What happens inside a pour-flush pit? Insights from comprehensive characterization

The pour-flush toilet is extensively used in many countries, but the biodegradation within pour-flush leach pits has not been fully characterised. We present a comprehensive physical, chemical, and microbiological analysis of pour-flush active and standing leach pits in South Africa. Four household toilet sites were sampled four times over 11 months. The pour-flush pit filling rate was estimated to be 0.11m3/y, which is lower than those of other sanitation technologies. Faecal sludge in active leach pits had similar ash, VS, CODT and TKN as other onsite technologies, but higher moisture content. The CODT in pour-flush sludge decreased 85% in 27 days in a short-term laboratory test. Microbial DNA sequencing showed that both aerobic and anaerobic degradation occurred in active and standing pits. Specific microorganisms were identified and differences in microbial communities in active, standing, and single pits were described, providing important insights into processes occurring within pour-flush pits.