Effects of settling time on the flocculation progress and treatment performance in the co-culture of microalgae-activated sludge photobioreactor

Abstract

The application of microalgae-based wastewater treatment systems using wastewater as a source of nutrients has been successfully developed in recent years and has brought about positive results in wastewater treatment and microalgal biomass recovery while producing valuable products. This study presents the application of a microalgae and activated sludge (AS) co-culture in a low agitation photobioreactor (aPBR), which could reduce energy usage. In addition, the results demonstrate the role of settling time on co-culture flocculation progress and wastewater treatment performance. The average Chemical Oxygen Demand (COD) removal was up to 76.1% of co-culture and was achieved using a PBR system with a low agitation speed of 80 rpm. Moreover, a high biomass growth was observed to be coupled with high nutrient removal. After 63 days of operation, heavy flocs with excellent settling ability were dominant in the photobioreactor. This would be a preliminary step for activated algae granulation in a co-culture system.