Influence of variations in wastewater on simultaneous nutrient removal in pre‑anoxic selector attached full‑scale sequencing batch reactor

Abstract

In addition to many other well-documented factors, local conditions are rudimentary conditions of sharp change observed in wastewater characteristics from place to place. The monitoring of 3 million liters per day-capacity full-scale Sequencing Batch Reactor (SBR) at Roorkee (India) 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 chemical oxygen demand (rbCOD). Regular monitoring of all the units revealed that the nutrient removal efficiencies were 94.9 ± 3.6% Chemical Oxygen Demand (COD) (17.9 ± 7.7 mg/L in effluent), 95.4 ± 2.7% Biochemical Oxygen Demand ( BOD5) (6.0 ± 2.2 mg/L in effluent), 95.4 ± 1.6% Total Suspended Solids (TSS) (9.4 ± 2.1 mg/L in effluent), 96.7 ± 2.6% Ammonia-N (0.7 ± 0.5 mg/L in effluent), 69.1 ± 11.5% Total Nitrogen (TN) (9.7 ± 3.0 mg/L in effluent), 31.3 ± 24.9% orthophosphate (1.8 ± 0.7 mg/L in effluent) and 42.0 ± 15.3% Total Phosphorus (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 76.4 ± 9.2% SND at rbCOD/COD of 0.12 ± 0.04 and showed linear relationship at R2 > 0.8, and COD/TN of 12.3 ± 4.7. 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.