Ultrafiltration-ultraviolet Treatment Technology For Water From Water Cellar In The Rural Areas Of Northwest China And Membrane Fouling Control

In view of the problems of turbidity,total bacterial colonies and other indexes of the water cellar in the rural areas of northwest China cannot meet the limit values in the Sanitary Standard for Drinking Water(GB5749-2006),the lack of purification technology,process and supporting equipment for water cellar,and the vulnerability of membrane filtration water purification process to biofouling,we conducted a study on ultrafiltration-ultraviolet treatment technology and membrane fouling control for cellar water in the rural areas of northwest China.The paper investigated the water quality and microbial community of water cellars in 10 villages in County H of Gansu Province,evaluated the risk of heavy metals in water cellars by using the ecological risk index method and the comprehensive heavy metal pollution index method,investigated the water purification effect of ultrafiltration-ultraviolet process on actual water cellars,developed ultrafiltration-ultraviolet purification equipment for water cellars and conducted engineering application demonstrations in villages B and J of Gansu Province,and verified The application effect of the 50 units of the demonstration bases.3 typical microorganisms,Staphylococcus aureus(S.aureus),Enterococcus faecalis(E.faecalis)and Pseudomonas putida(P.putida),were used in the laboratory to investigate the mechanisms of biofouling by ultrafiltration membrane and alleviation of biofouling by ultraviolet pretreatment.The results of the study showed that the total number of colonies in the cellar water samples ranged from 5 to 556.67 CFU/m L,turbidity from 4.7 to 58.5 NTU,and heavy metal contamination index from 6.287 to 163.020,with turbidity and total number of colonies exceeding the limits of the Sanitary Standard for Drinking Water(GB5749-2006),and the cellar water was at risk of microbial contamination and metal contamination.For the water quality of the water cellar,PP cotton-ultrafiltration-ultraviolet combination process was selected for the development of purification equipment,the results of the experiments of treating simulated cellar water showed that the turbidity of the effluent from the purification equipment was 0.15-0.22 NTU and the total number of colonies was 0-80 CFU/m L,which were reduced by 98.31%-98.85% and 96.36%-100%,respectively,compared with the original cellar water.The water quality testing data of the demonstration bases showed that the turbidity of the effluent from the purification equipment was 0.12～0.32 NTU and the total number of colonies was 2～53CFU/m L,which were reduced by 25%～99.07% and 22.67%～99.88%,respectively,relative to the original cellar water.The results of ultrafiltration membrane biofouling showed that the rodshaped P.putida caused a higher degree of membrane fouling than the spherical S.aureus and E.faecalis,which was mainly due to higher concentration of loosely bound EPS with apparent molecular weight smaller than 1 k Da.The computational fluid dynamics results suggested that the larger membrane filtration resistance caused by P.putida was due to more EPS secretion.According to the extended Derjaguin-Landau-Verwey-Overbeek(XDLVO)theory,higher interaction energy was induced because of the higher content of polysaccharides(e.g.,hydroxyl groups)and proteins(e.g.,aggregated strands of amide I band)in EPS from P.putida,resulting in a thicker biofilm and stronger biofouling degree than that caused by S.aureus and E.faecalis.In addition,both EPS secretion and microbial interaction energy were inhibited by ultraviolet treatment,resulting in fouling alleviated.The above study shows that the ultrafiltration-ultraviolet purification equipment has the ability to control the turbidity and total bacterial colony of the water from water cellar in the rural areas of northwest China so that its water quality meets the standard,which provides the technology and programs for the use of rain and snow water to produce safe drinking water,and provides novel approach and theoretical values for further biofouling control of the membrane treatment process.