Effects of food waste addition on biofilm formation and sulfide production in a gravity sewer.

The conversion of food waste (FW) into the sewage system is regarded as a promising method of relieving the burden of solid waste management. However, knowledge about its effects on sewer processes is limited, particularly in terms of biofilm formation and sulfide production. In this study, a gravity sewer system was set up to investigate the effects of the addition of FW on biofilm formation, the sulfate-reducing bacteria (SRB) population, and the sulfide production potential. The sewer biofilm characteristics changed with long-term FW addition, and a greater thickness (by 32%), an increased dry density (by 13%), and more extracellular polymeric substance (by 141%) were observed. The thicker and denser biofilm limited oxygen diffusion, enlarged the anaerobic area in the sewer biofilm, promoted an increase in the SRB population, and enhanced the sulfide production potential in the gravity sewer. Substantial differences in the HS profiles in the biofilm samples with and without the addition of FW were observed via microelectrode analysis. A model-based investigation of sewer biofilm formation with and without the addition of FW was conducted with a dynamic sewer biofilm model to gain further insights into sewer biofilm processes. The results suggest that the addition of FW can promote sulfide production and SRB growth in a sewer biofilm, which can be significantly affected by the ratio of FW to sewage. It is worth further investigations of the impacts of FW addition on the potential sulfide production in pressure sewers.