| For a long time,residents in rural arid and water-scarce areas in northwest China have been using rain and snow water as their domestic water source.Although the water shortage in the area has been alleviated,water pollution problems often occur in the process of rain and snow conflation and the storage of rainwater storage cellars,which makes some water quality indexes of rainwater storage water unable to meet the requirements of drinking water standards.Long-term consumption of untreated cellared water poses a potential health threat;Therefore,it is necessary to study the treatment technology suitable for the water quality in this area in view of the problem of some water quality exceeding the standard.Based on this background,this study took micro-polluted rainwater harvesting and storage water in rural areas of Northwest China as the research object,and studied the effects of enhanced coagulation,electroflocculation and ultrafiltration technology on effluent quality and membrane flux under separate treatment and combined treatment respectively.The main conclusions were as follows:（1）With polyaluminum chloride（PAC）and polyferric chloride（PFC）as coagulants,polyacrylamide（PAM）and polydimethyl diacrylamide（PDMDAAC）as coagulants,four different dosing combinations of inorganic polymer coagulants+organic polymer coagulants were composed,respectively.The effect of chemical coagulation on the treatment of micro-polluted cellaring water under different conditions（dosage of coagulant/coagulant aid,p H value of test water,hydraulic condition）was investigated comprehensively and systematically.The results showed that PAC alone had better effect than PFC,and better effect was obtained when the dosage was 40mg·L-1 and 50mg·L-1respectively.PFC has a wider adaptation range to p H value than PAC.According to the analysis,PAC+PAM is the best coagulant+coagulant aid combination.The influence of hydraulic conditions on the coagulation effect was not obvious.The optimal hydraulic conditions were as follows:fast stirring time was 2 min,the rotational speed was 400r·min-1,slow stirring time was 10 min,the rotational speed was 80 r·min-1;The response surface model was used to investigate the effect of three significant single factors（dosage of coagulant,dosage of coagulant aid and p H value of test water）on the treatment of cellar water.The results showed that under the conditions of 52.08 mg·L-1 PAC dosage,0.32 mg·L-1 PAM dosage and p H value of 8.03,The turbidity,permanganate index and ammonia nitrogen removal rate of micro-polluted water can reach 95.8%,81.1%and48.6%,respectively.（2）Using pure aluminum and pure iron as anode plates,and pure titanium and stainless steel as cathode plates,respectively,the electrode plate combination of active metal and inert metal was formed.The treatment effect and influence rule of electroflocculation on micro-polluted cellar water under different conditions（plate spacing,plate voltage and reaction time）were investigated comprehensively and systematically.The results show that the effect of Al-Ti plate combination is better,and the significant influence range of plate spacing,plate voltage and reaction time is 5～12mm,20～30 V and 20～30 min.The interaction of the above three factors was investigated and analyzed by using the response surface model.It is concluded that the reaction time has the greatest influence on the electroflocculation effect,followed by plate voltage and plate spacing.According to the optimal parameters predicted by the model and reasonable analysis,under the optimal conditions of plate spacing 9.0mm,plate voltage 22.2V and reaction time 25.9min,the turbidity of micro-polluted water,permanganate index and ammonia nitrogen removal rate are 96.9%,76.9%and 60.8%,respectively.（3）Polyacrylonitrile membranes with molecular weight of 10 k Da and 100 k Da were selected as ultrafiltration membrane materials,and the treatment effects of direct ultrafiltration,coagulation-ultrafiltration,coagulation-aid coagulation-ultrafiltration,and electric flocculation-ultrafiltration were investigated respectively.The results showed that:compared with the adsorption effect of pollutants,10 k Da ultrafiltration membrane was better than 100 k Da.Compared with the degree of membrane flux recovery,the 100 k Da ultrafiltration membrane is greater than 10 k Da,that is,the proportion of reversible pollution suffered by the membrane with small molecular weight is greater.Combined with the analysis ofζpotential and EEM spectrum,it is found that the absolute value ofζpotential of coagulation-aid-ultrafiltration is the lowest,and coagulation-aid-ultrafiltration and electroflocculation-ultrafiltration can effectively remove organic compounds such as humic acid and fulminic acid.On the whole,the effect of coagulation-coagulation-assisted ultrafiltration treatment is equivalent to that of electric flocculation-ultrafiltration treatment,and both of the two combined processes can reduce the excessive index,so that it can meet the requirements of the"drinking Water Sanitation Standard"（GB5749-2022）;The cost analysis of chemical coagulation and electroflocculation shows that the cost of chemical coagulation is significantly lower than that of electroflocculation. |
PDF Full Text Request