Microalgal-bacterial granular sludge process for non-aerated aquaculture wastewater treatment

Microalgal-bacterial granular sludge (MBGS) process has become a focal point in treating municipal wastewater. However, it remains elusive whether the emerging process can be applied for the treatment of aquaculture wastewater, which contains considerable concentrations of nitrate and nitrite. This study evaluated the feasibility of MBGS process for aquaculture wastewater treatment. Result showed that the MBGS process was competent to remove respective 64.8%, 84.9%, 70.8%, 50.0% and 84.2% of chemical oxygen demand, ammonia-nitrogen, nitrate-nitrogen, nitrite-nitrogen and phosphate-phosphorus under non-aerated conditions within 8 h. The dominant microalgae and bacteria were identified to be Coelastrella and Rhodobacteraceae, respectively. Further metagenomics analysis implied that microbial assimilation was the main contributor in organics, nitrogen and phosphorus removal. Specifically, considerable nitrate and nitrite removals were also obtained with the synergy between microalgae and bacteria. Consequently, this work demonstrated that the MBGS process showed a prospect of becoming an environmentally friendly and efficient alternative in aquaculture wastewater treatment.