Permeable Reactive Barrier (PBR) Method Analysis Report

This report provides an in-depth analysis of the Permeable Reactive Barrier (PBR) method, a technique used to treat contaminated groundwater. The report begins with an introduction to groundwater contamination and the PBR method, explaining how it works to remove or neutralize pollutants. It details the advantages of PBR, such as its ability to treat a broad spectrum of contaminants, low energy requirements, and cost-effectiveness, while also discussing its limitations, including potential issues with subsurface obstacles and long-term performance. A key component of the report is a comparison between the PBR method and the extraction and disposal method, highlighting the pros and cons of each approach. The report concludes by emphasizing the potential of PBR as a cost-effective and sustainable method for groundwater remediation, especially when compared to traditional methods. The report includes diagrams and a table summarizing the key differences between PBR and extraction/disposal methods, and is supported by multiple references.

Table of Contents
Permeable Reactive Barrier (PBR) Method....................................................................................2
Introduction..................................................................................................................................2
Advantages of PBR......................................................................................................................3
Disadvantages and limitations of PBR.........................................................................................3
Comparison of PBR with extraction and disposal method..............................................................3
Conclusion.......................................................................................................................................5
References:......................................................................................................................................6
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Permeable Reactive Barrier (PBR) Method
Introduction
Contamination of groundwater occurs when man-made materials such as petroleum, gasoline,
road salts, and pesticides contaminate the water, turning it hazardous for human consumption.
Materials from the surface of the land can pass through the soil and into the groundwater.
Pesticides and fertilizers, for example, can make their way into groundwater sources over time
(Thiruvenkatachari et al., 2008). Permeable Reactive Barrier (PBR) is the way of eliminating
contaminants from contaminated groundwater or transforming these to harmless compounds.
A permeable reactive barrier, or "PRB," is a subterranean wall that cleans polluted groundwater.
The wall is "permeable," meaning it allows groundwater to pass through it. In order to be treated,
water must pass through the PRB. The "reactive" components that make up the wall either trap or
lessen the effects of dangerous pollutants (Faisal et al., 2018). In most cases, PRBs are
constructed by excavating a long, narrow trench in the channel of polluted groundwater flow. To
remove impurities from groundwater, the trench is filled with a reactive substance such as iron,
limestone, carbon, or mulch.
Figure 1: Diagram of Permeable reaction barrier (He et al., 2019)
In PBR contaminants are removed by following processes
 Pollutants adsorb on the reactive material's surface. Carbon particles, in particular, have
a surface that pollutants like petroleum compounds bind to when groundwater runs
through.
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 Pollutants dissolved in groundwater precipitate out as solid particles when they react
with the reactive material in the wall.
 Pollutants react with the reactive substance to create less dangerous contaminants.
 Microbes in the reactive media decompose contaminants.
Advantages of PBR
 Treats broad spectrum of contaminants (organics, inorganics, radionuclides)
 Require low energy
 Low operational and maintenance cost
 Effective for long time
 No loss of groundwater
Disadvantages and limitations of PBR
 Large rocks below ground surface
 Existing infrastructures
 Performance may decrease over time due to befouling and reduction in permeability
 Complex process for monitoring and cleanup
Comparison of PBR with extraction and disposal method
Table 1: PBR VS extraction and disposal method
PRBs Extraction and Disposal
Permeable Reactive Barriers is a water
treatment approach for the management of
contaminated groundwater. The basic concept
of this remediation approach is to dig a trench
with fillers of permeable reactive materials in
the flow way of contaminated groundwater
(Snow, 1999).
The extraction and disposal or pump and treat
method is a traditional approach to address
contaminated groundwater to extract it from
the aquifer by well, treat it in the treatment
plant, and then a part of it is reinjected into
the ground and the other is disposed off-site
(Bradl & Xenidis, 2005).
With the flow of contaminated groundwater
through the reactive media, the active material
interacts with the contamination in the water
and being absorbed, precipitated, or degraded.
An area with contaminated source of water is
isolated with low permeability barriers or
covers to prevent the migration of pollutants,
but the pollution remains on-site.
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(Bolster et.al, 2009)
The nature of the Pollutants present in the
water is crucial to consider while selecting a
reactive material.
The method is also limited to some pollutants.
This treatment method has very less
operational and maintenance cost involved.
The operation and maintenance cost are
substantial also disposal cost is very high.
This is relatively expensive method and has
high energy requirements.
This method reduces the risk of contaminant
exposure to soil and humans and allows the
overlying land to be used for normal
activities. Actively
There is a high risk of exposure of human and
soil to contamination present. That can further
spread the pollution
The chances for soil contamination are
negligible.
This method is unable to remove
contaminants sorbed to the soil.
There is zero to very little chance of
recontamination. The technology is free from
the risk of recontamination.
The risk of recontamination of source through
the soil is present even after treatment
The efficiency of the treatment depends upon
the width of media and is far more than
conventional method like extraction and
disposal method.
The efficiency of extraction of contaminants
is the most difficult method and is highly
associated with the aquifer matrix.
This is a passive remedial approach that
doesn’t need any additional cleanup.
This is an infrequent method and has potential
to create the need for additional cleanup
options that are way more costly than other
methods.
Depends upon the PRB media, the heavy
metals and other hydrocarbons can also be
removed efficiently.
This method is ineffective for the areas with
heavy metal source, polycyclic aromatic
hydrocarbons with low bioavailability.
(Simon, 2000).
Groundwater flows through these PRBs by
natural gradient and the reactive media in the
The method needs pumps and other
machinery and a complete treatment plant.
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traps degrades the pollutants.
It is limited to shallow plumes and very
impractical for deep aquifers.
It is not limited to the shallow or deep aquifer.
Seasonal variations in the groundwater table
elevation affect the ability of PRBs to treat
the contamination.
This method does not affect by the seasonal
variations.
Due to the chemical reactions taking place in
the reaction zone, the formation of precipitate
on the media can limit the permeability and
effectiveness of PRBs.
There is no chance of precipitation formation
the efficiency of treatment plant may affect
the overall efficiency.
This method is Cost effective than extraction
and disposal method as it is 50% of the cost.
This method is not Cost effective.
Conclusion
Permeable reactive barrier is a relatively new technique for the treatment of contaminated
groundwater. There are various advantages of this process and the most important advantage
over traditional extraction and disposal or pump and treat methods is cost. Where the
conventional require large installation, as well as operational and maintenance costs, the only
expense of PRBs is effective design and installation and the operational and maintenance cost are
essentially zero. PRBs do not alter the groundwater flow and allow normal pre-treatment to use
of the land. Multiple contaminants can also be treated at the same time. Also, limitations are
there that need the use of PRBs in some specific situations). Evidence has shown that permeable
reactive barriers may be an enhanced alternative to treat contaminated groundwater and will be
the most cost effective and suitable method in future. When properly employed and operated
effectively, it decreases the risk caused by inorganics and radionuclides in ground water through
reduction-oxidation (redox) reactions. (Obiri-Nyarko, Grajales-Mesa, & Malina, 2014)
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References:
Thiruvenkatachari, R., Vigneswaran, S. and Naidu, R., 2008. Permeable reactive barrier for
groundwater remediation. Journal of Industrial and Engineering Chemistry, 14(2), pp.145-156.
Faisal, A.A.H., Sulaymon, A.H. and Khaliefa, Q.M., 2018. A review of permeable reactive
barrier as passive sustainable technology for groundwater remediation. International Journal of
Environmental Science and Technology, 15(5), pp.1123-1138.
He, Q., Si, S., Yang, J. and Tu, X., 2019. Application of permeable reactive barrier in
groundwater remediation. In E3S Web of Conferences (Vol. 136, p. 06021). EDP Sciences.
Bradl, H. and Xenidis, A., 2005. Remediation techniques. In Interface science and
technology (Vol. 6, pp. 165-261). Elsevier.
Obiri-Nyarko, F., Grajales-Mesa, S.J. and Malina, G., 2014. An overview of permeable reactive
barriers for in situ sustainable groundwater remediation. Chemosphere, 111, pp.243-259.
Snow, D.H., 1999. Overview of Permeable Reactive Barriers. Civil Engineering Dept., BYU.
Simon, F.G. and Meggyes, T., 2000. Removal of organic and inorganic pollutants from
groundwater using permeable reactive barriers: part 1. Treatment processes for pollutants. Land
contamination & reclamation, 8(2), pp.103-116.
Meggyes, T. and Simon, F.G., 2000. Removal of organic and inorganic pollutants from
groundwater using permeable reactive barriers. Land Contamination & Reclamation, 8(3), p.3.
Bolster, D., Barahona, M., Dentz, M., Fernandez‐Garcia, D., Sanchez‐Vila, X., Trinchero, P.,
Valhondo, C. and Tartakovsky, D.M., 2009. Probabilistic risk analysis of groundwater
remediation strategies. Water Resources Research, 45(6).
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