 The purpose of the video is to provide small water systems with an introduction to the use of an ion exchange as an arsenic removal technology. Ion exchange has been identified as a best available technology for removing arsenic from drinking water with low sulfate concentrations. Ion exchange is a treatment process that uses synthetic resin that exchange an ion for an unwanted ion in water. Many people are familiar with this process because it is often used in homes to remove hardness from water. In order to accomplish the exchange reaction, a packed bed of ion exchange resin bead is used and raw water is continuously passed through the resin bed until the resin is near exhaustion. If the resin is operated beyond exhaustion, breakthrough of the unwanted ion or ions will occur. When using ion exchange for arsenic removal an anion exchange resin is used whereby negatively charged arsenic five ions are exchanged for chloride ions of the virgin resin. The exchange process is reversed by flushing the resin with a concentrated sodium chloride brine solution. This causes the resin to release the arsenic five and other anions by replacing them with chloride from the brine and prepares the resin for reuse. It is important to remember that only the oxidized form of arsenic arsenic five can be removed using an ion exchange process. The process is not effective for the removal of arsenic three. Equally important is the fact that most resins preferentially remove sulfate over arsenic and nitrate. The resin loads from the top downward with the flow of raw water. As the resin bed becomes exhausted sulfate forces the arsenic and nitrate deeper into the bed. The treatment process must be stopped for regeneration of the resin prior to full exhaustion or the sulfate can force nitrate and arsenic to be discharged into the finished water at concentrations much higher than in the raw water. This phenomenon known as chromatographic peaking can cause health risks particularly so for nitrate which is an acute contaminant. Because the water contains orders of magnitude more sulfate and nitrate than arsenic the frequency of regeneration is dictated by the sulfate and nitrate concentrations. Ion exchange is being used at one of EPA's arsenic treatment technology demonstration sites located in Fruitland, Idaho. The treatment equipment and resin at this installation have been provided by Connecticut. The raw water is produced by a single well capable of up to 200 gallons per minute. The water contains about 35 micrograms per liter arsenic, 51 milligrams per liter sulfate from 12 to 15 milligrams per liter nitrate and has a pH of about 7.3. Here in Fruitland all of our water comes from groundwater sources and each well will be above the new regulations that go into effect in January. Most of our arsenic ranges from 20 parts per billion to about 38 parts per billion and some of our wells are fairly low in nitrate but over 50 percent of the wells are high in what I call borderline nitrates. They'll be anywhere from six milligrams per liter to nine milligrams per liter. The treatment process consists of a battery of 25 micron bag filters to remove sand or other sediment, two skid-mounted ion exchange vessels and brine production and storage facilities for regeneration of the resin. The groundwater at Fruitland contains primarily the oxidized form of arsenic, arsenic 5. Therefore pretreatment with an oxidant is not necessary although some states might require chlorination of the treated water to ensure microbial quality. Fruitland selected the ion exchange because in addition to arsenic 5 it also removes nitrate which is present at levels above the maximum contaminant level. Probably we most likely have to use ion exchange because of the borderline nitrates. We don't want to put a capital expense into removing arsenic and then find out six months or one year later that that borderline nitrate has elevated and exceeded the 10 milligrams per liter and therefore have to shut the water source down. After passing through the bag filters the raw water stream is split equally to flow from top to bottom half through each resin-filled vessel. This is called a parallel configuration and then and the arsenic and the nitrate stick to the resin come out the bottom and away they go and then then in a regeneration it also feeds from top to bottom. Since the raw water concentrations of sulfate arsenic and nitrate are relatively stable the process is predictable and has been adjusted such that regeneration of each vessel occurs after treatment of 335,000 gallons of water. When regeneration is called for a portion of the raw water flow for one vessel is diverted through a venturi that pulls in a concentrated brine solution to be mixed with the remainder of the water and then pass through the resin. Chloride ions from the brine replace the sulfate arsenic and nitrate attached to the exhausted resin. Salt for regeneration is stored in this 19 ton container that is filled to the 6 foot mark with water to ensure a constant supply of brine. There's a water level from the bottom of the top it's right about oh right in here somewhere it's about six foot six foot one it'll vary from six one to five seven on any given day. When you go into a regeneration this this valve will kick open off a timer from the computer it'll fill this up to the demand need and that's how you get your salt saturation brine for the regeneration. The City of Fruitland uses from 6,000 to 8,000 pounds of NSF approved salt per week at a delivered cost of about 10 cents per pound. The waste brine containing the arsenic and the rinse water is discharged to a floor drain from which it is transferred to the sanitary sewer. Waste brine produced by the ion exchange process may contain enough arsenic to be considered hazardous therefore ion exchange is often more cost effective when the brine can be discharged to a sanitary sewer. Ion exchange is also used for arsenic removal at Rimrock, Arizona. This system is a proprietary and ion exchange process provided by basin water. The treatment vessels pumps controls etc are delivered to a prepared site in a shipping container that contains several vessels operated in parallel. The basin water system has been used at numerous locations for nitrate removal and is now being used for arsenic removal. Arizona Water Company has selected basins ion exchange for several sites because it was found through a bidding process to be the most cost effective technology. Typically all but three vessels are in production. One vessel is in standby mode, one in the process of regeneration and one offline for regeneration. It goes offline when it regenerates. We at any given time several of the beds will be out up to three will be out in some sort of regeneration step but the remaining beds in this case we would have seven remaining online treating. So as a bed regenerates we don't have any reduction in capacity for the unit. The unit continues to operate. One advantage of multiple vessels is that a more constant flow of finished water can be produced. The two vessel system at Fruitland loses 50% of its production for nearly five hours during regeneration. Since an ion exchange also removes bicarbonate alkalinity the multiple vessels stage regeneration approach provides finished water with a more stable pH and alkalinity. This can be important for lead and copper control. This system is controlled by a computerized system that can be accessed remotely. It reuses brine three times and uses rinse water for brine production therefore reportedly produces a lesser quantity of waste. In some locations the waste brine is passed through absorptive media that will remove the arsenic. We have our absorptive media in here. We circulate the waste brine solution across this media and the arsenic then attaches to the media in here and now we have a brine solution which is low in arsenic. The arsenic is left behind in these drums and at that point the waste brine is then transferred to the waste tanks outside for disposal. That media typically passes the toxicity characteristics leaching potential test. The treated brine is then hauled away for disposal. In summary ion exchange may be a suitable arsenic removal technology for some small systems. It has the advantage of being able to remove other contaminants including nitrate and uses a relatively short empty bed contact time. However chromatographic peaking is a potential risk and large volumes of brine waste are produced. For more information on these and other EPA arsenic treatment technology demonstration sites you can visit EPA's website at the address shown on the screen.