Technologies and Costs for Removal of Arsenic From Drinking Water

5.5 ION EXCHANGEIon exchange (IX) has been used effectively for the removal of arsenic. There are two typesof IX systems, anionic and cationic. IX for arsenic removal is typically anionic since arsenic presentin natural waters is generally anionic. IX is a process wherein an ion in the solid phase (e.g., asynthetic resin) is exchanged for an ion in the source water. To accomplish this exchange, the sourcewater is passed through the IX bed in either a downflow or upflow mode until the resin is exhausted.Exhaustion occurs when unacceptable levels of the contaminant are observed in the bed effluent. InPOE and POU systems water often sits in the beds for extended periods of time because the requiredflow is not constant. It is possible that this leads to better than average removal of arsenic. Furtherresearch is needed to explain this effect. The IX removal mechanism is discussed in greater detail inChapter 2.5.5.1 Cost EstimatesThe Cadmus Group (1998) document was again used as the basis for estimates of POE andPOU treatment costs. The following assumptions were made to estimate the cost of POE and POU IX:# Average household - 3 individuals, 1 gallon each per day, 1,095 gallons per year.# Annual treatment - 1,095 gallons (POU), 109,500 gallons (POE).# Minimally skilled labor - $14.50 per hour (population less than 3,300 individuals).# Skilled labor - $28.00 per hour (population greater than 3,300 individuals).# Life of unit - 5 years (POU), 10 years (POE).# Duration of cost study - 10 years (therefore, two POU devices per household).# Cost of water meter and automatic shut-off valve included.# No shipping and handling costs required.# Volume discount schedule - retail for single unit, 10 percent discount for 10 or moreunits, vendor retains 30 percent profit on more than 100 units.5-10