life cycle assessment of active and passive groundwater remediation technologies
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evaluated by focusing on the main technical elements and their significance with respect to resource
funnel construction and by minimising the steel consumption for the gate construction. Granular activated
carbon (GAC) is exclusively considered as the treatment material, both in-situ and on-site. Here it is
Journal of Contaminant Hydrology 83 (2006) 171199
www.elsevier.com/locate/jconhyddepletion and potential adverse effects on ecological quality, as well as on human health. Seven impact
categories are distinguished to address a broad spectrum of possible environmental loads. A main point of
discussion is the reliability of technical assumptions and performance predictions for the future. It is
obvious that a high uncertainty exists when estimating impact specific indicator values over operation times
of decades. An uncertainty analysis is conducted to include the imprecision of the underlying emission and
consumption data and a scenario analysis is utilised to contrast various possible technological variants.
Though the results of the study are highly site-specific, a generalised relative evaluation of potential
impacts and their main sources is the principle objective rather than a discussion of the calculated absolute
impacts. A crucial finding that can be applied to any other site is the central role of steel, which particularly
derogates the valuation of FGS due to the associated emissions that are harmful to human health. In view of
that, environmental credits can be achieved by selecting a mineral-based wall instead of sheet piles for theLife cycle assessment of active and passive groundwater
Peter Bayer *, Michael Finkel
Center for Applied Geoscience, University of Tuebingen, Sigwartstrasse 10, 72076 Tuebingen, Germany
Received 17 June 2005; received in revised form 28 October 2005; accepted 10 November 2005
Available online 27 December 2005
Groundwater remediation technologies, such as pump-and-treat (PTS) and funnel-and-gate systems
(FGS), aim at reducing locally appearing contaminations. Therefore, these methodologies are basically
evaluated with respect to their capability to yield local improvements of an environmental situation,
commonly neglecting that their application is also associated with secondary impacts. Life cycle assessment
(LCA) represents a widely accepted method of assessing the environmental aspects and potential impacts
related to a product, process or service. This study presents the set-up of a LCA framework in order to
compare the secondary impacts caused by two conceptually different technologies at the site of a former
manufactured gas plant in the city of Karlsruhe, Germany. As a FGS is already operating at this site, a
hypothetical PTS of the same functionality is adopted. During the LCA, the remediation systems are0169-7722/$ - see front matter D 2005 Elsevier B.V. All rights reserved.
E-mail address: email@example.com (P. Bayer).ing author. Tel.: +49 7071 2973178; fax: +49 7071 5059.
identified as an additional main determinant of the relative assessment of the technologies since it is
D 2005 Elsevier B.V. All rights reserved.
Keywords: Life cycle assessment; Funnel-and-gate; Pump-and-treat; Remediation; Groundwater; Uncertainty; Monte
Carlo; Weighting triangle
Groundwater is one of the most valuable natural resources. Beside its central position for
terrestrial and aquatic ecosystems, groundwater is essential for drinking and industrial water
abstraction. It represents by far the largest reservoir of fresh water, with stored volumes over fifty
times greater than the amount of surface water. Growing populations, continual urbanisation and
industrialisation are increasing the risk of groundwater contamination, while simultaneously, the
living standards and demands on our natural environment are rising. Hazardous waste disposal
facilities, oil refineries and chemical plants are typical sources of waste streams, which can reach
the aquifer and produce long-term contaminations in the subsurface. Most contaminant sites in
industrialised countries are characterised by the occurrence of hazardous organic chemicals in
the underground. They can form separate, nonaqueous phases in the subsurface, which
continuously feed the passing groundwater with contaminants. Downgradient of these source
zones, plumes develop with significant concentrations of the contaminants dissolved in the
groundwater. Contaminants can also slowly diffuse into the low permeable aquifer matrix and,
because of the small mass transfer rates into groundwater, stay there as long-term secondary
sources (Grathwohl, 1998; Fetter, 1999). These aspects substantiate the importance of the
protection of groundwater from pollution and the control of already contaminated aquifer zones.
However, the considerably low mobility together with a typically high persistency of organic
contaminants is the crux for the development of suitable groundwater remediation technologies.
A still common and conventional bcleanupQ practice is pump-and-treat, meaning the pumpingof contaminated groundwater followed by on-site treatment. Pumping wells are installed in or in
the vicinity of the source or plume area in order to hydraulically capture the critical aquifer
zones. Experience shows that due to the limited mass transfer rates, aquifer restoration by
conventional pump-and-treat systems is, for the most part, not achievable within reasonable
timeframes (Eberhardt and Grathwohl, 2002; Stroo et al., 2003). Though the use of pump-and-
treat systems (PTS) is not the only technological option, it still seems to be the most favourable
because of the experience in appropriate hydraulic design, as well as its flexibility and simplicity
(US EPA, 1996; Bayer, 2004).
Meanwhile, permeable walls (PRBs) are a widely accepted alternative for long-term plume
management. Continuously or locally reactive vertical walls are installed in-situ for down-
gradient capture and treatment of the contaminated plume (US EPA, 2002). Funnel-and-gate
systems (FGS Starr and Cherry, 1994) are a variant based on the combination of impermeable
walls (funnels) and reactive zones (gates). Adjusted to the regional groundwater flow regime, the
funnels direct the contaminated water through the in-situ treatment facilities within the gates.
Compared to PTS, FGS and continuous permeable walls are denoted as bpassiveQ systems since,after proper installation of the technological devices, no active work, such as pumping, is
P. Bayer, M. Finkel / Journal of Contaminant Hydrology 83 (2006) 171199172In the presented study, the focus is set on the comparison of PTS and FGS, as typical active
and passive groundwater remediation options, in terms of their environmental impacts. Similar
to wastewater treatment or recycling techniques, the achievement of a local environmental
benefit, i.e. the control and removal of contaminants, is compromised by certain environmental
burdens caused during the construction, installation and maintenance of the technologies. These
so-called secondary impacts (Volkwein et al., 1999) can reach significant levels depending on
the type of materials and energy used, the size of the treatment system and its time of operation.
A life cycle assessment (LCA) framework is used to contrast the potential impacts in different
categories reflecting the inherent adverse effects on ecology, human health as well as the
depletion of energy resources. LCA considers the potential impacts associated with the supply
chains throughout a products (i.e. here, technologys) life cycle from raw material acquisition
through production, use and disposal (ISO, 14040, 1997).
2. Previous work
The most comprehensive approaches for using LCA to environmentally rate impacts from
remediation of contaminated sites have been presented by Beinat et al. (1997), Volkwein et al.
(1999) and Diamond et al. (1999). Sue`r et al. (2004) give a brief literature review of the few
available studies in this area. The REC method presented by Beinat et al. (1997) is a streamlined
decision support system for estimating the relevance of environmental impacts of technological
alternatives within a risk assessment framework. Volkwein et al. (1999) emphasize a difference
in their UVA approach to REC: While the REC tool can be applied to derive suitable clean-up
levels, the levels have to be assigned a priori when using the UVA method. Aside from this,
UVA is a more detailed and elementary approach, which operates on generic datasets processed
in over 50 modules (LfU, 1998). Volkwein et al. (1999) show the application of their method in
accessing the impacts caused by partial soil excavation, on-site ensuring and surface sealing.
Bender et al. (1998) also discuss the suitability of the UVA tool for analysing the impacts caused
by a number of different groundwater remediation technologies, such as long-term extraction of
groundwater, in-situ bioremediation and soil vapor extraction. Though their case study does not
exhibit a detailed site and inventory data description and no information is given on how the site
data is processed within the LCA framework, general conclusions are derived when comparing
the different remediation technologies. For examp