A thesis submitted in partial fulfillment of the requirement for the degree of Master of Engineering

Thesis (M.Eng.) - Asian Institute of Technology, 1993

Sequencing Batch Reactor (SBR) is known to remove carbon, nitrogen and phosphorus successfully. The five periods in SBR are Fill, React, Settle, Idle and Decant, can be controlled to achieve high removals of carbon, nitrogen and phosphorus. The removal of nitrogen in SBR was investigated in this study. The duration of each period, ratio of periods, oxygen availability in the period, as well as the characteristics of substrate affected the removal of nitrogen. Different operating conditions related to these factors were introduced in this study in order to achieve high nitrogen removal. F/R ratio of 0.5/5.5, with 5.5 hours aerobic react period was the optimum condition for SBR to remove nitrogen. Under this condition the highest ammonia removal efficiency of 82 % was achieved in Experiment I. The second anoxic time performed in react period did not improve both the removal of carbon and nitrogen. Under this condition efficiency removal of nitrogen was reduced to 48% and 78% in the Reactors 2 and 3, respectively. The COD concentration of 400 mg/l and NH3-N of 40 mg/l, with COD/N of 10 gave the highest removal of both carbon and nitrogen. 92% of COD removal and nearly 100% removal of ammonia were achieved. The highest nitrogen removal efficiency achieved in R3, Experiment Ill, which was 95 %. The nitrification specific rate and denitrification rate ranged between 0.0183 to 0.0642 days-1 and 1.3E-5 to 0.0019 days-1 respectively. Yield coefficients obtained ranged between 0.3 to 0.8 mg VSS/mg BOD and 0.1 to 0.2 mg VSS/mg NH3-N.