Coagulation-ultrafiltration Treatment Of Low Concentration Uranium Groundwater

Uranium-containing groundwater poses a serious threat to human health due to its radioactivity and chemical toxicity.Conventional processes sometimes cannot effectively remove groundwater uranium,so additional treatment processes are needed to meet drinking water quality requirements.Coagulation-ultrafiltration is a widely used technology in the field of membrane treatment.It has the characteristics of good treatment effect,low operating cost and easy automation.However,at present,there are few studies on the application of coagulation-ultrafiltration in the treatment of groundwater containing uranium.The mechanism of the coagulation process is still unclear.In this study,through the combination of actual water treatment engineering and laboratory experiments,the treatment effect and influencing factors of coagulation-ultrafiltration treatment for low-concentration groundwater containing uranium are explored,and the membrane pollution during the treatment process is also discussed.The actual application of membrane combination process was performed to treat actual radioactive contamination of groundwater.Membrane combination process was adopted to treat the uranium-containing groundwater.The uranium removal during 6 months of operation was monitored and the results showed that the removal of uranium by coagulation precipitation,ultrafiltration,and reverse osmosis were approximately 75%,86%and almost 100%,respectively.Membrane pollution was established after a long-term operation and it obviously affected the effluent quality.Then through a comparative study,it was found that the removal of uranium by coagulation-precipitation process in pure water was very high.Subsequently,the effects of various coexisting ions and organic humic acid on the coagulation and removal of aluminum salts by aluminum salts were investigated.The results show that the effect of coexisting substances on uranium removal rate includes promotion,inhibition and no effect.The main reasons uncovered by zeta potential and aluminum retention rate,includes:?the formation of aluminum hydrolytic flocs;?the zeta potential of aluminum salt flocs;?the variation of coexisting ions and uranium morphology with pH.The removal of uranium in raw water is significantly lower than that of pure water and the adaptability to pH was poor.The optimal treatment effect is achieved at pH=6.Adding PAM is beneficial to further uranium reducing,and the best dosage of PAM is 0.2 mg/L.Finally,the process of coagulation-ultrafiltration treatment of groundwater was simulated in the laboratory and the membrane contamination was investigated.Under different conditions,it was found that the dosage of coagulant was controlled at 5-10 mg/L,pH=8,and dosage of PAM was 0.2 mg/L,which could effectively reduce the ultrafiltration membrane contamination.Combining properties of flocs and SEM characterization of ultrafiltration membrane surface,we found that the degree of membrane contamination was mainly related to the size of flocs particle size.The larger the particle size of flocs,the looser the filter cake layer on the membrane surface and the less membrane pollution.