Determination of pit latrine volume from an anaerobic digestion model: perceptive of nightsoil in tropical condition

Abstract

Using the anaerobic model, the pit-latrine (Accumulation system, AC) volume was studied under tropical conditions in Dar-es-Salaam, Tanzania. The obtained field data was used as input into the model. It was important to use a model since anaerobic digestion requires a lot of time before its completion while designers need design information for and people would like to get answers to complex systems urgently. Through the model it is possible to determine the COD fractions entering and leaving the pit-latrine. The amount of seed sludge to be used in the pit-latrine could use to determined upfront from the model. It was clear from the study which took 380 days that, at the pit closing time, the maximum possible gas produced was 554 gCOD-CH₄/day and the sludge had reached a stabilization level of 97%. The model indicated that 14 more days were required without adding new sludge for complete stabilization (Xdeg = 0 gCOD/l). This study shows that the model is a powerful tool in determining the volume of the pit required for latrine use.

Keywords: anaerobic digestion, pit-latrines volume, accumulation systems, model