<p class="first" id="P1">Mining-influenced water (MIW) remediation is challenging,
not only due to its acidity
and high metal content, but also due to its presence in remotely located mine sites
with difficult surrounding environments. An alternative to common remediation technologies,
is the use of sulfate-reducing bacteria (SRB) to achieve simultaneous sulfate reduction
and metal removal in on-site anaerobic passive systems. In these systems, the organic
carbon source (substrate) selection is critical to obtaining the desired effluent
water quality and a reasonable treated volume. In this study, we evaluated the use
of two different substrates: a chitinous product obtained from crushed crab shells,
and a more traditional ligneous substrate. We put the substrates, both with and without
water pretreatment consisting of aeration and pH adjustment, in anaerobic experimental
columns. The treatment with the chitinous substrate was more effective in removing
metals (Al, Cu, Fe, Cd, Mn, Zn) and sulfate for a longer period (458 days) than the
ligneous substrate (78 days) before suffering Zn breakthrough. The reactors fed with
pretreated water had longer operational periods and lower metals and sulfate concentrations
in the effluent than those with untreated influent water. Zn was consistently removed
to levels <0.3 mg/L for 513 days in the chitinous substrate columns, while levels
<0.3 mg/L were maintained for only 140 days in the ligneous substrate pretreated
column.
The highest sulfate removal rates achieved in this study were in the range of 5–6
mol/m
<sup>3</sup>/d for the chitinous substrate and 1–2 mol/m
<sup>3</sup>/d for the ligneous substrate. Overall, the chitinous substrate proved
to be more
efficient in the removal of all the aforementioned metals and for sulfate when compared
to the ligneous substrate. This could be the determinant when selecting a substrate
for passive systems treating acidic MIW, particularly when Zn and Mn removal is necessary.
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