The Effectiveness and Safety of Vermi- Versus Conventional Composting of Human Feces with Ascaris suum Ova as Model Helminthic Parasites

Composting toilets have been promoted for management of human waste at remote sites in parks and alpine areas of recreation, but they may not be effective for producing a stable and safe end product. Vermicomposting has been shown to result in a more degraded final product but its effectiveness for pathogen destruction was unclear due to conflicting information in the literature. This study sought to resolve the debate on whether or not vermicomposting could produce a hygenic end product that would be safe for disposal locally. Vermicomposting was tested for destruction of the model pathogens, helminthic parasites, in an experiment with highly concentrated and viable Ascaris suum (2626±1306 ova/g, 61.6±8.7% viable) inoculated into fecal matter and coir (30:70 ratio) with and without Eisenia fetida worms. After 90 days at 19±3 oC six, eight, and 12 worms were found alive with no significant difference between treatments or through time found in TS% (12-15%), ova concentration and ova viability. A 100 times reduction in the concentration of Escherichia coli resulted from the worm treatment versus the control. Significantly higher nitrate (22 735±4 741 mg/kg NO3-) and lower pH (pH 4.60±0.01) were found in the treatment as compared to the control (5 078±2 167 mg/kg NO3-) (pH 6.56±0.30). Despite these improvements in fecal matter processing, vermicomposting was found ineffective at reducing Ascaris suum ova concentration and viability. Decentralized vermicomposting can efficiently stabilize and mature fecal matter; however prior to unrestricted end product use, an additional sanitation step is necessary.