British Columbia Mine Reclamation Symposium

Beneficial reuse of municipal biosolids as low-permeability, low cost oxygen barrier in capillary barrier covers for reactive mine tailings Hey, C. M.; Simms, P. H.


Financial costs and material quantities required for mine reclamation can be astronomical. Municipal biosolids present a potential low-cost alternative to traditional materials used in construction of multilayer covers for reclamation of mine wastes and disturbed lands. A blended biosolids referred to as Custom Reclamation Mix or CRM (1:1 volumetric mix of anaerobically digested biosolids and leaf and yard waste) was evaluated as a candidate barrier layer in a Capillary Barrier Cover (CBC) through material characterization, laboratory column testing of biosolids CBCs, and numerical unsaturated flow modelling. The CRM exhibited strong potential for use as in oxygen barrier covers, demonstrating low saturated hydraulic conductivities (k = 4.21 x 10 -⁷ cm/s at e = 4.01) and an air-entry value of approximately 400 kPa. Throughout laboratory column testing biosolids layers within the CBCs remained highly saturated, acting as a barrier to oxygen diffusion and water flux. Numerical modelling showed reduction in oxygen diffusion by up to three orders of magnitude when using biosolids CBCs relative to uncovered tailings. Biosolids present a promising low-cost alternative to traditional low-permeability materials in multilayer covers for mitigation of acid rock drainage.

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