Research Of Application And Optimization On "Conventional+Ultra-filtration" For Drinking Water Treatment

Biological Activated-Carbon Filter(BACF)is widely used in the process of water treatment,especially in drinking water.However,BACF could make the head-loss increase quickly,and the activated carbon is easy to harden which could cause great distress to back-washing of filter and the high cost in practice.In addition,the turbidity is not entirely the reflect of the content of impurities,especially in low turbidity raw water.Based on these reasons,“conventional+UF” process was developed to tackle these problems.In particular,the combination of Suspended Media Biological Filter(SMBF)and UF Experimental mainly attempts to study the effect of the “conventional+UF” on water purification,including the study on the loss of smaller SMBF as well as “conventional+ UF” process of pilot test,and optimized its operation parameters.And finally combined with actual project to analyze the effect of process.Test results of the study were as follows:(1)The increase of the head-loss of SMBF was caused by the growth of biofilm,and the growth rate is very small.In the actual application,SMBF can effectively reduce the operating cost of biological filter.Compared with the BACF,backwash cycle of SMBF extended 11 days,and intensity is lower,which the gas intensity is 8L/(m~2·s),the water intensity is about 5~7L/(m~2·s).(2)“Conventional +UF” effluent turbidity on average about 0.051 NTU.Water particle number(>2um)is about 14 per milliliter,relative removal rate as high as 99.99%.In addition,CODMn and ammonia nitrogen removal rely mainly on SBMF biodegradation.The removal rate of "coagulation and precipitation + sandfiltration +SMBF + UF” for CODMn is about 64.33%.After the success of the biofilm formation,the removal rate for ammonia nitrogen is about 89.74%.(3)Under the suitable operation parameters,the UF membrane fouling rate can be effectively slowed down.In application of UF,the appropriate flux for UF membrane is 40L/(m~2·s),and UF membrane operation pressure should not be more than-50 KPa,and the appropriate time of single filtration is 40 min,and the appropriate aeration intensity is 1L/(m~2·s),water backwashing time for the 90 seconds.(4)The effluent turbidity of “coagulation and precipitation + sandfiltration +SMBF +UF” project is 0.056 NTU,and the turbidity removal rate is about 99.62%.The removal rate of CODMn is about 69.34%,and the effluent concentration is about 1.114mg/l.For ammonia nitrogen removal rate is 89.54%,and the effluent concentration is about 0.24mg/l.The number of particles(>2um)is around 17 per milliliter,and the removal rate is as high as 99.92%.Meeting the drinking water health standards(GB5749-2006),meanwhile,which better ensure the safety and health of drinking water.(5)The project test showed that the timing of the chemical cleaning can improve the permeability of membrane in the filtration process,and membrane flux recovery rate is about 92.19%,which can effectively reduce membrane fouling rate.To a certain extent,which could save the cost of water system.