Combined immobilisation and bioremediation of contaminated soil

Uchechukwu E Duru, Cambridge University
Geotechnical Engineering Group


Soil contamination involving heavy metals and hydrocarbons is a major problem facing the environmental management community. Soil stabilisation which involves the use of inorganic and organic binder materials for contaminant immobilisation as well as bioremediation which involves the biodegradation of contaminants are remediation techniques recognised to be cost effective.

Laboratory scale investigations were carried out to study the functionality of different materials including industrial by products such as pulverised fuel ash, coir compost, sawdust and novel materials such as zeolite as soil stabilisation additives for the treatment of heavy metal contamination. The effect of bioaugmentation on the performance of these additives was also studied. The performance of these materials in supporting the microbial population of commercially available consortium of hydrocarbon degrading microorganisms in heavy metal contaminated soils was investigated. Laboratory prepared model soil samples simplifying soil conditions and contaminant profile at a former chemical works site at West Drayton were used in these studies.

Batch and flow-through leaching tests were employed to access the effect of the binder and bioaugmentation treatments on heavy metal leachability under varied test conditions, over a 28 days test period. Changes in hydrocarbon degrading microbial population in the bioaugmented treatments were monitored using modifications of the standard plate count technique.

Results show that binders were able to reduce metal leachability under various test conditions. The binders generally performed better when applied at a lower quantity with the compost treatment performing better than other treatments under acidic conditions. The performance of the zeolite treatment was better under less acidic conditions. The bioaugmentation treatment reduced the ability of the binder materials to reduce metal leachability. Microbial population was supported most in combined mixes of zeolite and compost.