Influence of dissolved oxygen concentration and aeration time on nitrite accumulation in partial nitrification process

Abstract

This study investigated the influence of dissolved oxygen concentration and aeration time on nitrification and nitrite accumulation in an attempt to optimize the recently developed biological-partial-nitritation process for the treatment of strong nitrogen wastewaters. Investigation of dissolved oxygen concentration on ammonium and nitrite oxidation was carried out in a batch reactor. The dissolved oxygen concentration of 0.5 mg O 2 /L inhibited both ammonium as well as nitrite oxidation, while increase of dissolved oxygen concentration to ~1 mg O 2 /L increased the ammonium oxidation rate and was comparable to that at higher dissolved oxygen concentrations. Experiments were carried out in a sequencing batch reactor for more than 100 days to investigate the influence of aeration time on nitrite accumulation. The dissolved oxygen concentration was controlled at ~1.0 mg O 2 /L (in the range of 0.8-1.5 mg/L) during the aeration stage, and volatile suspended solid was maintained at 2.0 g/L while temperature and pH were 30±1ºC and 8.3±0.1, respectively. In a typical cycle, complete nitrification occurred at aeration time longer than 6 h. When the aeration time was reduced to 4 h., ~80 % of partial nitritation was achieved. With a further reduction in aeration time to 3 h., nearly 1:1 nitrite/ammonium ratio was yielded. This result revealed that for the reactor design, aeration time determined by feasibility experiments must be considered based on the nitrogen strength in wastewater and biomass concentration in the reactor with dissolved oxygen concentration of ~1.0 mg O 2 /L for satisfactory partial nitrification with subsequent processes such as anaerobic ammonium oxidation.

Post-aerobic digestion of waste sludge: performance analysis and modelling of nitrogen fate under alternating aeration

“…6a, b. These results show that the DO level is a critical operating parameter to optimize in order to achieve efficient nitrogen removal, as also reported in Guo et al (2008).…”

The Operating Characteristics of Partial Nitrification by Controlling pH and Alkalinity

“…The closeness of the ammonianitrogen removal efficiency and the nitrite conversion efficiency indicates that AOB activity improved and NOB was gradually eliminated. In the first few days of the SBR operation, the higher nitrate concentration of the effluent was likely due to the controlled DO range of 0.3-1.0 mg/L (0.65 mg/L on average) [18]. After reducing the DO to 0.2-0.7 mg/L (0.45 mg/L on average) the nitrate concentration in the effluent was reduced to below 5 mg/L.…”

Nitrogen and phosphorus removal and physiological response in aquatic plants under aeration conditions

“…Thus, the organic materials were purified and the water quality was improved (Subhasis et al, 1999;Soltanali and Haghani, 2008;Madukasi et al, 2010). Engineering practices also demonstrated that aeration technique was effective to help treating polluted water (Scholz and Lee, 2005;Ouellet-Plamondon et al 2006;Guo et al, 2008;Thakre et al, 2009;Igbinosa and Okoh, 2009). Floating-beds form natural phytodepuration systems and artificially constructed floating-beds are currently used extensively for the purposes of treating domestic, agricultural and industrial effluent (Davies et al 2005;Kovacic et al 2006;Nahlik and Mitsch, 2006;Dhote and Dixit, 2009).…”