| In recent years,with the water resource problem becoming more and more serious in our country,and the higher standard of the quality of drinking water and the deficiency of the normal water treatment,ultrafiltration membrane water treatment is widely used in the water supply treatment.However,the pore size of the ultrafiltration membrane is various in the market,and there is still not a standard of the pore size of ultrafiltration membrane.Besides,the pore size can also be different if the water quality is different.The thesis mainly focuses on the characteristics of the mountainous city water quality and the choice of the pore size of ultrafiltration membrane.The thesis investigates 4 sampling points in Chongqing respectively in the wet period and the rainless period,and evaluates the characteristics of the mountainouscity water quality by analysing 12 water quality standards including physics chemistry and microbiology.The raw water is made according to the characteristics of water quality of Chongqing to do the experiment.By making the raw water filter through different ultrafiltration membrane with different pore size,we choose the better treatment efficiency kind.And also by considering the single-family and not very well geographic spots,we filter the raw water in the situation of low flux,and choose the better kind in the end.The result is as follows:?1?According to the survey and the data,we can know the water quality of Chongqing: PH 8.01,weak alkaline;Turbidity is around 4NTU;Total hardness average value is 80mg/L.Chongqing locates in the southwest,and the total hardness of water in the south is mostly less than in the north;oxygen consumption(CODMn)is around4mg/L.According to the surface water quality standards,we can know that the water quality is over class II if the CODMn in the water is less than 15mg/L;the average value of total numbers of colony is 120CFU/ml,the average value of the total coliforms is29CFU/ml;the average value of Fe is 0.375mg/L,and the average value of Mn is0.154mg/L.The overproof of Fe and Mn often happens in the northeast and the south.Chongqing locates in the south,and the value of Fe and Mn in the water is not low,and the value in the wet period can be higher than in the rainless period.The reason is that there is more suspended matter in the water in the wet period,which brings more Fe and Mn.?2?The turbidity removal efficiency of the 0.01?m kind and the 0.05?m kind is respectively turbidity:97.4%,89.8%;UV254:11.1%,6%;CODMn:25.3%,12.4%;total numbers of colony:100%,97.4%;total coliforms:100%,100%?The formeris better than the later;As to the removal efficiency of UV254,both two kinds are very low;As to CODMn,with 10 times of outlet of the 0.01?m kind,CODMn is less than3mg/L,which can reach the standard of drinking water,reaching the rate of 100%,while the 0.05?m kind is just 70%,there are 3 times that it doesn't reach the standard;As to the total coliforms and total numbers of colony,both two kinds can reach the standard,while the 0.01?m kind can reduce the total numbers of colony to zero.Therefore,as to the characteristics of water quality of Chongqing,the 0.01?m kind is better.?3?As to the 0.01?m kind,when the operating flux rises from 25 L/?m2·h?to 30L/?m2·h?,the trans-membrane pressure drop changes,rising from22 k Pa to 23 k Pa,which indicates that membrane fouling occurs.So the critical flux is between 25L/?m2·h?and 30 L/?m2·h?,and the average value is 27.5 L/?m2·h?.Also,when the operating flux of the 0.01?m kind rises from 20 L/?m2·h?to 25 L/?m2·h?,the trans-membrane pressure drop rises from 7k Pa to 10.5k Pa,so the critical flux is between 20 L/?m2·h?and 25L/?m2·h?,and the average value is 22.5 L/?m2·h?.?4?In the situation of low flux,the turbidity removal efficiency of the 0.01?m kind and the 0.05?m kind is respectively turbidity:98%,89.8%;UV254:12.7%,7.5%;CODMn:24.8%,18.8%;total numbers of colony:100%,97.6%;total coliforms:100%,100%?The former turbidity removal efficiency is 10% higher than the later.As to the UV254 removal efficiency,the former is twice than the later;As to the removal efficiency of UV254,the result is not ideal of both two kinds;As to CODMnin the water,the 0.01?m kind is better,the outlet standard-reaching rate is 100%,while there are 4times that the outlet rate exceeded the limit with 0.05?m;As to the total coliforms in the water,which both two kinds can remove completely,the standard-reaching rate are both100%;As to the total numbers of colony,only the 0.01?m kind can reduce the total numbers of colony to zero.In conclusion,in the situation of low flux,the efficiency of the 0.01?m kind is better concerning the water quality of Chongqing.?5?As to the membrane fouling,the growth rate of trans-membrane pressure drop of the 0.05?m kind is faster and much easier to result in membrane fouling.The reason is that the size of the impurities in the micro-polluted water in the ground of the mountainous city is various.But 50 nm is just a critical point,the 0.05?m kind can not only lead to cake layer in the surface of the membrane,but also can lead to membrane pore blocking,which is more difficult to clean compared with cake layer and sometimes even irreversible... |
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