Removal of Dissolved Organic Carbon and Color from Dyeing Wastewater by Pre-Ozonation and Subsequent Biological Treatment Using Test-Scale Plant

Abstract

The effects of pre-ozonation and subsequent biological treatment process on the decrease in dissolved organic carbon (DOC) and color were investigated in a test-scale plant of 5 m³/d capacity using actual raw wastewater (RW) from a dye works. Ozone dosage rate and contacting time were around 70 mg/L on average and 30 min, respectively. The DOC concentration was gradually decreased from 36.1 to 19.3 mg/L on average through the process and the DOC removal rates were 24.4% after ozonation and 46.5% after subsequent biological treatment. The average color value was rapidly decreased from 1.75 to 0.20 after ozonation, and the color removal rate was 88.6%. The values of adsorbable organic halide formation potential (AOXFP) and trihalomethane formation potential (THMFP) were gradually decreased by each treatment process, indicating the increased safety of the treated water. Slight morphological differences due to decomposition of the predominant bacteria by residual ozone were observed. The DOC removal rate brought about by pre-ozonation was slightly higher than that by the process consisted of biological treatment and post-ozonation, although no obvious difference in the color removal was observed between them.

Keywords:

• Ozone
• Pre-ozonation
• Biological Treatment
• Dyeing Wastewater
• DOC
• Color
• AOXFP
• THMFP

ACKNOWLEDGMENT

This research was financially supported by New Energy and Industrial Technology Development Organization (NEDO) as a part of the project (Development of Energy Efficient Waste Water Treatment Technology). The authors are very thankful for the financial support. We also thank Mr. Haijima for supplying dyeing wastewater.