Page 46 - Fundamentals of Water Treatment Unit Processes : Physical, Chemical, and Biological

Part I

Foundation

Taking time to assimilate themes common to all unit pro- Models: In Chapter 3, the idea of a ‘‘model’’ is described in
cesses helps to put order and understanding into learning terms of its variety of forms. Models are at the root level of
about water treatment as opposed to a collection of facts and design. We use models in everyday life ranging from mental
equations. Therefore, Part I describes some of the founda- images to photographs. The designer uses whatever may be
tions, or ‘‘building blocks,’’ of the field. This foundation available, for example, inspections of existing plants, judgment,
constitutes the first four chapters. rules of thumb, equations, mathematical models, physical
Unit processes: Chapter 1 describes how water treatment as a models, computer animations, etc. All of these are models and
topic can be disaggregated to unit processes, principles, and are means to project from the abstract to operation and design.
technologies. Examples of treatment trains illustrate a variety Reactors: The idea of the ‘‘reactor,’’ in Chapter 4, applies to
of treatment applications. These expand beyond the traditional many unit processes. It is the notion that if we pass a dissolved
municipal potable water and wastewater to include tertiary or particulate contaminant through a particular kind of ‘‘black-
treatment, modified water treatment, industrial process water, box,’’ changes will occur. The reactor concept is the basis for
and industrial wastewaters. The variety of applications is formulating these changes mathematically. The general idea
almost without limit. applies to a variety of unit processes, for example, settling,
Contaminants: Chapter 2 looks at the variety of contaminants mixing, deep bed filtration, adsorption in packed columns,
found in water. Selected ones must be removed in order to ion-exchange, membranes, gas transfer, disinfection, precipi-
provide for further uses of water either as required by law or tation, oxidation, activated sludge, bioreactors, etc. The con-
as motivated by a private need such as for industrial process cept applies to natural systems where ‘‘passive’’ changes
water. occur, as well as to engineered systems.