ABSTRACT
This chapter considers the water treatment unit processes that include coagulation, flocculation, sedimentation, and filtration and combinations of these processes. The viruses present in raw water contribute virtually nothing to the turbidity, they, along with other colloidal materials, are removed with varying degrees of efficiency by these unit processes. Coagulation-flocculation processes are optimized for the removal of hydrophobic colloids, which constitute the major part of turbidity in water. Although seeded virus concentrations were sufficiently high to allow direct assay of the influent water, alginate membrane and membrane adsorption concentration methods were necessary for assaying viruses and phages in filter effluent samples. The efficiency with which turbidity is removed by sedimentation and filtration processes is indicative of the efficiency of virus removal. Water contaminated with feces believed to contain infectious hepatitis virus and treated by coagulation, settling, and diatomaceous earth filtration caused disease in 43% of the volunteers who ingested it.
