1.1.09 VEGAS research facility – ecological remediation without digging up and shipping out

Pollution is contaminating soil and groundwater all over the world. Land affected by this is difficult to use and hard to sell because remediation of the soil and groundwater is extremely complex and expensive. It therefore often remains unused. At the same time, an area of around 90 hectares a day in Germany alone is being redeveloped as green-field land. The specialists at the Versuchseinrichtung zur Grundwasser- und Altlastensanierung (research facility for the remediation of groundwater and abandoned waste, VEGAS) are therefore developing technologies that enable efficient surveying and remediation of contaminated land to render it marketable once more.

The soil and groundwater at many former industrial sites and also in numerous urban areas has been contaminated through improper disposal methods, accidents, the effects of war and careless handling of hazardous substances. Consumers have also worsened the problem in the past: household chemicals, paint and other toxins that are now dealt with as specialist waste were disposed of at unsecured landfill sites with permeable ground underneath. For example, exhausted gravel pits were filled with all kinds of refuse and then planted over.

Conventional in-situ remediation techniques are often protracted and expensive. The physical properties of the pollutants means that they collect in the soil pores and are difficult to remove with traditional flushing methods. However, if contaminated material is dug out and disposed of at a dump, this only serves to delay the problem. Built-up land or land with deep-lying, hard-to-pinpoint sources of pollution cannot be dug up in any case. One of the most important tasks we face today therefore is to develop new technologies offering economical and ecological remediation before the abandoned waste poses a threat to both people and protected natural resources.

The VEGAS concept

With support from the BMBF and the Ministry of the Environment in Baden-Württemberg, the major research facility VEGAS was established by the University of Stuttgart in September 1995 (size: 670 m2; large-scale test rig surface area 18 x 9 m, height 4.5 m, divisible into three compartments). The engineers and scientists there develop surveying and remediation technologies and operate field applications and technology transfers. The large-scale test rigs are used to perform experiments under near-natural conditions, their dimensions being somewhere between conventional lab equipment and actual field conditions. There are good reasons for such middle ground: conventional lab tests are not directly transferrable to actual conditions “in the field”, and the results from time and costintensive field studies at existing pollution sites are only meaningful to a limited extent. This is because more often than not the remediation specialists are unaware of both the overall amount of pollution and its precise spatial distribution. The few distributed measurement points do not produce a sufficiently detailed overview. Furthermore, environmental protection laws currently in force prohibit the injection of remediation chemicals into the aquifer if it cannot be guaranteed that they are harmless. However, such a guarantee cannot be given when testing new technologies under development.

Innovations in technology

Abandoned waste in the soil can either be cleaned up or safeguarded. The remediation approach involves removing the source of the contamination or the plume through chemical, biological or hydraulic methods. Safeguarding prevents the further spread of the pollution, e.g. by containing the source. In the last few years, VEGAS has concentrated primarily on source surveying and remediation. Appropriate procedures, some of which have already been put into practice in the field in collaboration with companies include:

• Thermal remediation technologies: Energy feeds – either in the form of vapour or a vapour-air mix or as a fixed source of heat – increase the temperature of the contaminated soil and groundwater areas. This reduces the surface tension, viscosity and density of the pollution while simultaneously increasing its vapour pressure. This boosts its transformation into gas and enables it to be sucked out via the soil gas.
• In-situ reduction of pollution through minute pieces of iron (nanoscale iron) in treatment walls: this remediation procedure is applied to CHC plumes. Experts are currently examining how this technology could also be applied within built-up areas. This involves injecting nanoscale iron directly into the source of the contamination by means of suspension. The issues of transportation, reactivity, and long-term stability and also economics still need to be clarified; these too must be answered through the pilot sites within various research consortia.

Other types of technology (further) developed by universities, companies, local authorities and institutes within VEGAS involve procedures such as the injection of tensides, alcohol cocktails or microemulsions. Other new options included special remediation wells, in-situ chemical oxidation (ISCO) and reduction (ISCR), immobilisation of heavy metals and improvement of the natural degradation processes within the aquifer (enhanced natural attenuation, ENA) through the addition of nutrients.

Focus on measurement technology

The field of measurement technology has been consistently expanded within VEGAS:

1. Surveying: The position and concentration of a pollution source must be precisely identified in order to implement remediation. The VEGAS researchers have therefore developed new methods, e.g. based on sensors and fibre optics, to enable a quick and cost-effective way of pinpointing sources of pollution.
2. Monitoring: New instruments for on-site measurement technology enable a prompt return of information on the distribution of and decrease in pollution, thus lowering the cost of remediation.
3. Long-term observation: Once remediation is complete, the experts must use automated long-term observation to prove that the concentration of pollution is not rising again and that the threat is therefore effectively neutralised.
4. Geothermal energy: To date there has been little research on the influence of geothermal systems on groundwater. The monitoring of water temperature and quality in the vicinity of geothermal probes is intended to contribute to their safe use in the long term.

Transfer of technology and knowledge

In order to ensure sustainable protection for soil and groundwater, it is not enough simply to develop technology. That is why the research facility holds regular training events for specialists working at authorities and engineering bodies. The technologies developed are conveyed to a broad specialist audience through pilot schemes conducted at actual pollution sites.

Project website www.vegasinfo.de

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1.1.10 Remediation using alcohol

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1.1.08 Direct oxygen injection