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Worm toilet & flexigester; promising feacal sludge treatment methods

In the framework of Emergency Sanitation Project (ESP), WASTE is monitoring the sanitization effectiveness of two innovative methods to treat faecal sludge, the so-called ‘worm toilet’ and ‘flexigester’.

Both appear to be very promising.

In the framework of Emergency Sanitation Project (ESP), WASTE is monitoring the sanitization effectiveness of two innovative methods to treat faecal sludge, the so-called ‘worm toilet’ and ‘flexigester’.
The Flexigester, designed by SOWTech, is an aboveground anaerobic faecal sludge treatment system. The main processes involved in the Flexigester system are stabilisation and gas production through anaerobic digestion and sanitisation through pasteurisation utilising solar thermal heating. The system also provides gas storage for the produced methane gas as well as a digested sludge evaporation unit. A key advantage of the Flexigester system is that no electricity of external power is required for the system to operate.
Onsite system, the flexigester was installed adjacent to the toilet block and opposite the kitchen, where the produced biogas is used for cooking. In order to assess the functionality of the treatment system a weekly sampling is taken at three points: Input, digested sludge output tank and pasteurisation output. In the following months WASTE will be publishing the results and recommendations to optimize this potential treatment system.


On the other hand, in order to assess the feasibility of using a worm-based system to treat faecal sludge on a large scale and in a humanitarian setting, WASTE is monitoring a pilot-scale system installed in Blantyre, Malawi. The worm toilet utilizes worms to digest the faecal matter and produce vermin-compost suitable for agriculture. A key advantage of this system is reduced pit volume. Like in the case of flexigester, in the coming months WASTE is going to publish the results focusing on sanitization & stabilization effectiveness and nutrients concentration in the final product.