Work packages

The work packages provided a breadth of investigation covering the key issues in this field: fundamental understanding of processes, evaluation of technological innovations and methods used to treat contamination, socio-economic aspects and knowledge transfer.

This provided a holistic network to integrate knowledge, methods and skills from numerous disciplines to answer the specific problems relating to contaminated land and groundwater in Europe.

Each work package was led by a partner organisation, with significant input from other academic and industry partners, ensuring productive research collaboration. With the team of academic and industry partners represented, this structure maximised the impact of cross-institutional, cross-disciplinary, cross-sectoral and transnational collaboration for the benefit of the fellows.

The following descriptions outline the work packages (WP) as proposed at the start of the project:

WP1: Socio-economic and sustainability aspects of in situ remediation

A decision framework will be developed to integrate ISR within sustainable development, emphasising the role of stakeholder interaction, communication and governance issues in the scientific, social and political procedures used for remediation situations. It will provide new insights and guidelines for how scientists and policymakers can effectively engage with such challenges.

This highly innovative approach is crucial for future successful remediation, especially at complex contaminated sites. Sustainability indicators will be devised, which will consider stakeholder perceptions and problem definitions of actors on sites and their vicinity. PC-based decision-support tools will be produced to coordinate sustainable measures within the water sector, where this is important for decision making, for value to different end-users (e.g. investors, policymakers, citizens).

Scientific and social issues (e.g. decision-making with uncertainties) of site remediation will be considered together, to devise recommendations on long-term management for contaminated sites. By harmonising these issues, effective long-term management strategies for sites can be a starting point to manage human/non-human relationships at national, international and global levels.

WP2: Linking soil and vadose zone processes to in situ remediation of groundwater

This work package will develop an improved conceptual model for contaminant attenuation in the vadose zone (VZ) and fluxes to the saturated (SZ), and evidence-based predictive tools for groundwater impact assessment and optimisation of remediation design. This will involve lab, field and modelling studies that will determine how VZ hydraulic and physico-chemical properties control the attenuation of common contaminants.

Molecular microbiology, stable isotopes, high-resolution multilevel samplers (MLS), tracer tests and hydrogeophysical techniques (e.g. electrical resistivity tomography, ground-penetrating radar, electromagnetic induction tomography) will be used to quantify contaminant transport, biogeochemical processes and degradation at the field scale, supported by lab-scale model systems to quantify attenuation according to saturation, contaminant flux, oxidant availability, organic matter content and microbiology.

Control plane approaches at the VZ-SZ interface and in groundwater will be used to quantify contaminant attenuation and mixing (dilution) efficiency. This will establish how heterogeneity and up-scaling affect attenuation. The analysis will identify key processes for contaminant attenuation in the VZ, the measurements needed to predict attenuation and provide data for modelling. 2-D and 3-D finite-element modelling tools will be used to interpret the results.

WP3: Groundwater-surface water interaction and in situ remediation

Field, lab and modelling studies will quantify the capacity for attenuation of nutrients (e.g. nitrate and phosphate) and organic contaminants (e.g. chlorinated aliphatic hydrocarbons, pharmaceuticals, personal care products and endocrine disrupting compounds) at the biogeochemically active groundwater-surface water interface (GSI) in lowland river catchments.

Using existing test sites, field studies will determine the spatial and temporal variability in attenuation, linking these to hydrogeology, relevant geochemical properties, redox conditions and microbiological activity. The research will study the effect of heterogeneity in flow, transport and reactions at the GSI continuum on contaminant attenuation. The expected variations in degradation rate constants, microbiological data and geochemical data will be obtained using results of experimental lab-scale tests carried out in the framework of other EU projects.

Additional field data (from multilevel samplers and flux samplers) will be collected to deduce the heterogeneity of flow and transport across the GSI. The results will be interpreted with advanced modelling tools, to validate conceptual models of contaminant attenuation, deduce transfer functions that allow up-scaling of attenuation and identify how variation in these due to heterogeneity affects the prediction of attenuation.

The output will be a methodology allowing natural attenuation at the GSI to be included in catchment water quality assessments.

WP4: In situ remediation of metal-contaminated sites

This work package evaluates in situ bioprecipitation (ISBP) and selected physical-chemical processes and their engineering application for ISR of heavy metals at field-scale. The research will focus on fundamental processes (eg reaction mechanisms, rates, microbiological constraints, bioavailability, metal release, remobilization reactions) and the effect of environmental controls (eg carbon sources, reactant concentrations, toxicity, soil/aquifer properties, pH) on ISBP at the laboratory-scale, to develop performance criteria for the design of field-scale systems.

An evaluation will be made of the ISBP concept for metals in controlled field experiments using a test cell at a mega-site, considering heterogeneity and up-scaling of processes on remediation performance. Novel molecular microbiological and stable isotope analysis, supported by mathematical modelling, will be used to interpret natural processes. The aim will be to devise design criteria for ISBP remediation systems and a technical basis for performance assessment.

WP5: Developing in situ treatment strategies for mixed contaminants using sequenced reactive biobarriers

Sequenced biobarriers use successive treatment zones containing different reactive materials or reactants which modify the system biogeochemical conditions to remediate a wide range of complex waste streams (eg mixed metal-organic wastes and mixed solvent plumes) in situ.

Lab studies will deduce processes, biogeochemical limitations and design parameters (e.g. residence time, reaction kinetics, biofilm stability and barrier composition) for treatability, in model barriers using organic-metal contaminant mixtures. Related field studies at sites with existing reactive barriers and diffuse pollution will examine up-scaling of design parameters from lab to field applications, the effect of heterogeneity in system properties (e.g. hydrogeology, contaminant flux) and treatment optimisation.

Geochemical, molecular microbiological and stable isotope analysis will be used to study biogeochemical processes at the lab and field-scale. The effect of non-target species on the treatment of target compounds and the link between hydrodynamic flux, microbiological activity and biofilm growth in the lab and field-scale biobarriers will be examined.

At field-scale, changes in treatment capacity from variations in hydrogeological, geochemical and microbiological parameters controlling attenuation will be quantified using similar approaches.

The results will be interpreted with multi-scale modelling tools and statistical methods to develop performance-based criteria for the design, monitoring and assessment of sequenced reactive barriers.

WP6: Enhancing bioremediation processes

Mass transport phenomena which affect the supply or mixing of contaminants, oxidants and microorganisms needed for biodegradation and the enhanced bioremediation of contaminated soil and plumes will be examined. Bench-scale physical aquifer model experiments will be used to establish mathematical relationships between hydrodynamic dispersion and plume geometry, source strength and oxidant amendment supply in heterogeneous systems.

Plumes will be created in the model aquifers using reactive tracers and analysed with state-of-the art methods. The mathematical relationships developed in the lab studies will be a valuable tool to estimate contaminant plume length under natural conditions and assess the value of amendments (eg oxidant delivery) or procedures (eg hydraulic manipulation) used to enhance biodegradation. These relationships will be tested at field scale using data from well-characterised sites, for validation and to identify monitoring requirements.

A separate study will explore the development of soil microbial fuel cells to enhance soil and groundwater bioremediation. Electrodes inserted in soil can increase oxidant delivery to support anaerobic biodegradation of organic compounds. The electron transfer created by in situ microbial degradation reactions can be coupled to reduction of oxygen in the atmosphere and generates an electrical current as an energy source to sustain the process for bioremediation.

Using lab-based model soil systems containing different organic compounds, the research will deduce the fundamental electron transfer mechanisms, the efficiency of treatment for specific contaminants and develop design criteria to optimise treatment performance for a range of conditions.

The output from these studies will be a quantitative basis to predict mass transport limitations in heterogeneous media and predict the technology performance, and new techniques which can enhance biodegradation processes in situ.

WP7: Performance assessment of natural attenuation at field-scale

This work package will explore the respective roles of hydrogeological, geochemical, microbiological and environmental controls on the performance of natural attenuation at field-scale for common organic contaminants in groundwater.

Using field sites within this project, one study will explore the development of non-reactive and reactive tracer mixtures to characterise the relevant properties of aquifers which influence contaminant transport and natural attenuation processes. These methods have not been widely applied in the context of natural attenuation. The research will focus on characterisation which leads to new conceptual ways of modelling that account for the properties of, and interactions between, selected reactive tracers and soil/aquifer materials, and on optimised single and multiple-well tracer techniques for performance assessment of natural attenuation. Monitoring techniques will in particular include geophysics, to target specific processes, and tracers with a greater spatial coverage. Experiments will be undertaken at the laboratory-scale, using a model aquifer, and at the field-scale on a contaminated site.

Another study will examine the dynamics of microbiological community development, structure and metabolic function at the bioreactive fringe of contaminant plumes (interface between groundwater and the plume). This narrow zone (<1m) has enhanced microbial activity in plumes, due to supply of oxidants and organic substrates (pollutants) by hydrodynamic dispersion in aquifers. The research will establish the factors that lead to microbial succession and diversity in the indigenous microorganisms at the fringe of plumes, considering environmental pressures (organic contaminant type, concentration and toxicity) and molecular controls on behaviour. It will deduce how these selection pressures are expressed in the relative dominance of specific microbial populations, their interactions and biodegradation potential for organic contaminants at the plume fringe. This will be compared with the behaviour predicted for lab-scale plumes in WP6.

This work package will provide an improved conceptual model of the spatial and temporal variation in organic contaminant biodegradation potential in plumes, to support management decisions on the implementation of natural attenuation in groundwater.

WP8: Network knowledge transfer and research dissemination

Knowledge transfer activities and public outreach will be developed in collaboration with CL:AIRE, to promote the network, disseminate the research and profile the achievements of ADVOCATE. This will be coordinated with other knowledge transfer networks and industry groups within Europe and overseas to maximise cross-sectoral and cross-disciplinary impact of the research at all levels, and develop longer term research and training collaboration beyond the project.

Example activities include online dissemination of ADVOCATE and its training events, co-hosted network workshops, summer schools and thematic conference, with outputs including monthly newsletters and technical bulletins (case studies, research advances and technology demonstration).