Microbial As (III) Oxidation in a Continuously Stirred Tank Reactor

Microbial As (III) oxidation was investigated for 204 days in a continuous stirred tank reactor (CSTR) with a pure culture of Alcaligenes faecalis strain O1201 under a range of hydraulic retention times (12.8, 25.6, 51.9, 67.4, and 90.7 hours) and influent As (III) concentrations (1,000, 2,000, 4,000, and 8,000 mg/L ). Air was supplied through a gas diffuser to maintain a minimum level of dissolved oxygen of 2 mg/L throughout the entire operation. NaOH was fed into the CSTR to neutralize hydrogen ions produced during As (III) oxidation and maintained pH at 7±0.1. Temperature was maintained at 30±2 degrees C using a heating tape equipped with a temperature controller. Nine steady-state operation conditions were obtained with near-complete oxidation of As (III) for each phase.