As the introduction of dehydrating toilets progresses, the safety of handling and reuse of their biosolids remains a question. A new study [1] investigated the storage conditions of selected faecal indicators in four urine diverting dehydrating toilet units in Kathmandu Valley, Nepal. It examined presumptive Escherichia coli, total coliforms, enterococci and different fractions of Clostridium perfringens under field storage conditions, and investigated chemo-physical and chemical (carbon, nitrogen, phosphorous content) parameters.

No single factor of the studied chemo-physical and chemical parameters could be found to account for the reduction of the indicators in any of the toilets. By time series analysis of the investigated strata in the faecal heaps, the determined reduction rate showed increasing persistence characteristics for E. coli, coliforms and enterococci. No significant reduction was observed for the different fractions of C. perfringens determined for the non-pasteurised and pasteurised fraction at 60°C and 85°C. 72% of randomly selected and analysed samples were found to contain helminth eggs. The used 6 months storage time did not prove sufficient to reach appropriate safety levels for handling and reuse of the biosolids.

[1] Sherpa, A.M. ... [et al] . (2009). Use of faecal pollution indicators to estimate pathogen die off conditions in source separated faeces in Kathmandu Valley, Nepal. Journal of water and health ; vol. 07, no. 1 ; p. 97-107. doi:10.2166/wh.2009.149

Contact: Andreas H. Farnleitner, Institute of Chemical Engineering, Research Area Applied Biochemistry and Gene Technology, Vienna University of Technology, Austria, tel: +43-1-5880117251, a.farnleitner@aon.at

Tags: ecological sanitation, south asia, water-related diseases