The role of the filter media is to provide a substrate surface through which the suspension passes, and suspended solids are captured onto the surface and within the pore structure of the substrate. As described in Chapter 1, when pressure or a vacuum is applied over one side of the media, the liquor is drawn through the filter media, leaving behind suspended particles retained on the media, with the clean filtrate discharged from the apparatus. This simplified view is illustrated in Figure 1. In many ways the media is the workhorse of any filtration apparatus. The properties, durability and cost are key characteristics that we need to examine when making selections. In this chapter we examine criteria for selecting different filter media. The discussions focus only on conventional filter media, and other, less conventional systems are discussed in later chapters. As with other chapters you will find a series of sidebar discussions that offer additional information and highlighted factors that you should consider. And at the end of this chapter are some Questions for Thinking and Discussing. Remember to refer to the Glossary at the end of the book if you run across any terms that are unfamiliar to you.
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