SELECTION OF ARSENIC TREATMENT TECHNOLOGIES FOR SMALL COMMUNITY WATER SYSTEMS IN NEW MEXICO: GEOCHEMICAL (AND OTHER) DETERMINANTS

Six years after the new drinking water regulations for arsenic took effect, many small community water systems still struggle to meet the Maximum Contaminant Level requirement of 10 micrograms per liter. Selection of the appropriate technology for a community depends on both geochemical and socioeconomic factors. Adsorptive media, coagulation/filtration and reverse osmosis treatment technologies are commonly considered. Co-occurrence of arsenic with other solutes may either aid or hinder arsenic removal processes. This talk will present the results of pilot studies in 3 New Mexico communities characterized by drinking water sources with contrasting water compositions and infrastructures.

The relatively simple water chemistry at Socorro Springs facilitated the comparison of several different adsorptive media. The comparable performances of iron-oxide, hybrid oxide-resin and titanium-oxide adsorbents provided the operator with flexibility to choose the treatment system based on economic factors. A pilot study at the Paakweree Water Coop in the southwestern part of Albuquerque, evaluated the relative effectiveness of a hybrid oxide-resin, a titanium-oxide sorbent, and reverse osmosis (RO) for water with high vanadium and arsenic concentrations. Here, compatibility with point-of-use systems was an important consideration due to uncertainties about infrastructure development in the area. The RO system is the preferred treatment option at this site due to superior performance and a water source with a high production rate. At another site near the Zuni Mountains, co-occurrence of arsenic with high concentrations of iron and radium necessitated a more complex treatment approach. Here, an oxidation/coagulation/filtration system proved superior to adsorptive systems using multiple media, however, operator training and waste disposal must be considered in the final design.