Real Wastewater Treatment Using a Moving Bed and Wastewater-Borne Algal–Bacterial Consortia with a Short Hydraulic Retention Time

Abstract

Algal–bacterial consortium is a promising technology, combined with wastewater treatment plants, because algae produce molecular oxygen for nitrification and organic removal and reduce carbon dioxide emissions. However, algal–bacterial consortia based on suspended growth require a relatively long hydraulic retention time (HRT) of 4 d to 6 d for removal of organic matter and nutrients. For the algal–bacterial consortia in a photobioreactor (PBR) containing a moving bed, the organic matter and nutrient removal and the community structure of algal–bacterial consortia were investigated to determine the performance under a relatively short HRT of 2.5 d. Moving media containing algal–bacterial consortia enhanced the photosynthetic oxygen concentration (0.2 mg dissolved oxygen (DO)·L−1 to 5.9 mg DO·L−1), biochemical oxygen demand removal (88.0% to 97.2%), ammoniacal nitrogen removal (33.8% to 95.3%), total nitrogen removal (61.6% to 87.7%), total phosphate removal (66.4% to 88.7%), algal growth (149.3 mg algae·L−1 to 285.4 mg algae·L−1), and settleability (algae removal efficiency of 20.6% to 71.2%) compared with those of a PBR without moving media (SPBR). Although biomass uptake was the main mechanism for nutrient removal in the SPBR, both biomass uptake and denitrification were the main mechanisms in the PBR with moving media (MBPBR). The bacterial community also changed under the moving media condition. This study shows that moving media might be an essential parameter for PBRs with a short HRT to enhance nutrient removal and settleability.