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Standard Methods for Examination of Water & Wastewater_7

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Chương này sẽ tiếp tục các cuộc thảo luận trên lọc bắt đầu trong Chương 7, ngoại trừ việc nó đề với lọc tiên tiến. Chúng tôi đã xác định lọc như là một hoạt động đơn vị tách chất rắn hoặc các hạt từ chất lỏng. Một hoạt động đơn vị lọc được thực hiện bằng cách sử dụng màng lọc phương tiện truyền thông tiên tiến lọc. Chương này thảo luận về lọc tiên tiến sử dụng màng electrodialysis và màng áp lực | 8 Advanced Filtration and Carbon Adsorption This chapter continues the discussion on filtration started in Chapter 7 except that it deals with advanced filtration. We have defined filtration as a unit operation of separating solids or particles from fluids. A unit operation of filtration carried out using membranes as filter media is advanced filtration. This chapter discusses advanced filtration using electrodialysis membranes and pressure membranes. Filtration using pressure membranes include reverse osmosis nanofiltration microfiltration and ultrafiltration. In addition to advanced filtration this chapter also discusses carbon adsorption. This is a unit operation that uses the active sites in powdered granular and fibrous activated carbon to remove impurities from water and wastewater. Carbon adsorption and filtration share some similar characteristics. For example head loss calculations and backwashing calculations are the same. Carbon adsorption will be discussed as the last part of this chapter. 8.1 ELECTRODIALYSIS MEMBRANES Figure 8.1a shows a cut section of an electrodialysis filtering membrane. The filtering membranes are sheet-like barriers made out of high-capacity highly cross-linked ion exchange resins that allow passage of ions but not of water. Two types are used cation membranes which allow only cations to pass and anion membranes which allow only anions to pass. The cut section in the figure is a cation membrane composed of an insoluble matrix with water in the pore spaces. Negative charges are fixed onto the insoluble matrix and mobile cations reside in the pore spaces occupied by water. It is the residence of these mobile cations that gives the membrane the property of allowing cations to pass through it. These cations will go out of the structure if they are replaced by other cations that enter the structure. If the entering cations came from water external to the membrane then the cations are removed from the water thus filtering them out. In .