Effective cod and color removal with integrated ozonation and biological treatment approaches in textile wastewater: A review

Textile industry produces significant amount of wastewater with high pollution loads. Textile wastewater is generated in different steps of production, such as desizing, mercerization, dyeing, and washing containing considerable amounts of organic compounds and colored effluent. The major pollutants in textile effluents are BOD, COD, suspended solids and heavy metals. Particularly, the color of the effluent is a serious environmental and esthetic problem. Therefore, studies on color removal were intensively concerned. This study presents: (a) a critical review of current literature on effective COD and color removal with integrated ozonation and biological treatment approaches in textile wastewater and (b) a case study. In the case study, sequential anaerobic-aerobic processes and integrated treatment approach were applied to composite textile effluent containing reactive and indigo dyes. The sequential anaerobic-ozonation-aerobic treatment enabled 78% of COD and 81% of color removal, respectively. However, sequential anaerobic-aerobic system yielded lower COD and color removal efficiencies. Respirometric modeling study revealed that anaerobic pretreatment resulted in 40% of Ss and %23 of SH removal without altering the aerobic heterotrophic kinetics. The Standard Vibrio fischeri test showed that anaerobic and ozone application increased the toxicity of effluent. On the other hand, elevated toxicity could be eliminated by post-aeration which turn the treated effluent characteristics into non-toxic.