Advanced aerobic digestion to optimize pathogen reduction: Staged pre-treatment in aerobic digestion

Abstract

Land application of biosolids is a desirable solution for smaller communities that utilize aerobic digestion. However, traditional aerobic digestion produces Class B biosolids at best which raises public concern regarding the fate of pathogens following land application. The main goal of this work was to determine a plan to help an aerobic digestion WWTP achieve improved pathogen destruction. An approach of studying the effect of a pre-treatment step prior to digestion was developed following site visits to eight aerobic digestion facilities in Ontario. The experimental phases of this work evaluated the effect of aeration rate, temperature and retention time on pathogen reduction in 12 setups. The four best conditions were carried out with digestion to evaluate the ultimate impact of pre-treatment on digestion. The results indicated that a micro-aerobic, highly reducing environment produces adverse conditions within the pre-treatment column which also impact subsequent digestion and resulted in decreased pathogens.