However they are classified, the fact remains that all the individual technologies available each have their limitations. As a result, one potential means of enhancing remediation effectiveness which has received increasing attention is the use of a combination approach, integrating different processes to provide an overall treatment. The widespread application of this originated in the USA and the related terms used to describe it, ‘bundled technologies’ or ‘treatment trains’ have quickly become commonly used elsewhere. The goal of process integration can be achieved by combining both different fundamental technologies (e.g. bio-logical and chemical) and sequences of in situ or ex situ, intensive or extensive regimes of processing. In many respects, such a ‘pick-and-mix’ attitude makes the whole approach to cleaning up land far more flexible. The enhanced abil-ity this confers for individually responsive interventions stands as one of the key factors in its wider potential uptake. In this way, for example, fast-response appli-cations can be targeted to bring about a swift initial remediation impact where appropriate, switching over to less engineered or resource-hungry technologies for the long-haul to achieve full and final treatment.
As has been mentioned before, commercial applicability lies at the centre of biotechnology, and process integration has clear economic implications beyond its ability simply to increase the range of achievable remediation. One of the most significant of these is that complex contamination scenarios can be treated more cheaply, by the integrated combination of lower cost techniques. This opens up the way for higher cost individual methods to be used only where abso-lutely necessary, for example in the case of major contamination events or acute pollution incidents. With limited resources typically available for remediation work, treatment trains offer the possibility of maximising their utilisation by enabling responsible management decisions to be made on the basis of meaning-ful cost/benefit analysis.
This is an important area for the future, particularly since increased experience of land remediation successes has removed many of the negative perceptions which were previously commonplace over efficiency, speed of treatment and general acceptability. For many years remediation techniques, and bioremedia-tion especially, were seen in a number of countries as just too costly compared with landfill. As changes in waste legislation in several of these regions have driven up the cost of tipping and begun to restrict the amount of biodegradable material entering landfills, the balance has swung the other way, making remedi-ation the cheaper option. There is a certain irony that the very alternative which for so long held back the development of remediation should now provide such a strong reason for its use. In the future, wider usage of extensive technologies may increase the trend, since they offer the optimum cost/benefit balance, with inten-sive processes becoming specialised for fast-response or heavy contamination applications. In addition, the ‘treatment train’ approach, by combining technolo-gies to their maximum efficiency, offers major potential advantages, possibly even permitting applications once thought unfeasible, like diffuse pollution over a large area.