Substrate degradation patterns in acid‐phase anaerobic digestion of municipal primary sludge

Abstract

This study investigated the effect of certain operational and environmental parameters [hydraulic retention time (HRT), solids retention time (SRT), pH, and reactor configuration] on substrate degradation during the acid‐phase digestion of municipal primary sludge. Experiments were conducted using two bench‐scale, continuous‐flow bioreactors, having different configurations: a completely mixed reactor (CMR) with clarifier and sludge recycling; and an upflow anaerobic sludge blanket (UASB) unit. Results indicate that the utilization percentages of the three major constituents of primary sludge (carbohydrates, proteins, and lipids) are significantly affected by variations in HRT and pH. Changes in SRT however influence only protein dissimilation, at least in the range investigated. Moreover, carbohydrate and lipid degradation patterns are dependent on reactor configuration, whereas protein utilization appears to be independent of the reactor regime.