How to Approach the Undermining of Surface Structures With Emphasis on Wetlands

Practical guidance for opencast operations covers early detection with low cost thermal cameras, prevention, and the treatment methods in current use: water sprays and cannons, sand cladding of highwalls and stockpiles, removal of burning coal by dragline, tipping into water ponds and the treatment of sinkhole areas. A three month full scale trial of sprayed fly ash as an antioxidant is reported.

Co-treating coal discards with sewage sludge by hydrothermal carbonisation gave hydrochars with better physicochemical properties than treating either waste alone. The blended hydrochar reached a surface area of 20.35 m2/g and a pore volume of 0.38 cm3/g, and removed 97.19% of nevirapine and 93.32% of lamivudine from recycled water. Routes to activated carbon and hydrogen storage were also assessed.

Conventional rehabilitation relies on lime, fertiliser and compost to build fertility and select adaptive species, which produces short term cover but rarely a self sustaining ecosystem. The work argues for treating soil microbes as part of the system, since bacteria drive nutrient cycling, organic matter breakdown and soil aggregation, and proposes conditioning plants with adapted rhizosphere bacteria on coal waste substrates.

The separator handled fine coal and produced a 28 MJ/kg product, but its measured separation efficiency was lower than that of conventional dense medium cyclones and it was harder to operate. Two efficiency tests produced no evidence that the unit outperforms cyclones on fine coal, so cyclones were recommended when the plant was rebuilt at its next site.