Full-scale bioreactor pretreatment of highly toxic wastewater from styrene and propylene oxide production

• We showed a principal possibility of petrochemical wastewater biological pretreatment.
• The studied wastewater was characterized as highly polluted and highly toxic.
• The full-scale bioreactor allowed wastewater contamination to be reduced up to 88 percent.
• The stabile microbial community contained eleven species of bacteria.
• Biodegradation capacities were demonstrated for some of the isolated representatives.

The wastewater originating from simultaneous production of styrene and propylene oxide (SPO) is classified as highly polluted with chemical oxygen demand level in the range 5965 to 9137 mg L−1—as well as highly toxic. The dilution factor providing for a 10 percent toxic effect of wastewater samples in a test with Paramecium caudatum was 8.0–9.5. Biological approach for pretreatment and detoxification of the wastewater under full-scale bioreactor conditions was investigated. The number of suspended microorganisms and the clean up efficiency were increased up to 5.5–6.58×108 CFU mL−1 and 88 percent, respectively during the bioreactor’s operation. Isolates in the Citrobacter, Burkholderia, Pseudomonas, and Paracoccus genera were dominant in the mature suspended, as well as the immobilized microbial community of the bioreactor. The most dominant representatives were tested for their ability to biodegrade the major components of the SPO wastewater and evidence of their role in the treatment process was demonstrated. The investigated pretreatment process allowed the wastewater to be detoxified for conventional treatment with activated sludge and was closely related to the maturation of the bioreactor’s microbial community.

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