Application of compost in bioremediation

Excavated soil is typically arranged into a biopile or windrow, and aerated with a passive or active system. Inorganic nutrients or microbial cultures can be added to improve the process. Alternatively, contaminated soil can be mixed with composts in situ to reduce contaminant levels and improve soil structure and fertility. 

The rate of application of BSI PAS 100 compost is influenced by the type and concentration of contaminants and the pH. The end use of the site also influences the appropriate rate of compost application. Particularly high application rates must be justified with scientific evidence as to why these rates are required. If high application rates are required, care must be taken to minimise the risk of pollution. 

At Ebbw Vale, soils from the former steel works were contaminated with polyaromatic hydrocarbons and petroleum hydrocarbons. BSI PAS 100 green compost was mixed at a ratio of 3:1 (contaminated soil to compost) and placed in biopiles. Within 11 week, levels of contamination had reduced by a third of original levels.

Adequate aftercare to a project must be provided to ensure good long-term performance. On some sites, nutrients in compost may need to be supplemented with organic fertiliser, to further enhance growing potential. On other sites, the addition of chemical substances may be required to further reduce toxic substance concentration. Ongoing monitoring and aftercare will allow for problems to be identified and remediated early.