PHYSICO CHEMICAL TREATMENT METHODS FUNDAMENTALS AND DESIGN GUIDELINES

This chapter is focused on the main physicochemical methods used in the treatment of waste– and ground-waters. The bases, selection rules, and the main guidelines for the design of distillation-evaporation, adsorption-ion exchange, air stripping, chemical precipitation and chemical reduction/oxidation processes are briefly summarized in the present work. In order to systemize this study, these physico–chemical processes were classified according to their controlling mechanism: phase equilibrium (adsorption), chemical equilibrium (precipitation), kinetics (reduction and oxidation processes), or mass transfer (desorption, distillation). The selection of the most appropriate physicochemical treatment for a given water treatment problem –in terms of matrix properties, degree of depuration and economics – has been afforded in this work through several industrial examples. The main calculations needed for each treatment, (equilibrium, stoichiometry, pumping and mixing requirements) are also summarized. Although most of these operations are well–known within the field of the Chemical Engineering, their application to water treatment presents additional difficulties, such as the complexity of the matrix, the higher conversion levels usually needed, or the difficulty for parameter estimation. Therefore, the use of approximate rules (rules of thumb) is usually needed for preliminary design of physicochemical operations. Finally, a reference to updated available information on this issue in Europe (BREF documents) and United States (EPA resources), is provided in order to advise the reader into the selection of a physic-chemical treatment for a given water treatment problem.