Contaminated Land and Bio-Remediation - Environmental Biotechnology: Theory and Application - page 108

Figure5.7 Illustrativelong-termmonitoringscheme
future. Under these circumstances, a comprehensive environmental management
and audit scheme can be put in place to monitor environmental effects of such
operations and Figure 5.7 shows a suitable illustrative outline.
Under this system, the methodology adopted would be to identify key activities,
list the sources of environmental effect to establish quantities and controls and
then finally make a determination of their significance. The results would then, of
course, feed back into the decision-making process and ultimately help to shape
the ongoing environmental management regime of the site.
Ex situ techniques
Again, there are three principal approaches in common use, namely Land Farm-
ing, Soil Banking and Soil Slurry Bioreactors. Though inevitably there are distinct
similarities between all applications of bioremediation, for obvious reasons of
fundamental biology, these techniques are generally more distinct and separate.
The major benefits of ex situ methods are the greater ease of process optimi-
sation and control, relatively shorter treatment time and the increased potential
for the safe introduction of specialised organisms, if and as required. However,
the increased transport costs, additional land requirement and higher levels of
engineering often combine to make these technologies more costly options.
Land farming
This technique is effectively accelerated natural attenuation, taking place off-site,
within constructed earthwork banking to provide what is essentially a low-tech
bioreactor. The pre-treatment stage involves the soil being excavated from site,
screened for rocks, rubble and any other oversize inclusions before typically being
stored prior to the commencement of actual remediation, either at the original
location or on arrival at treatment site.
The processing itself takes place in lined earthworks isolated from the sur-
roundings by an impermeable clay or high density polyethylene (HDPE) liner,
as shown diagrammatically in Figure 5.8, and typically relies on the activities