| Water pollution and shortage has become a critical and serious challenge to society progress and economy development in the world. As an important strategic solution to water shortage, seawater desalination has been playing an increasingly momentous role. The desired performance of seawater desalination systems is guaranteed by appropriately designed pretreatment to face the varying seawater quality. It is of great theoretic and practical importance to focus on Ultrafiltration (UF) as an effective alternative to conventional pretreatment system prior to seawater reverse osmosis (SWRO). To evaluate the performance of UF as the pretreatment method, pilot testing and membrane fouling in the filtration process should be considered. In this paper, pilot test were carried out at Jiaozhou bay by dead-end and cross-flow ultrafiltration technique using UFI and UFII hollow fiber UF membranes. The performance of designed project proves that UF system is feasible in either economy or technology,and is totally suitable for the preconditioning craft of seawater desalination. The results are shown as follows:1. By investigating the removal effect of turbidity of sand filter and hydroclone, it is found that the removal rate of sand filter is 76%, and hydroclone is 14%. So sand filter is choosed as pretreatment prior to UF.2. During pilot testing of dead-end operating mode, the best operation parameters and the removal effect of turbidity have been investigated using two different hollow fiber UF membranes. Permeate flux and SDI15 of ultrafiltration have been measured against time to evaluate performance of pretreatment systems. It has been found that the performance of UFI is better than UFII, the removal rate of turbidity is 100%, the SDI15 of UFI is about 2.0, which satisfies the requirement of SWRO feed water. The method of chemical cleaning has been investigated in the course of long-period investigation on UFI membrane. It is found that best method is that the membrane is soaked in 0.5% NaOH(AR) with 200mg/LNaClO(pH=12.82)for one hour, and rinsed for two hours;then soaked in 0.1%HCl(AR)(pH=2.25)for one hour, and rinsed for two hours. The recovery of permeate flux can be up to 98.62%. All the course of pilot, the recovery rate of permeate water all can be up to 95%. The primary technical feasibility of UF membrane as pretreatment prior to seawater desalination gained to be evaluated.3. The main purposes of pilot testing on cross-flow operating mode are to find the optimum recovery, permeate flux and filtration duration. Based on maximum net product volume, performance of the UF system is good with the following conditions: recovery is 80%, permeate flow rate is 1200L/h, and filtration duration t = 30 min. A short-period investigation has been carried out in this filtration mode. According to the consumption of energy and chemical reagents, the direct operational cost of both dead-end and cross-flow mode has been briefly analysed. The results indicate that the cost per ton in dead-end mode is 0.42 yuan less than in cross-end mode which is 0.49 yuan.4. A mathematics model to simulate the condition of cross-flow UF process is provided. Many date of turbidity, CODMn of UF feed water as well as corresponding permeate water flux are recorded. Linear regression method is applied to the experimental data, and the UF membrane flux model is presented as follows: Jv =△P(turbidity)-0.03 (CODMn) -0.06/6.7568×105μw. The results indicate that the relative error of flux between simulation and experimental measurement is less than 15%. As a result, the model can be used as a reference to design UF process for similar liquid mixture system.
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