Organic Matter Degradation Rate in a Sulfate-Reducing Wetland
Principal Investigator: Dr. Bill Drury
bdrury@mtech.edu
Solid substrate bioreactors and subsurface flow wetlands offer a
low maintenance option for treating water from remote abandoned
mine sites. However, without periodic substrate replacement, a sulfate-reducing
environment is not maintained. Estimates of the useful lifetime
of substrate material vary widely, thus this project attempted to
determine the specifications that are necessary for a solid substrate
to perform as long as possible between replacements. A bench-scale
bioreactor containing a compost substrate was constructed and chemical
oxygen demand (COD) and total organic carbon (TOC) measurements
were made over a 22 month period. Samples of the same compost were
placed in an operating wetland, and the same measurements were made.
The 22 month laboratory experiment showed no statistically significant
(95% confidence interval) change in either COD or TOC. Mass balance
calculations of total solids, TOC, and COD indicated that the compost
mass decreased by 30% over the length of the study. The compost
samples in the field setting displayed no change in TOC concentration
over a 345 day period, but COD concentrations did make a statistically
significant decrease in that time period.
MWTP Activity IV, Project 22/26
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