Full Description

Coagulation is a process that has been applied in U.S. water treatment practice for over ahundred years. This long history can provide an illusion of familiarity, but changes ingoals have altered its application in recent years, suggesting a need for new levelsof understanding.Prior to 1989, filtered turbidities of less than 1 NTU were accepted for compliance withregulations. Progressive changes in regulations andgreater awareness of the need for more efficient filtration have evolved since this period.Goals for increased levels of performance have emerged, requiring improved control over coagulation since it provides the processmechanisms required for effective removal of particles by granular media filtration.Additional changes in goals have occurred in association with applyingcoagulation for removal of naturally occurring organic matter (NOM), which reacts withdisinfectants to form disinfection byproducts. NOM removal, as measured by changes intotal organic carbon (TOC) and UV254, has thereby been proposed as a new focus forcoagulation. While goals for this aspect of coagulation are different from those associatedwith turbidity removal, the set of conditions that must be satisfied can overlap and it isimportant not to focus entirely on one set of objectives. As such, it is important that anunderstanding of the coagulation process be advanced in a way that consolidates goals forturbidity and NOM removal as integrated objectives. Includes 4 references, figures.

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Edition: Vol. - No. Published: 11/01/2008 Number of Pages: 11File Size: 1 file , 990 KB