Filtration generally requires the use of various chemicals known as filter aids. These chemicals include those used in the process of coagulation, and to accelerate and enhance the particle sedimentation process (called flocculants), as well as to provide a precoat filter to enhance the suspended particle removal efficiency. Both an understanding of the physical and chemical forces involved in the filtration process are important to proper selection and operation of filters in waster treatment applications. This chapter covers widely used chemical additives employed in water filtration operations. After reviewing some of the properties of these chemical additives, our attention will focus on the actual mechanisms and roles that these chemicals play in the filtration process. An understanding of the role that chemicals play in the process is important to equipment selection and sizing, but also, this will help us to understand the operating regimes and limitation of filtration hardware. 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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