Application of integrated ozone biological aerated filters and membrane filtration in water reuse of textile effluents

A combined process including integrated ozone-BAFs (ozone biological aerated filters) and membrane filtration was first applied for recycling textile effluents in a cotton textile mill with capacity of 5000 m3/d. Influent COD (chemical oxygen demand) in the range of 82–120 mg/L, BOD5 (5-day biochemical oxygen demand) of 12.6–23.1 mg/L, suspended solids (SSs) of 38–52 mg/L and color of 32–64° were observed during operation. Outflows with COD ⩽ 45 mg/L, BOD5 ⩽ 7.6 mg/L, SS ⩽ 15 mg/L, color ⩽ 8° were obtained after being decontaminated by ozone-BAF with ozone dosage of 20–25 mg/L. Besides, the average removal rates of PVA (polyvinyl alcohol) and UV254 were 100% and 73.4% respectively. Permeate water produced by RO (reverse osmosis) could be reused in dyeing and finishing processes, while the RO concentrates could be discharged directly under local regulations with COD ⩽ 100 mg/L, BOD5 ⩽ 21 mg/L, SS ⩽ 52 mg/L, color ⩽ 32°. Results showed that the combined process could guarantee water reuse with high quality, and solve the problem of RO concentrate disposal.