recent advances in contaminated site remediation

Recent Advances in Contaminated Site Remediation

Ravi Naidu

Received: 31 October 2012 /Accepted: 14 May 2013 /Published online: 19 November 2013# Springer Science+Business Media Dordrecht 2013

Keywords Contaminants . In-situ remediation .

Soil - Groundwater

1 Introduction

The recent poisoning of thousands of people throughexposure to arsenic, asbestos (Naidu et al. 1996) andbenzene has highlighted the massive challenge that con-taminants pose risk for both human and environmentalhealth. Globally, there are more than 3,000,000 potential-ly contaminated sites (Singh and Naidu 2012) whichbesides posing risks to the health and well-being ofhumans and the environment, also represent a large losteconomic opportunity. Contamination is the legacy ofindustrialization, inadequate environmental laws and

inconsistent and lacking enforcement. At the biennialInternational Committee on Contaminated Land, theWorld Bank reported that it had integrated contaminationinto its ‘Greening Development and Sustainable UrbanDevelopment’ agenda. Although site contamination hasbeen recognised since the 1960s, less than a tenth ofpotentially contaminated sites globally have beenremediated due to the complex and challenging natureof both surface and subsurface contamination. Thesechallenges are further exacerbated by the cost and tech-nical difficulty of dealing with contaminant mixtures, aswell as recalcitrant and persistent pollutants. Commoncontaminants include petroleum hydrocarbons, chlorinat-ed solvents, persistent organic pollutants, pesticides, in-organics, heavy metals and radioactive constituents. The-se contaminants can be found in a variety of sites such asoil and gas operations, service stations, mines, industrialcomplexes, landfills, waterways, harbours and even inrunoff from urban and residential settings.

In most countries, the scale of the problem is difficultto assess, as ‘contaminated land’ or ‘site contamination’are often subjectively or poorly defined, even in statute.Very few efforts have been made to develop an inventoryof contaminated sites in developing countries, althoughindustrial practices and the societal drive for economicgrowth continue to increase contamination of both landand water bodies. Although most developing countrieshave stringent regulatory guidelines, adherence to andpolicing of these remains a major problem. The rapidexpansion of the urban fringe due to mass migration ofpeople from rural into urban areas is causing substantial

Water Air Soil Pollut (2013) 224:1705DOI 10.1007/s11270-013-1705-z

Guest Editors: R Naidu, Euan Smith, MH Wong, MegharajMallavarapu, Nanthi Bolan, Albert Juhasz, and Enzo Lombi

This article is part of the Topical Collection on Remediation ofSite Contamination

R. NaiduCentre for Environmental Risk Assessment andRemediation (CERAR), University of South Australia,Building X, University Boulevard, Mawson Lakes, SA5095, Australia

R. Naidu (*)CRC for Contamination Assessment and Remediation of theEnvironment (CRC CARE), University of South Australia,Building X, Mawson Lakes, SA 5095, Australiae-mail: [email protected]

pressure on available land for residential and other usesincluding infrastructure, water and power distribution. Asa result, development is being driven into disused formerindustrial zones which are often contaminated. This hasled to significant demand for remediation and protectionfrom residual contaminants as well as cost-effective andsustainable techniques for managing contamination toensure the land is suitable for its new,more sensitive uses.

2 Remediation Technologies

Contaminated site remediation technologies fall intotwo principal approaches: in-situ (soil and water aretreated in the ground) or ex-situ (treatment is carriedout above ground). While in-situ remediation dealswith contamination without removing soil or waterfrom the ground, ex-situ remediation requires the ex-cavation of contaminated soil or abstraction of pollutedwater and/or soil vapour for treatment or disposal else-where. The techniques available for in-situ or ex-situremediation can be prohibitively costly, resulting inpoor rates of adoption in most countries, unless thereis a very large increase in the value of the remediatedsite. Many different in-situ and ex-situ technologies areused to remediate contaminated soils and groundwater(Table 1). While many of these technologies areclassed as ex-situ, the recent emphasis on minimisationof greenhouse gas emissions has ignited interest in in-situ technologies that do not require transport of con-taminated soils to prescribed landfills. However, de-spite significant investment in the development of re-mediation technologies, especially in USA and Eu-rope, contaminated site remediation remains a majorchallenge due to the complex nature of contaminantsand their bioavailability, the presence of mixtures andthe complexity of the local geology and hydrology.Readers are directed to an excellent publication byDavis (1997) on the pros and cons of disposal and in-situ and ex-situ remediation which provides a view ofwhat we thought at that time.

3 Advances in In-Situ Remediation Technologies

For the last three decades, both soil and groundwaterremediation technologies have continued to evolve;however, the main advance has not been many brandnew technologies but rather in the application of

techniques once seen as novel (for example, in-situthermal treatment of hydrocarbon contaminated soils,etc.) and the development of novel uses of existingtechnologies (for example, in-situ chemical oxidation,etc.). Some of these technologies are discussed in thefollowing sections focussing on contaminated soil andgroundwater.

3.1 Contaminated Soil

Unlike the manufacturing and sensor tool industries,progress in the development of new technologies forthe remediation of contaminated soils has been slow.Conventional technologies used for the remediation ofcontaminated soils include bioremediation usingbiopiles, bio-slurry reactors, thermal desorption, soilwashing, bioventing, bio-slurping and air sparging (seeTable 1). While most of these technologies work forhydrocarbons, their main problem with metal(loids) istheir inability to degrade the metal, although the treat-ment may result in changing the valence state of themetal resulting in either a more or less mobile, more orless toxic constituent depending on specific geochemi-cal conditions. Also, when introduced into the soil en-vironment metal(loids) bind to colloidal matter formingmatrices, from which the metal(loid)s can either leachdown to the groundwater or be taken up by plants.Human exposure can occur via the food chain, waterand soil or dust inhalation (example methyl mercury)and ingestion. The most common approach to deal withmetal(loid)-contaminated soils has been excavation andtransport to prescribed landfills. However, landfills arenow seen to have intergenerational impacts and for thisreason, some regulators in Australia have introducedadditional legislation which increases landfill costs andthereby encourages in-situ management of contaminat-ed material. Such an approach minimises greenhouseemissions from transport and at the same time forces theremediation industry to think laterally and develop newways to manage and/or remediate metal contaminatedsoils. Recent advances over the last 15 years include thefollowing technologies.

3.1.1 Electrokinetic Remediation

The technique uses low-level direct current of the orderof mA/cm2 of cross-sectional area between the elec-trodes or an electric potential difference of the order ofa few volts per centimetre across electrodes placed in

1705, of 11 Water Air Soil Pollut (2013) 224:1705

Tab

le1

Asummaryof

techno

logies

forcontam

inated

soilandgrou

ndwater

remediatio

n(http

://www.epa.gov

/sup

erfund

/rem

edytech/remed.htm

;Naidu

etal.19

96).Con

ventional

techno

logies

arethosethatarecommon

lyused,w

hiledeveloping

techno

logies

arethosethatarestill

beingfine-tun

ed,emerging

techno

logies

thatareno

wfind

ingsuccess

Rem

ediatio

ntechno

logies/m

anagem

entstrategies

Mod

eof

operation

Techn

olog

ytype

References

Con

taminated

soil

Bioremediatio

nMicrobialactiv

ityisop

timised

fordegradationof

contam

inantsespecially

hydrocarbo

ns—often

largevolumes

ofsoilareremediatedusingbiopiles

Con

ventional

Jørgensenetal.2

000;

Bento

etal.2

005;

Megharajetal.2

011;

Rayuetal.2

012

Phy

toremediatio

nPlantsthataccumulatetoxicmetalsor

biod

egrade

organics

intheirroot

zone

Con

ventional

Cun

ning

ham

etal.1

996;

Pulford

and

Watson20

03;G

erhardtetal.2

009

Vapou

rextractio

nTechn

iquesrang

efrom

relativ

elysimpledesign

sforremediatio

nof

volatilehy

drocarbo

nsin

perm

eablesoilto

high

-perform

ance

system

sfortreatm

entof

lower-permeabilitysoils.T

hey

includ

ethermaldesorptio

nplantsthatheatsoil

inarotary

kiln

toatemperature

atwhich

target

organiccompo

unds

aretransferredto

thegasph

ase

Con

ventional

Frank

andBarkley

1995

;Zevenbergen

etal.1

997;

Soaresetal.2

010;

Chien

2012

Soilw

ashing

Avo

lumeredu

ctionmetho

dthatuses

chem

icalsto

remov

econtam

inants

Con

ventional

Sem

erandReddy

1996

;Mullig

anetal.

2001

a;Dermon

tetal.2

008

Solidification-stabilisatio

nApp

licationof

aspecially

form

ulated

(usually

prop

rietary)

additiv

emix

togeneratealow-hazard,

low-leachability

materialusually

foron

-site

re-use

Con

ventional

Bolan

andDuraisamy20

03;Kum

piene

etal.2

006;

Sarkaretal.2

012a

Electrokinetic

App

licationof

alow-intensity

currentthatcreatesa

gradient

forions

tomov

efrom

either

cathod

eto

anod

eor

vice

versa.Anewtechno

logy

being

trialledin

Europ

eandUSA

Develop

ingtechno

logies

Otto

senetal.1

997;

Yeung

2006

;Yeung

andGu20

11

Ultrason

icUltrason

icwaves

have

been

used

toremediate

hydrocarbo

ncontam

inated

soils

Innovativ

eandem

erging

Shresthaetal.2

009;

Thang

avadivel

etal.2

009,

2011

Therm

alNum

erou

sin-situ

andex-situ

thermaltechno

logies

areavailableforsoilandgrou

ndwater

remediatio

nEmerging

Mullig

anetal.2

001b;Khanetal.2

004

Risk-Based

LandManagem

ent

Universally

accepted

asacost-effectiv

estrategy

forim

plem

entin

g‘fitforpu

rpose’

useof

contam

inated

land

Inno

vativ

eFergu

sonetal.1

998;

Naidu

etal.2

008a,

2008

b;Nathanail20

09;DTZ20

10

Groun

dwater

Pum

pandtreat

Operatio

nrequ

ires

pumping

ofcontam

inated

water

throug

hachem

i-or

bioreactor

thatremediates

contam

inants.C

leansedwater

isthen

reinjected

back

into

theaquifer

Con

ventional

MackayandCherry19

89;Baú

and

Mayer

2008

;Higgins

andOlson

2009

Insitu

chem

icalox

idationandredu

ction

Invo

lves

introd

uctio

nof

reactiv

ematerialsinto

thesubsurface

todestroyorganiccontam

inants.

Avarietyof

chem

icalox

idantsandredu

ctants

makes

thisauseful

techniqu

ewhere

intensive

source-zon

etreatm

entisrequ

ired

Con

ventional

Seoletal.20

03;Fergu

sonetal.2

004;

Krembs

etal.2

010

Water Air Soil Pollut (2013) 224:1705 of 11, 1705

http://www.epa.gov/superfund/remedytech/remed.htm

Tab

le1

(con

tinued)

Rem

ediatio

ntechno

logies/m

anagem

entstrategies

Mod

eof

operation

Techn

olog

ytype

References

Bioremediatio

nRange

from

therelativ

elysimple(e.g.p

lacement

ofox

ygen

ornu

trient-releasing

agentsto

stim

ulate

biod

egradatio

nactiv

ity)to

themorecomplex

process-basedsystem

s(e.g.for

chlorinated

solventsource

areas)includ

ingenhanced

anaerobicdechlorinatio

n,anaerobicbiov

entin

g,in-situ

co-m

etabolism

andbioaug

mentatio

n

Conventionalto

emerging

Knapp

andFaison19

97;Franzmann

etal.1

999,

2000

;Farhadian

etal.2

008;

Davisetal.2

009

Vapou

rextractio

nVapou

r-extractio

ntechniqu

es(soilvapo

urextractio

n,sparging

andslurping

)rang

efrom

relativ

elysimple

design

sforremediatio

nof

volatilehy

drocarbo

nsthroug

hcomplex

multip

hase

extractio

nsystem

scapableof

dealingwith

soilgas,grou

ndwater

andNAPLmixtures

Con

ventional

USEPA

1989

;John

ston

etal.1

998;

John

ston

andDesvign

es20

03;

Patterson

andDavis20

08

PermeableReactiveBarriers(PRBs)

PRBsofferpo

tentialforlong

-term,low

-intensity

treatm

entof

grou

ndwater

plum

es.P

RBscomprise

oneor

morezonesof

reactiv

ematerialplaced

inthesubsurface

todegradeor

sorb

dissolved

contam

inantsas

thegrou

ndwater

passes

throug

h

Conventionalto

emerging

Patterson

etal.2

002,

2004

;Gibertetal.

2008;Thiruvenk

atacharietal.2

008

Mon

itoredNaturalAttenu

ation(M

NA)

MNAisarisk

managem

entapproach

forcontam

inated

grou

ndwater

plum

esthatevaluatesandmon

itorsthe

combinedeffectof

naturalprocesses(e.g.sorption,

dilutio

n,biod

egradatio

n,etc.)

Con

ventional

Davisetal.1

999;

Franzmannetal.

1999;Prommer

etal.2

002;

Naidu

etal.2

010,

2012

Nanotechn

olog

y-environm

entalremediatio

nArecent

techno

logy

focuseson

thein

situ

useof

nano

materialsforthedegradationof

contam

inants

Develop

ing

Cun

dyetal.2

008;

Karnetal.2

009;

Grieger

etal.2

010;

Sun

kara

etal.

2010;Sarkaretal.2

012b

Risk-Based

Managem

ent

Universally

accepted

asacost-effectiv

estrategy

for

implem

entin

g‘fitforpu

rpose’

useof

contam

inated

grou

ndwater

Inno

vativ

eSwartjes19

99;DavisandJohn

ston

2004


the ground in an open flow arrangement. Moisture inthe soil or groundwater in boreholes acts as the con-ductance medium. This is one of the few soil remedi-ation technologies that has been developed during thepast 20 years and is currently being extended fromlaboratory based studies to field remediation. Thisprocess results in significant change in pH which canbe managed by using certain surfactants or buffer so-lutions (Yeung and Gu 2011). However, field scaleremediation is still to be demonstrated from perfor-mance as well as cost perspective.

3.1.2 Thermal Immobilisation

This is not a new technology given its long use inEurope and relatively common consideration in NorthAmerica. However, it has evolved considerably over thelast decade and is now being used for the remediation ofboth organic and inorganic contaminants. While organiccontaminants degrade and/or volatilise at elevated tem-peratures, metals are immobilised thus minimising theirbioavailability and hence ability to leach or pose risk tohumans (Singh et al. 2007; Gomez et al. 2009).

3.1.3 Risk-Based Land Management

This approach to manage contaminated sites was in-troduced in 1990s following recognition of the prohib-itively expensive cost of ex-situ and in-situ remedia-tion. Risk-based land management (RBLM) aims tomanage the risks posed by historic contamination andto mitigate those risks deemed unacceptable. The de-cision of what level of risk is unacceptable has a socio-economic dimension but is based on robust scientificestimates of the level of risk. Together, these conceptsform the basis of RBLM, which represents a mature,sustainable approach to the challenges of contamina-tion (Ferguson et al. 1998; Nathanail and Smith 2007;Naidu et al. 2008a; Nathanail 2009). RBLM is a com-mon and well-developed consideration for contaminat-ed site management in the USA.

To undertake RBLM, a chemical substance must bepresent in a form and at level that pose risks to possiblereceptors, including humans. Using this as the basis formanagement of contaminated sites, RBLM has oftenbeen employed to demonstrate ‘fit for purpose’ use ofthe contaminated land. Using this approach, when the siteis found to have contaminant levels which exceed resi-dential thresholds but fall within commercial/industrial

guidelines, the site may be used for industrial but not forresidential purposes. This approach has greatly expandedthe availability of inner urban land for industrial or com-mercial purposes which was previously unused becauseof contamination.

However, risk-based land management can be furtherrefined to ensure in-situ management of contaminatedsites by distinguishing between hazard and risk and,based on this distinction, minimising the risk by in-situtreatment of contaminated material. The presence ofchemical substances in soils and groundwater (the haz-ard) is of concern, but for harm to result to the environ-ment or human health, they must be exposed. For there isto be risk, pathways must exist which connect the sourcesof contamination to the receptors that can be harmed. Themanagement of these risks posed by historically-releasedchemicals should drive remedial action, and secondly, therisk is a function of the dose–response relationship foreach chemical substance (Naidu and Bolan 2008). Thismeans that a chemical substance must be present in aform and at levels sufficient to pose a risk to the receptor.Contaminant bioavailability determines effective intakeand hence the level of risk posed: this is a critical param-eter that ought to be used in all cases of RBLM. Sites withhigh contaminant bioavailability may be managed withtreatments that demonstrably reduce bioavailability in thelong-term. An example is the immobilisation of metals tominimise their bioavailability. Immobilisation refers tothe process of transferring an aqueous phase of highly-mobile metals to a solid, stable phase that is lockedwithinthe soil. This phase transfer prevents the continued mi-gration of contaminating metal plumes and can offer apermanent solution depending on the metal and site-specific geochemistry.

The most common mechanisms for in-situ metalsimmobilisation are metal adsorption to soil particles orthe precipitation of metal solids that are chemicallyfixed to soil particles. Both of these mechanisms canpermanently remove metals from the aqueous phase,restoring the aquifer and the desired usability of thewater. Cooperative Research Centre for ContaminationAssessment and Remediation of the Environment(CRC CARE) has advanced this technology by devel-oping a composite material known as MatCARETM

that immobilises both organic and metal contaminantspermanently. This is a modern remediation technologyfor the in-situ treatment of both metals and hydrocar-bon contaminated soils. The material is a compositemixture of a naturally occurring mineral that has been


modified to increase its capacity to immobilise bothmetals and hydrocarbon contaminants. Field-scale tri-als conducted in 2009 demonstrated the immobilisa-tion of these contaminants was sustainable, with noobserved leaching.

Rather than using the ‘fit for purpose’ approach, thedemonstration of limited risk to humans and the envi-ronment following immobilisation of contaminants (nomatter what changes occur in the environment) oughtto be sufficient to permit human occupation and use ofthe land. However, this approach requires significantcommunity participation in the process to allaypublic fears of perceived risk from exposure to boundsubstances.

3.2 Contaminated Groundwater

With the exception of nanotechnology, no major newgroundwater remediation technology was developedduring the first decade of the twentyfirst century. How-ever, major advances were made in existing technolo-gies which have made the remediation process a lotmore efficient. Table 1 presents a summary of existingtechnologies including those that may be consideredinnovative, emerging and developing. Rapidly advanc-ing technologies include Permeable Reactive Barriers(PRBs), enhanced anaerobic dechlorination, especiallyfor DNAPLs, anaerobic bioventing and in-situ co-metabolism with some new technologies including,bioaugmentation and bioengineering.

3.2.1 Permeable Reactive Barrier

This technology is an underground barrier positioned tointercept a contaminated flow and charged with specialsubstances that remove or degrade the contaminants.While the technology initially used zero valent iron asthe reactive medium for the remediation of groundwatercontaminated with chlorinated hydrocarbons (with thefirst field trials in the early 1990s and the first commercialdeployment in late 1994), recently a range of materials forthe remediation of other organics have been deployed(Warner et al. 1994). For example, investigators usedsaturated peat in a reactive barrier for the remediation ofBTEX and inorganic contaminants (see Cohen et al.1991; Guerin et al. 2002) and polymer mat for the remov-al of ammonium-contaminated groundwater (seeSchipper and Vojvodić-Vuković 2001). Recent studiesby our group demonstrated the use of RematTM (a propri-etary material) for the remediation of TCE in groundwa-ter. RematTM was specially developed for the remediationof both chlorinated and petroleum hydrocarbons. Thesestudies showed that zero valent iron (ZVI) was ineffectivein alkaline water as it poisoned the ZVI surface withcarbonate. In a further development, the team installedthe PRBwithwide-diameter wells throughwhich ground-water was extracted by solar pumping through the barriermaterial after which the cleanwater was injected back intothe aquifer (see Fig. 1). Recent reviews by Warner andSorel (2003) and Thiruvenkatachari et al. (2008) presentan excellent overview of PRBs and their application to

Fig. 1 Large permeable reactive barrier for the remediation of TCE-contaminated groundwater


organic and inorganic contaminant remediation ingroundwater. Readers are also directed to additional re-views on PRBs by Warner (2011, 2012).

3.2.2 Bioremediation

In-situ bioremediation of contaminated groundwater isseen as a cost-effective and green technology. Often thisinvolves the use of indigenous microbes and where in-situ bioremediation is slow, the process is enhanced viavarious techniques that range from biostimulation (theinjection of growth substrates, co-substrates and electronacceptors which are limiting the biodegradation reaction)to bioaugmentation (the injection of bacteria to increasethe subsurface population). Biostimulation requires thebacterial species or consortia responsible to degradedissolved phase contaminants are indigenous and it as-sumes that reactions are limited by population densitiesor by the absence of key electron acceptors. Much morestill needs to be done in this field to enhance success rateespecially for non-aqueous phase liquids and under chal-lenging conditions such as fractured rocks.

3.2.3 Enhanced Anaerobic Dechlorination

Chlorinated solvents are sparingly-soluble, dense, non-aqueous phase liquids (DNAPL) that can contaminategroundwater in the long term due to their persistence inthe aqueous environment. Many contaminated sites oc-cur in areas within fractured sedimentary or bedrocksystems (Chapman and Parker 2005), where the releasedDNAPLs penetrate into the flow pathways formed by thefractures and can then rapidly dissolve and diffuse fromthe fractures into the matrix (Falta 2005; Chambon et al.2010). Even after the removal of the physical sourcefrom the site, the contaminant can re-diffuse back intothe fracture network for hundreds of years, causing long-term contamination of an underlying aquifer (Harrisonet al. 1992; Reynolds and Kueper 2002). Such contam-inated sites have proved extremely challenging and ex-pensive to remediate. Enhanced anaerobic biodegrada-tion has shown to be effective for the treatment ofchlorinated hydrocarbon contaminated groundwater insome of these settings. The process includes adding anelectron donor (hydrogen) to groundwater and/or soil toincrease the number and vitality of indigenous microor-ganisms performing anaerobic bioremediation. A greathydrogen release material is ZVI—the hydrogen is re-leased during the corrosion process and will continue to

be released for decades and at fairly high levelsdepending on the amount of iron emplaced. This isanother positive attribute to granular iron as a treatmentmaterial. While this approach to remediate DNAPL con-tamination has been successful at some sites, those withfractured rocks continue to pose significant problems inboth delineating and remediating the contaminant.

3.2.4 Surfactant Enhanced In-Situ Chemical Oxidation

It is based on the ability of the surfactants to increasethe aqueous solubility of and/or displace non-aqueousphase liquids (NAPLs) from porous media includingfractured rocks (Taylor et al. 2001; Abriola et al. 2005).Above the critical micelle concentration (CMC) sur-factant molecules aggregate to form micelles that isable to solubilise organic contaminants. The displace-ment of NAPLs as free products may also occur if theinterfacial tension between the organic liquid and theaqueous phase is reduced to such an extent that viscousand buoyancy forces exceed the capillary forces actingon the NAPL. The contaminant that is mobilised canthen be chemically oxidised. This approach has provedquite successful in soils contaminated with chlorinatedhydrocarbons; however, additional design issues in-clude assuring that newly mobilised organic chemicalsare fully captured and do not migrate outside the reme-diation area into zones not previously contaminated.

3.2.5 Anaerobic Bioventing

It is often used for the treatment of chlorinated hydro-carbons in the vadose zone (Shah et al. 2001;Mihopoulos et al. 2002). In-situ remediation of vadosezone soils requires, among other factors, the establish-ment of highly reductive anaerobic conditions in theunsaturated subsurface. The process includes deliver-ing an appropriate gas mixture into the subsurface(anaerobic bioventing) to create the conditions thatenhance anaerobic biodegradation of contaminants.The gas mixture contains an electron donor for thereduction of these compounds.

3.2.6 Monitored Natural Attenuation

Although Monitored Natural Attenuation (MNA) is amanagement strategy, it has been extensively adoptedfor the remediation of groundwater in many countries.Natural attenuation includes both microbial degradation


of contaminants and other processes (e.g. sorption, etc.)that either degrades or binds contaminants to sorbent(soil) (Sarkar et al. 2005; Naidu et al. 2010, 2012). Forinstance, in Australia, EPA Victoria has introducedClean up to the Extent Practicable (CUTEP) that recog-nises natural attenuation of the contaminant in ground-water. Application of CUTEP requires regular monitor-ing of contaminants to demonstrate both attenuation aswell as a steady decline in contaminant concentration ingroundwater. However, MNA and the application ofCUTEP have posed significant challenge to the man-agement and/or remediation of Light Non-AqueousPhase Liquids (LNAPLs). LNAPLs may consist of vol-atile organic compounds (VOCs), semi-volatile organiccompounds (SVOCs), non-volatile organic compoundsand trace metals. When released into the subsurface,they can release dissolved contaminants to groundwateror VOCs into the subsurface atmosphere and potentiallyinto indoor air for an extended period of time. In addi-tion, sites which have complex or heterogeneous sub-surface environments (such as low-permeability soils)pose particular difficulties in terms of characterisationand remediation of LNAPLs. No single technology hasbeen identified as the best solution for all sites and allsoil types contaminated with LNAPLs. LNAPL man-agement in the subsurface is a particularly challengingproblem in Australia given the wide range of soil typesand hydrogeological conditions.

4 Challenges and Conclusions

Although the potential impact of contaminants on theenvironment and human health was first recognisedmore than half a century ago, contaminated sites stillpose major challenges in terms of site assessment andremediation. These challenges include:

(a) inadequacy in site characterisation and delinea-tion of subsurface contamination including soiland groundwater

(b) lack of trialled and tested tools for estimating themass flux of contaminants

(c) cost of assessment and remediation, which is of-ten hard to quantify

(d) lack of advanced technologies for subsurfacegroundwater remediation

(e) inadequacy of policies supporting or defining endpoints for remediation and

(f) fractured rocks and recalcitrant contaminants(such as DNAPLs) and their remedial endpoints

To sum up, there needs to be a far more consistentand global effort to develop site characterisation andsustainable but green remedial technologies, if humanityis to avoid the health and environmental well-beingpenalties of spreading contamination driven by the com-bination of world population and economic growth,which are likely to double our use of resources by themid-twentyfirst century. Additionally, the continuedstress on available water resources, in both developedand developing countries and communities require thatwe further isolate contaminated ground- and surfacewater from potable water resources, while we continueto develop reliable remediation methods.

Acknowledgments The financial support from CRC CAREfor this work is gratefully acknowledged. Author also acknowl-edges excellent review comments from Drs Scott Warner, GregDavis and Binoy Sarkar.

References

Abriola, L.M., Drummond, C.D., Hahn, E. J., Hayes, K. F., Kibbey,T. C. G., Lemke, L. D., Pennell, K. D., Petrovskis, E. A.,Ramsburg, C. A., & Rathfelder, K. M. (2005). Pilot-scaledemonstration of surfactant-enhanced PCE solubilization atthe BachmanRoad site. 1. Site characterization and test design.Environmental Science and Technology, 39, 1778–1790.

Baú, D. A., &Mayer, A. S. (2008). Optimal design of pump-and-treat systems under uncertain hydraulic conductivity andplume distribution. Journal of Contaminant Hydrology,100, 30–46.

Bento, F.M., Camargo, F. A. O., Okeke, B. C., & Frankenberger,W.T. (2005). Comparative bioremediation of soils contaminatedwith diesel oil by natural attenuation, biostimulation andbioaugmentation. Bioresource Technology, 96, 1049–1055.

Bolan, N. S., & Duraisamy, V. P. (2003). Role of inorganicand organic soil amendments on immobilisation andphytoavailability of heavymetals: a review involving specificcase studies. Soil Research, 41, 533–555.

Chambon, J. C., Broholm, M. M., Binning, P. J., & Bjerg, P. L.(2010). Modeling multi-component transport and enhancedanaerobic dechlorination processes in a single fracture–claymatrix system. Journal of Contaminant Hydrology, 112, 77–90.

Chapman, S. W., & Parker, B. L. (2005). Plume persistence dueto aquitard back diffusion following dense nonaqueousphase liquid source removal or isolation. Water ResourcesResearch, 41, W12411. doi:10.1029/2005WR004224.

Chien, Y. C. (2012). Field study of in situ remediation of petro-leum hydrocarbon contaminated soil on site usingmicrowaveenergy. Journal of Hazardous Materials, 199–200, 457–461.


http://dx.doi.org/10.1029/2005WR004224

Cohen, A. D., Rollins, M. S., Zunic, W. M., & Durig, J. R.(1991). Effects of chemical and physical differences inpeats on their ability to extract hydrocarbons from water.Water Research, 25, 1047–1060.

Cundy, A. B., Hopkinson, L., & Whitby, R. L. D. (2008). Use ofiron-based technologies in contaminated land and ground-water remediation: a review. Science of The Total Environ-ment, 400, 42–51.

Cunningham, S. D., Anderson, T. A., Schwab, A. P., & Hsu, F. C.(1996). Phytoremediation of soils contaminated with organ-ic pollutants. In L. S. Donald (Ed.), Advances in Agronomy(pp. 55–114). New York: Academic.

Davis, G. B. (1997). Site clean-up—the pros and cons of disposaland in situ and ex situ remediation. Journal of Land Con-tamination and Reclamation, 5(4), 287–290.

Davis, G.B., Johnston, C.D. (2004). Australian and internationalresearch and its implications for the risk based assessmentand remediation of groundwater contamination. Enviro 04:Managing Contaminated Land, Sydney, 28 March-1 April2004, Paper No. e4335, 12p.

Davis, G. B., Barber, C., Power, T. R., Thierrin, J., Patterson, B.M., Rayner, J. L., &Qinglong,W. (1999). The variability andintrinsic remediation of a BTEX plume in anaerobicsulphate-rich groundwater. Journal of Contaminant Hydrol-ogy, 36, 265–290.

Davis, G. B., Patterson, B. M., & Johnston, C. D. (2009). Aerobicbioremediation of 1,2 dichloroethane and vinyl chloride atfield scale. Journal of Contaminant Hydrology, 107, 91–100.

Dermont, G., Bergeron, M., Mercier, G., & Richer-Laflèche, M.(2008). Soil washing for metal removal: A review of phys-ical/chemical technologies and field applications. Journalof Hazardous Materials, 152, 1–31.

DTZ. 2010. Bioaccessibility Testing of Contaminated Land forThreats to Human Health: Summary of Impacts. Reportprepared for the Natural Environment Research Council.http://www.nerc.ac.uk/business/casestudies/documents/bioaccessibility-report.pdf

Khan, F. I., Husain, T., & Hejazi, R. (2004). An overview andanalysis of site remediation technologies. Journal of Envi-ronmental Management, 71, 95–122.

Falta, R.W. (2005). Dissolved chemical discharge from fracturedclay aquitards contaminated with DNPALs Dynamic ofFluids and Transport in Fractured Rock. GeophysicalMonograph, 162, (pp. 165–174). New York: AmericanGeophysical Union.

Farhadian, M., Vachelard, C., Duchez, D., & Larroche, C. (2008).In situ bioremediation of monoaromatic pollutants in ground-water: a review. Bioresource Technology, 99, 5296–5308.

Ferguson, C., Darmendrail, D., Freier, K., Jensen, B.K., Jensen,J., Kasamas, H., Urzelai, A., & Vegter, J. (Editors). (1998).Risk Assessment for Contaminated Sites in Europe. Volume1. Scientific Basis. LQM Press, Nottingham. http://www.commonforum.eu/Documents/DOC/Caracas/caracas_publ1.pdf

Ferguson, S. H., Woinarski, A. Z., Snape, I., Morris, C. E., &Revill, A. T. (2004). A field trial of in situ chemical oxida-tion to remediate long-term diesel contaminated Antarcticsoil. Cold Regions Science and Technology, 40, 47–60.

Frank, U., & Barkley, N. (1995). Remediation of low permeabilitysubsurface formations by fracturing enhancement of soil vaporextraction. Journal of Hazardous Materials, 40, 191–201.

Franzmann, P. D., Zappia, L., Tilbury, A. L., Patterson, B. M.,Davis, G. B., &Mandelbaum, R. T. (2000). Bioaugmentationof atrazine and fenamiphos impacted groundwater: laborato-ry evaluation. Bioremediation Journal, 4(3), 237–248.

Franzmann, P. D., Zappia, L. R., Power, T. R., Davis, G. B., &Patterson, B. M. (1999). Microbial mineralisation of ben-zene and characterisation of microbial biomass in soilabove hydrocarbon contaminated groundwater. FEMS Mi-crobial Ecology, 30, 67–76.

Gerhardt, K. E., Huang, X. D., Glick, B. R., & Greenberg, B. M.(2009). Phytoremediation and rhizoremediation of organicsoil contaminants: potential and challenges. Plant Science,176, 20–30.

Gibert, O., Pomierny, S., Rowe, I., & Kalin, R. M. (2008).Selection of organic substrates as potential reactive mate-rials for use in a denitrification permeable reactive barrier(PRB). Bioresource Technology, 99, 7587–7596.

Gomez, E., Rani, D. A., Cheeseman, C. R., Deegan, D., Wise,M., & Boccaccini, A. R. (2009). Thermal plasma technol-ogy for the treatment of wastes: a critical review. Journal ofHazardous Materials, 161, 614–626.

Grieger, K. D., Fjordbøge, A., Hartmann, N. B., Eriksson, E.,Bjerg, P. L., & Baun, A. (2010). Environmental benefits andrisks of zero-valent iron nanoparticles (nZVI) for in situremediation: risk mitigation or trade-off? Journal of Con-taminant Hydrology, 118, 165–183.

Guerin, T. F., Horner, S., McGovern, T., & Davey, B. (2002). Anapplication of permeable reactive barrier technology topetroleum hydrocarbon contaminated groundwater. WaterResearch, 36, 15–24.

Harrison, B., Sudicky, E. A., & Cherry, J. A. (1992). Numerical-analysis of solute migration through fractured clayey de-posits into underlying aquifers. Water Resources Research,28(2), 515–526.

Higgins, M. R., & Olson, T. M. (2009). Life-cycle case studycomparison of permeable reactive barrier versus pump-and-treat remediation. Environmental Science and Technology,43, 9432–9438.

Johnston, C. D., & Desvignes, A. (2003). Evidence for biodeg-radation and volatilisation of dissolved petroleum hydro-carbons during in situ air sparging in large laboratory col-umns. Water, Air and Soil Pollution: Focus, 3, 25–33.

Johnston, C. D., Rayner, J. L., Patterson, B. M., & Davis, G. B.(1998). The contribution of volatilisation and biodegrada-tion during air sparging of dissolved BTEX-contaminatedgroundwater. Journal of Contaminant Hydrology, 33(3–4),377–404.

Jørgensen, K. S., Puustinen, J., & Suortti, A. M. (2000). Biore-mediation of petroleum hydrocarbon-contaminated soil bycomposting in biopiles. Environmental Pollution, 107,245–254.

Karn, B., Kuiken, T., & Otto, M. (2009). Nanotechnology and insitu remediation: a review of the benefits and potential risks.Environmental Health Perspective, 117, 1813–1831.

Knapp, R. B., & Faison, B. D. (1997). A bioengineering system forin situ bioremediation of contaminated groundwater. Journalof Industrial Microbiology and Biotechnology, 18, 189–197.

Krembs, F. J., Siegrist, R. L., Crimi, M. L., Furrer, R. F., & Petri,B. G. (2010). ISCO for groundwater remediation: analysisof field applications and performance. Groundwater Mon-itoring and Remediation, 30, 42–53.


http://www.nerc.ac.uk/business/casestudies/documents/bioaccessibility-report.pdf

http://www.nerc.ac.uk/business/casestudies/documents/bioaccessibility-report.pdf

http://www.commonforum.eu/Documents/DOC/Caracas/caracas_publ1.pdf



Kumpiene, J., Ore, S., Renella, G., Mench, M., Lagerkvist, A., &Maurice, C. (2006). Assessment of zerovalent iron forstabilization of chromium, copper, and arsenic in soil. En-vironmental Pollution, 144, 62–69.

Mackay, D. M., & Cherry, J. A. (1989). Groundwater contami-nation: pump-and-treat remediation. Environmental Sci-ence and Technology, 23, 630–636.

Megharaj, M., Ramakrishnan, B., Venkateswarlu, K.,Sethunathan, N., & Naidu, R. (2011). Bioremediation ap-proaches for organic pollutants: a critical perspective. En-vironment International, 37, 1362–1375.

Mihopoulos, P. G., Suidan, M. T., Sayles, G. D., & Kaskassian,S. (2002). Numerical modeling of oxygen exclusion exper-iments of anaerobic bioventing. Journal of ContaminantHydrology, 58, 209–220.

Mulligan, C. N., Yong, R. N., & Gibbs, B. F. (2001a). Surfactant-enhanced remediation of contaminated soil: a review. En-gineering Geology, 60, 371–380.

Mulligan, C. N., Yong, R. N., & Gibbs, B. F. (2001b). Remedi-ation technologies for metal-contaminated soils andgroundwater: an evaluation. Engineering Geology, 1–4,193–2007.

Naidu, R., & Bolan, N. S. (2008). Contaminant chemistry insoils: key concepts and bioavailability. In A. E. Hartemink& R. Naidu (Eds.), Chemical bioavailability in terrestrialenvironment (pp. 9–38). Amsterdam: Elsevier.

Naidu, R., Kookana, R. S., Oliver, D., Rogers, S., & McLaughlin,M. J. (1996). Contaminants and the soil environment in theAustralasia-Pacific region. Dordrecht: Kluwer.

Naidu, R., Megharaj, M., Malik, S., Rachakonda, P.K.,Sreenivasulu, C., Perso, F., Watkin, N., Chen, Z., & Bowman,M. (2010). Monitored natural attenuation (MNA) as a cost-effective sustainable remediation technology for petroleumhydrocarbon contaminated sites: Demonstration of scientificevidence. Proceedings of the 19th World Congress of SoilScience: Soil solutions for a changing world, Brisbane,Australia, 1–6 August 2010. (pp. 3839). International Unionof Soil Sciences (IUSS).

Naidu, R., Nandy, S., Megharaj, M., Kumar, R., Chadalavada,S., Chen, Z., & Bowman, M. (2012). Monitored naturalattenuation of a long-term petroleum hydrocarbon contam-inated sites: a case study. Biodegradation, 23(6), 881–895.doi:10.1007/s10532-012-9580-7.

Naidu, R., Pollard, S. J. T., Bolan, N. S., Owens, G., &Pruszinski, A. W. (2008a). Bioavailability: the underlyingbasis for risk based land management. In A. E. Hartemink &R. Naidu (Eds.), Chemical bioavailability in terrestrialenvironment (pp. 53–72). Amsterdam: Elsevier.

Naidu, R., Semple, K. T., Megharaj, M., Juhasz, A. L., Bolan, N.S., Gupta, S., Clothier, B., Schulin, R., & Chaney, R.(2008b). Bioavailability, definition, assessment and impli-cations for risk assessment. In A. E. Hartemink & R. Naidu(Eds.), Chemical bioavailability in terrestrial environment(pp. 39–52). Amsterdam: Elsevier.

Nathanail, C. P. (2009). The role of engineering geology in risk-based land contamination management for tomorrow’s cities.InM. G. Culshaw, H. J. Reeves, I. Jefferson, & T. Spink (Eds.),Engineering geology for tomorrow's cities, engineering geol-ogy special publication SPE 22. Bath: Geological Society.

Nathanail, C. P., & Smith, R. (2007). Incorporating bioaccessibi-lity in detailed quantitative human health risk assessments.

Journal of Environmental Science and Health, Part A, 42,1193–1202.

Ottosen, L. M., Hansen, H. K., Laursen, S., & Villumsen, A.(1997). Electrodialytic remediation of soil polluted withcopper from wood preservation industry. EnvironmentalScience and Technology, 31, 1711–1715.

Patterson, B. M., & Davis, G. B. (2008). An in situ device tomeasure oxygen in the vadose zone and in groundwater:laboratory testing and field evaluation. Groundwater Mon-itoring and Remediation, 28, 68–74.

Patterson, B. M., Grassi, M. E., Davis, G. B., Robertson, B. S., &McKinley, A. J. (2002). Use of polymer mats in series forsequential reactive barrier remediation of ammonium-contaminated groundwater: laboratory column evaluation.Environmental Science and Technology, 36, 3439–3445.

Patterson, B. M., Grassi, M. E., Robertson, B. S., Davis, G. B.,Smith, A. J., & McKinley, A. J. (2004). Use of polymermats in series for sequential reactive barrier remediation ofammonium-contaminated groundwater: field evaluation.Environmental Science and Technology, 38, 6846–6854.

Prommer, H., Barry, D. A., & Davis, G. B. (2002). Modelling ofphysical and reactive processes during biodegradation of ahydrocarbon plume under transient groundwater flow con-ditions. Journal of Contaminant Hydrology, 59, 113–131.

Pulford, I. D., & Watson, C. (2003). Phytoremediation of heavymetal-contaminated land by trees—a review. EnvironmentInternational, 29, 529–540.

Rayu, S., Karpouzas, D., & Singh, B. (2012). Emerging technolo-gies in bioremediation: constraints and opportunities. Biodeg-radation, 23(6), 917–926. doi:10.1007/s10532-012-9576-3.

Reynolds, D. A., & Kueper, B. H. (2002). Numerical examina-tion of the factors controlling DNAPL migration through asingle fracture. Groundwater, 40(4), 368–377.

Sarkar, B., Naidu, R., Rahman, M., Megharaj, M., & Xi, Y.(2012a). Organoclays reduce arsenic bioavailability andbioaccessibility in contaminated soils. Journal of Soilsand Sediments, 12, 704–712.

Sarkar, B., Xi, Y., Megharaj, M., Krishnamurti, G. S. R., Bowman,M., Rose, H., & Naidu, R. (2012b). Bioreactive organoclay: anew technology for environmental remediation. Critical Re-views in Environmental Science and Technology, 42, 435–488.

Sarkar, D., Ferguson, M., Datta, R., & Birnbaum, S. (2005).Bioremediation of petroleum hydrocarbons in contaminat-ed soils: comparison of biosolids addition, carbon supple-mentation, and monitored natural attenuation. Environmen-tal Pollution, 136, 187–195.

Schipper, L. A., & Vojvodić-Vuković, M. (2001). Five years ofnitrate removal, denitrification and carbon dynamics in adenitrification wall. Water Research, 35, 3473–3477.

Semer, R., & Reddy, K. R. (1996). Evaluation of soil washingprocess to remove mixed contaminants from a sandy loam.Journal of Hazardous Materials, 45, 45–57.

Seol, Y., Zhang, H., & Schwartz, F. W. (2003). A review of insitu chemical oxidation and heterogeneity. Environmentaland Engineering Geoscience, 9, 37–49.

Shah, J. K., Sayles, G. D., Suidan, M. T., Mihopoulos, P., &Kaskassian, S. (2001). Anaerobic bioventing of unsaturatedzone contaminated with DDT and DNT.Water Science andTechnology, 43, 35–42.

Shrestha, R. A., Pham, T. D., & Sillanpää, M. (2009). Effect ofultrasound on removal of persistent organic pollutants


http://dx.doi.org/10.1007/s10532-012-9580-7

http://dx.doi.org/10.1007/s10532-012-9576-3

(POPs) from different types of soils. Journal of HazardousMaterials, 170, 871–875.

Singh, B., & Naidu, R. (2012). Cleaning contaminated environ-ment: a growing challenge. Biodegradation, 23(6), 785–786.doi:10.1007/s10532-012-9590-5.

Singh, I. B., Chturveth, K., & Yegneswaran, A. H. (2007).Thermal immobilization of Cr, Cu and Zn of galvanisingwastes in the presence of clay and fly ash. EnvironmentalTechnology, 28, 713–721.

Soares, A. A., Albergaria, J. T., Domingues, V. F., Alvim-Ferraz,M. C. M., & Delerue-Matos, C. (2010). Remediation ofsoils combining soil vapor extraction and bioremediation:benzene. Chemosphere, 80, 823–828.

Sunkara, B., Zhan, J., He, J., McPherson, G. L., Piringer, G., &John, V. T. (2010). Nanoscale zerovalent iron supported onuniform carbon microspheres for the in situ remediation ofchlorinated hydrocarbons. ACS Applied Materials and In-terfaces, 2, 2854–2862.

Swartjes, F. A. (1999). Risk-based assessment of soil andgroundwater quality in the Netherlands: standards and re-mediation urgency. Risk Analysis, 19, 1235–1249.

Taylor, T. P., Pennell, K. D., Abriola, L. M., & Dane, J. H.(2001). Surfactant enhanced recovery of tetrachloroethyl-ene from a porous medium containing low permeabilitylenses: 1. Experimental studies. Journal of ContaminantHydrology, 48, 325–350.

Thangavadivel, K., Megharaj, M., Smart, R., Lesniewski, P.,Bates, D., & Naidu, R. (2011). Ultrasonic enhanced desorp-tion of DDT from contaminated soils. Water, Air, and SoilPollution, 217, 115–125.

Thangavadivel, K., Megharaj, M., Smart, R. S. C., Lesniewski, P.J., & Naidu, R. (2009). Application of high frequency ultra-sound in the destruction of DDT in contaminated sand andwater. Journal of Hazardous Materials, 168, 1380–1386.

Thiruvenkatachari, R., Vigneswaran, S., & Naidu, R. (2008). Per-meable reactive barrier for groundwater remediation. Journalof Industrial and Engineering Chemistry, 14, 145–156.

USEPA. (1989). Evaluation of groundwater extraction remedies,1–2. Washington, DC: EPA Office of Emergency and Re-medial Responses.

Warner, S.D. (2011). PRB for Contaminated Groundwater,” TheMilitary Engineer, Society of American Military Engineers,Volume 104, No, 675, Page 53–54, January-February 2012

Warner, S. D. (2012). Permeable Reactive Barriers: advancingnatural in-situ remediation for treatment of radionuclides ingroundwater, radwaste solutions. American Nuclear Socie-ty, 18(14), 2011.

Warner, S.D., Yamane C.L., Bice, N.T., Szerdy, F.S., Vogan, J.,Major, D.W., Hankins D.A. (1994). The First CommercialPermeable Treatment Zone for VOCs. Proceedings of the FirstInternational Conference on Remediation of Chlorinated

Warner, S.D., Sorel, D. (2003) Ten Years of Permeable ReactiveBarriers, Lessons Learned and Future Expectation. In Chlo-rinated Solvent and DNAPL Remediation: Innovative Strat-egies for Subsurface Cleanup, ACS Symposium Series 837,American Chemical Society, pp. 36–50.

Yeung, A. T. (2006). Contaminant extractability by electrokinet-ics. Environmental Engineering Science, 23, 202–224.

Yeung, A. T., & Gu, Y. Y. (2011). A review on techniques toenhance electrochemical remediation of contaminated soils.Journal of Hazardous Materials, 195, 11–29.

Zevenbergen, C., Honders, A., Orbons, A. J., Viaene, W., Swennen,R., Comans, R. N. J., & van Hasselt, H. J. (1997). Immobili-sation of heavy metals in contaminated soils by thermal treat-ment at intermediate temperatures. In J. J. J.M. Goumans, G. J.Senden, &H.A. van der Sloot (Eds.), Studies in environmentalscience—waste materials in construction—putting theory intopractice (pp. 661–673). New York: Elsevier.


http://dx.doi.org/10.1007/s10532-012-9590-5