Biotechnology is a cost-effective and sustainable alternative for cleaning up contaminated land and tackling VOC abatement. Nick Warburton reports on the Government's BIO-WISE programme and how it can assist EHOs with contaminated land remediation and air quality management.

Britain's industrial activity has left an indelible mark on the nation's landscape. As the Government encourages sustainability in future developments, the demands of industry and pressure to meet housing shortages have to be balanced against restrictions on greenfield development and tighter pollution controls. Local authorities have a key role to play through the remediation of contaminated areas to free up brownfield land for development and volatile organic compound (VOC) and odour abatement to meet stringent emission controls.

CONTAMINATED LAND
Under the provisions of the Environment Protection Act 1990, Part 2A, environmental health officers have been apportioned the responsibility to decide whether land should be defined as "contaminated", and are obliged to manage the consequences of such declarations (EHJ, May 2001, page 139). In addition, EHOs are required to complete contaminated land strategies, and to carry out risk assessments of sites if pollution linkages have been identified - a process that is not only time-consuming, but also costly.
As Roger Braithwaite, author of a series of articles in EHJ on the contaminated land regime points out: "EHOs have a difficult role because as well as being the enforcing authority for contaminated land, local councils are also probably the largest owners of contaminated sites in the UK". For example, every local authority will have houses built on sites known to be associated with a type of contamination, such as sewage works, scrap yards and landfill sites (EHJ, February 2000, page 42). In other words, local authorities may find themselves drawn into a dual role of "poacher" and "gamekeeper". Consequently, as Mr Braithwaite argues: "It is vitally important that EHOs actively resist this conflict as the Government emphasises the need for openness and transparency in self-regulation. They should advise that independent advice should always be sought on council-owned sites which they could then assess in the normal way".
In the past, EHOs have largely relied on containment, excavation and disposal as methods for cleaning up contaminated land, but the combination of long-term monitoring, excavation, transport, replacement of soil etc can place great strains on local authority budgets and has necessitated a new approach. In addition, the combination of statutory limits on VOC and odour emissions, and greater public awareness of the negative effects of odours have increased the pressure for cost-effective air pollution controls.
Biotechnology has increasingly become an attractive option. A Department of Trade and Industry funded programme called BIO-WISE was launched in 1999, with the specific remit of encouraging the wider use of biotechnology within manufacturing industry. Although not appropriate in all situations (biotechnology is not compatible with non-organic wastes and is not suitable when dealing with emergency incidents that require immediate action), it can offer a cost-effective alternative that actively promotes the principles of sustainability.
In simple terms, biotechnology harnesses the power of living organisms in industrial biological and chemical processes. An important application of biotechnology is for environmental improvement. Such processes exploit the ability of naturally occurring microbes to "break down" or degrade a wide range of hazardous substances in water or land, into less toxic or non-toxic substances. Certain microbes work by digesting "organic" substances (compounds containing carbon and hydrogen atoms) such as fuels or solvents and breaking them down so that they become harmless to humans.1
These natural processes can be used to remediate contaminated land or to treat VOC emissions to atmosphere. The bioremediation of contaminated land is fairly straightforward - the user encourages the growth of active and healthy microbes that are either "indigenous" or "exogenous" to a specific site. Indigenous, as the term suggests, refers to microbes that already exist at a specific site, and tend to act without any assistance. However, in some cases, the conditions may need to be created to stimulate their production such as proper soil temperature, oxygen and nutrient content. On the other hand, and on rare occasions, the microbes needed to stimulate the break down of contaminants may not be present in the soil and consequently need to be brought in from elsewhere and added to the contaminated area. These exogenous microbes may additionally require adjustments to the soil conditions at the new site to allow them to flourish.
At present, bioremediation can degrade a wide range of chemicals in soil, including chlorinated solvents, petroleum hydrocarbons such as petrol and diesel, and oxygenated hydrocarbons, like detergents, and pesticides. As technological improvements continue to be made, the diversity of contaminants that can be treated will grow.
Bioremediation is an effective tool for cleaning up contaminated land, but the choice of remediation approach will inevitably depend on a good site investigation. During this initial period, information on the amount and distribution of the pollution and the microbiological make up and nature of the site will need to be collected. As EHOs predominantly carry out risk assessments of sites, the information available from the BIO-WISE programme2 will be of particular interest to practioners:
- a helpline and website offering free advice about the different biotechnology techniques available in the UK;
- free technical advice for small to medium-sized enterprises helping them to benefit from the application of biotechnology;
- free booklets describing the economic and environmental benefits of using biotechnology with a wealth of material on how the technology is employed;
- examples of best practice, case studies and technical reviews of industrial biotechnology; and
- the encouragement of partnerships between suppliers, intermediaries and end users.
Two publications are specifically useful to EHOs - Contaminated land remediation, which offers a wealth of material covering on-site assessment using risk management, the different types of bioremediation methods and the cost benefits of using biotechnology, and VOC and odour abatement.3
Bioremediation of contaminated land employs two methods - ex-situ and in-situ. The first method removes soil from the contaminated area (but may involve keeping it on site) before treatment takes place, while the second leaves the soil undisturbed during the entire treatment process. Ex-situ can be used to treat a wider range of contaminants and soil types than in-situ methods. However, the problem here is that ex-situ methods require treatment of contaminated soil before, and sometimes after, the bioremediation step. In-situ, meanwhile, may offer a less expensive alternative to ex-situ bioremediation by the very fact that soil is not removed. Consequently, it creates less dust and releases less pollutants. However, the process may be a lot slower than ex-situ techniques, may prove more difficult to manage and is most effective at sites with permeable soil.
Both methods include a range of techniques, which are briefly outlined below:4

EX-SITU
- Landfarming - a simple process particularly suited to the treatment of hydrocarbon-contaminated surface soils. Its effectiveness depends on the soil properties, the nature and concentration of the contaminants, the available space for on-site treatment and the climatic conditions.
- Composting - can treat more soil per unit than landfarming and is more suitable for colder climates, due to the fact that heat generated during biodegradation can be retained. Faster than landfarming in biodegrading pollutants, the technique is also appropriate for the treatment of hydrocarbon-contaminated soils.
- Engineered biopiling - a more intensive version of composting. Biopiling is best suited to sites where space is limited. It optimises the biodegradation process through a greater control of oxygen, water and nutrient levels.
- Bioreactor treatments - ideally suited to the treatment of complex mixtures of compounds. It may involve a combination of different chemical and biological processes depending on the nature of the contaminants.

IN-SITU
- Monitored natural attenuation (or bioattenuation) - this is a process that allows nature to do the work. It involves monitoring the natural, physical, chemical and biological processes in soil and groundwater that are used to degrade the pollutant or limit its spread. The advantage over other in-situ methods, which require a degree of intervention, will depend on whether there are any unacceptable impacts or risks to receptors. The availability of oxygen, nitrate or sulphate for sustaining this natural process, the biodegradability of the contaminants on site and the microbial activity of the indigenous microbes will also be influencing factors.
The following in-situ techniques require the introduction of oxygen and nutrients to the contaminated area. In some instances, the surface treatment of contaminated water and vapours will need to be included. The following methods all require modifications to the conditions within the soil or groundwater.
- Bioventing - best suited to permeable, well-aerated soils such as sand and gravel, this technique combines supplying extra oxygen with vapour extraction to promote air flow through the area contaminated thereby enhancing natural biodegradation.
- Biosparging - like bioventing, this technique uses equipment that is both easy to install and is readily available. Biosparging is suitable for breaking down contaminants both below the water table (or saturated zone) and in the overlying contaminated area. The supply of oxygen is increased by pumping air into the water table via boreholes, and its success depends on diffusing the injected air into the surrounding groundwater and soil.
- Injection and recovery systems or pump and treat - pollutants from the water table are pumped via a recovery well to a treatment tank on the surface. Following this stage, nutrients, oxygen and other chemicals such as sulphate are added to the mix and then pumped back into the ground via an injection well and re-circulated through the contaminated area. Once this has taken place, the injected groundwater stimulates the microbes already present in the contaminated area to break down the pollutants.

VOC ABATEMENT
As noted earlier, Biotechnology can also be harnessed to reduce VOCs and odour-causing compounds to below statutory levels. VOCs, which are one of the contributing factors to photochemical smog or low-level ozone, can be particularly harmful to human health through its toxicity and impact on the environment - polluting vegetation and crops, for example.
As required by the Environmental Protection Act (EPA), 1990, Part 1, all sites in the UK that use more than five tonnes of solvent per year must comply with stringent air emission standards. For industries using conventional practices and local government, which is responsible for authorising sites under the Act, this can pose serious problems, especially as the pressure to find suitable, cost-effective techniques for the removal of VOCs from factory emissions grows. Biotechnology systems are particularly suitable for the treatment of solvents and odour-forming compounds produced by companies that dry or cook material, process organic matter, and heat, paint, print, coat or glue things.
According to Marc Willimont, senior EHO at Herefordshire Council, and author of "Disaster at Dinmore Hill" (EHJ, January 2001, page 11):, "Biological abatement of VOCs can be a successful BATNEEC (best available technology not entailing excessive costs) route, but the technology is still considered new and largely untried in the long term". He believes that the lack of industry awareness of biotechnology has been tempered by the fact that many of the EPA PG guidance notes were written in the 1990s when biological treatment was not used in the VOC sector. Hopefully this will change when Defra and the Environment Agency revise the notes.
Essentially, there are three main types of biological abatement equipment available. Each needs to be considered on its own merit due to differences in application, advantages in use and the conditions required:
- Biofilters - easy and cheap to operate and set up, the advantage of biofilters is that they can degrade a wide range of compounds, including insoluble VOCs. On the other hand, the productivity is relatively low due to the process design and there is a long retention period while the odour-causing compounds and VOCs are broken down. Biofilters are widely used in the food and related industries such as animal carcass disposal. It is also frequently used for dealing with odours stemming from composting and sewerage treatment.
The other types of treatment are most applicable for the printing industry and other solvent-using processes, assisting in the reduction of VOC emissions below statutory limits:
- Bioreactors - cheap to operate, bioreactors can treat high volumes of contaminants over a short period. However, the system needs to be designed to cope with fluctuating concentrations of waste gas.
- Bioscrubbers - can deal with high flow rates, although compounds need to be water soluble. Bioscrubbers can be complicated to operate and maintain and the process produces excess sludge, which requires disposal.
Herefordshire Council authorises industrial processes using biofilters and bioreactors for VOC and odour abatement and Mr Willimont believes that the technology may offer a more sustainable and economical alternative to incineration. "The overall costs have been in the region of £120 - £150,000 for bioreactors in the printing sector, which compares favourably with incineration alternatives such as regenerative thermal oxidisers (RTOs), the industry standard, which cost between £150 - £500,000. As a rule of thumb, our link authority group for the printing sector have found that bio systems are best suited to processes using between 5 and 150 tonnes on VOC per year. Above this, RTOs tend to be favoured, but this is probably because it is the established BATNEEC route".
Mr Willimont argues that even though biological systems will not abate VOCs to the same level as incineration, they will meet the emission limits set by the EPA Printing on Flexible Packaging PG notes, which are currently 150mg/m3 and soon to be reduced. He adds: "As they are biological systems, they are best suited to constant processes and not batch ones. As a result, care must be taken if a process shuts down at night or weekends, as no VOC will cause a drop in the microbe population, which may in turn lead to a problem when the process starts up again. For this reason, local authorities are requiring processes to be continuously monitored, which is expensive for the process operators. The latest draft PG note appears to deal with this, but we'll have to wait and see what happens".
Bioremediation should not be dismissed as an "alternative" technology - it is an established technology with proven results. For EHOs involved in pollution and contaminated land issues, BIO-WISE provides practical advice and solutions on the use of biotechnology as a clean-up option.

1 United States Environmental Protection Agency fact sheet "A citizen's guide to Bioremediation". To access visit: www.epa.gov/swertio1/products/citguide/biorem.htm
2 For more information about BIO-WISE and its services visit: www.dti.gov.uk/biowise
3 Contaminated land remediation: A review of biological technology and VOC and odour abatement: a review of biological abatement technology can be obtained from the DTI BIO-WISE website.
4 Additional information about the techniques, can found in the BIO-WISE publication Contaminated land remediation: A review of biologicial technology.