Pilot scale (0.5-m diameter) and prototype (2.0-m diameter) rotating biological contactors (RBC) were investigated for oxidation of ferrous Fe(II) iron contained in six heterogeneous mine waters located at three coal mining sites in Pennsylvania and West Virginia. Continuous biological oxidation of Fe(II) and Fe(III) was accomplished at natural mine water temperatures as low as 0.4C at Hawk Run, PA. and as high as 29C at Crown, WV. Reduction of Fe(II) oxidation efficiency at 0.4C amounted to 10 to 20 percent of that achieved at 10C. Oxidation efficiency was above 80 percent at mine water temperatures of 10 to 29C. Microbiological oxidation with the 0.5-m RBC was unaffected at influent mine water pH values in the range of 2.18 to 5.50 (Crown, WV.). Fe(II) oxidation was an average 10 percent less efficient for a mine water treated under similar operating conditions with the 2.0-m than with the 0.5-m RBC. The observed decrease may be due to nonmicrobiological factors such as increased short-circuiting, lower residence time, and a smaller effective surface area which may be increased through proper design. Costs for Fe(II) oxidation with the RBC were estimated to be about twice the amortized capital costs and one-half the operating costs compared to a conventional chemical oxidation process. Neutralization of RBC effluent and separation of precipitated iron solids is required to produce water of suitable quality for stream-release. Both iron-oxidizing and heterotrophic bacteria existed in a gelatinous matrix present on disc surfaces of RBC units operating at Hollywood, PA.

"EPA 600-7-80-006." "January 1980." Cover title. "Project Officer Roger C. Wilmoth, Resource Extraction and Handling Division." Includes bibliographical references (pages 91-96). "Grant No. R-805132."