REMIDIATION STRATEGIES FOR PUBLIC AND PRIVATE WATER SUPPLIES- OVERVIEW
Bernard Lucey, P.E.
NH Department of Environmental Services, PO Box 95, Concord, N.H. 03302-0095.

Selection of an arsenic treatment system is a multi faceted process. Non treatment based alternatives include such options as interconnection with another water system free of arsenic, development of an addi-tional well(s) and abandonment of the contaminated supply, and blending of supplies to dilute the arsenic to an acceptable level. Principle considerations are political practicality, loss of local control of the utility, and availability of a regional water supply alternative. Arsenic removal options must first consider system size (and thus economies of scale) and the level of operator expertise. The greatest impact of the arsenic rule will generally be on very small water systems. At a small-scale facility, process sophistication and instrumentation are normally minimal. Treatment pro-cesses must be accommodated within the existing floor plan or a costly expansion of the control building will be needed.Cost effective arsenic treatment methods vary with system size. For very small systems two methods look favorable: adsorptive media and anion exchange. These methods are easily automated, have a small foot print and require little operator knowledge. For much larger water systems, conventional coagulation with membrane filtration are favored. Also the element iron provides substantial arsenic removal when pre-cipitated. As important as the above criteria are, the disposal of the arsenic waste by-product is a key element in selecting a treatment process. Most treatment processes produce a liquid waste, which is categorized as hazardous. Adsorptive medias, on the other hand, hold the arsenic contaminant permanently attached on the adsorptive surface as documented by the Toxic Characteristics Leachate Procedure and thus the media can be disposed of at an ordinary landfill without special considerations.