Chapter 3 - Chemical Additives that Enhance Filtration

Abstract

Various chemicals, known as filter aids, are used in filtration. The chemicals are used in the process of coagulation and to accelerate and enhance the particle sedimentation process called flocculants. The chemicals are also used to provide a precoat filter to enhance the suspended particle removal efficiency. This chapter discusses the widely used chemical additives that are employed in water filtration operations. After reviewing some of the properties of the chemical additives, the chapter focuses 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, and it also helps people to understand the operating regimes and limitation of filtration hardware. The chapter also discusses aluminum based chemical additive compounds and iron-based compounds. It elaborates on the filter aids that are employed to improve the filtration characteristics of hard-to-filter suspensions. The chapter discusses the different ways in which filter aids can be applied.