Japanese Journal of Water Treatment Biology

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Synthetic wastewater containing 32 mg/L Reactive Black 5 （RB5） or 32 mg/L Reactive Orange 16 （RO16） was treated using ozonation in a 2 L batch reactor. The color units of wastewater containing RB5 and RO16 were reduced respectively from 835 to 50 and from 2780 to 750 after 8 min. Each was reduced to less than 50 after 15 min ozonation （6.3 g－O₃/m³, 4 L/min）. The first-order decolorization constant was 0.35 min^－1 for RB5 and 0.47 min^－1 for RO16. Biodegradation tests using activated sludge microorganisms showed increased biochemical oxygen demand of the wastewater by ozonation. The total organic matter （TOC） concentration of RB5-containing wastewater was decreased from 8.9 mg/L to 8.4 mg/L by biodegradation alone, 5.8 mg/L by ozonation alone, and 3.3 mg/L by ozonation followed by biodegradation. The TOC concentration of RO16-containing wastewater was decreased from 13.9 mg/L to 12.9 mg/L by biodegradation alone, 7.1 mg/L by ozonation alone, and 4.0 mg/L by ozonation followed by biodegradation. These results suggest that installing the ozonation process as a pretreatment for conventional bioprocesses can achieve enhanced and robust dye treatment.

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