TECHNOLOGY COMPARISON AND ANALYSIS ON COD REMOVAL UPGRADING OF WASTEWATER TREATMENT PLANTS FOR HIGH PROPORTION OF INDUSTRY WASTEWATER

The dissolved refractory organic compounds with high concentration and complex components in wastewater were the problems encountered by many urban wastewater treatment plants (WWTPs) which occupied a relatively higher proportion of industrial wastewater, in the new round of upgrading. In this paper, four typical wastewater treatment plants in Taihu Basin were taken as the research objects, and the removal efficiency of COD by hydrolysis acidification and various advanced wastewater treatment technologies were analyzed. The results showed that hydrolytic acidification technology could improve the biodegradability of wastewater to a certain extent, and the addition of fillers could improve the effect. Moreover, the removal efficiency of the two advanced treatment technologies, coagulation sedimentation and membrane filtration, was only about 30%~35%. Furthermore, the mineralization ability of the ozone oxidation technology for the partial refractory organics was poor, so this technology was influenced by the organics in the influent. The adsorption of organics by activated carbon was universal, and in this study, the efficiency of adsorption of dissolved refractory organics in wastewater by activated carbon at empty bed hydraulic retention time (HRT) of 10 minutes was studied. It was found the COD of the effluent was stable at less than 20 mg/L. Besides, the operation cost of activated carbon adsorption process was high, and the regeneration and disposal of activated carbon should be considered. Therefore, the selection of COD advanced treatment process should be based on the influent quality, full technical demonstration under the premise of feasibility of small-scale and pilot scale test, and comprehensive consideration of construction, operation, land occupation, elevation and other factors to select the suitable technology for upgrading.