Study On Removal Effect On Bio-treated Effluent Of Textile And Dyeing Wastewater By Iron-carbon Process And UV/TiO₂Process

At present, physical-biochemical processes arc generally applied to treat printing and dyeing wastewater in Chinese textile and dyeing industry. The effluent’s quality can basically reach the second class of Discharge Standard of Water Pollutants for Dyeing and Finishing of Texitile Industry (GB4287-1992), but it was often difficult to meet its first class of the standard, and more difficult to reuse. Therefore, it will be significant for sustainable development of textile and dyeing industry that advanced treatment is applied to treat bio-treated effluent of dye wastewater to remove various kinds of organic matters and colourity so that the effluent can meet the standard for reuse.Advanced treatment of bio-treated effluent of dyeing wastewater from one industrial zone in Kunshan was studied. The dissolved organic matters of bio-treated effluent was divided into four different fractions:hydrophobic acids, non-acid hydrophobics, transphilics and hydrophilics by XAD-4/XAD-8resins fraction. Removal effect of four fractions by iron-carbon process and UV/TiO2process were studied. The paper attempted to discuss mechamism for these two processes, review and summarize removal behavior under different conditions and removal characterisitics of different processes, and provide a theoretical guideline for the further treatment process.The results showed that:(1) combination process of iron-carbon and coagulation:the condition, iron-carbon ratio of1:1, pH=4-5, RT=60min, was a reasonable and economical condition for the process. Under the condition, UV254, ADMI7.6, DOC and COD removal efficiency were60%,87%,61%and68%, respectively. After41days of stable running, it was believed that the equipment had good stability and strong impact.(2) Iron powder process:the condition, iron dosage=4g·L-1, t=150min, pH=3-5, was a reasonable reaction conditions. Under the condition, removal efficiency of ADMI7.6reached about50%; When pH is1-2,55-63%of ADMI7.6was removed by iron reduction, and37-45%was removed by coagulation\flocculation; When the pH is3-5, about40%of ADMI7.6was removed by iron reduction, and about60%was removed by coagulation\flocculation.(3) UV/TiO2process: the condition, TiO2dosage of800mg·L-1, reaction time8h, pH (6.5-8.0) using original water, was the optimal condition. Under the condition, ADMI7.6, UV254, DOC and the COD removal efficiency were86%,65%,20%and45%, respectively. The results of DOM fractions removal effect showed that:hydrophobic substances were the main pollutants in the original water, and transphilics and hydrophilics followed. The combined process of iron-carbon and coagulation, iron powder process and UV/TiO2process could effectively remove hydrophobic acids, non-acid hydrophobics and transphilics, but couldn’t remove hydrophilic substances effectively.In summary, iron-carbon and coagulation combined process was stable, high removal efficiency and low cost, so it was an effective method for bio-treated effluent of textile and dyeing wastewater. Although UV/TiO2could remove some pollutants in the original wastewater, its reaction time was long and the effect was general. Therefore, it’s not an ideal advanced treatment for bio-treated effluent of textile and dyeing wastewater.