Combined Sewer CWIS approach in Manila
From the IWA Regulating CWIS project (thanks to Patrick Ty, MWSS RO Regulator) and from the World Bank CWIS Video it is interesting to see one of the solutions Manila has been piloting to address the challenge of septic tank effluent in high-density urban areas as well as grey water disposal to surface water drains.
The approach is to focus mainly on developing combined sewer systems that intercept wastewater discharged to surface drainage systems and treat it to an acceptable standard before it reaches the receiving waters.
Patrick Ty explaining that “The infrastructure is more cost-effective and technically feasible, and it allows for faster pollution reduction than a separate sewer system would, because it treats wastewater from the city’s drainage system. It also removes that additional cost to the consumer, because the effluent overflow from the septic tanks is caught in the drainage system, so consumers don’t need to connect anymore to a particular line. They don’t have to do anything beyond connecting their overflow to the drainage system, and most have done that already. With sewerage connections, there has been the issue of destroying or digging a hole in your property if you want to have it connected. These are the things that we avoided by using a combined water system, combined sewerage system. It is basically removing that additional cost to the consumer."
Hopefully more of this interview will become available when the IWA Regulating CWIS Case Studies are published. The image below is the author's IWA version of what can be seen in the World Bank CWIS video.