NIRE Annual Report 1999

NIRE Annual Report

1999

Variation of Organic Halide Formation Potential of Dyes and Intermediates by Ozonation

Objectives: Effluents containing various dyes, intermediates and auxiliaries, which are known to have high trihalomethane formation potential (THMFP) as well as intense color. In this study, sixwater soluble dyes and five intermediates were ozonated to investigate the variations of total organic halide formation potential (TOXFP) and THMFP. The decrease in color and the change in biodegradability were also studies.

Results: The target compounds were roughly divided into two groups: (1) compounds showing a maximum in the initial stage of ozone consumed of 0.50~1.10mgO₃/mgTOC and (2) compounds showing a uniform decrease with the increase of ozone consumed. In spite of the different variation patterns and initial values, ozonation of about 2.50mgO₃/mgTOC could decrease the TOXFP of all the target compounds to 50.0mg/mgTOC and the THMFP to 20.0mg/mgTOC.; Rapid decoloration was attained by short-term ozonation. The BOD5/TOC values for all the dyes other than Methylene Blue gadually increased with the increase of ozone consumed, showed a maximum of 1.20~1.70mgO₃/mgTOC, and then slightly decreased. In case of Methylene Blue, the value uniformly increased. Fig. 1 showed the relationship between the variations of TOXFP and THMFP and those of color and biodegradability. Rapid decoloration was attained by short-term ozonation. Moreover, short-term ozonation was effective for the enhancement in biodegradability. However, it was not necessarily sufficient for the decrease in TOXFP and THMFP. These results indicate that long-term ozonation is necessary for the removal of precursors to organic halides.


Fig. 1	Relationship between TOXFP, THMFP, color and biodegradabillity in Orange II

1)	Variation of organic halide formation potential of dyes and intermediates by ozonation, Proc. 13th ozone world congress, 307-312. 1997.

National Institute for Resources and Environment