Technologies and Costs for Removal of Arsenic From Drinking Water

5.3.1 Case Study 1: Fairbanks, Alaska and Eugene, OregonThe EPA Drinking Water Research Division (DWRD) conducted field POU studies inFairbanks, Alaska and Eugene, Oregon (Fox and Sorg, 1987; Fox, 1989). Pilot systems were installedin two homes in each community, and each system consisted of an activated alumina bed, ion exchangebed and reverse osmosis system. Influent arsenic concentrations ranged from 0.05 to 1.16 mg/L andwas believed to be naturally occurring.The RO systems at each of the four locations performed well on start-up, achieving 60 to 80percent removal of arsenic. Over time, however, the arsenic removal efficiency decreased to 50percent or less. At the initial removal efficiencies, effluent arsenic levels met the current MCL of 50ppb, but over time failed to sufficiently reduce the levels to below the MCL.Low-pressure RO units (40 - 60 psig) consistently achieved greater than 50 percent removal,but with high influent arsenic concentrations, much higher removal efficiency is necessary to achievethe MCL. The high-pressure unit (196 psig) operated for 350 days and produced 684 gallons oftreated water which met the MCL.The IX beds evaluated were 1 cubic foot in size and were filled with a strong base anionexchange resin (Dowex-SBR). The IX beds effectively reduced arsenic levels to below the MCL,but required pre-treatment to ensure effective removal. This involved regeneration and chemicaltreatment of the resin to the chlorine form.The AA beds were identical to the IX beds with the exception that they were filled withgranular activated alumina (Alcoa-F1) rather than resin. Over the course of this study, the AA bedseffectively reduced arsenic levels; however, the media required pre-treatment to reduce the pH of theAA to 5.5 - 6.0 (the pH at which AA most effectively removes arsenic). Pre-treatment of the AA bedinvolved passing a sodium hydroxide solution through the tank, rinsing with clean water, and thentreating with dilute sulfuric acid. Improperly treated alumina performed poorly initially (30 to 40percent removal), and performance significantly deteriorated over time (5 to 20 percent removal).Proper pre-treatment, however, allowed for efficient operation periods of longer than one year.5.3.2 Case Study 2: San Ysidro, New MexicoA field study was also conducted in San Ysidro, NM to evaluate the effectiveness of POU ROunits. This work is documented in several sources (Thomson and O’Grady, 1998; Fox, 1989; Fox andSorg, 1987; and Clifford and Lin, 1985). San Ysidro source water is from an infiltration gallery underthe local river banks and contains 5.2 mg/L fluoride and 0.23 mg/L arsenic. The water is also highin other inorganic contaminants, including iron (2.5 mg/L), manganese (0.6 mg/L) and total dissolved5-5