The impact of various ozone pretreatment doses on the performance of endogenous microbial communities for the remediation of oil sands process-affected water

• The combination of ozonation with biodegradation was applied to treat OSPW.
• Ozone was applied as pre-treatment to enhance the biodegradability of OSPW.
• Increasing the utilized ozone dose increased the removal of organic compounds.
• By increasing the utilized ozone dose, the total bacterial number increased.
• Acute toxicity of OSPW toward Vibrio fischeri decreased after combined treatment.

The effects of different ozone pretreatment doses on the performance of endogenous microbial populations in degrading naphthenic acids (NAs) for the treatment of oil sands process-affected water (OSPW) were evaluated in this study. Ozone pretreatment enhanced OSPW biodegradability and accelerated the growth of microbial populations in bioreactors. After ozone pretreatment, the maximum chemical oxygen demand (COD) removal through biodegradation occurred at an ozone dose of 50 mg/L. Although OSPW pretreated with a higher ozone concentration removed a higher COD concentration and acid extractable fraction (AEF), organics removal through biodegradation was not further improved. After pretreatment with an ozone dose of 200 mg/L and bioreactor operation for 73 days, the batch bioreactor removed more than 80% of the COD and more than 95% of AEF. High-resolution mass spectrometry analysis showed complete degradation of NAs with specific degrees of cyclization (Z = −2 and −4) after combined treatments of ozonation and biodegradation. At high pretreatment doses of ozone (116 and 200 mg/L), biodegradation completely eliminated the toxicity of OSPW toward Vibrio fischeri (IC20 > 100% v/v).

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