Co-utilisation of mineral and biological wastes in mine site restoration

This paper proposes a new approach to the restoration of contaminated land, particularly former colliery and demolition sites. Mineral mass is employed in designed formulations with organic wastes to provide artificial topsoils and permanent engineering foundations. mplify the behaviour of artificial topsoils, ochreous wetland sludge was mixed in various proportions with local silty sand, wood chips and/or compost, and seeded with perennial ryegrass. It was found in the laboratory and at the Imperial College field station at Silwood Park that the grass grew robustly in 1:1 sludge/sand alone. Although the sand was largely devoid of nutrients, the sludge contained sufficient organic carbon and N, P and K. The high iron content did not significantly immobilise phosphorus or leach into the surroundings. ements suitable in principle for engineering groundwork were observed at the previously restored Reden tip (Saarland, Germany). Surface compactions, 2 m in depth, of mixed coarse shale (80%), wood chips (10%) and weathered sewage sludge (10%) were found to be largely unaltered after six years, e.g., most of the carbon content remained in place. The main mass was anaerobic, low in permeability and mechanically hard. An outline is provided of preliminary experimental results obtained and of the material, technical, economic and regulatory issues involved in exploiting such emplacements.