Has bioremediation finally come of age in the UK? Recent developments in speed and reliability have led property developers, working under tight deadlines, to choose bioremediation for improving hydrocarbon contaminated soils on major city centre sites. But what are the long term prospects?
It has long been recognised that bioremediation offers advantages compared to traditional landfill techniques. Contamination, for example, is completely mineralised never to reappear; soils are recycled, aiding sustainability; there are no muddy lorries to clog up busy roads; transport costs are removed; and finite landfill space is not needlessly filled. But until recently clients have been reluctant to accept it.
In fact a number of proven techniques are available in the UK from contractors each experien- ced in their own field of expertise. The most common options are insitu techniques, in which stimulants, nutrients and oxygen or bacteria are added to the soil through boreholes, often in conjunction with pump- and-treat; or ex-situ techniques where the soil is excavated and treated in piles on the site surface.
Insitu methods are suited to sites where surface disturbance must be minimised such as active railway stations or factory storage yards. In particular they can be used on sites with granular soils, relatively light hydrocarbon fractions, deep contamination where excavation would be impractical or very disparate plumes where long term groundwater control is required.
Perhaps the greatest advancements have been in the treatment of large quantities of contaminated soils ex-situ. Recent developments in actively turned biopiles have slashed treatment times for individual biopiles to as little as three to four weeks in a highly controlled and environ- mentally contained process.
The advantages of ex-situ treatment are clear. It is easy to validate that the contamination has been completely removed from all the soil on a site. By careful control of the excavation works it is possible to ensure with confidence that the entire plume is treated and so reliance on the original site investigation is reduced. Unsurprisingly then insurance companies are more relaxed about providing insurance and warranties on ex-situ sites, where every cubic metre can be inspected and tested by the client's consultants.
The ease of control on an ex-situ site also means the method is fast and has low cost. In most areas of the country the cost of treatment is now significantly cheaper than landfill or any other option at between £15/m3 and £20/m3 (£8/t-£11/t). Land- fill, including trans- port, costs as much as £50/m3 to £80/m3.
So why are brownfield devel- opers not falling over themselves to appoint bioremed- iation contractors to clean every oily smudge in the country? There is still a reluctance in certain areas of the industry to turn from the traditional landfill route which is after all thoroughly tried and tested. However the ever increasing list of project successes is slowly winning over even the most sceptical.
There is also undoubtedly some effect from the new generation of senior project managers and developers who have been educated to be more environ- mentally aware. As Pat MacGillycuddy, construction director at Gazeley Properties said of his decision to opt for £500,000 worth of bioremediation on a city centre site: 'It wasn't just the financial savings - we felt there was an element of risk in using bioremediation - but in the back of my mind was the thought of what we would be leaving for our children if we chose the low risk unsustainable option'.
Timescales are also perceived to be a problem even with the treatment times for actively turned biopiles often being as little as two to three weeks. This is often the result of the extremely rapid development times required once funding is in place for a development. As Glasgow-based remediation contractor Bio-Logic's managing director Colin Grant says 'The key is early identification of the cost savings available and perhaps appointing a contractor to clear the site, bioremediate the pollution and prepare the infrastructure in advance of the more complicated main contract. The savings can be a considerable dividend for a developer.'
Perhaps one of the most frustrating problems for all on-site operations involving contaminated soils has been the classification of the soils as waste and the necessity for some sort of waste management licensing. Professional bioremediation con- tractors have never objected to the principle of licensing but it has been difficult to achieve a consensus of opinion with the waste regulators as to how this should be achieved. A full Waste Management Licence has rarely been an appropriate tool for redevelopment sites where devel- opers naturally view the long term implications of a licence as a potential blight even if they have the time to wait the four months an application takes.
The other course has been to operate under the provisions of one or other of the exemptions to the Waste Manage- ment Regulations. These have always been an uncomfortable fit with bioremediation
as they are open to widely varying inter- pretation by Environ- ment Agency officers and, not surprisingly, bioremediation com- panies.
Following determined lobbying by the market leaders with assistance from the Environ- mental Industries Commission, Secretary of State for the Environment Michael Meacher has endorsed the principle of Mobile Plant Licences for ex-situ bioremediation. This will allow the regions of the Environment Agency to take a consistent approach to new technology.
So, the future for bio- remediation in the UK is looking rosier. However the industry has grown up in the face of com- petition from some of the cheapest landfills in the developed world and the difficulties presented by the wet marine climate. This has resulted in unique solutions and con- sequently some very cost effective and cheap remedial technology. The export oppor- tunities are considerable and it is possible that bioremediation will become one of the UK's most successful environmental com- modities on the world market.
Alistair Kean is technical services director of Bio-logic