Overview of Common External Treatment Process Technologies

1 OVERVIEW OF COMMON EXTERNAL TREATMENT PROCESS TECHNOLOGIES 

The term external treatment is used to describe all of the different types of essential nonchemical processes employed to condition or remove some or all impurities in water before it reaches the FW pumps. There is often considerable overlap in the scope of common water treatment process technologies, and each of the primary processes can be divided into several subsets, giving rise to a wide range of impurity removal efficiencies for each process. 

Where higher quality water is required, there is no single technology that can provide all the answers to impurity removal requirements. Consequently, it is common practice to employ two, three, or even more processes in sequence. In view of the different water sources, final quality requirements, and permutations of technologies and subsets, there is no universally agreed upon order in which the technologies are sequenced. Nevertheless, there are some purification processes that, because of specific technical or economic advantage, enjoy popular appeal and are commonly specified. 

Leaving aside FW deaeration (which is usually provided as the final type of external treatment in the pre-boiler section), the primary forms of treatment processes commonly employed can be conveniently categorized into three areas  

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