In compost bioreactor systems, a commonly deployed technology at passive mine water treatment sites, metals accumulate in the treatment system substrate. Ultimately, this substrate becomes exhausted and requires disposal. An assessment was undertaken using a case study site in northern England, investigating how metal recovery might be used to reduce the whole life-cycle cost of treatment. The large-scale system at Force Crag mine harnesses bacterial sulphate reduction, primarily to remove zinc within a compost substrate.
Data presented in this paper suggest that recovery of metals from treatment system substrates might offer substantial passive treatment system life-cycle cost reductions. At Force Crag, it is estimated that discounted life-cycle costs can be reduced from €1.63M to €1.12M over 10 years. Allowances for substrate decontamination processes should therefore be considered by treatment system operators from project inception, in order that these savings can be realised.