Metrics for stabilization of fecal sludge and relation to dewatering metrics

Abstract

Stabilization and dewatering are essential treatment mechanisms for the management of fecal sludge (FS) that accumulates in onsite containment. FS is typically 80–95% water, which needs to be removed, with varying levels of organic matter that require stabilization. Observed levels of FS stabilization are related to dewatering performance. This study evaluated rapid and low-cost metrics of stabilization and their relation to dewaterability. Potential metrics were selected through a two-stage process: screening using a decision matrix and laboratory evaluation to determine method performance and suitability. FS samples (n = 27) were collected and nine parameters related to stabilization and dewatering performance were analyzed. The study found that metrics based on physical–chemical characteristics such as volatile/total solids (VS/TS) and biological oxygen demand/chemical oxygen demand (BOD/COD) were not reliable for measuring FS stabilization and its relation to dewaterability. Metrics that rely on microbial activity such as SOUR (Specific Oxygen Uptake Rate) are more promising based on the consistent results obtained throughout this study.