The attenuation and leaching behaviour of colliery spoils

This paper describes the results of a test programme investigating the leaching and attenuation behaviour of a range of colliery spoils from around the U.K. Various chemical species were monitored. Rapid batch testing techniques were used to screen the spoils and then longer term permeation tests were conducted in an attempt to replicate more accurately the probable behaviour on site. Distilled water and an artificial leachate were used as permeants. The results indicated that for some leaching/attenuation processes the rapid batch tests give a good indication of the longer term behaviour but that for others, e.g. some time-dependent metal ion sorption processes, the batch tests were not good indicators of long-term behaviour. The initial attenuation performance of the spoils was adequate in that the spoils significantly reduce the chemical oxygen demand, the total Kjeldahl nitrogen and the concentration of the metal ions in the permeant but this process had generally ceased by 60 days testing.