Improved phosphorus removal in wastewater through combined bacterial and algal treatment

Abstract

[ACCESS RESTRICTED TO THE UNIVERSITY OF MISSOURI AT REQUEST OF AUTHOR.] Increasingly strict nutrient regulations propel the need to develop more sustainable methods to remove nitrogen (N) and phosphorus (P) from wastewater. Algae show promise in their ability to uptake P. The purpose of this research was to propose an ANOA system (ANoxic, Oxic, Algae), testing a bench scale modified Ludzack-Ettinger (MLE) system coupled with an algaebasedcontinuous stir tank reactor (algae CSTR). The system was tested for its P treatment efficacy, focusing on the performance of the algae CSTR. The algae system could uptake up to 55% of P at the influent concentration of 6 mg/L. However, the presence of large flocs of bacteria in the algae CSTR resulted in a decrease and eventually a ceasing of P uptake. Phosphorus adsorption and uptake resulted in the algal biomass containing P at about 6% of the total biomass dry weight. Based on cellular P distribution with about 90% extracellular (physic-chemical sorbed) and 10% intracellular P (biological uptake) by using an oxalic acid rinse reagent, P removal in algae CSTR was mainly attributed to physical/chemical processes including P adsorption and coprecipitation with cations at relatively high pH environment dueto algal growth.