Influence of Variations in Wastewater on Simultaneous Nutrient Removal in a Pre-anoxic Selector Attached Full-scale Sewage Treating SBR

In addition to many other well-documented factors, local conditions are rudimentary conditions of sharp change observed in wastewater characteristics from place to place. An optimized and flexible treatment strategy is required to handle these fluctuations and variations in quality. Pre-anoxic selector-equipped sequencing batch reactors (SBR) perform efficiently in removing COD, BOD5, TSS, NH4+-N, TN, and Fecal Coliforms. The monitoring of 3-MLD Full-scale SBR installed at IIT, Roorkee, drew attention to the processes involving simultaneous nitrification and denitrification (SND) and biological phosphorous removal (BPR) undergoing with the variations in influent wastewater, particularly the readily biodegradable COD (rbCOD), and their effects on micro-biota. Regular monitoring of all the units for a period of six months revealed that the overall average treatment/ removal efficiencies were >94% COD (17.9±7.7 mg/L in effluent), >95% BOD5 (5.9±2.2 mg/L in effluent), >95% TSS (9.3±2.1 mg/L in effluent), >96% NH4-N (0.7±0.5 mg/L in effluent), >86% TKN (4.2±2.9 mg/L in effluent), >69% TN (9.7±3.0 mg/L in effluent), >31% Ortho-PO4-P (1.8±0.7 mg/L in effluent) and >42% TP (3.6±1.8 mg/L in effluent) and achieved <50 MPN/ 100 mL fecal coliform in the final effluent after disinfection. Anoxic tri-sectional selector and an aeration tank constituted one SBR followed by the other availed 76± 9% SND at rbCOD/TCOD of 0.12±0.04, rbCOD/sCOD of 0.33±0.10, sCOD/TCOD of 0.35±0.06, and COD/TN of ~13. The study clarifies the degree of variations in key factors included in design guidelines for laying out an optimized treatment system for COD, Nitrogen, and Phosphorus removal in the Indian scenario.