Polishing the secondary effluent and biomass production by microalgae submerged membrane photo bioreactor

Abstract

Microalgae are used in wastewater treatment successfully by the uptake of nutrients in secondary effluents that can be used as a valuable biomass. In this study, mixed microalgae culture was used for real wastewater treatment plant (WWTP) for polishing the effluent instead of the specific culture, because the specific culture is contaminated under real environmental conditions. Nutrient removal rates, protein and lipid content of the biomass were determined. Volumetric microalgae productivity was found as 0.037 g/L.day with 3 days of sludge retention times (SRT) and 24 h of hydraulic retention time (HRT) in a 5.5 L microalgae submerged membrane photo bioreactor (msMpBR). Total nitrogen (TN) and phosphate phosphorus (PO4-P) removal rates were found to be 5.55 and 0.40 mg/L.day, respectively, while Navicula sp. and Chaetophora sp. cultures were found to be dominant in steady state. The lipid content was 14.33% and raw protein content was 32.69% in dry biomass. The results showed that N and P can be effectively removed from the real wastewaters by mixed microalgae culture and msMpBR and also algal biomass could be produced with good lipid and protein content.