Single-step treatment of primary effluent by Galdieria sulphuraria: Removal of biochemical oxygen demand, nutrients, and pathogens

Abstract Our previous reports have documented a single-step algal process for removing biochemical oxygen demand (BOD 5 ) and nutrients from primary effluent in batch mode. In the current study, we report results from continuous fed-batch operation of this algal system demonstrating consistent removal of BOD 5 and nutrients as well as significant reduction of pathogenic bacteria from primary effluent. The active volume of the algal bioreactor under fed-batch operation was 700 L, of which, 400 L was discharged at the end of every cycle and replenished with fresh primary effluent to start a new cycle. Results from thirty such cycles run over 120 days, under varying influent loadings and ambient conditions, confirmed that the discharge standards for BOD 5 and nutrients could be attained in a fed-batch cycle time of 5 , ammoniacal nitrogen and phosphates over the 120 days were 16.5 mg/L-d, 6.1 mg/L-d, and 1.4 mg/L-d, respectively. Fecal and total coliform were also reduced to non-detectable levels within these three days.