Integrating the Removal of Nutrients with Anaerobic Digestion of Primary and Waste Activated Sludge Mixture

Abstract

One of the techniques used for the stabilization of sewage sludge is anaerobic digestion. The effluent from anaerobic digesters usually requires further treatment since they contain high concentrations of N and P as a result of volatile solids destruction. In this study, a control was developed over the nutrient ions within the anaerobic digester by using substrate enriched in Mg²⁺ ion. The amount of Mg²⁺ ion added was determined based on the release rate of N and composition of magnesium ammonium phosphate. The results showed 50% removal of NH₄⁺ and PO₄^3- can be achieved without compromising the performance of the reactor in COD and VSS removal and biogas formation. The stability of the digesters was checked by investigating the distribution of the most sensitive two main anaerobic genera: Methanosaeta and Methanosarcina. The numbers of Methanosaeta and Methanosarcina in the samples did not show a significant difference indicating that Mg²⁺ ion did not affect the microbial diversity during the period of operation.