Towards a rational design to sanitation systems in developing countries

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Global sanitation infrastructure remains extremely poor. This contributes to the situation in which four-in-ten people live surrounded by human excrement. Many of the technical challenges in on-site sanitation are thought to result from a lack of adequate design guidelines based on sound science and engineering. One of the most pressing problems in peri-urban communities is that of rapidly-filling pit-latrines. Poor residents many times do not have resources to safely empty their pits, resulting in open defecation. Evidence indicates that the filling rate of pits may be affected by inhibitive effects of ammonia (present in human waste) and a lack of engineered conditions favouring biomass conversion. The overall objective is to better understand sludge accumulation and degradation processes in pit latrines, leading to a rationale design of sanitation systems for the poor. Within this theme, the specific objectives of the proposed project are to (1) characterise ammonia inhibition of methanogenisis in pit-latrines; (2) evaluate benefits of urine diversion and raised pit-latrine temperatures to accelerate anaerobic digestion within pits; and (3) explore promising pit waste treatment technologies/methods that could benefit from the further understanding of pit-latrine processes to protect human health and the environment. Once pit-latrines move from being poorly-conceived "holes in the ground" that only capture and store human waste to engineered "reactors" that can treat faecal sludge, their health benefits can be bolstered through an extended service life.