Development of a high rate biological system (Anammox + phosporous) for the treatment of low strength wastewaters

Abstract

Since their detection and abundance are disrupted by a number of unidentified conditions, anaerobic ammonium oxidising bacteria (anammox) play a vital role in wastewater. Low Strength Wastewaters (LSW) are those that have a chemical oxygen demand (COD) < 1000 ppm. Nitrogen and phosphorus are the major nutrients present in LSW in addition to the organic carbon. The biological nitrogen removal was studied through using a recent process of anaerobic ammonium oxidation (Anammox) process. A thorough explanation of the anammox substrate removal mechanism and denitrification phosphorus removal is provided. Denitrification was studied in a high rate anoxic hybrid reactor (HR) which yielded NO3−-N removal in the range of 92–100% till a Hydraulic Retention Time (HRT) of 0.3 d and 79% at 0.24 d respectively for an inlet NO3−-N concentration of 500 ppm. Total kjedahl nitrogen (TKN) removal of 91%, 77%, 69% and 61% were obtained in the HR containing anammox and denitrifying granules at a HRT of 2.14, 0.94, 0.56 and 0.4 per day respectively for an inlet TKN concentration of 500 ppm. Phosphorus removal of 100, 83 and 72% was obtained for an inlet PO43−- P concentration of 50, 75 and 100 ppm, respectively at an optimum anaerobic HRT of 0.06 d (1.5 h) and aerobic HRT of 0.94 d. It is evident that the phosphorus removal efficiency is better in continuous mode than in the batch mode.