Contaminated Land and Bioremediation - Environmental Biotechnology: Theory and Application - page 112

CaseStudy5.2 AnnelidBioreactors(UnitedKingdom)
The principle of providing optimised conditions for microbial action is well
established, but actually achieving this is one of the biggest practical difficulties
for the bioremediation of contaminated land. This is a significant potential problem
for insitusystems, because the soil is treated lying in its natural place, thus making
control of the microbes' environment difficult to achieve. In particular, ensuring
maximum contact between the microbes and the contaminated soil, the provision
of adequate aeration and the maintenance of suitable moisture content can be
very difficult.
An approach proposed, and currently being patented, by Taeus Biotech involves
using species of earthworm to act as discrete, self-propelled bioreactors, effectively
bringing the benefits of exsituremediation to an insitucontext, thereby overcoming
many of the latter's shortcomings at the same time.
Once the nature of the contamination has been established, a suitable culture of
microbes with the necessary competence to degrade it can be produced, typically
drawing on micro-organisms indigenous to the site, training them as required.
Appropriate earthworm varieties are kept in growing units, which contain a soil
medium which has been heavily inoculated with the microbial culture. The natural
burrowing and feeding activities of the worms ensure that they pick up large numbers
of microbes, which then remain resident in their gut.
The prepared earthworms are then introduced to the contaminated site and assist
in its remediation in two main ways. Firstly, as they move around, the contaminated
soil they ingest is brought into direct contact with the cultured micro-organisms,
while mucus-secreting glands within their gut maintain adequate internal moisture.
Secondly, many of the competent microbes are carried out in the soil, as it passes
through the worms, effectively becoming an in situ site inoculant to multiply and
continue the clean-up process, aided by the improved aeration provided by the
earthworm burrows.
This technique is still in the first stages of development and it is, clearly, limited to
certain kinds of contamination, present in relatively low concentrations. However,
for such instances, particularly when the pollution is widespread throughout a site,
the early indications are that it could be a cost-effective means of low intervention
bioremediation.