Bioremediation

The concept of judiciously exploiting biological approaches is also a subject of debate  

Others would extend the fertiliser concept to the simultaneous addition of readily biodegradable substrates along with the fertiliser nutrients to stimulate the growth of contaminant-degrading organisms most rapidly, and to aid in the rapid utilisation of the fertiliser nutrients before they might be leached from the contaminated area. The specific requirements for the most efficacious substrates is an area of current research. 

An alternative use of added readily degradable substrates is to drive the local environment toward anaerobiosis so that reactions such as reductive dechlorinations or reductive removal of nitro-groups are promoted. 

A broader view would include the addition of a substrate to stimulate the growth of organisms known to degrade the contaminant of interest only as an incidental part of their metaboHsm, one might almost say serendipitously. This process is sometimes called co-metaboHsm, and it too has had success. 

Others would include the addition of materials aimed at increa sing the bioavailabiUty of the contaminant to the degrading organisms. The most studied compounds are surfactants, but cations have been reported to increase the bioavailabiUty of some organic compounds, and sorbents and clays are also considered. The dispersion of spilled oil on water by the appHcation of dispersants is perhaps the major commercial use of this idea. 

Alternate pathways for the degradation of a substituted benzene, toluene. (Adapted from Rochkind, M.L., J.W. Blackburn, and G.S. Sayler. 1986. Microbial Decomposition of Chlorinated Aromatic Compounds. EPA/600/2-86/090.) 

TCHQ = Trichlorohydroquinone TCHBQ = Trichlorohydroxybenzoquinone CHQ = Chlorohydroquinone DCHQ = Dichlorohydroquinone 

Incomplete chloride release ring fission questionable 

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