Triple bonanza

Faecal sludge management is not only cost-effective but also generates livelihood opportunities. Some technologies do not even require electricity

: The technology uses larvae of a benign fly species, Hermetia illucens, to feed on the faecal matter. As the larvae grow and proliferate, they drastically reduce the volume of the waste within a couple of days and convert the dangerous pit material into a potentially useful soil conditioner or fertiliser. Once the larvae attain the prepupae stage, they can be harvested, processed to remove any possible pathogens and sold as animal feed. Because of high fat and protein content, there is an increasing demand for these animal feed.

The technology is gaining ground in South Africa's Ethekwini municipality. The country, which launched a sanitation programme similar to Swachh Bharat Mission in the 1990s, is innovating ways to dispose of the huge loads of faecal sludge and septage.

At a faecal sludge treatment plant, sludge is dried naturally in a sealed shallow pond with several layers of fliters and with evaporation facility. While this simple method can produce soil conditioners, one can plant wetland plants on the bed for efficient drying-up. It has an added advantage: the filters do not need to be desludged after each drying cycle. Fresh sludge can be directly applied onto the previous layer as the plants and their root systems maintain the porosity of the filter. Compared to unplanted drying beds, planted drying beds (also called humification beds), require desludging only once every five to 10 years and the removed sludge is a nutrient-rich soil conditioner.

While Ghana has experimented with unplanted drying bed, planted drying bed is popular in Bangkok.