KÖKSAVFALLSKVARNAR FÖR UTSORTERING AV ORGANISKT HUSHÅLLSAVFALL FÖR RÖTNING OCH JORDBRUKSANVÄNDNING- AVSKILJNINGSSYSTEMET OCH RÖTNINGSPROCESSEN / Kitchen disposers for source-sorting of organic household waste for anaerobic digestion and agricultural reuse - the separation system and the anaerobic digestion process

In the newly built urban area Västra hamnen, in Malmö, Sweden, a new system for source-sorting of organic municipal waste, was constructed. The organic waste is disposed through a kitchen disposer, and is then led into a separate pipe, passes a cutting pump and is separated in a settling tank in the area. The material is then transported with a truck to Sjölunda wastewater treatment plant (WWTP) in Malmö, where it is pumped into one of the mesophilic anaerobic reactors. Supernatant is lead in pipes to the WWTP.

Investigations of the system have been done, to analyse the effects of the disposer and the pump, the function of the settling tank, the methane potential of the waste, and a probable inhibiting factor within the waste (dishwashing detergent). The anaerobic tests were carried out in 2-liters batch reactors, for 3-6 weeks.

The results showed that the dry matter content in the settling tank was 0.1 %, and that the material was very fine-grained. The methane-potential of the material was 550 Nml CH4 /gVSin. The anaerobic digestion was inhibited by rather low concentrations (1 g/1) of an ordinary dishwashing detergent. The main problem with the system is that the dry matter content in the settling tank is too low to be digested directly at the WWTP.