The Experimental Study On Cellar Water In Northwest Towns By Combined Process Of Ultrafiltration

China Northwest is one of the world’s most arid areas and seriously lacks water.Although rainwater harvesting cellar in solving water shortage problem played anirreplaceable role as the main source of water in most towns and villages, the cellar waterquality becomes inferior, such as high organic matters, high turbidity and ammonia nitrogen,bacteriological indicators significantly exceeding standard, and if not treated, it will directlyundermine the health of people in northwest China, hinder the economic development andlocal residents’ living standard.This research on the characteristics of cellar water quality in Northwest China reasonablyintegrated the technology and equipment for processing cellar water in northwest rural area,that is, we take ultrafiltration as the core technology, integrating hydrogen peroxide modifiedactivated carbon-ultrafiltration water purification process equipment. First the experimentfocuses on the factors of activated carbon adsorption, including adsorption time, dosage, pHand temperature, then activated carbon was modified through various modifiers to select thebest modified activated carbon packed column, and after that activated column filtration ratewas selected. Then we conducted dead-end filtration and cross-flow filtration for fourdifferent ultrafiltration membrane molecular weight cut, analyzing the distribution ofmolecular weight of contaminants in the cellar, and finally detected water quality of the entiredevice and considered the cost of the device and application prospects.In the experiment of factors affecting the activated carbon adsorption, the resultsdemonstrate that the adsorption equilibrium time for activated carbon to adsorb pollutants incellar water in the rural areas of northwest China was10h; the optimal dosage of activatedcarbon was2.0g/L, at the time when the removal rate of the raw water ammonia, CODMnandUV254basically reached their maximum,25.24%,45.74%and54.74%respectively; theadsorption of activated carbon on CODMnis corresponding to the Freundlich adsorptionisotherm model; within the modulated pH range, when pH=3.39, CODMn, UV254removalrate reaches the maximum,50%and74.58%respectively, and the optimum pH of ammoniaremoval appears when pH=10.02, with the removal rate of18.44%; in the four temperaturevalues selected in the experiments:20℃,30℃,40℃,50℃, by comparing to theexperimental results, the effect of temperature on the activated carbon adsorption of organicmatters is ineffective.We carried out the orthogonal experiment of three factors and three levels on activatedcarbon by selecting six kinds of modifiers NaOH, HNO3, HCl, NH3-H2O, KMnO4, H2O2, withCODMnas a test standard. The results showed that the optimum concentration of the modifiedcombination regimen of six modifiers were40%,4mol/L,4mol/L,12.5%,0.01mol/L,5%; oscillation time was2h,2h,2h,8h,8h,8h; modification temperature was40℃,30℃,30℃,30℃,40℃,40℃. By comprehensive comparing the removal effects of six kinds of modifiedactivated carbon with unmodified activated carbon on CODMn, ammonia and UV254, wefinally selected5%H2O2of modified activated carbon to oscillate8h under40℃condition toconduct the subsequent experiments.In the activated carbon filtration rate selection experiments, with the optimal choice ofthe filtration rate6m/h, the removal efficiency of modified activated carbon column onammonia, CODMn, UV254and turbidity was14.37%,51.16%,54.95%and20.17%.After the measurement experiments on organic molecular weight distribution in cellarwater:78.57%of CODMn,68.21%of UV254are within the range of <6KDa, and the mostorganic molecular weight distribution of the cellar water can be within the range <6KDa. Indifferent experiments on ultrafiltration filters, with dead-end filtration mode, the removalrates of the6K ultrafiltration membranes which has the best removal efficiency, for ammonia,CODMn, UV254and turbidity were24.05%,21.88%,20.41%and92.17%; with cross-flowfiltration mode, the removal rates of the6K ultrafiltration membrane for ammonia, CODMn,UV254and turbidity were26.46%,22.67%,24.66%and93.23%. There is no significantdifference of the membrane in effluent quality between the two modes. However, withcross-flow filtration mode, water production of ultrafiltration membrane became slowly overtime, while with dead-end filtration mode, membrane flux ratio declined slightly faster thanwith crossflow filtration.Modified Activated Carbon-50K ultrafiltration membrane integrated ultrafiltrationtechnology has a very good effect on removing water pollutants. After treatment, totalammonia removal rate in cellar water was37.71%; CODMntotal removal rate was50%, UV254removal rate reached78.65%; and total removal of turbidity was up to95.32%. Effluentammonia content was0.337mg/L, CODMnwas1.78mg/L, UV254content0.019, turbidity0.38NTU, and all these indexes have met the “Drinking Water Health Standards”(GB5749-2006). Thus we reached conclusion that the water treatment technology lived up tothe original expectation, and fully met the drinking water requirements. While computing theoperation costs of the device, it is rational and economical. All in all, water treatmenttechnology we chose realized our initial expectations.