying with a high groundwater table. The onsite systems, therefore, no longer work well. Available building plots are small in size and the existence of shallow wells in nearby lands makes it difficult to build proper septic tanks with soil absorption systems.
With rains, the groundwater table rises. And as the soil is not permeable enough, wastewater from poorly functioning septic tanks and soakage pits enter roadside drains and adjacent surface water courses. This contaminates both ground and surface water bodies, including the Diyawanna Oya.
Grey water from kitchens and bathrooms also enters roadside drains. It contains soap, shampoo, shower gel, spices, house cleaning liquids, and vehicle and floor cleaning chemicals.
The EIA on the ‘Sri Jayawardenepura Kotte Wastewater Collection, Treatment and Disposal Project’ is now open for public comment on the Central Environmental Authority (CEA) website. The initiative aims to provide a piped sewage system for safe collection, treatment and disposal of wastewater from homes, public and private institutions, businesses and industries. A treatment plant will be built in an abandoned five-acre paddy field at Heenatikumbura, Walpola.
The population density of Sri Jayawardenepura Kotte is 73 persons per hectare. But more than 100,000 people commute to the area daily to work in 235 public and private offices–raising this figure to 140 persons per hectare during daytime. This requires a near 100 percent increase in the existing wastewater disposal capacity. There are also 16 low-income settlements.
Wetland encroachment is common, causing prominent deterioration of surface and ground water quality. “Faecal contamination was highly present in all the studied wells which are used for washing and bathing,” the EIA says.
The Diyawanna Lake now gets untreated or partially treated wastewater from its catchment area which brings in a high quantity of organic matter and ammonium. The project, once completed, is expected to cause significant improvement in the quality of surface water bodies.
Sri Lanka sought Japan International Cooperation Agency (JICA) assistance to develop a strategic master plan for sewage. Completed in May 2017, it identified Sri Jayawardenepura Kotte as one of the most prioritised areas for such a project.
The areas to be covered are the administrative areas within Sri Jayawardenepura Kotte Divisional Secretariat Division (DSD), Battaramulla, Rajamalwatte and Thalangama areas of the Kaduwela DSD, Himbutana East Grama Niladhari Division (GND), Himbutana West GND, and a part of Udumulla South GND of the Kolonnawa DSD, and Udahamulla, Thalapathpitiya areas of the Maharagama DSD.
After preliminary treatment, the wastewater will receive biological treatment through naturally occurring bacteria. The sludge that is eventually produced will be dried, then composted or used in waste-to-energy plants.
If the prevailing situation continues, however, ground water quality in the 2,924 hectares will continue to degrade. This includes surface streams, the Diyawanna Oya and canals. There is also likely to be a stench from faulty onsite systems. Aquatic habitats, especially the Diyawanna Oya, will experience nutrient enrichment, algal blooms and fish kills as was once experienced in the Beira Lake.
While residents are largely supportive of the project, those around Heenatikumbura are worried. They fear the wastewater treatment plant might not be maintained to national and international standards and that, therefore, they will have an unpleasant living environment. They are afraid of having to experience gulley bowsers loaded with sewage coming frequently to their neighbourhood and of being exposed to health risks.
Several other reasons emerged during community consultations.
The EIA says, however, “Most of the the residents’ fears and anxieties are reversible and could be mitigated with increased awareness, design stage measures, implementation of comprehensive contingency plans, operational procedures, and plat management plans”.