Development of a Kinetics Based Onsite Treatment System for Faecal Sludge Treatment and Resource Recovery

Abstract

The management of faecal sludge in cities without a sewerage system is a challenging problem that requires immediate attention. The high organic and nutrient content, pathogen load, and pharmaceutical residues in faecal sludge necessitate special attention for its treatment to ensure environmental and public health safety. Onsite treatment of faecal sludge with a focus on resource recovery is a sustainable approach to its management. However, studies in these areas are limited, particularly in the Indian context. In this study, the aim is to generate primary data on the current status of faecal sludge management in a model region without a sewerage network. Additionally, kinetic parameters were examined to design an anaerobic bioprocess and an engineered system for resource-oriented faecal sludge treatment. One of the wards in Thiruvananthapuram Corporation, Kerala was selected for the study. Fresh faecal sludge collected from an apartment complex was used for the experimental studies. Anaerobic treatment of fresh faecal sludge was validated in bench-scale experimental bioreactors using different combinations: with mixing without inoculum, with mixing with inoculum, without mixing without inoculum, and without mixing with inoculum. The primary focus was on monitoring the organic removal efficiency as Chemical Oxygen Demand (COD) of these combinations. Among the four combinations tested the units "without mixing with inoculum" and "with mixing with inoculum" demonstrated COD removal efficiencies of 20.89% and 18.91%, respectively, with a first-order rate constant of 0.0008 hr-1 for both combinations. The other combinations exhibited comparatively lower COD removal efficiency and rate constants. Since the combinations with mixing and inoculum showed higher COD removal efficiency, either of them can be adopted for design purposes. Based on these results, a combined anaerobic-aerobic treatment unit is proposed for the treatment of faecal sludge.