Indian Institute of Technology Hyderabad, United States
Abstract Submission: Microalgal-bacterial hybrid systems are gaining significant attention as sustainable alternatives for wastewater treatment due to their effective nutrient removal and simultaneous production of biomass for value-added product synthesis. The present study evaluates the performance of an 80-cubic-meter pilot-scale anaerobic-aerobic biofilm carrier-assisted algal-bacterial hybrid reactor treating real domestic wastewater. The reactor was operated at different hydraulic retention times (HRTs) of 12, 9, 6, and 4 h in continuous mode for over a period of 200 days. The aerobic chambers of the reactor were inoculated with mixed microalgae and heterotrophic bacterial culture. The aerobic chambers were illuminated by blue light-emitting diode (LED) lights to facilitate algal photosynthesis. At 9-h HRT, the average removal efficiencies for chemical oxygen demand, dissolved organic carbon, total nitrogen and phosphorus were observed to be 95.5%, 76.3%, 54.0%, and 71.8%, respectively. The sludge volume index of the mixed liquor ranged between 44 and 65 mL/g, indicating a high biomass settleability. A maximum chlorophyll content of 1.65 mg/L was observed in the mixed liquor, while the average chlorophyll content on biofilm carriers was observed to be 47±9 µg/carrier. Metagenomic analysis revealed that Thauera, Streptomyces, and Pseudomonas were the dominant bacteria, while Epipyxis, Fistulifera, and Chlorella were the major microalgal genera present. The hybrid reactor showed an energy consumption of 0.18-0.4 kWh/m3 of water treated. In-situ photosynthetic oxygen by microalgae significantly reduced the mechanical aeration requirements for organic matter degradation. Fatty acid analysis of the biomass showed presence of palmitic, and stearic acid esters, which are suitable for biodiesel synthesis.
