How Ozonation Removes Color from Textile Dye Wastewater
Ozonation is a documented route for color removal from textile dye wastewater, and the cited excerpts describe its performance alone, in combination with Fenton or peroxide reagents, and as a catalytic trend [S1][S2][S3].
Why textile dye wastewater resists conventional treatment
Due to the complex structure of high molecular weight azo dye molecules containing azo (N–N) and sulfonic (–SO3–) linkages, textile dyeing effluent has little biodegradability, which motivates the use of oxidative processes for color and COD removal [S1].
The role of ozone in decolorization
In the cited work on real textile dyeing effluent, ozonation alone gave 75% color removal and 65% COD removal, whereas the Fenton process alone gave 80% color removal and 70% COD removal under the conditions tested [S1]. In the same study, however, the influence of ozone concentration on color and COD removal efficiency of textile dyeing effluent was not remarkable, indicating that further increases in ozone dose were not the dominant driver of performance [S1].
Why ozonation is combined with Fenton or peroxide
To intensify the decolorization of azo dye in real textile dyeing effluent, the cited study incorporated the Fenton process with ozonation in a single step as O3/Fe2+/H2O2, optimizing ozone dosage, initial pH, Fe (II), and H2O2 concentration using RSM [S1]. A separate study applied ozonation together with peroxide (peroxydisulfate or percarbonate) treatments to a simulated reactive dyebath effluent bearing Reactive Red 21, commercially known as Remazol Brilliant Red BB, at 100 mg/L reactive dye and 25 mg/L TOC, with 50 g/L NaCl and 15 g/L Na2CO3, under previously optimized reaction conditions of 1.5 mM peroxide and 72 mg/min ozone feed rate [S2].
Catalytic ozonation as a recent trend
One of the recent trends in textile wastewater treatment has become catalytic ozonation, and the necessity of effective color removal in a short treatment time is a standard during industrial implementation [S3].
Resource-efficient reuse of ozonated effluent
Recycling textile dyeing effluent through ozonation treatment was found to be a resource efficient approach, significantly reducing wastewater volumes and freshwater demand without compromising the colour-related qualities of dyed fabrics [S4].
What the excerpts do and do not establish
The excerpts do not provide a single recommended ozone dose for all textile wastewaters, and the reported percentages are tied to specific effluents and reaction conditions, including the O3/Fe2+/H2O2 operating point and the simulated RR21 dyebath recipe [S1][S2]. The cited study explicitly frames performance as depending on ozone dosage, initial pH, Fe (II), and H2O2 concentration optimized for the given textile dyeing effluent, rather than as a universal value [S1].