title: Toxicity reduction of municipal wastewater by anaerobic-anoxic-oxic process.
abstract: OBJECTIVE
  This study was conducted to optimize the operational parameters of anaerobic-anoxic-oxic (A²/O) processes to reduce the toxicity of municipal wastewater and evaluate its ability to reduce toxicity.
  
  
  METHODS
  A luminescent bacterium toxicity bioassay was employed to assess the toxicity of influent and effluent of each reactor in the A²/O system.
  
  
  RESULTS
  The optimum operational parameters for toxicity reduction were as follows: anaerobic hydraulic retention time (HRT) = 2.8 h, anoxic HRT = 2.8 h, aerobic HRT = 6.9 h, sludge retention time (SRT) = 15 days and internal recycle ratio (IRR) = 100%. An important toxicity reduction (%) was observed in the optimized A²/O process, even when the toluene concentration of the influent was 120.7 mg·L⁻¹.
  
  
  CONCLUSIONS
  The toxicity of municipal wastewater was reduced significantly during the A²/O process. A²/O process can be used for toxicity reduction of municipal wastewater under toxic-shock loading.
authors.affiliation: State Key Laboratory of Pollution Control and Resources Reuse, College of Environmental Science and Engineering, Tongji University, Shanghai 200092, China.
authors.forename: Man-Hong
authors.initials: MH
authors.lastname: Huang
authors.forename: Yong-Mei
authors.initials: YM
authors.lastname: Li
authors.forename: Guo-Wei
authors.initials: GW
authors.lastname: Gu
mesh_terms: D000693:Anaerobiosis; D019149:Bioreactors; D010100:Oxygen; D012722:Sewage; D013997:Time Factors; D014865:Waste Disposal, Fluid / Q000379:methods*
chemical_list: D012722:Sewage; D010100:Oxygen