Use of steel slag and limestone quarry dust for remediation of acidity arising from runoff from colliery spoil – pilot study

Runoff water from colliery spoils can be very acidic with a pH of perhaps as low as 2.5. Iron pyrites in the colliery spoil react with the oxygen and water to form iron and sulphates together with hydrogen, giving rise to high acidity. During research at the University of Birmingham, basic oxygen steel slag was found to release alkalinity gradually. BOS slag was used to treat colliery spoil and it was found that elevated levels of pH could be maintained in the field. However, pH of the treated spoil in the pilot study was too high to support vegetation. Nevertheless, the concept was proven and a further trial was initiated with a range of mixtures, which included BOS slag and limestone quarry fines together with compost.