1.1.01 In-situ remediation of abandoned waste – making good use of biological cleaning processes

Experience has shown that conventional remediation procedures are often hit by technical or financial limitations, meaning that impurities cannot be fully removed from soil and groundwater. Natural processes for reducing hazardous substances could be of great support here. Research was undertaken under the BMBF KORA principle (retention and degradation processes to reduce contaminations in groundwater and soil) between 2002 and 2008 to determine how and whether these natural processes could be used in the remediation of abandoned waste.

In the past, more and more sites were being uncovered that were polluted with substances hazardous both to health and the environment as a result of previous production and storage activities. Before now, such abandoned waste was sanitised by digging up and removing the polluted soil or pumping out then treating the contaminated groundwater. Alternatively, safeguarding measures can prevent further spread of harmful substances or treatment (decontamination) with chemical or biological agents can be carried out. However, these conventional remediation methods are often subject to technical and economic limitations, e.g. due to deep aquifersIn the field of hydrogeology, an aquifer (from the Latin words aqua = water, and ferre = to bear or carry) is an underground layer carrying groundwater. Aquifers are also referred to as water-bearing strata. Different types of aquifer are distinguished depending on the individual rock type (and thus the rock’s porosity)., heterogeneous underground conditions, builtup areas, the type of toxic substances present and their often uneven distribution.

Building on natural processes

It has been determined at a number of sites that naturally occurring processes such as biological degradation, chemical precipitationIn this process, chemical reactions cause the transformation of dissolved substances into insoluble substances, which then settle at the bottom of a vessel or water body – e.g. in the form of flocs – where they can be more easily removed from the water., decomposition, sorptionProcess whereby a solid or liquid substance takes up or holds another gaseous or dissolved substance. The term sorption refers to processes resulting in the enrichment of a substance within a phase (absorption) or on an interfacial surface between two phases (adsorption). The term is used when absorption and adsorption cannot be clearly distinguished. The sorbing substance is also referred to as the sorbent (or sorbent material)., dilution and volatilisation can render harmless or withhold hazardous substances in groundwater and soil under the right conditions. As such, contaminant plumesThe spread of dissolved contaminants in the ►aquifer. expand only to a limited degree in the groundwater and diminish once the source of the toxin runs dry. Great emphasis has been placed on researching, evaluating and finally utilising these processes in a targeted manner for a sustainable way to handle our resources.

Systematic investigations at 24 reference sites

The natural retention and degradation of hazardous substances depends on the type of contamination and the conditions in the soil and groundwater. A few key questions must be answered to be able to assess whether natural processes for reducing contamination (referred to as “natural attenuation” (NA) processes) can be used or stimulated at a given location:

• Are the hazardous substances being effectively broken down or withheld by natural processes under the prevailing conditions underground?
• Are any (undesirable) intermediary products accumulating through biological degradation?
• Could degradation be stimulated through the targeted modification of on-site conditions?

The diverse range of issues related to NA processes was what prompted the BMBF to provide approximately EUR 20 million of support to the “retention and degradation processes to reduce contaminations in groundwater and soil” (KORA) principle between 2002 and 2008. In total, 74 projects were carried out at 24 typically contaminated sites representing a wide range of comparable cases in Germany, testing whether and under what conditions natural degradation and retention processes could be put to effective use – in particular:

• Assessing the risks associated with contaminated groundwater and soil
• Calculating and performing hazard control measures (specific remediation)
• Calculating and performing follow-up measures.

Overview of the thematic networks (TN) and working aids from the KORA funding principle

In order to assess whether natural toxin reduction processes can be used and to monitor their effectiveness, regular soil and groundwater samples must be taken (monitored natural attenuation, MNA). The use of NA processes is therefore not a “do-nothing option”. Quite the opposite: only through clear and thorough data collection (monitoring) and assessment (forecasting) can the anticipated processes be implemented effectively and natural methods of reducing contamination be a viable alternative or supplement to conventional remediation methods.

Toxin-related research

The aim of the research performed under KORA was to form the basis for considering natural processes for reducing contamination and to derive plausible opportunities and parameters for implementation from an ecological, economic and administrative perspective. This not only required the development of appropriate methods to prove the efficacy of the NA processes, but also the validation of tools for their assessment. Universities, engineering bodies and authorities worked together to develop MNA concepts for the 24 investigated sites with tailored solutions for each one, and in many cases these processes were implemented too. In doing so, they created reference sites to be used as examples of how NA processes can be recorded, assessed and considered in a graduated procedure. The experts further developed innovative in-situ remediation procedures based on stimulating natural processes for reducing contamination. They also investigated various measures that are to encourage acceptance of NA processes for abandoned waste remediation through (risk) communication.

Industry guidelines and handling recommendations for practical application

The results of this funding principle were documented in the KORA handling recommendations (with integrated method collection), in six sets of industry guidelines and in the KORA synopsis “Systemanalyse, Modellierung und Prognose der Wirkungen natürlicher Schadstoff-minderungsprozesse” (systems analysis, modelling and forecasting effects of natural processes for reducing contamination) (see table). There is thus a variety of supplementary material available to assist authority representatives, engineering planners and those in charge of remediation. They can be used to check the potential ways in which NA processes and MNA concepts can be applied to treat abandoned waste. The working aids provide recommendations and assistance in using monitored or stimulated natural contamination reduction processes to treat abandoned waste in Germany and cover NA processes for groundwater that is already contaminated. Relevant existing (inter)national working aids, concepts and guidelines were considered during the compilation of the handling recommendations and industry guidelines. The working aids can be referenced at the website for this principle (www.natural-attenuation.de/bestellung) or downloaded in PDF format.

Projekt website www.natural-attenuation.de

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1.1.02 Keeping tabs on pollutants

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1.1 Groundwater