Resumen
The batik industry generates large amounts of highly colored wastewater. Azo dyes in batik wastewater can cause environmental pollution. In this study, synthetic batik wastewater containing 32 mg/L Reactive Black 5 (RB5) and 32 mg/L Reactive Orange 16 (RO16) was treated by ozonation in a 2 L batch reactor. The wastewater color unit was reduced from 4240 to 70 after 10 min ozonation and to below 50 after 15 min ozonation (7.3 g O3/m3, 4 L/min). The first-order decay constant for 5 min ozonation was determined to be 1.11 min-1 for RB5 and 0.82 min-1 for RO16. Biodegradation tests using activated-sludge microorganisms showed the toxicity of RB5 and RO16 for microbial respiration and revealed the detoxification of the dyes by ozonation. Three-dimensional fluorescence spectroscopy analysis indicated the temporal accumulation of ozonolysis products of RO16 and RB5. The chemical oxygen demand concentration of the wastewater was reduced from 86 mg/L to 73 mg/L by biodegradation alone, 63 mg/L by ozonation alone, and 54 mg/L by ozonation followed by biodegradation. Existing wastewater treatment plants using conventional bioprocesses can be upgraded to achieve robust dye treatment by installing the ozonation process as a pretreatment.