Nutrient removal by thermophilic Fischerella (Mastigocladus laminosus) in a simulated algaculture process

Abstract A novel nutrient removal/waste heat utilization process was simulated using semicontinuous cultures of the thermophilic cyanobacterium Fischerella . Dissolved inorganic carbon (DIC)-enriched cultures, maintained with 10 mg l −1 daily productivity, diurnally varying temperature (from 55°C to 26–28°C), a 12:12 light cycle (200 μE sec −1 m −2 ) and 50% biomass recycling into heated effluent at the beginning of each light period, removed > 95% of NO 3 − + NO 2 − −N, 71% of NH 3 -N, 82% of PO 4 3− −P, and 70% of total P from effluent water samples containing approximately 400 μg l −1 combined N and 60 μg l −1 P. Nutrient removal was not severely impaired by an altered temperature gradient, doubled light intensity, or DIC limitation. Recycling 75% of the biomass at the end of each light period resulted in unimpaired NO 3 − + NO 2 − removal, 38–45% P removal and no net NH 3 removal. Diurnally varying P removal, averaging 50–60%, and nearly constant > 80% N removal, are therefore projected for a full-scale process with continuous biomass recycling.