... pursuing a doctoral degree at the University of Canterbury in New Zealand. ... and non-transient, non-community water systems to comply with the new .... City of Fruitland ..... bottles were new and contained appropriate preservatives.
EPA/600/R-09/113 October 2009
Arsenic Removal from Drinking Water by Coagulation/Filtration U.S. EP A Demonstration Project at City of Three Forks, MT Final Performance Evaluation Report
by Abraham S.C. Chen Brian J. Yates Wendy E. Condit Lili Wang 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 ground water; 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 during and the results obtained from the arsenic removal treatment technology demonstration project at the City of Three Forks, MT facility. The objectives of the project were to evaluate: 1) the effectiveness of Kinetico’s FM-248-AS Arsenic Removal System using Macrolite® media in removing arsenic to meet the maximum contaminant level (MCL) of 10 µg/L, 2) the reliability of the treatment system for use at small water facilities, 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 characterized water in the distribution system and residuals generated by the treatment process. The types of data collected included system operation, water quality, process residuals, and capital and O&M cost. After review and approval of the engineering plan by the State, the FM-248-AS treatment system was installed and became operational on October 30, 2006. The system consisted of two 63-in × 86-in fiber reinforced plastic (FRP) contact tanks and two 48-in × 72-in FRP pressure filtration vessels, both configured in parallel. Each pressure filtration vessel was loaded with 25 ft3 of Macrolite® media to which filtration rates up to 10.0 gpm/ft2 was applied. During the performance evaluation study from November 27, 2006, and February 8, 2008, the system operated at an average flowrate of 206 gal/min (gpm) for 8.9 hr/day, producing 30,499,000 gal of water. This average flowrate corresponded to an average contact time of 6.2 min and an average filtration rate of 8.0 gpm/ft2. Problems encountered during the performance evaluation study included programmable logic controller (PLC) settings, arsenic and iron particulate breakthrough, and increased differential pressure across the media beds, which led to shorter useful run lengths and more frequent backwashing. The actions taken to address these problems are detailed in this report. Source water from Well 2 had an average pH value of 7.5 and contained 59.8 µg/L to 96.7 µg/L of total arsenic, 46.8 to 50.8 mg/L of silica (as SiO2), and 17.1 to 53.7 µg/L of phosphorus (as P). The predominant soluble arsenic species was As(V) with an average concentration of 74.5 µg/L. Total iron concentrations were below the method reporting limit, therefore, in order to make the planned coagulation/filtration process work, an iron addition system was installed to provide iron for soluble As(V) removal. The amounts of iron added ranged from 1.1 to 2.5 mg/L (as Fe), compared to the target dosage of 2.0 mg/L (as Fe). After the contact tanks, most soluble As(V) was converted to particulate arsenic, presumably via adsorption and coprecipitation. As much as 10.6 µg/L of soluble As(V), however, remained in the contact tank effluent. Higher iron dosages appear to have very little effect on additional soluble As(V) removal. Silica and phosphorus in the raw water might have competed with arsenic for available adsorptive sites, thus rendering the coagulation process less effective. The use of higher iron dosages also increased solid loading to the pressure filters, causing premature breakthrough of arsenic-laden particles within 2 to 4 hr of filter runs. Filter effluent samples taken during the first three weeks of system operation contained 17.3 to 30.6 µg/L of total arsenic and 236 to 936 µg/L of total iron. Of the total amount of total arsenic measured, 23.5 µg/L, on average, existed as particulate arsenic. All iron existed in the particulate form. These results suggest that arsenic-laden particles broke through the pressure filters during the filter runs. To examine breakthrough characteristics and methods to improve the filter performance, several special studies, including some jar tests, were conducted, which included the use of a higher iron dose, implementation of a finer Macrolite® media size fraction, and addition of a polymer/coagulant aid. However, only a
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blending scheme using water from Wells 5, 6, 8, and 9 was successful in reducing arsenic concentrations to below the MCL. In general, filter backwash was triggered manually three times a week (i.e., Monday, Wednesday, and Friday) for the first five months and then automatically 5 times a week by the 8 hr run time setpoint. Approximately 1,173,000 gal of wastewater, or 3.8% of the amount of water treated, was generated during the study. However, because the useful filter run length (i.e., the maximum filter run length that consistently yielded
