Study On Advanced Treatment Of Textile Wastewater

Water reuse is the first choice to solve the problem existing in the world which is the shortage of water resource. The object of this research was the advanced treatment of textile wastewater. Based on analyzing source, characteristic, and common advanced treatment technology of textile wastewater, according to nonbiodegradable organic matter removal and desalination problems, the combined technology of pretreatment system and membrane system were used as the advanced treatment technology of textile wastewater. The pretreatment system included integrated device of ozone-biological aerated filter(BAF) and BAF, and the membrane system were composed of ultrafiltration(UF) and reverse osmosis(RO).The optimal conditions of pretreatment system were as follows: gas/water ratio is five, organic load 2.1, 1.0 kgCOD/m3?d, DO 3.8 mg/L, temperature 35~45℃, ozone was directly injected into BAF to form the integrated device of ozone-BAF, ozone dosage 20~30 mg/L. Influent average COD of the pretreatment system was 101.3 mg/L, turbidity 8.0 NTU, SS 21.9 mg/L, ammonia nitrogen 3.4 mg/L, and color 21 times. After being steadily treated by the pretreatment system, COD, turbidity, SS, ammonia nitrogen and color reduction average were 72.7%, 45.3%, 82.6%, 78.8% and 89.3% respectively. And the corresponding effluent concentrations were 27.4 mg/L, 4.2 NTU, 3.0 mg/L, 0.7 mg/L and 2 times respectively. Studies showed that the pretreatment system effectively guaranteed the water quality of the membrane system. And more importantly, concentrated water of membrane system could still meet water discharge standard even if being concentrated 3 times on the condition of the effective pretreatment system. In the pretreatment system, the integrated device of ozone-BAF showed the advantages of higher efficiency, smaller area, and lower energy consumption than that ozonation and BAF were separated.After being steadily treated by the membrane system, permeate water pH value is 7.4~7.9, conductivity 50~200μs/cm, total hardness 2~10 mg/L, total alkalinity 25~60 mg/L, and sulfate 22.4~90.5 mg/L. The results showed that the permeate water quality of the membrane system was up to the water reuse standard for the company. Meanwhile, the quality of concentrated water of membrane system was monitored. The pH value of concentrated water was 7.3~8.3, color 32 times, and COD 45.7~97.9 mg/L. This indicated that concentrated water from the membrane system could be discharged directly without additional treatment since it met the discharge standard.Gas chromatography coupled with mass spectrometry (GC-MS) analysis of organic compounds was studied in influent and effluent of the integrated device of ozone-BAF. It was found that the amount of detected organic compounds were 82 and 22 respectively. The results showed that the integrated device of ozone-BAF could effectively degrade organic compounds.