Ozonation of Dyestuffs and Intermediates and Further Decrease in Dissolved Organic Carbon by Post-Biodegradation

Abstract

Four each of water-soluble dyestuffs, intermediates and reference compounds were examined to determine the effect of the combined use of ozonation and post-biodegradation on the decrease in the amount of dissolved organic carbon (DOC) and the synergistic effect induced by ozonation. The amount of DOC removed by ozonation was increased initially with increasing ozonation time, and showed a plateau thereafter. The amount of ozone required to remove 1 mg of DOC (ΔO₃/ΔDOC) ranged from 5.2 to 18.6 mgO₃/mgC for the dyestuffs and the intermediates. The DOC concentrations of all the ozonized solutions were decreased with incubation time. In the case of the dyestuffs and the intermediates, the total amounts of DOC removed were increased with increasing ozonation time and showed a plateau thereafter. The synergistic effect (the ozonation-induced increase in the amount of DOC removed by the biological process) was dependent on the initial biodegradability, and was observed in all the dyestuffs and the intermediates in the range of 0.2 to 42.7 mgDOC. On the other hand, no synergistic effect was observed in the reference compounds of high biodegradability.

Keywords:

• Ozonation
• Post-biodegradation
• Dyestuff
• Dissolved Organic Carbon (DOC)
• Biodegradability
• Synergistic Effect

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.

Notes

*1.4 mM, **0.4 L, ***Previous report (0.4 g/L).