Understanding the impact of a pressure sewer on municipal wastewater: a pre-treatment for AGS plants

Abstract

The performance of AGS reactors treating municipal wastewater can be optimised by converting influent particulate matter into readily available substrate. This can be done via anaerobic hydrolysis and fermentation of the influent. Anaerobic processes taking place in pressure sewers are not fully understood but show the potential to act as a pre-treatment for the wastewater reaching AGS reactors. Moreover, the contribution of the influent to the hydrolytic activity of the reactor is unknown. This research evaluated the impact of a pressure sewer on wastewater characteristics, as a possible pre-treatment of sewage before reaching the treatment plant. The variations of sewage in terms of physicochemical composition and microbial activity were monitored in a full-scale pressure sewer, focusing on the hydrolysis and fermentation of organic matter for further treatment in AGS reactors. Moreover, the contribution of the influent to the enzymatic activity of a full-scale AGS reactor was assessed.
Inaccuracies deriving from sampling on a full-scale pressure sewer might have affected the results. However, statistical analyses helped to derive trends from the collected data. The pressure sewer primarily affected the degree of fermentation of the wastewater and the concentration of suspended solids. It is hypothesised that such variations could benefit the performance of AGS reactors. Although the biodegradability and enzymatic activity of the wastewater did not improve significantly, anaerobic conveyance seemed more appropriate than aerobic transport for AGS reactors. However, the influent did not seem to have a large contribution to the total reactor activity, due to the high concentration of granular biomass.