 This video is brought to you by the Environmental Protection Agency. The use of any trade names or commercial products does not constitute an endorsement on the part of the Environmental Protection Agency. For the arsenic rule, EPA evaluated several technologies as candidates for best available technology, BAT, for arsenic removal including conventional iron and manganese removal. During the iron and manganese removal process, iron and manganese are oxidized to form insoluble precipitates that are subsequently filtered out. If arsenic is present in the water, it is removed either by adsorption or co-precipitation. In this pressure tank system, the oxidation process converts the iron to insoluble iron hydroxide and any arsenic 3 to arsenic 5. The arsenic 5 is attached to the iron oxides through adsorption and or co-precipitation and is removed by filtration. EPA determined that they would list oxidation filtration as a BAT only under the condition that the iron to arsenic mass ratio was greater than 20 to 1. This treatment method can be used to meet the revised MCL of 10 micrograms per liter. The practice of aeration for iron oxidation has been shown to be ineffective to convert arsenic 3 to arsenic 5. A stronger oxidant such as chlorine or potassium permanganate is needed. Iron plays a unique role in the removal of arsenic and the presence of iron in the source water will play a big role in the selection of the treatment process. In this chart, the horizontal axis represents the concentration of iron in the source water while the vertical axis reflects the concentration of arsenic. The vertical line at 0.3 milligrams per liter iron is the EPA recommended secondary standard for iron. Using the 20 to 1 iron to arsenic mass ratio, you can create a graph with three segments to assist in the identification of arsenic treatment processes. If a system's water falls within either zone A or B, the system is probably already treating for iron removal and the treatment process can be optimized or modified to meet the arsenic removal requirements. If the system's water quality is in zone B, it is also treating for arsenic and in this case additional iron can be added to meet the arsenic removal requirements. These systems will then have sufficient iron to be oxidized to iron hydroxides, giving the arsenic adequate adsorption sites so that it can be removed by filtration. Systems with water quality in zone C should look at a larger array of treatment options. Two of EPA's arsenic treatment technology demonstration projects that are using the oxidation filtration process are featured in this video. Ledgerwood, North Dakota and Saban, Minnesota. Ledgerwood, North Dakota is an agricultural community of about 750 to 800 people. During the 1930s, arsenic-based insecticides were used to control grasshoppers. The overuse of the chemicals contaminated the site to the point today it is listed as a superfund clean-up site. The source water for the community is two wells. Each well is used for one month, then the other is used. The wells produce about 250 gallons per minute each and are about 100 feet deep. The community uses between 80,000 gallons per day and 160,000 gallons per day. Normally it will run about two hours stretches and probably run about six times during the day for 12 to 14 hours in a 24-hour period. The raw water arsenic concentration ranged from 40 to 150 micrograms per liter predominantly as arsenic-3. The iron in the raw water ranges from 1.3 to 1.6 milligrams per liter. This puts the system in zone B on the chart. The treatment in place before the EPA demonstration project included. Chlorination with gas chlorine for biological growth control on the filters and oxidation of the iron in the raw water. Aeration consisting of cascading the water over redwood slats with a countercurrent forced air blower for iron oxidation. Potassium permanganate for iron oxidation and regeneration of the filter media. Polymer filter aid addition. Chlorination with gas chlorine for biological growth control on the filters and oxidation of the iron in the raw water. One hour detention time to facilitate the iron oxidation. Gravity filtration through 24 inches of anthra sand. Post-chlorination prior to storage in a clear well and fluoridation before being pumped to the distribution system. The spent filter backwash water is held in a retention tank below the plant. The decant off the holding tank is recycled to the plant. The sludge is pumped to a dewatering tank. The sludge is hauled to a non-hazardous landfill at the rate of about 20 cubic yards every two years. The EPA demonstration technology for this system was a modification of the existing system to add more iron. The natural iron to arsenic ratio was only about 10 to 1. Again, this ratio places the system in zone B on the chart. Therefore the project included dosing the raw water with ferric chloride to increase the iron to arsenic ratio to 20 to 1. To assist in the filtration process, an additional filter aid polymer was added. Turbodimmoners were installed on the filters to monitor the treatment process. Before the project started, we were getting raw water removed with the iron and manganese. The arsenic was coming down to about 35 parts. With this test project now, we're approximately running at about 7.5 to 8 parts. Another existing iron removal facility that is participating in the EPA demonstration project is at Saban, Minnesota. This small community of 400 needed to replace their existing iron removal plant. So the EPA was helpful in letting us know what arsenic was and what we should be aware of and how to get rid of it. So the demo site in that sense was good for us because it allowed us to give a technical aspect to it. The raw water arsenic concentration was below the old arsenic MCL, but above the revised MCL of 10 micrograms per liter. The existing plant consisted of aeration to oxidize the iron. Though that part of the plant was not functional, gravity filtration through a sand filter, fluoridation and chlorination. The raw water has sufficient iron in the water to provide a 35 to 40 to 1 iron to arsenic ratio. This ratio places the system in zone A on the chart making the plant an ideal candidate to use the iron in the raw water to work for the removal of the arsenic. The present plant has deteriorated to the point that the raw water arsenic concentration is 45 micrograms per liter and the treated arsenic concentration is about 40 micrograms per liter. The community is combining the EPA demonstration project with other funds to complete a $1.1 million dollar expansion project. The new treatment facility will be constructed on the existing site and will be an oxidation to filtration treatment system using the Kineticco macro light media. The water will be chlorinated to oxidize the iron to iron hydroxide and convert all of the arsenic to arsenic 5. The precipitates will be filtered out in the pressure filters. This will remove both the iron and arsenic from the water supply. The backwash water will go to the community lagoon. One of the community concerns was to minimize the volume of waste discharged to the lagoon due to maintaining lagoon capacity for future growth. The coagulation to filtration treatment process minimizes the water loss for the treatment process. The EPA demonstration project is allowing the community to leverage many sources of funds to complete the needed improvements. The community has learned many lessons during this project. I would say that's the biggest thing to investigate and figure out as much as you can and then have it the whole system make sense for your community. You know, this might not work somewhere else and but for us it was a good fit. 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.