Research On Improvement Technology Of Activated Carbon Filter On Organic Matter Removal In Source Water From The South-Tonorth Water Diversion Project

The implementation of the South-to-North Water Diversion Project caused the original water supply plant to face the problem of multiple water sources.The activated carbon advanced treatment unit has become the focus of attention for the pollution of organic matter in the water.Therefore,it was necessary to reestablish the performance evaluation system of the activated carbon filter,improve the activated carbon filter technology and promote the chemical safety and biological safety of the activated carbon filter effluent according to the water quality characteristics of the new water source.In this paper,activated carbon filter columns of different carbon ages were selected for one-year continuous operation based on the pilot plant of J Water Plant in the North.The effect of carbon age on the removal of organic matter in water was compared and the activated carbon replacement cycle was determined.Combined with a small trial test,the effect of the existing process units and sequence changes of the water plant on the removal efficiency of the activated carbon filter was explored,and the activated carbon filter was coupled with the front-end process to collaboratively remove organic matter.Finally,a new backwashing method of low-frequency ultrasonic combined backwashing was established to further extend the activated carbon replacement cycle and improve the safety of the effluent water quality of the activated carbon filter.The specific research results were as follows:(1)Through the comparison of the operating efficiency of the activated carbon with different ages,it was found that the 2.5-year and 4.5-year activated carbon filter columns had little difference in the removal of organic matter,the removal effect of the two was better than the new carbon filter column with unstable biofilm;high-throughput sequencing analysis revealed that Sphingomonas,DSSF69,etc.were the dominant functional bacteria.The carbon filter column with long carbon age was richer in biodiversity;the removal effect of the filter column on organic matter was related to the concentration of organic matter in the influent.When the concentration of dissolved organic matter in the influent was low,the activated carbon filter would have the phenomenon of reverse diffusion of adsorbed substances,so when the water quality was relatively good,the effect of the activated carbon filter on the removal of organic matter would be weakened;the adsorption value of activated carbon had a certain correlation with the carbon age,but it was not necessarily related to the effluent water quality.Based on the water quality of the South-to-North Water Diversion,the activated carbon replacement cycle could be extended to 4-5 years.(2)From the impact of process operation to investigate the effectiveness of activated carbon,it was found that when sodium hypochlorite was pre-hydrogenated,the optimal level of the dosage of Na Cl O3 was 3mg/L.Excessive addition of sodium hypochlorite had an effect on the adsorption performance of activated carbon,the amount of Na Cl O3 entering the carbon filter should be as low as possible;the O3-BAC combination process could help to improve the removal of organic matter in water.After combined use of ozone and activated carbon,the removal rates of DOC,UV254 and CODMn were increased from 9.68%,10.12% and 14.16% to 19.39%,26.82%,27.82%.(3)Investigate the influence of the sequence change of activated carbon filter and sand filter process units,it was found that the combination of pre-activated carbon filter+ quartz sand filter(carbon-sand)was superior to quartz sand filter + activated carbon filter(sand-carbon).The combination was more suitable for the source water mainly based on the South-to-North Water Diversion Project.The average removal rates of carbon-sand combination for DOC and UV254 are 18.19% and 32.06% respectively,which were higher than the 14.33% and 24.01% of the sand-carbon combination.Activated carbon filter is the main unit for removing organic matter.(4)The application of backwashing technology of low frequency ultrasonic combined with water washing in carbon filter showed that ultrasonic washing could effectively improve the removal effect of activated carbon on organic matter,prolong the replacement cycle of activated carbon and reduce the risk of reverse diffusion of adsorbed substances of adsorption-saturated activated carbon when the concentration of pollutants in the inlet water was low.Ultrasonic backwashing could effectively increase the activated carbon iodine value and methylene blue value.The activated carbon iodine adsorption values of the two filter columns were increased by 36.89% and 26.89%respectively,and the methylene blue adsorption values were increased by 34.68% and21.05% respectively;Simultaneously multiple ultrasonic backwashing did not significantly affect the strength and uniformity coefficient of activated carbon.The activated carbon filter backwashing method could be a combination of ultrasonic backwashing and ordinary backwashing.The ultrasonic backwashing cycle can be from1 to 2 months according to the quality of the influent water.The optimal duration of ultrasonic backwashing is 60 minutes.