Study On The Efficiency Of Ozone-biological Activated Carbon In Treating Micro-polluted Surface Water And Engineering Applications

With the continuous development of China’s economy,people’s requirements for drinking water quality and national water quality standards are constantly improving,but the raw water of water treatment plants is increasingly coming from micro-polluted surface water.The conventional"four-step"water treatment process has been difficult to meet the new version of the"Sanitary Standards for Drinking Water."Therefore,the advanced treatment process of drinking water has been valued by the water supply industry.The most widely used is the ozone-biological activated carbon process.It integrates oxidation,adsorption,biodegradation,and can effectively remove pollutants that are difficult to remove by conventional water treatment processes such as ammonia nitrogen,organic matter,and disinfection by-products in raw water.This research mainly focuses on the relative position of the conventional treatment process and the ozone-biological activated carbon process.At the same time,it optimizes the operating parameters and explores its treatment effect in the actual water supply project.First,the operating parameters of the ozone-biological activated carbon process were determined and optimized.By exploring the influence of the residence time of the activated carbon filter,the filtration cycle and the backwash intensity on the effluent quality of the filter,it is recommended that:the residence time of the carbon filter is 15 minutes,and the removal rates of UV₂₅₄,COD_Mn,and ammonia nitrogen are 34.68%,42.12%,60.25%.From the third day of operation of the carbon filter,the removal rate reached a relatively stable state and continued until the eighth day.Therefore,the recommended filtration cycle is 7 days,and the removal rates of UV₂₅₄,COD_Mn,and ammonia nitrogen are 34.68%,46.18%,64.46%.Using a separate high-speed water flow backwashing method,the best backwashing intensity is determined to be 15 L/（㎡·s）,and the backwashing time is 8-11min.Subsequent ozone dosage optimization experiments show that when the dosage is 2.0mg/L,the comprehensive water treatment effect is better.At this time,the removal rates of UV₂₅₄,COD_Mn,and ammonia nitrogen are 70.31%,57.5%,67.65%,.Secondly,through the coagulation test of five commonly used coagulants,the results show that:the removal rate of polyaluminum chloride on various pollutants is high,and the effect is best when the dosage is 2.0mg/L.The removal rates of turbidity,COD_Mnand ammonia nitrogen were 87.96%,39.25%,25.11%.Research on the relative sequence of the three water treatment units of coagulation,ozone-biological activated carbon,and sand filter shows that the pre-coagulation has a better turbidity removal effect,and the average removal rate is 2.35%higher than that of the post-coagulation;The removal effect of pre-coagulation on ammonia nitrogen is better,the average removal rate is 3.10%higher than pre-coagulation,and there is not much difference between the two in the removal of COD_Mn.Finally,by comparing the influence of the relative position of the sand filter and the ozone-biological activated carbon on the effluent quality in the actual project,the data shows that the relative position of the sand filter has little effect on the removal rate of turbidity and ammonia nitrogen.The oxygen removal effect is better.Through the analysis of the water quality of the incoming and outgoing water of a water plant in the past three years,it is found that the ozone-biological activated carbon advanced treatment unit has a good removal effect on the micro-polluted surface water in the actual water supply engineering application.The average removal rate of turbidity,oxygen consumption and ammonia nitrogen are respectively can reach 90%,50%,70%.