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Keywords:

  • ozone;
  • municipal wastewater;
  • kinetics;
  • biofuels

Abstract

The results of a laboratory scale investigation on ozone pretreatment of primary-treated municipal wastewater for potential reuse in fermentation processes for the production of biofuels and bio-based feedstock chemicals were presented. Semi-batch preozonation with 3.0% (w/w) ozone at 1 L min−1 resulted into a considerable inactivation of the indigenous heterotrophic bacteria in the wastewater with less than 0.0002% comprising the ozone-resistant fraction of the microbial population. The disinfection process was modeled using first-order inactivation kinetics with a rate constant of 4.39 × 10−3 s−1. Chemical oxygen demand (COD) levels were reduced by 30% in 1-h experiments. COD depletion was also modeled using a pseudo-first-order kinetics at a rate constant of 9.50 × 10−5 s−1. Biological oxygen demand (BOD5) values were reduced by 60% up to 20 min of ozonation followed by a plateau and some slight increases attributed to partial oxidation of recalcitrant materials. Ozone also had no substantial effect on the concentration of ammonium and phosphate ions, which are essential for microbial growth and metabolism. Preliminary tests indicated that oleaginous microorganisms could be cultivated in the ozonated wastewater, resulting in relatively higher cell densities than in raw wastewater and comparable results with autoclave-sterilized wastewater. This process could potentially produce significant quantities of oil for biofuel production from municipal wastewater streams. © 2010 American Institute of Chemical Engineers Environ Prog, 2010