ABSTRACT
<p><b>OBJECTIVE</b>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.</p><p><b>METHODS</b>A luminescent bacterium toxicity bioassay was employed to assess the toxicity of influent and effluent of each reactor in the A²/O system.</p><p><b>RESULTS</b>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.</p><p><b>CONCLUSIONS</b>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.</p>
Subject(s)
Anaerobiosis , Bioreactors , Oxygen , Sewage , Time Factors , Waste Disposal, Fluid , MethodsABSTRACT
Enhanced biological phosphorus removal (EBPR) is widely accepted as one of the most economical and sustainable processes to remove phosphorus from wastewater.Poor performance or complete failure of EBPR processes has been substantially reported because of the proliferation of glycogen-accumulating organisms (GAOs) in the system.This paper presented the GAOs' metabolic mechanism and the impact factors, such as influent substrate, P/C ratio, pH value, temperature and SRT, on competition between GAOs and PAOs to better understand GAOs' characteristics and improve the performance and reliability of EBPR systems.