Microalgal growth in municipal wastewater treated in an anaerobic moving bed biofilm reactor

Nutrient removal from the effluent of an anaerobic moving bed biofilm reactor (AnMBBR) treated with microalgae was evaluated. Algal treatment was highly efficient in removal of nutrients and discharge limits were met after 3 days. Extending the cultivation time from 3 to 5 days resulted in a large increase in biomass, from 233.3 ± 49.3 to 530.0 ± 72.1 mg L−1, despite nutrients in the water being exhausted after 3 days (ammonium 0.04 mg L−1, orthophosphate <0.05 mg L−1). Biomass productivity, lipid content and quality did not differ in microalgal biomass produced in wastewater sampled before the AnMBBR. The longer cultivation time resulted in a slight increase in total lipid concentration and a significant decrease in linolenic acid concentration in all treatments. Differences were observed in chemical oxygen demand, which decreased after algal treatment in wastewater sampled before the AnMBBR whereas it increased after algal treatment in the effluent from the AnMBBR.