Microbial Lipid Production through Integrated Anaerobic-Aerobic Biotreatment Process: An Urban-Based Biorefinery Concept

Abstract

Current operations within wastewater treatment plants (WWTPs), particularly the anaerobic digestion and activated sludge processes, can be tapped for production of microbial lipids. This can be accomplished by directing the anaerobic digestion to produce short chain carboxylic acids (SCCAs) that can then be used as substrates for lipid production using activated sludge microbial consortium in an add-on aerobic lipid production unit (similar to an activated sludge process). This study was conducted to assess the suitability of a Test Medium (previously proven suitable for aerobic lipid production in activated sludge) for the proposed integrated system. Results showed that, when used for anaerobic fermentation, the Test medium produced 0.48 g-SCCAs/g-substrate that includes acetic, butyric, and predominantly (∼89 wt%), lactic acid. Subsequently, the Test Medium resulted to a peak lipid yield of ∼0.17 g/g-SCCAs. Complete substrate consumptions were observed without pH control when the Test Medium was used for both bioprocesses. These results suggest the suitability of the Test Medium for the integrated system for microbial lipids production. This could significantly simplify the implementation of the proposed integrated system, which could provide the basis for future urban biorefineries through existing WWTPs.