Page 234 - Fundamentals of Water Treatment Unit Processes : Physical, Chemical, and Biological

Part III

Microscopic Particles

Microscopic particles include those that do not settle readily The traditional means to remove small particles (and
and must be removed by means other than settling. The sizes NOM) is by coagulation as a first step. Subsequent steps
of such particles are <100 mm. Number concentrations may depend on the treatment train. In ‘‘conventional’’ filtration,
range from 1,000 #=mL to perhaps 100,000 #=mL. the subsequent steps are mixing (Chapter 10), flocculation
A ‘‘quasiparticulate’’ material is natural organic matter (Chapter 11), settling (Chapter 6), and filtration (Chapter 12).
(NOM), which is macromolecular and behaves like colloidal In flotation (Chapter 8), the sequential steps are coagulation,
matter. Practice has evolved since about 1900 to remove flocculation, flotation, and filtration. For ‘‘in-line’’ filtration,
NOM by coagulation. the steps are coagulation and filtration.