No abstract

Previous reviews made by Clarke and Chang, and the Task Group 2760 P report pointed out that there was a need for much more quantitative information regarding the fate of human viruses in the environment and water treatment plants. This was particularly true in the matter of filtration, both in the ground and in rapid filters that usually follow flocculation and settling. In an effort to fill some of the gaps, pilot water plant studies were carried out with poliovirus at the R. A. Taft Sanitary Engineering Center for 20 months, and the significant findings to date are presented in this article. The article includes a discussion by Herbert O. Hartung of the St. Louis County Water Company, and also Chairman of the Task Group 2760 P – Viruses in Water. He congratulates the authors for accurately reporting their observations without attempting to draw general and definitive conclusions or to prescribe standards. Because of relatively gross laboratory methods and lack of epidemiological correlations, Task Group 2760 P – Viruses in Water recommends additional studies to show the effect of lime softening and excess lime softening on virus removal. Because of the value of excess lime softening for removing some other protein‐type substances, such a study for virus removal seems appropriate. The task group also recommends that the capacity of activated carbon to absorb viruses be studied.

This article discusses the effectiveness of water treatment processes in coping with relatively small concentrations of pesticides in raw water. Duplicate pilot water treatment plants at the Taft Center were used to evaluate the effectiveness of conventional and auxiliary treatment processes. The methods and procedures used included: the chromatographic method; solubility and incidental loss; coagulation and filtration; chlorine; potassium permanganate; ozone; powdered activated carbon; and, granular activated carbon.

This article discusses treatment modifications including high‐rate filtration with coarse, lightweight media on top of sand; control of floc strength and its passage with polyelectrolytes in the filter influent; the use of filters for flocculation of low alum doses as well as for removal of turbidity; and, the use of granular activated carbon in filter beds. The effect of these innovations was studied in pilot plants of various sizes to determine the passage of coliform bacteria, powdered activated carbon, virus, and gross turbidity through the filters.