Resource recovery from an aerobic granular sludge process treating domestic wastewater

This study presents the application of resource recovery from domestic wastewater such as irrigation water, structural extracellular polymeric substances (EPS), and polyhydroxyalkanoates (PHAs). The resource recovery system consisted of an aerobic granular sludge (AGS) reactor processing domestic wastewater and an external membrane reactor receiving the AGS effluent. The AGS effluent contained large numbers of biomass patches detached from the granular sludge. Therefore, the external membrane served to eliminate the biomass patches and individual bacteria from the AGS effluent. The permeate of the membrane reactor was compared with the national irrigation water standards. The results showed that the membrane effluent was suitable to be used as irrigation water, but the boron parameter should be checked for long-term irrigation. Extracellular polysaccharides recovered from the granular sludge were characterized as structural EPS. The analyses showed that PHA accumulating organisms, namely Uncultured Candidatus Competibacter sp. and Competibacteraceae, were dominant in the AGS reactor, and the PHA content of the AGS was approximately 10 % when operated under high organic loading rate conditions. PHAs, therefore, may also be obtained from AGS. For the management of membrane concentrate and zero-waste discharge approach, it is recommended to investigate the recovery possibilities of structural EPS and PHA biopolymers from the membrane concentrate further because the effluent of AGS contained mostly biomass patches detached from granular sludge.