Anoxic-oxic treatment of abattoir wastewater for simultaneous removal of carbon, nitrogen and phosphorous in a sequential batch reactor (SBR)

Abstract

In the case of abattoir effluent, biological nutrient removal in sequential batch reactor (SBR) is achieved typically through pre-denitrification, which can be accomplished during the anoxic fill phase or an anoxic react phase between the fill and the aerobic react phase. The study includes phosphorus reduction from abattoir wastewater in a SBR under anoxic-oxic environment in presence of Phosphorous Accumulating Organisms (PAOs). The PAOs utilizing organic carbon for enabling simultaneous nitrification, denitrification and phosphorous uptake from the wastewater. The reactor was operated in three different variations of anoxic(A)-oxic(O) sequence, viz. (4+4,A/O), (3+3+2,A/O/A) and (3+4+2,A/O/A) hr of total react period with influent soluble chemical oxygen demand (SCOD), ammonia nitrogen (NH4+-N) level and phosphorous concentration of 2250±20 mg/L, 150±10 and 24±2 respectively. At (4+4,A/O) combination total phosphorous (TP) removal efficiency was found to be 84.34% at the end of settle period. Other combinations i.e. (3+3+2,A/O/A) and (3+4+2,A/O/A) were basically resorted to obtain nitrification and subsequent denitrification in a greater extent. The effective removal of SCOD, NH4+-N and TP were 95.14, 78.04 and 86.60%, at the initial concentration of SCOD, NH4+-N and TP 2265.52, 148.28 and 25.68 mg/L, respectively was achieved in the present SBR system under (3+4+2,A/O/A) combination operating condition which indicates that an intermittent aeration strategy in the form of (3+4+2,A/O/A) is distinctly advantageous compared to other two combinations (4+4,A/O) and (3+3+2,A/O/A).