Case analysis on textile wastewater subjected to combined physicochemical-biological treatment and ozonation

The large amount of wastewater produced by the textile industry necessitates a cost-effective technology for enhanced wastewater treatment. In this study, a combined processing method was established to enhance discharge water quality. This process incorporated a pretreatment system, a biological contact oxidation unit, an ozone oxidation unit, and an intensive treatment system. Through this treatment approach, the ozonation of textile wastewater was examined to determine the effects of ozone dosage, ozonation time, and color/chemical oxygen demand (COD) of feed wastewater. Results revealed that the color and COD removal rates increased with increased ozone dosage. Color and COD decreased whereas NH3-N slightly increased with the progress of ozonation. Color removal rate decreased whereas ozone dosage increased with increased feed color and COD. Feed color greatly influenced ozone dosage but not COD. Color removal rate during ozonation can be controlled to 50%-55% at a response time of approximately 2 h. The average ozone dosage was 51 g m(-3). After treatment by the combined process, the final discharge water was able to meet the national first-grade emission standard (GB4287-2012). The total removal rates of COD and color reached 95.2% and 95.4%, respectively. The cost of wastewater treatment amounted to only approximately 1.70 Yuan RMB m(-3) wastewater.