The capital investment cost was $63,547, which included $22,422 for equipment, ...... GFH granular ferric hydroxide gpd gallons per day gpm gallons per minute.
EPA/600/R-09/013 February 2009
Arsenic Removal from Drinking Water by Iron Removal U.S. EPA Demonstration Project at Big Sauk Lake Mobile Home Park in Sauk Centre, MN Final Performance Evaluation Report
by H. Tien Shiao Abraham S.C. Chen Lili Wang Wendy E. Condit Battelle Columbus, OH 43201-2693
Contract No. 68-C-00-185 Task Order No. 0029
for Thomas J. Sorg Task Order Manager Water Supply and Water Resources Division National Risk Management Research Laboratory Cincinnati, Ohio 45268
National Risk Management Research Laboratory Office of Research and Development U.S. Environmental Protection Agency Cincinnati, Ohio 45268
DISCLAIMER
The work reported in this document was funded by the United States Environmental Protection Agency (EPA) under Task Order 0029 of Contract 68-C-00-185 to Battelle. It has been subjected to the Agency’s peer and administrative reviews and has been approved for publication as an EPA document. Any opinions expressed in this paper are those of the author(s) and do not, necessarily, reflect the official positions and policies of the EPA. Any mention of products or trade names does not constitute recommendation for use by the EPA.
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FOREWORD
The U.S. Environmental Protection Agency (EPA) is charged by Congress with protecting the nation’s land, air, and water resources. Under a mandate of national environmental laws, the Agency strives to formulate and implement actions leading to a compatible balance between human activities and the ability of natural systems to support and nurture life. To meet this mandate, EPA’s research program is providing data and technical support for solving environmental problems today and building a science knowledge base necessary to manage our ecological resources wisely, understand how pollutants affect our health, and prevent or reduce environmental risks in the future. The National Risk Management Research Laboratory (NRMRL) is the Agency’s center for investigation of technological and management approaches for preventing and reducing risks from pollution that threaten human health and the environment. The focus of the Laboratory’s research program is on methods and their cost-effectiveness for prevention and control of pollution to air, land, water, and subsurface resources; protection of water quality in public water systems; remediation of contaminated sites, sediments and groundwater; prevention and control of indoor air pollution; and restoration of ecosystems. NRMRL collaborates with both public and private sector partners to foster technologies that reduce the cost of compliance and to anticipate emerging problems. NRMRL’s research provides solutions to environmental problems by developing and promoting technologies that protect and improve the environment; advancing scientific and engineering information to support regulatory and policy decisions; and providing the technical support and information transfer to ensure implementation of environmental regulations and strategies at the national, state, and community levels. This publication has been produced as part of the Laboratory’s strategic long-term research plan. It is published and made available by EPA’s Office of Research and Development to assist the user community and to link researchers with their clients.
Sally Gutierrez, Director National Risk Management Research Laboratory
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ABSTRACT
This report documents the activities performed and the results obtained from the one-year arsenic removal treatment technology demonstration project at the Big Sauk Lake Mobile Home Park (BSLMHP) in Sauk Centre, MN. The objectives of the project are to evaluate (1) the effectiveness of Kinetico’s Macrolite® pressure filtration process in removing arsenic to meet the new arsenic maximum contaminant level (MCL) of 10 µg/L, (2) the reliability of the treatment system, (3) the required system operation and maintenance (O&M) and operator skill levels, and (4) the capital and O&M cost of the technology. The project also is characterizing water in the distribution system and process residuals produced by the treatment system. BSLMHP provided water to 37 mobile homes with an average daily demand of 7,500 gal. Source water contained 27.5 µg/L (on average) of total arsenic, 2,385 µg/L of total iron, and 130 µg/L of total manganese. Because of the reducing condition with the source water, almost all iron and manganese existed in the soluble form and over 80% (on average) of arsenic existed as soluble As(III). The remainder of arsenic was present as soluble As(V) (13%) and particulate arsenic. The source water also contained, on average, 3.3 mg/L of total organic carbon (TOC), 1.2 mg/L of ammonia (as N), and 417 µg/L of phosphorous (as P). The Macrolite® CP-213f arsenic removal system evaluated consisted of a KMnO4 feed system, two 36-in × 57-in contact tanks (205 gal each), and four 13-in × 54-in pressure filters (two for each duplex unit) arranged in parallel. Potassium permanganate (KMnO4) was used to oxidize As(III) and Fe(II) prior to Macrolite® pressure filtration. KMnO4 was selected over chlorine due to the presence of elevated TOC and ammonia in source water. Each pressure filter contained 20 in (or 1.5 ft3) of Macrolite®, a lowdensity, spherical media (40 × 60 U.S. Standard Mesh) designed for a filtration rate two times higher than a conventional gravity filter. The design flowrate was 20 gal/min (gpm), which yielded 20 min of contact time prior to filtration and 5.4 gpm/ft2 of hydraulic loading to the Macrolite® filters. Because of the ondemand operation, the actual flowrates ranged from 1 to 15 gpm, corresponding to 27 to 412 min of contact time and 0.3 to 4.1 gpm/ft2 of hydraulic loading. From July 13, 2005, through October 1, 2006, the well operated for a total of 2,052 hr at approximately 4.6 hr/day. The system treated approximately 2,017,000 gal of water with an average daily demand of 4,523 gal. KMnO4 effectively oxidized As(III) in source water even in the presence of TOC, as evidenced by reducing its concentrations from 21.9 µg/L (on average) to 1.0 µg/L after contact tanks and forming an average of 22.7 µg/L of particulate arsenic with arsenic presumably bound to iron particles. During the performance evaluation study, total arsenic levels in the treated water were reduced to an average of 6.4 µg/L mainly in the soluble form. Out of 60 sampling events, arsenic concentrations in treated water exceeded the 10-µg/L MCL for a total of 13 times, mostly due to particulate breakthrough from the Macrolite® filters. To address particulate arsenic breakthrough, the backwash frequency was increased incrementally from every 2,743 gal to every 916 gal of throughput for each filter. With an average soluble iron to soluble arsenic ratio of 88:1, there was sufficient natural iron present in the source water for effective arsenic removal. Soluble iron was oxidized by KMnO4 to form iron particles, which adsorbed and/or co-precipitated with arsenic before being removed by the filters. Total iron concentrations in the treated water ranged from
