What is the situation of wastewater treatment and disposal in Sri Lanka, and what is the non-sewered sanitation system? What are the challenges related to it, and what is the current state of treatment plants in the country? What actions are recommended to improve the fecal sludge management situation in the country?
Sri Lanka faces mounting pressure on its wastewater management system due to aging infrastructure and growing urban populations. Less than 3% of the rural and about 12% of the urban population in Sri Lanka discharge their wastewater from toilets into sewers. In Colombo, over 100,000 cubic meters of untreated sewage are discharged into the ocean every day due to the limitations of the sewer network. High costs and a lack of suitable land have stalled the expansion of sewer networks, and treatment systems are limited in the country.
To address this, non-sewered sanitation (NSS) or ‘on-site’ sanitation (OSS) has been adopted, in which 95% of households contain their toilet waste near its origin in below-ground storage tanks. This system is suitable for low- and mid-income countries, as it doesn’t require large amounts of water or extensive piped infrastructure. However, the main disadvantage of OSS is that if not maintained properly, it can cause harm to public health and the environment.
When the tanks are full, the sludge is emptied by special collection services (‘gully-bowsers’) that suck it out of the tanks. However, there are challenges related to the lack of knowledge of when the tank is getting full, and there are not enough treatment plants in close vicinity to communities. There are only 20+ fecal sludge treatment plants in the country, and many are too far away for the gully-browsers to use, resulting in illegal sludge dumping, which leads to environmental pollution.
Most of the treatment plants operating in Sri Lanka are functioning, and resources such as nutrients and organic matter are recovered and recycled as organic fertilizer. Liquid effluent is discharged after treatment into nearby wetlands, rivers, or drains. However, many treatment plants visited are under-dimensioned and overloaded, and others are too large, and only a fraction of their treatment capacities are utilized.
To improve fecal sludge management in Sri Lanka, a septic tank census should be conducted to advise households on appropriate emptying frequency, and estimates of the demand for fecal sludge collection and capacity to do so should be provided. It is also essential to identify septic tanks that do not work and that should be repaired or renewed, and to apply and enforce industrial standards for septic tanks. Fecal sludge treatment plants should be implemented, rehabilitated, and renewed according to the data from the septic tank census. Finally, qualified public or private service providers should be contracted on a long-term basis to make fecal sludge management services more sustainable.