Preecha Kasikamphaiboon, Juntima Chungsiriporn, Charun Bunyakan, and Wisitsree Wiyaratn

pp. 73 - 80

Abstract

Lab-scale upflow bioreactor system without biomass-liquid separation unit was built to treat low-strength nitrogenous
wastewater based on intermittent aeration under low-shear environment. Biomass zone formed in the absence of gas bubbles
provided simultaneous biomass retention, biodegradation of nitrogenous and carbonaceous compounds, and biomass-liquid
separation. Biomass zone was stable as indicated by insignificant biomass washout rates (14–29 mg VSS/day) and relatively
constant biomass zone height (26–30 cm) up to the shear gradient of 1.8 s^-1. Nitrogen treatment efficiency of wastewater
containing 15 mg NH4⁺
-N/L was 15.3±1.96% under continuous oxygen influx of 95 mg O₂
/L/day and autotrophic environment,
whereas it increased significantly, 88.2±7.05%, after intermittent aeration (3 hrs air-on and 3 hrs air-off) and organic carbon
source were supplied to the bioreactor system. Carbon removal efficiencies for both continuous and intermittent aeration
were comparable reported at 85±1.76% and 91±2.1%, respectively