Thermophilic composting – a hygienization method of source-separated faecal toilet waste

Aims: To evaluate the sanitizing effect of thermophilic composting of faecal material from urine diverting toilets as a function of temperature and exposure-time. Methods and Results: A composting lab with reactors imitating centralized in-vessel composting systems was used. The elimination of indicator organisms was investigated at temperatures between 50 and 65C. Salmonella serotype Senftenberg 775W and thermotolerant coliforms were rapidly inactivated during less than one day at all tested temperatures. Enterococcus spp. showed a tail-shaped die-off and was not totally inactivated during the investigation. Salmonella serotype Typhimurium phage 28B showed an initial slower reduction at 50 and 55C. Phage 28B had the highest T90-values of the tested indicator organisms except at 50C, when comparing the rapid inactivation phases of the different test organisms. Conclusions: Aerated in-vessel composting at 55C for five days gives a satisfying hygienization of faecal material from urine-diverting toilets. Inactivation of phage 28B can be used as an indicator for inactivation of other similar thermoresistant microorganisms, inclusive viruses. Significance and Impact of Study: Analysis of inactivation of indigenous enterococci in combination with added Salmonella serotype Typhimurium phage 28B is an effective tool for evaluating the sanitizing effect when composting faecal material at thermophilic temperatures