Sequencing batch membrane photobioreactor for real secondary effluent polishing using native microalgae: Process performance and full-scale projection

Microalgae technology can play important roles in wastewater management, carbon dioxide fixation and as biofuels feedstock if managed properly. The core challenge is to substantially lower the cultivation and harvesting costs. This study assesses performances of batch wise photobioreactor (PBR) and sequencing batch membrane photobioreactor (SB-MPBR) for polishing real secondary effluent, and at the same time producing lipid by cultivating a native strain of Euglena sp. Lab-scale data were used to project large-scale performance of an SB-MPBR and its economic potential was compared with established conventional biological nutrients removal technologies. Results show that the SB-MPBR with 4 days retention was found to be optimum in terms of nutrients removal (≥95% and ≥70% respectively for total nitrogen and total phosphorous), water treatment capacity and lipid yield (≥10%). However, an energy audit on the process shows that the chemical energy from the produced lipid is still at least 111 fold short of meeting an energy neutral process. However, results of preliminary cost analysis indicate that SB-MPBR (0.113 $/m3) is highly attractive technology for biological nutrients removal than the conventional technologies (0.65-0.96 $/m3).