Summary

Statusprojekt

Since 1996, the Danish Environmental Agency has rendered financial support for the development of cleanup and remediation techniques in the field of soil and groundwater pollution under “The Technology Development Programme for Soil and Groundwater Pollution”. The financial support is primarily applied for special investigations, monitoring or documentation of activities in relation to cleanup projects financed by the Danish Regions (the former counties) or under private management.

Parallel to the activities under the Technology Programme, development and testing of the cleanup and remediation techniques has been conducted under other management. These projects have been financed by the Danish Regions (the former counties), Municipal authorities, private builders, and by education and research institutions.

This report gives a status for the total general development within cleanup and remediation techniques in Denmark up to ultimo 2007. The report is primarily based on the activities under the Technology Programme, but also on information on remediation techniques developed and/or tested elsewhere. The report does not include a total list of all cleanup and remediation techniques applied in connection with soil and groundwater pollution, but is merely a status of the most significant techniques tested in Denmark up to ultimo 2007.

The descriptions in the report are prepared from the extensive data collection made on basis of the status descriptions in the “Technology Programme for Soil and Groundwater Pollution 2007”, Information from the Danish Environmental Protection Agency No. 1 (2007), and on the basis of an interview survey in the Danish Regions (the former counties), private builders, and education and research institutions. The interview survey was based on two different questionnaires, which were drawn up partly to achieve a general overview of the activities carried out in Denmark (pilot or full-scale), partly to collect information on the extent of the application of the different techniques, and the need for further technology development.

Each of the remediation techniques has been examined with respect to the principle of the technique, activities carried out, and the remediation results. Hereafter, the overall perspective for each technique is characterised. The techniques are divided into two main groups: “Techniques for cleanup of sources” and “Techniques to prevent pollution spreading”, and listed in a block diagram with key-figures, Appendix 2. Using the block diagram, the report can be used as a reference manual.

Finally, the report gives an overall assessment/perspective with regard to future technology development needs based on experience from the Danish Regions, Municipalities, and private builders.

On background of the examination, the following overall conclusions concerning the remediation techniques have been made.

Techniques for cleanup of source zones

Vacuum ventilation. The technique is well-documented and is today applied at a large number of polluted sites in Denmark. The technique is proven effective for reduction of gaseous pollution in the unsaturated zone. The interview survey pointed out that results achieved through development projects under the Technology Programme have been used in connection with the choice of technique, the design of the system and vacuum ventilation, and that the need for further technology development of this technique is minimal.

Air sparging. The technique has been applied at a number of Danish sites, and is based on removal of the pollution by stripping to the air phase or by stimulated aerobic degradation. The interview survey pointed out that results achieved through development projects under the Technology Programme have been used in connection with the choice of technique and the design and planning of the system, and that the need for further technology development of this technique is minimal.

Multi-phase extraction. The technique has only been applied at a limited number of sites for reduction of source pollution in the capillary zone between the saturated and the unsaturated zone. No investigation activities using multi-phase extraction have been made under the Technology Programme. However, the interview survey pointed out that there is a need for technology development of this technique.

Enhanced leaching of tar components. The technique has only been applied at a limited number of Danish sites for leaching and stimulated degradation of diffuse tar pollution in the unsaturated zone. The interview survey pointed out that results achieved through development projects under the Technology Programme have only been used to a minor extent, and that there is a need for further technology development of this technique.

Flushing. No data to document the application of flushing in Denmark has been identified. However, the interview survey pointed out that there is a need for further technology development of this technique.

Soil washing (ex-situ). The technique has only been applied at a limited number of sites in Denmark and includes a group of methods for either soil washing or separation of the different fractions of soil. The interview survey pointed out that the Danish Regions have no knowledge as to whether results achieved under the Technology Programme have been used in connection with soil washing at treatment plants, and it is assessed that there is no need for further technology development of this technique.

Vapour stripping. The technique belongs to the group of thermic methods for in-situ cleanup of soil and groundwater in source areas and is applied at only few Danish sites. The interview survey pointed out that results achieved through development projects under the Technology Programme have been used in connection with choice of technique, the design and planning of the system, and that there is a need for further technology development of this technique.

Thermic conductivity. The technique belongs to the group of thermic methods for in-situ cleanup of soil and ground water in source areas, and has been applied at a number of Danish sites. The interview survey pointed out that results achieved through development projects under the Technology Programme have been used in connection with the choice of technique, the design and planning of the system, and that there is a great need for further technology development of this technique.

Thermic soil treatment (ex-situ, on-site). The technique has only been applied to a limited extent in Denmark. The interview survey pointed out that the Danish Regions have no knowledge as to whether results achieved under the Technology Programme have been used in connection with thermic treatment of soils, and it is assessed that there is no need for further technology development of this technique.

Electrochemical soil treatment (ex-situ, on-site). There is no knowledge of application of this technology as part of the remediation strategy at Danish sites. The interview survey pointed out that the need for further technology development of this technique is minimal.

Enhanced biological degradation – oxidation. The technique has been applied at a number of Danish sites to enhance in-situ degradation of organic pollution components under oxygenic conditions. The interview survey pointed out that results achieved through development projects under the Technology Programme have been used to a limited extent in connection with the choice of technique, and the design and planning of the system. The Danish Regions assess that there is a need for further technology development of this technique.

Enhanced biological degradation – reduction. The technique has been applied at a number of Danish sites for enhancing in-situ degradation of organic pollution components under anaerobic conditions. The interview survey pointed out that results achieved through development projects under the Technology Programme have been used in connection with the choice of technique, and the design and planning of the system. The Danish Regions assess that there is a great need for further technology development of this technique.

Phytoremediation. The technique has only been applied at few Danish sites for fixation, degradation or evapotranspiration of pollution components. The interview survey pointed out that results achieved through development projects under the Technology Programme have been used in connection with the choice of technique, the design and planning of phytoremediation projects, and furthermore that there is a need for further technology development of this technique.

Chemical oxidation. The technique has been applied at a number of Danish sites primarily for the in-situ chemical degradation of dissolved and adsorbed pollution in saturated formations. The interview survey pointed out that results achieved through development projects under the Technology Programme have been used in connection with the choice of technique, the design and planning of cleanup projects using chemical oxidation, and that there is a need for further technology development of this technique.

Geo oxidation. There is no knowledge of any application of this technology as part of the remediation strategy at Danish sites. The interview survey pointed out that there is no need for further technology development of this technique.

Hydraulic fracturing. The technique has been applied at several Danish sites for formation fracturing of low-permeable formations to allow contact between the “remediation agent” and the pollution components. The interview survey pointed out that results achieved through development projects under the Technology Programme have been used in connection with the choice of technique and the design and planning of the system. The Danish Regions assess that there is a great need for further technology development of this technique.

Pneumatic fracturing. The technique is still in the development stage, but has already been applied at a few Danish sites for formation fracturing of low-permeable formations to allow contact between the “remediation agent” and pollution components. The interview survey pointed out that results achieved through development projects under the Technology Programme have been used in connection with the choice of technique, and the design and planning of the system. The Danish Regions assess that there is a great need for further technology development of this technique.

Techniques for spreading control

Passive ventilation. The technique has been applied at a large number of polluted sites in Denmark for reduction of pollution in the unsaturated zone. The interview survey pointed out that results achieved through development projects under the Technology Programme have been used in connection with the choice of technique and the design and planning of vacuum ventilation systems, and that there is a need for further technology development of this technique.

Reactive permeable wall (permeable iron wall). The technique is still in the development stage, but has already been applied as part of the remediation strategy at a few Danish sites for degradation or immobilization of pollution in the saturated zone. The interview survey pointed out that results achieved through development projects under the Technology Programme have been used in connection with the choice of technique, and the design and planning of vacuum ventilation systems, and that there is a need for further technology development of this technique.

Biological reactive barrier – oxidation. The technique is still in the development stage, but has already been applied as part of the remediation strategy at a few Danish sites for degradation of pollution in the saturated zone. No investigation activities using this technique have been made under the Technology Programme. However, the Danish Regions assess that there is a great need for further technology development of this technique.

Biological reactive barrier – reduction. The technique has been applied at a number of Danish sites to enhance in-situ degradation of organic pollution components under anaerobic conditions. The interview survey pointed out that results achieved through development projects under the Technology Programme have been used in connection with the choice of technique, and the design and planning of the system. The Danish Regions assess that there is a great need for further technology development of this technique.

Monitored natural degradation. The technique has been applied as part of the remediation strategy at a number of Danish sites for control of the pollution spreading in the unsaturated as well as the saturated zone. The interview survey pointed out that results achieved through development projects under the Technology Programme have been used in connection with the choice of technique and the design of system, and that there is a need for further technology development of this technique.

In-Well Aerator. The technique is still in the development stage, and has only been applied at a few Danish sites. The interview survey pointed out that the Danish Regions have no knowledge as to whether results achieved under the Technology Programme have been used in connection with In-well aerators, and that there is no need for further technology development of this technique.

Iron filter for cleanup of chlorinated solvents (on-site). A project using this technology has been carried out under the Technology Programme, but there is no information about any application of the technique as part of the remediation strategy at Danish sites. The interview survey pointed out that there is no need for further technology development of iron filters for cleanup of chlorinated solvents.

Iron filter for cleanup of chromium (on-site). A project using this technology has been carried out under the Technology Programme, but there is no information about any application of the technique as part of the remediation strategy at Danish sites. The interview survey pointed out that there is no need for further technology development of iron filters for cleanup of chromium.

Chemical-biological iron filters (on-site). A laboratory test using this technology has been carried out under the Technology Programme for cleanup of chlorinated solvents, but there is no information about any application of the technique as part of the remediation strategy at Danish sites. The interview survey pointed out that there is no need for further technology development of this technique.

Biological degradation of MTBE (on-site). A laboratory test using this technology has been carried out under the Technology Programme, but there is no information about any application of the technique as part of the remediation strategy at Danish sites. The interview survey pointed out that there is no need for further technology development of this technique.

Cleanup of MTBE pollution in ground water (on-site). A laboratory test with sorption of MTBE to different materials for cleanup of MTBE polluted groundwater has been carried out under the Technology Programme. There is, however, no information about any application of the technique as part of the remediation strategy at Danish sites. The interview survey pointed out that there is no need for further technology development of this technique.

Biological air filters (on-site). There is no information about application of the technique as part of the remediation strategy at Danish sites. The interview survey pointed out that there is no need for further technology development of this technique.

Technology development - needs

It is assessed that there is general need for a continued transfer, adaptation, refining, and redevelopment of new as well as old remediation techniques. Furthermore, there is a need to develop and test methods at pilot-scale to evaluate whether it is realistic to continue the development of these methods. There is also a need to evaluate the sustainability of the remediation techniques. In this connection, it is important to focus on a sustainable development of the remediation techniques.

Significant reductions of CO₂ emissions in cleanup projects will help to draw the attention to the sustainable remediation techniques at the Climate Conference to be held in Copenhagen in Denmark in 2009. The concept of sustainability in relation to remediation techniques has yet to be defined.

A number of techniques which on the basis of the data material collected are assessed to be relevant to develop are listed below.

Iron particles - nano or micro size
International experience and Danish laboratory tests show that iron particles of nano or micro size can be applied for remediation of groundwater pollution with chlorinated solvents and many other components as well.

Microbiological cleanup methods
Microbiological methods are assessed to have a great potential as cleanup methods. There is a continued need for knowledge collection and documentation of well-known biological processes, and for further development of the methods for example by addition of enzymes, nutrients, and/or bacteria.

Enhanced reductive dechlorination
Enhanced reductive dechlorination is making progress as an in-situ cleanup technique for pollution with chlorinated solvents in both the USA and Europe. It is assessed that there is a great potential for this technique, and that there is a need for further documentation and optimization of the technique.

Chemical oxidation
The application of the method is in growth, but there is a need for further testing and documentation. Furthermore, there is the need for assessment of different means of oxidation, and a deeper understanding of related geochemical effects as well as better methods for optimal management of the injection of chemicals.

Fracturing
There is a need for development and testing of methods for cleanup in low-permeable sediments. The methods are assessed to have potential, but there is still a need for further testing and documentation.

Thermic methods
The thermic methods are well-documented for efficient cleanup of source areas in different soil layers. Electrical heating is not used in Denmark, but is considered to have potential.

Cleanup of free phase chlorinated solvents
There is a need for development and testing of cleanup methods for management of free phase chlorinated solvents.

Injection methods
The success of cleanup by reductive dechlorination and chemical oxidation is very much dependent on the extent of the distribution of the treatment additives. It is considered relevant to improve the existing method and also develop new methods for this technique.

Reactive walls – soil mixing
It is assessed that there is a potential for further development and testing of reactive walls – to begin with via knowledge collection from existing projects. The method is being developed and tested in the USA and Denmark, and is assessed to have a potential in Denmark.

Ex-site soil handling
It is assessed that there is a need for development and testing of ex-site methods that can remediate for example heavy metals.

In-Situ Air sparging, IAS
In-situ air sparging is applied as remediation method for volatile or aerobic degradable components in the saturated zone, and previously there has been much focus on this technique. However, a number of limitations have been identified for this method. The development of the method is, however, continuing in other countries, and the applicability of the method has been improved in many ways. There is a need for a survey of experience with this method.

Investigation methods
There is a great need for further development of the investigations methods, not least for the detection and quantification of free phase and methods for the determination of reliable average levels in soil gas, groundwater and surface water/streams.