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Gregory Korshin and Steve Reiber Gregory Korshin and Steve Reiber (partly based on materials prepared for the American Water Works Association, AWWA) Drinking Water Treatment in Small Utilities: a Review of Considerations Typical for the United States
Requirements for small water utilities in the United States Water quality and treatment are under control of the U.S. Environmental Protection Agency The mission is to provide safe drinking water and protect public health. Small utilities must comply with the maximum contaminant level (MCL) established by the EPA for many contaminants Regulations are same for large and small utilities, with some exceptions Water systems with < 15 connections (buildings) or serving < 25 people at least 60 days per year (campgrounds, schools, summer houses) are not regulated under the National Primary Drinking Water Regulations.
U.S EPA regions 10 EPA regions and 50 state agencies State regulations may be much more stringent than those the EPA California is a typical example Very concerned with perchlorate, Cr (VI), emerging contaminants
4 Roles and Responsibilities under Safe Drinking Water Act (SDWA) EPA sets health-based drinking water standards and oversees state programs State environmental/public health agencies – Primary enforcement responsibility/implement standards Public water systems are the regulated entity Consumers – Ultimate end-users Receive benefits/pay costs Consumers – Ultimate end-users Receive benefits/pay costs
Small system definitions US EPA defines small water systems as those serving less than 3,300 population. In 2011, small water systems (>60,000 in total) had significant problems: They contributed to 95% of all community water systems with monitoring and reporting violations 93% of systems with an maximum contaminant and treatment technique violations. Violations of Total Coliform Rule ranked the highest (48%) Chemical Contaminant Group (25%), Disinfectants and Disinfection Byproduct Rule (16%).
Issues typical for small utilities For small water systems several issues are challenging: Complying with monitoring and reporting requirements; Compliance with several EPA rules such as: Total Coliform Rule, Lead and Copper Rule Radionuclide Rule and many new regulations.
Special Challenge for Small Utilities: Arsenic Rule Arsenic Rule Introduced in mg/L (or 10 ppb) 5 years given to comply (Feb 2006) Includes non-community/non-transient water systems Costs to utilities exceeding $ 5.4 billion Sampling requirements -Annual for surface waters -Every three years for groundwater
Occurrence of arsenic in the US (red dots correspond to As> 1ppb) Arsenic occurrence map Population density in the United States (> 317 million total)
Outline of the “New” Arsenic Rule The standard applies to 20,000 non-community systems that serve at least 25 of the same people more than six months of the year. Schools, churches, nursing homes, and factories. The EPA estimates that 5%, of these water systems, serving 2 million people, have taken measures to meet the new arsenic standard. This EPA rule applies equally to small and large systems. Of the affected systems, 97% are small systems that serve < 10,000 people This EPA rule applies equally to small and large systems. Of the affected systems, 97% are small systems that serve < 10,000 people. The rule does not apply to individual household well systems, of which there are at least 50 million in the US.
Major arsenic removal technologies Coagulation/filtration Excellent for point-of-entry treatment Requires more sophisticated equipment and training Ion exchange Can be highly efficient Good for point-of-entry and point-of-use applications Problems in costs, high sulfate, brine handling
Adsorption Processes Adsorption Relatively popular As treatment method A variety of excellent materials are available Needs equipment, trained personnel, disposal of spent media, may be costly
Sorption Processes: Adsorptive Media Iron based media Granular Ferric Hydroxide, GFH (Siemens) E-33 (Severn Trent), Chemiron Regenerable Iron coated resin Regenerable Iron coated resin (Solmetex) Iron Modified Activated Alumina Iron Modified Activated Alumina (Alcan) Other activated alumina products Other adsorbents
Realities of implementation of the arsenic rule Many of the small utilities with As issues did the following Many of the small utilities with As issues did the following: The high arsenic wells are frequently abandoned. Or to blend with water from lower arsenic wells to bring the blend below the 10 ppb MCL. Adsorption of ferric hydroxide based media is relatively popular But the adsorbent is pricey, and used on critical wells.
Arsenic Treatment Experiences (EPA) EPA Treatment Demonstration Studies 50 selected water systems in the US 31 Adsorption (62%) 2 Ion Exchange (4%) 15 Oxidation/Coagulation/Filtration (30%) 2 Reverse Osmosis (4%) 16
Arsenic Treatment in the Washington State 17
Realities of implementation of the arsenic rule Ion-exchange is relatively rare Costs, sulfate and other limitations Very few small systems resorted to RO Too expensive for most systems. If they got federal funding to do so, they may buy an RO system. Typically, federal funding is available for Indian tribal reservations.
Occurrence of fluoride in the US (red dots correspond to F> 0.4 ppm) Maximum contaminant level for fluoride is 4 ppm Many utilities add fluoride for dental health Some people do not like this Added fluoride concentration close to 0.8 ppm May be reduced to 0.6 ppm
Removal of fluoride If high fluoride is an issue, the well is usually abandoned. one of the few solutions is activated alumina. If this is not an option, then one of the few solutions is activated alumina. Maintaining an activated alumina system is a serious chore for a small system. Point-of-use devices (e.g., “under the sink” cartridges or small reverse osmosis system) are popular with some people
Activated alumina columns (also good performance for arsenic)
Removal of salinity Secondary MCL of 1000 mg/L High salinity is a huge problem in many countries but genetally less so in the US Very few utilities use reverse osmosis Typically high salinity sources are abandoned or blended Point-of-use devices are also popular
Small systems and US realities Most areas of North America have reasonably abundant water sources. If a source becomes insufficient, an alternative source is typically developed. This will change due to global climate effects and population growth. Over 95% of small systems take water directly from the ground, chlorinate and distribute.
24 Drinking Water – Missions and Visions America’s drinking water is safe, affordable, and secure everywhere, every day and Americans know it.