Study On Strontium-containing Wastewater Treated By Microfiltration Combined Process And Membrane Fouling Alleviation

Based on the situation of the serious membrane fouling of strontium-containing wastewater treated by hydraulic mixing coprecipitation-microfiltration combined process,this experiment improve the mode of operation which added an intermediate water tank,transformed from continuous feeding to sequencing batch,extended coagulation time.The new process still operated with an automatic control,had a stable operation and good effluent quality.This paper compared the membrane fouling and treatment effect between new process and primary process.The result indicated that new process could reduce membrane fouling rate obviously,at different temperature the membrane fouling rate both dropped over 50 percent,the extention of coagulaton time could coagulate more sufficiently,enlarge the size of particles in the mixed liquer in the membrane separator,had conducive to alleviate membrane fouling.New process reduced the effect of strontium removal slightly than primary process,but also kept a good removal rate.This paper explored the way of alleviating membrane fouling futher basis on new process,the effect of PAC added as pretreatment on membrane fouling and treatment efficiency were studied which compared two experiments between PAC dosing of 0.5 g/L and with dosing.The result indicated that the experiment which added PAC could reduce membrane fouling rate than that without PAC dosing,disposed water volume increased 300 L.The PAC in membrane separator could attached to membrane surface gradually and formed a loose PAC cake layer which could resist fine particle from entering into membrane hole effectively,slowing down the decrease of membrane flux.PAC added could brough down effluent strontium concentration and decontamination factor(DF)were 990 and 744 respectively,concentration factor(CF)were 3750 and 3667 respectively,indicated that PAC added could not have an effect on sludge quantity.Ferric chloride served as flocculant,its dosage could influence coagulation effect.The effect of ferric chloride flocculant dosage(10-30 mg/L)on membrane fouling and treatment efficiency were studied.The result indicated that there was a linear growth between the suspended solid in membrane separator and flocculant dosage,and a proper flocculant dosage could increase partical size.In the aspect of membrane fouling,increasing flocculant dosage could help coagulation effect and slowing down the reduce of membrane flux effectively in preliminary stage,but in final stage oversize flocculant dosage leaded to a high concentration of suspended solid in membrane separator and serious concentration polarization which go against to reduce membrane fouling.Flocculant dosage had no much effect to strontium removal,concentration factor and dosage had a linear growth relationship.Therefore,the best ferric chloride flocculant dosage could be 20 mg/L.