Simultaneous biological removal of nitrogen and phosphorus using the SBR process for a bench-scale test

A bench-scale reactor using the SBR (sequencing batch reactor) process was experimented with synthetic wastewater. The main purpose of this investigation was to evaluate applicability in the field and process removal efficiencies in terms of BOD, TN and TP and its corresponding kinetic parameters. The removal rate of nitrogen was 71% in terms of total nitrogen and that of phosphorus was 77% in terms of total phosphorus. Effluent concentrations were 9.8 mg/L BOD, 11.2 mg/L TN, and 1.1 mg/L TP. Effluent quality was maintained consistently stable by controlling decant volume and operating cycles. Denitrification/nitrification were accomplished during anaerobic/aerobic processes and the conversion rates were 4.8 mg/kgMLSS/hr and 1.6 mg/kgMLSS/hr, respectively. During the anaerobic phase, corresponding to the end of denitrification, the pH profile showed a maximum due to alkalinity production during the reactions. During the aerobic phase, pH showed a rapid increase due to CO2 stripping and pH started to increase again when ammonia nitrogen reached the minimum level. The sludge yield coefficient was 0.28 whereas sludge phosphorus luxury uptake was as high as 5.8 wt% at the end of aerobic cycle. Microscopic examination revealed that microcytes that were observed predominantly in sludge were Vorticella, Epistilis, Opercularia, Aspidisca, Chilodonella that are protozoa as well as Philodina, Rotaria, Notommata, Nematoda that are rotatoria.