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چكيده انگليسي :

Evaluation of Nitrate Rejection of Isfahan Groundwaters by Nanofiltration NF Membranes Ahmadreza Ghahremanfard a ghahremanfard@ce iut ac ir Date of Submission 19 04 2011 Department of Chemical Engineering Isfahan University of Technology Isfahan 84156 83111 Iran Degree M Sc Language FarsiSupervisor Morteza Sadeghi m sadeghi@cc iut ac irSupervisor Ahmad Moheb ahmad@cc iut ac irAbstractPollution of the water resources by nitrate ion is an important and severe threat for human health The maximaladmissible nitrate concentration for drinking water is fixed at 50 ppm by the health organisations Nitrate ionreduction to nitrite can cause a fatal disease in infants known as blue baby syndrome Also there is thepossibility that certain forms of cancer may be associated with the formation of nitrosamines in older agegroups The classical processes used for nitrate elimination from drinking water are catalytic conversion ionexchange biological de nitrification and electrodialysis but all of them have shown some drawbacks andlimitations Among other methods considered for removal of nitrate ions Nanofiltration NF has proved to be apromising and efficient method for this purpose This process falls between Ultrafiltration UF and ReverseOsmois RO In this study the effects of different parameters of operational temperature and pressure as well aspH of the on nitrate removal efficiency and water permeability through NF90 nanofiltartion membrane wereinvestigated To conduct the experiments both synthesized and ground water with nitrate ion concentration of100 and 95 mg l respectively were used Response surface methodology RSM and Central composite design CCD method were used to find the optimum condition of the process to reach simultaneous optimum valuesfor nitrate removal and permeability In addition the economical evaluation and optimization of the process wasperformed by using Verberne cost model According to the obtained results the minimum and maximum waterpermeability for the synthesized water were 16 5 and 84 3 L m 2 h 1 respectively These marginal values fornitrate removal were found to be 44 1 and 78 4 respectively Also as expected the permeability and nitrateremoval both were enhanced with increase in the operational pressure The temperature had a reverse effect onthe nitrate removal where it decreased with increasing temperature Increasing the pH had a negligible effect onthe permeability whereas it improved nitrate removal By comparing the results of the two kinds of water it wasfound that the effects of parameters are nearly the same except the effect of pH For natural ground water incontrast to the synthesized water permeability decreased with increasing pH The experimental results showedthat permeability and nitrate removal for the case of groundwater were generally lower than those of thesynthesized water This could be due to the effects of concentration polarization and fouling of the membrane inthe case of groundwater The economic evaluation of the process showed that increasing capacity of the processleads to higher capital and operating costs while it results in decreasing of producing cost for each cubic meterof water Also increasing the operational pressure causes higher capital cost In fact the cost of producing eachcubic meter of purified water decreases with increasing the pressure from 3 to 7 bar whereas it increases athigher pressures Therefore the optimum pressure of the process was found to be 7 bar However furthereconomic evaluation of the membrane process showed the lowest cost of water treatment can be achieved byconducting the process in the temperatures range of 13 to 27 C Keywords Membrane nanofiltration nitrate rejection permeate flux verberne model

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بررسي حذف نيترات از آب هاي زير سطحي اصفهان با استفاده از غشاهاي نانو فيلتراسيون

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