Comparing chitin and organic substrates on the national tunnel waters in Blackhawk, Colorado for manganese removal

C. Venot, L. Figueroa, Rachel Alice Brennan, T. R. Wildeman, D. Reisman, M. Sieczkowski

Research output: Chapter in Book/Report/Conference proceedingConference contribution

9 Scopus citations

Abstract

The National Tunnel is a part of the Central City / Idaho Springs Superfund site. Because passive treatment is an important possibility for removal of contaminants from the water, the USEPA and the Colorado Division of Public Health and Environment (CDPHE) have been sponsoring a bench-scale study of different organic substrates for sulfate-reducing bioreactors (SRBRs). The substrates being tested include ethanol, woodchips and hay, woodchips and corn stover, and crab-shell chitin. After 6-18 months of operation, all of the reactors are showing significant amounts of sulfate reduction. In all of the reactors, Cu and Zn are removed to below their respective ambient water quality criteria of 0.010 and 0.100 mg/L. As is commonly observed in SRBRs, Mn removal is significantly less, with the exception of the chitin reactors. The reason for chitin's superior Mn removal may be the dissolution of calcite from the crab shell. In the chitin reactors, Ca has increased from 210 to 870 mg/L and alkalinity has increased from zero to up to 5,000 mg CaCO 3 / L. Furthermore, the pH of the effluent leaving the chitin systems averages 6.9. In most SRBRs, Mn is precipitated as MnCO 3 and significant removal does not occur until the pH is raised to between 7 and 8. This is the case in the other types of SRBRs being tested at the National Tunnel, as their Mn removal efficiencies have only approached 50 % at pH values ranging from 6.5 to 7.5. However, in the chitin reactors, 86% of the influent Mn is being removed from 21.5 mg/L to an average of 3 mg/L. The high removal is very similar to the removal of Mn in pulsed limestone beds that are maximized for the dissolution of calcite. These chitin reactors have been operating for six months while the other substrate reactors have been operating for over one year.

Original languageEnglish (US)
Title of host publication25th Annual Meetings of the American Society of Mining and Reclamation and 10th Meeting of IALR 2008
Pages1264-1278
Number of pages15
StatePublished - Dec 1 2008
Event25th Annual Meetings of the American Society of Mining and Reclamation, ASMR 2008 and 10th Meeting of International Affiliation of Land Reclamationists, IALR 2008 - Richmond, VA, United States
Duration: Jun 14 2008Jun 19 2008

Publication series

Name25th Annual Meetings of the American Society of Mining and Reclamation and 10th Meeting of IALR 2008
Volume2

Other

Other25th Annual Meetings of the American Society of Mining and Reclamation, ASMR 2008 and 10th Meeting of International Affiliation of Land Reclamationists, IALR 2008
CountryUnited States
CityRichmond, VA
Period6/14/086/19/08

All Science Journal Classification (ASJC) codes

  • Geotechnical Engineering and Engineering Geology

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