Treatment of biosolids flushed from sewer systems: characterization of biosolids and the sand extracted and the handling of washing water

A research program on the characteristics of biosolids flushed from sewer systems in Toulouse (southwest France) and on the quality of sand extracted from these biosolids by hydrocycloning was carried out using samples from different sites. The treatment of washing water through air flotation was also studied. These initial results show the difficulty in establishing a strict typology for each family of flushed biosolids. On the other hand, the measurements done after hydrocycloning the biosolids clearly show that it is possible to imagine high performance treatment centers which would be able to provide a homogeneously treated product only slightly polluted, starting from very variable waste. Under certain operating conditions. The flotation of washing water thus perfectly completes the treatment of biosolids, and allows one to obtain the weakest possible volume of residue.