Enhanced Nutrients Removal in Conventional Anaerobic Digestion Processes

One of the main challenges for one phase anaerobic digestion processes is the high concentration of NH4 and PO4 ions in the digested sludge supernatant. This project focuses on enhancing the removal of nutrients during the anaerobic digestion process through fixing both NH4 and PO4 ions in the form of struvite (magnesium ammonium phosphate, MAP, MgNH4PO4.6H2O) within the anaerobic sludge. Batch anaerobic digestion tests showed that Mg concentration in the range 279 – 812 mg/L had insignificant effect on CGP but incurred a slight increase in COD removal. The reactor that had soluble Mg:NH4:PO4 at a molar ratio of 1.28:1:00:1:00 achieved the best performance enhancement of 8% increase in COD removal and 32% reduction in NH4 in the reactor supernatant. Overall, the results show that there is a potential to optimise conventional anaerobic digestion such that supernatant lean in P and N, and sludge rich in nutrients are obtained. Keywords—Anaerobic Digestion, Nutrients, Struvite, Waste Activated Sludge (WAS)