Mixotrophic cultivation of microalgae coupled with anaerobic hydrolysis for sustainable treatment of municipal wastewater in a hybrid system of anaerobic membrane bioreactor and membrane photobioreactor

Abstract

This study investigated the possibility of coupling anaerobic hydrolysis in an anaerobic membrane bioreactor (AnMBR) with mixotrophic microalgae cultivation in a membrane photobioreactor (MPBR) for the sustainable treatment of municipal wastewater. Using the hydrolyzed wastewater discharged from AnMBR, Chlorella pyrenoidosa in MPBR grew in a mixotrophic mode and realized rapid growth. During the stable operation, MPBR achieved average carbon capture rate of 42.82 mg L^-1 d^-1 and algal lipid production rate of 19.66 mg L^-1 d^-1. The average reduction in TN, TP, and TOC during stable operation was 96.7%, 98.0%, and 95.9%, respectively. Mass balance analysis showed that the overall system captured 14.76 mg of carbon from the atmosphere per liter of wastewater treated. Therefore, this AnMBR-MPBR hybrid system simultaneously realized advanced treatment of municipal wastewater, efficient production of algal lipid, and carbon capture from atmosphere, and thus has a good potential in the sustainable treatment of municipal wastewater.

Keywords: Algal lipid; Carbon capture; Microalgae; Nutrient removal; Sustainable treatment; Wastewater.