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Standard Methods for Examination of Water & Wastewater_6

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Lọc cũng phân tách vật liệu khác nhau "kích thước, do đó, nó là một hình thức kiểm tra, nhưng lọc nghiêm ngặt liên quan đến việc tách các chất rắn, các hạt và chất lỏng như trong nước. Microstrainer thảo luận trong chương 5 là một bộ lọc. | 7 Conventional Filtration Filtration is a unit operation of separating solids from fluids. Screening is defined as a unit operation that separates materials into different sizes. Filtration also separates materials into different sizes so it is a form of screening but filtration strictly pertains to the separation of solids or particles and fluids such as in water. The microstrainer discussed in Chapter 5 is a filter. In addition to the microstrainer other examples of this unit operation of filtration used in practice include the filtration of water to produce drinking water in municipal and industrial water treatment plants filtration of secondary treated water to meet more stringent discharge requirements in wastewater treatment plants and dewatering of sludges to reduce their volume. To differentiate it from Chapter 8 this chapter discusses only conventional filtration. Chapter 8 uses membranes as the medium for filtration thus it is titled advanced filtration. Mathematical treatments involving the application of linear momentum to filtration are discussed. Generally these treatments center on two types of filters called granular and cake-forming filters. These filters are explained in this chapter. 7.1 TYPES OF FILTERS Figures 7.1 to 7.8 show examples of the various types of filters used in practice. Filters may be classified as gravity pressure or vacuum filters. Gravity filters are filters that rely on the pull of gravity to create a pressure differential to force the water through the filter. On the other hand pressure and vacuum filters are filters that rely on applying some mechanical means to create the pressure differential necessary to force the water through the filter. The filtration medium may be made of perforated plates septum of woven materials or of granular materials such as sand. Thus according to the medium used filters may also be classified as perforated plate woven septum or granular filters. The filtration medium of the microstrainer .