Hannover Milieu- en Veiligheidstechniek B.V.

An overviewHMVT INNOVATIVE AND EFFECTIVE

Twenty years of experience in soil,

water and air remediation

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Table of contents

Profile 4

Physical remediation 6

Biological remediation 9

Chemicalremediation 14

Test facilities 19

Purificationinstallations 21

Want to know more? 23

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‘Where traditional methods are inadequate or

too costly, HMVT tackles soil challenges

with specialist in-situ remediation’

Profile

In-situ techniquesIn-situ remediation removes subsoil and residual contamination on site. The advantages? Profound contamination and large-scale plume areas are more accessible and there is no need to demolish buildings. Soil remediation no longer stands in the way of constructing new buildings or infrastructure. We can deploy various in-situ techniques depending on the type and magnitude of the pollution.

Why HMVT?You are looking for an experienced remediator who can solve soil problemssmartlyandefficiently.Acompanywhichwilltackleevery soil problem individually and which uses state of the art remediation technology. Public authorities, industrial concerns, property developers and large-scale remediators know our strengths. HMVT has been involved in hundreds of projects at home and abroad since 1988, ranging from soil surveys to pilot projects, from complex decontaminations to after-care programmes, both small and massive. We have applied virtually every method and we have experience of almost every pollution scenario. Not only do we implement projects but we also offer advice and design.

Our companyHMVT employs experienced environmental scientists and technicians. On average, our employees have been working in this fieldfortenyears.Qualityandsafetyareatthecoreofourcompanystrategy. We work in teams, put together on the basis of knowledge and experience. We don’t impose sections or other barriers between our staff. Our staff consciously exchange practical experiences and are trained in-house in our specialised professional area.

How we operate Remediation is always a custom job. Besides that, we have also found that the social and other costs of soil remediation should not be excessive. That is why we aim to achieve remediation goals that arefeasibleanduseresourcesandenergyasefficientlyaspossible.Aspecialistteamisallocatedtoeachproject.Thisteamdrawsupanaction plan for each soil contamination problem and then designs, constructs and maintains the necessary remediation installations.

Remediation techniquesHMVT is an all-round, in-situ soil remediator which uses the following treatment methods: • physicalremovalofpollutants• biologicaldegradationofpollutants

• chemicaldegradationofpollutants• monitoringthestabilityofdegradationprocesses(monitoringofnatural degradation/stability is a passive remediation technology that requires no active/physical remediation. This remediation method will not be discussed in this document

For optimum results, we combine various remediation techniques where necessary within our remediation solutions. Our R & D team is continually researching innovations that can deal with contamination evenmoreefficiently.Weworkwithstudents,researchlaboratoriesand consultancies on this.

Besides soil remediation, HMVT has also gained a lot of experience withmanytypesofairand(waste)watertreatmentinthepast20years,bothwithinandoutsidetheremediationmarket.Asaresult,HMVT not only has the necessary expertise to design air and waste water treatment systems, but also has available a very broad range ofmeasuringtoolsandpurificationequipment.

The following pages give a detailed explanation of the various remediation techniques and other services which HMVT can offer.

A floating crust of diesel under a former industrial site, polluted groundwater or hydrocarbon contamination in the

inner city. When contamination is complex, you want to keep the risk to humans and the environment as small as

possible. At the same time you want building development to carry on. This demands the right response. Where

traditional methods are inadequate or too costly, HMVT tackles soil challenges with specialist in-situ remediation.

We have been doing this since 1988. Efficiently, lean and saving costs.

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HMVT innovative and effective in-situ remediation

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‘Contamination is extracted from

the subsoil and treated above ground

using various technologies’

Physical remediation

Physical remediation technology is understood to consist mainly of methods by which contamination is extracted from the subsoil and treated above ground. We apply the following physical techniques:

1. soilvapourextraction(bioventing)2. various types of groundwater extraction - dewatering by vacuum drainage - gravity drainage - deep well drainage -re-infiltrationbypercolation3. MultiPhaseExtraction(MPE)

1. Soil vapour extractionSoilvapourextraction(SVE)isatechnologythattakesoutairinthesubsoil from the unsaturated area by means of vertical extraction filtersorhorizontaldrains.Thepurposecanbebothtoevaporatevolatile pollutants and to stimulate biological degradation by injecting additional oxygen into the ground by means of the induced air,amethodknownasbioventing(EPA,1995).

Nutrients are often also injected when using this technique to give nature a helping hand. Figure 2 is a representation of this technology.

ApplicabilityFor a large part, the porosity of the subsoil will determine the applicability of bioventing. Bioventing can be applied in naturally unsaturated,moderatelyporousground,finesandandloamysoils.Asregardscontamination,thistechnologycanbeappliedtotheremovalofvolatilecompoundswhichhaveaHenricoefficientexceeding0.01oravapourpressureexceedingapprox.0.7mbar.

Professional practice1.Nijlen,Belgium(projectvalueEUR130,000):Combinationofair sparging, bioventing and groundwater extraction. Remediation resultedinareductionofthepollutingchemicalcocktail(styrene,cresol,phthalates,isopropylbenzeneandbtex)downtobelowthepost-remediation value.2. Mechelen,Belgium(projectvalueEUR95,000):Combinationofair sparging, bioventing and groundwater extraction. Remediation of MTBE, volatile aromatics and mineral oils to below the post-remediation value imposed by the authorities.

Figure 1: Bioventing system

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Figure 2: high vacuum bioventing system

3. 3. Multi phase extraction (MPE)Athirdmethodforextractinggroundwaterismultiphaseextraction. In this method a mixture of air, water and/or oil/oil products in the crust is extracted from the top layer of thegroundwater.Figure4showsadiagramofMPE.Itisoftheutmost importance in MPE to specify the scope of the water andairpurificationinstallationproperly.Bycarryingoutanoil characterisation, it is possible to determine beforehand inwhichphase(airorwater)theoilcomponentscanbemosteffectivelyextractedandpurified.Itisoftenalsoimportanttotake additional measures because of the high concentrations ofcontaminants(e.g.LELmeter).

2. Groundwater extractionGroundwater extraction is a perfect technology for extractingpollutedgroundwater(seefigure3).Itismoreoverused as an auxiliary method for biological and chemical remediations. When nutrients or oxidants are injected into theground(reinfiltration),groundwaterextractionhelpstodisperse these throughout the soil substrates. Groundwater extraction includes gravity drainage, vacuum drainage and/ordeepwellreinfiltration.

ApplicabilityTop and subsoils often consist of layers with different porosities. The degree to which the porosity of these layers differs and the thickness of these layers determine theheterogeneityofanareaofground.Ahighdegreeofheterogeneity negatively impacts the effectiveness of the transportflow.

Theairorgroundwateroftenflowsthroughthelayerswithhigherporosity,whereasthesecanhardlyflowthroughtheless porous layers. There are various ways substances can be transported through the soil. Figure 6 gives a summary of these methods. We often encounter situations in the soil remediation business where the contamination is adsorbed intothesoilmatrix(includingclaymineralsandorganicsubstances).Thisresultsinacertainequilibriumbetweenthecontamination that is dissolved in the groundwater and the pollution adsorbed into the soil matrix.

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Figure 3: Gravitational pumping

Figure 4: Multiple phase extraction

Figure 5: impression photo remediation installation at a large oildepot

ThisisexpressedinthedistributioncoefficientKd.Itisessentialtofactor in both when calculating the load. Because bodies of water are usually in motion, there are two processes taking place, namely adsorption where pollution transforms from the water phase to theadsorbedstate(oftenatthefront)andretardationwherethepollution transforms from the adsorbed state to the water phase. This latter phenomenon makes the front of the concentration move more slowly than the actual water body. This is also known as delayedflow.

Referentie HMVT1. Antwerp,Belgium(projectvalue>EUR2,000,000):Crustlayerremediationonalargescalewithmorethan600remediationfilters.Afloatingcrustofmorethan1,500m3wasremoved.

2. Antwerp,Belgium(projectvalueEUR280,000):Combinationofcrust remediation with groundwater extraction, bioventing and air sparging.Thefloatingcrustwascompletelyremoved.

3. Dendermonde,Belgium(projectvalueEUR92,000):RemovaloffloatingcrustwithMultiPhaseExtraction.Crustwascompletelyremoved thus achieving the remediation objectives.

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Figure 6: Different forms of substance transport

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‘Biological degradation is stimulated by

optimising the conditions under which

degradation occurs’

Biological remediations

HMVT has technologies at its disposal which stimulate both aerobic and anaerobic degradation. Designing and monitoring degradation processes forms part of our activities. In some cases natural degradationissuchthatmonitoringissufficient.

We apply the following methods:1.Aerobicdegradation:injectionofdonoroxygen2.Anaerobicdegradation:injectionofcarbonsource

Ourexpertscanfindoutwhethercontaminationcanbedegradedby aerobic or anaerobic means. Biological techniques can offer an affordable option as a biological protective screen in large plume areas.

1. Aerobic degradationStimulated aerobic degradation is performed by introducing oxygen and/or nutrients. This can be done with methods that use compressedairinjection(CAI)orsparging,soilvapourextraction(SVE)and/ordirectinjection.

Compressed air injection (air sparging)Sparging air means injecting air under pressure using a compressor into the subsoil below the groundwater level. This method involves placingagridoffilters(coveringthesurface)belowthewatertablelevel. This technique is used to evaporate the contamination from thegroundwater(in-situstripping)andtointroduceoxygenintothepolluted groundwater. This stimulates the naturally occurring aerobic degrading process.

Thedistancebetweenthefilterstobeemplaceddependslargelyontheimpactareaoftheinjectedair.Areasonableprimaryestimateof this distance can be made by applying the principle that is illustratedinfigure8.However,specificsoilcharacteristicssuchasthetypeofsubsoilanditsporositywillinfluencetheimpactareatoagreatextent.Weadvisethatatrialiscarriedoutfirstbeforeafull-scale system is installed. The necessary parameters can then be determined during the trials.

Biological remediation stimulates the degradation of contaminants. Biological degradation is stimulated by optimising

the conditions under which degradation occurs. The redox conditions (oxidation reduction) are crucial to this process.

If anaerobic conditions are desirable, for instance when tetrachloroethene (PCE) and trichloroethene (TCE) degrade,

a sustainably degradable substrate is added. The degradation of the substrate activates the naturally present electron

acceptors and helps to reduce the contamination. If there is too little natural substrate for reductive degrading to take

place, inserting additional substrate is the logical measure to take in this case. In the case of aerobic degradation, for

instance in the degradation of BTEX and oil, oxygen will be added. This can be done by injecting air or pure oxygen or

injecting substances which increase the level of oxygen. Any further stimulation is done by optimising the management

of nutrients.

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Figure 7: manifold with 20 connections for largescale

substrate injection

Figure 8: principal biosparging and influence

ApplicabilitySparging is suitable for the treatment of a saturated area, during which the unsaturated area is treated at the same time. When applying sparging for stripping, the released air is always captured in the unsaturated area and removed under controlled conditions. The most crucial parameters that determine whether sparging is feasible are the porosity of the subsoil, the ground strata structure and the extent of the volatility of the contamination.

Professional practice1. Vilvoorde,Belgium(projectvalueEUR800,000):CombinationofMulti Phase Extraction, sparging and bioventing. Chlorohydrocarbon contamination was remediated by means of air sparging down to below the value imposed by the Belgian authorities. Bioventing ensured that the vapours released in the sparging process were extracted.2. Oosterhout,TheNetherlands(projectvalueEUR200,000):Combination of chemical oxidation with bioventing and air sparging. The volatile aromatics and mineral oil contamination present in the plume area were reduced to below the post-remediation value by means of sparging. The combination of chemical oxidation and spargingresultedinreductionoftheloadbymorethan90%.

Bioventing (soil vapour extraction)The method of extracting air from the soil known as bioventing treatstheunsaturatedzonebycreatingavacuuminthesubsoil.This causes air in the soil to be refreshed with the ambient air. This change of air introduces oxygen into the soil which stimulates the biological aerobic activities of the micro-organisms. If there are volatile air pollutants present, vaporisation can take place simultaneously, which extracts any contaminated air that needs to be decontaminated. The amount of air to be extracted is determined by the quantity and degradability of the substance. The vacuum required will be determined by the permeability of the substrate.

Subsoilaircanbeextractedviaverticalfilters.Ifthereareanybuildings present, drains can be installed with the help of a directional rotary well-sinking drill or high pressure drillings at an angle underneath the buildings in order to enable the directional extraction of air.

ApplicabilityContamination which is aerobically and biologically degradable can be remediated with the help of this technology. It has to be saidthatoilpollutionwithachainlengthexceedingC30isverydifficulttoremediateusingthistechnology.AnyNAPLstratamustbe removed prior to the remediation because these will prevent any remediation.

Heterogeneous soil structures can have a negative impact on the remediation period and the result of the remediation because lesspermeablelayersdonotpermitanefficientflowofair.Heterogeneity could also change the impact area to a large extent.Afieldtrialwillprovidemorecertaintyinthisregard.Thepermeability of a homogeneous soil stratum with poor porosity could potentially be increased with the application of a fracturing process.

Professional practice1. Antwerp,Belgium(projectvalueEUR200,000):Acombinationof technologies arrived at values below the post-remediation value for volatile aromatics and mineral oils. Zero contamination has now been measured at several spots. The biological degradation conditions were at an optimum. 2. Bilthoven,TheNetherlands(projectvalueEUR205,000):Combination of air sparging with nutrient injection. The mineral oil and BTEX contamination found in the groundwater was remediated andcertifiedbythecompetentauthorities.3. Amsterdam,TheNetherlands(projectvalueEUR95,000):Airsparging for the biological degrading of volatile aromatics and mineral oil contamination.

2. Anaerobic degradationContamination can also be degraded under anaerobic conditions by means of reductive processes. In contrast to oxidative degradation by means of bioventing and air sparging, the primary method is not the application of an electron acceptor but the application of an electrondonor(substrate)usingtheinjectionmethod.Therearemany different ways to introduce substrates into the soil and there are many organic substances that are suitable as a substrate.

BiologicaldegradingofVOClcontaminants(includingthedegreasingsubstancestetrachloroethene(PCE)andtrichloroethene(TCE)is possible in the right redox conditions and in the presence of substrate(DOC).Amicro-organismusesadifferentsubstance(thesubstrate)asfoodandbreaksdownthechloratedhydrocarbonsinthe process.

The contamination is broken down to a harmless ethene in several steps. For example, contamination due to PCE and TCE but also the degradation products CIS and VC can be degraded anaerobically. Figure10showsthisprocess.

ENNA injection (shock load)HMVTselectsthesubstrateonthebasisofthespecificsitesituation.We frequently inject slow-release soya-based electron donor, which wasdevelopedbyourownR&Dsection.ENNA(EnhancedNaturalAttenuation).WiththeENNAmethod,adurablesubstrateisinjectedinto the ground as shock-load. When using more common substrates such as molasses, several injection booster sessions will be required forsustainedstimulationofdegradation.TheENNAsubstrateis

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Figure 9: subsoil tubing for bioventing system

mixed on site and consists of an emulsion with extremely small particles(2to10µm)whichcanbepressedintotheporesofthesubsoils. The substrate is a mixture of soya and various agents, which ensures that the nutrients will be released slowly over an extendedperiod(slowrelease).Thisenablesthebacteriatobreakdown the contamination in the soil over a period of a few years up toamaximumoffiveyears,dependingontheothercharacteristicsof the soil. This is biological attenuation. The technology can be appliedtoboththesourceandtheplumearea.ENNAcanalsobeused as a biological screen to contain contamination. Compared to other substrates that are often used such as lactates, protamylasses, nutrolasesandmolasses,ENNAoffersthefollowingadvantages:

•Afineemulsionispreparedwhichcloselyresemblesmilk.Thiscanbe easily injected to a considerable depth in the ground. The small particles(2tot10µm)easilyspreadandpenetrateintothesoilmatrix. •Overtime,thesubstraterevertsgraduallytoabiologicalstate;•Ahugeamountofsubstrateisinjectedallatthesametime,thereforeonesingleinjectionissufficientinprinciple;•ENNAisrelativelyinexpensive;•ThereishardlyanyacidificationwithENNAsuchasoccurswith,forexample,lactatesandmolasses.AlowpHasaconsequenceofacidificationhasanegativeimpactonbiologicalbreakdown;•Becauseoftheslow-releaseeffect,theconditionsforbiologicalactivity remain very favourable and constant for a long time. •Contaminantslosetheirmobility:VOClcontaminantsdissolvebetterinsoyaoilthaningroundwaterbyafactorof1200times.Ashifttakesplace:thecontaminantsdissolveintothesubstrateduring the water and soil phases. The degree of contamination in the groundwater decreases very quickly at the location of the substrate injection because the pollutants dissolve into the substrate. This simultaneously creates an optimum mixture of the substrate and the pollutant.Thiseffectisparticularlyapparentinresidualandpurifiedproducts.

•Weareabletoinjectlargequantities–onaverage20to40m3perday–withournewlydeveloped‘biostimulator’.Figure11 gives an impression of the biostimulator. The container on the left has three holding tanks and the container on the right has mixing and injection tanks.

ApplicabilityStimulated reductive attenuation is in principle suitable for all organic pollutants that can be converted reductively. In practice however its application is largely limited to chlorohydrocarbons and a few particular pollutants such as HCH andchlorobenzene.Theredoxconditionsinthegroundwaterprovide an important precondition for the success of stimulated reductivedechlorination.Underanaerobicconditionswherea complete breakdown into harmless end products occurs naturally, successful remediation is much more likely than in a situation with aerobic conditions. Besides the electron donor, there may be other limiting factors, such as the availability of the contamination in the source area for example, or indeed the absence of suitable bacteria. If need be, we can inject supplementary bacteria.

Professional practice1.Dordrecht,TheNetherlands(projectvalueEUR73,000):groundwaterextractionandinfiltrationofgroundwaterwith biological stimulants: By pumping groundwater to the surface,providingasubstrateandreinfiltratingthismixture,we successfully remediated a large plume area by means of anaerobic breakdown.2.Zwolle,TheNetherlands(projectvalueEUR700,000):chemical oxidation in combination with stimulated breakdown. Chemical oxidation removed a large part of the VOCl source. Biological breakdown followed successful stimulation after the injectionofENNA,developedbyourselves.Savefor1levelindicator, the concentrations dwindled to below the post-remediation value.3.Veghel,TheNetherlands(projectvalueEUR350,000):stimulatedbreakdownofVOClcontaminationwithENNA.Emplacement of bio-screen with injection of long-lasting ENNAcarbonsource.Thepollutantsintheplumearea,whichextends a few hundred metres, were stopped by three bio-screens.

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Figure 10: principal biological degradation with ENNA

Figure 11: the biostimulator

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‘A technology that has proven itself in

recent years is chemical oxidation’

Chemical remediations

Itmayhappenthattheriskofmobilepollutantsspreading(e.g.heavymetals)cannotbereversedorisveryhardtostembyusingextractive, biological or other chemical remediation techniques. One solution can be to immobilise the contamination, a technique also knownas‘stabilisation’.Thesetechniquescomeundertheheadingof‘chemicalremediations’becausestabilisationisa(bio)chemicalreaction where the contamination reacts with a substrate that is introduced, rendering it immobile. You can read more about this undertheheading‘2.Chemicalreduction’.

1. Chemical oxidationDuringin-situchemicaloxidation(ISCO),astrongoxidationagentinthe form of a solid substance is diluted in water or injected into the soil together with air. When the oxidation agent comes into contact with the contamination in the ground, the pollutants are broken downbyachemicalroute-oxidisation–intoharmlesscompoundswhich include water and carbon dioxide. Several oxidation agents are used in the soil remediation sector, where the contamination breaks down indirectly via very highly oxidising small particles or the contamination breaks down directly with the oxidation agents, depending on the oxidation agent.

AlargenumberofpollutantscanbebrokendownusingISCO,depending on which pollutants the oxidising agent can deal with. Table 1 gives a summary of which oxidation agents can remove certain pollutants.Chemicalshavebeenarrangedfromvigorous(top)tolessactive(bottom).Lessfrequentlyoccurringcontaminationswhichcould potentially be remediated by ISCO have not been included in theoverview.AfeasibilitytestbytheHMVTspecialisttestlaboratorycould resolve this question.

Fenton’s reagentHMVT applies traditional Fenton’s Reagent. Fenton’s Reagent consists ofhydrogenperoxideasoxidatorandiron(2+)ascatalyst.Ifappliedcorrectly,thisformstheextremelyreactivehydroxylradical(OH•).The reaction equation is as follows:

H2O2+Fe2+ Fe3++OH-+OH•

These radicals are highly reactive and oxidise the most organic compounds, which releases a lot of reaction heat. Hydrogen peroxide is not a stable compound and breaks down into water and oxygen within a few days. This makes the reaction period in the ground quite short. On the other hand, no reaction products are generated which could lead to problems. The Fenton reaction is only effective at a low pH level between 2 and 6. The ideal pH level isat4to5becauseFe2+ remains stable at low pH levels and does not entirely deposit as iron oxide or hydroxide under the aerobic conditions created.

Thegroundisfirstmade‘oxidationready’intheprocessusedbyHMVT.ThisisdonebyloweringthepHofthesoiltobetween3.5and4whileat the same time introducing iron in the form of iron sulphate. One problem in this process can be the large buffer capacity of the ground, for example because of a high calcium content.

Afterthegroundhasbeenpreparedforoxidation,thehydrogenperoxide is injected into the ground. The hydrogen peroxide is injected

There are two distinct types of chemical remediation: chemical oxidation (1) and chemical reduction (2).

A technology which has proven itself in recent years is chemical oxidation. This remediation technology yields very

high efficiencies in a short period of time. This technique is often applied particularly to core areas with high pollutant

concentrations. Depending on the local contamination situation, HMVT applies the following chemical oxidation

tehniques:

- chemical oxidation using hydrogen peroxide (Fenton’s reagent)

- chemical oxidation using ‘Enhanced’ Fenton’s

- chemical oxidation using permanganate

- chemical oxidation using activated persulphate

The correct application depends on the local circumstances and also on the applicability in combination with other

remediation methods.

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Figure 12: injectorhead

inconcentrationsofbetween5and15%peroxide.Duringtheinjectionof the hydrogen peroxide the concentrations of hydrogen peroxide, the temperature,pH,Ec,oxygenlevel,ironII,pressures,yieldperfilterandredox are all measured on the ground. Everything is aimed at keeping the process under control.

Enhanced Fenton’sHMVT also makes use of Enhanced Fenton’s Reagent. The catalyst iron chelate is applied instead of acid and iron sulph ate in the Enhanced Fenton procedure. This makes it unnecessary to lower the pH level to 3.5. Compared to traditional Fenton’s Reagent, this has the following advantages:

• thepHisnotreduced;thisisadvantageousifthenextstepinvolvesbiologicalbreakdown;• thiscanalsobeusedforsoilswithahighbufferingcapacity,suchaschalkysoils;• theironbecomesavailablegradually;theFentonreactionthereforehappens more gradually and the Fenton’s Reagent continues to be effective for a longer period.

In addition to using Fenton’s Reagent, HMVT is also experienced in the applications of permanganate and activated persulphate.

ApplicabilityISCO can be deployed in a source area of the contamination but also in the rest of the plume area. The decision whether to enlist a given oxidation medium in a source or plume area depends on the location ofthecontaminationintheground,whetherthereisanypurifiedproduct, the period of time allowed for remediation and the cost. Some oxidation agents are too expensive to deploy where there are low contaminant concentrations in a plume area. Table 1 lists the oxidationagentsthatcanbeusedinagivensituation.Anumberofoxidation agents are used for remediating soil contamination.

This technique is particularly suitable for well to moderately draining soils. If the ground is almost impervious, special application techniques such as fracturing can be deployed. Natural organic substances(OS)and/orreducedinorganiccompoundssuchasFe2+candramatically increase the quantity of oxidants required: the so-called matrix requirement of the soil.

The application of permanganate should be avoided for soils with poor drainage.Manganeseoxide(MnO2¬)iscreatedinthereactionwith

Oxidant Pollution situation Can be applied to Cannot be applied toFenton’s reagent and Enhanced Fenton’s reagent

source area - may or may not contain pure product, high groundwater levels

(chloro)ethenes, (chloro)ethanes,BTEX, light fraction mineral oilandPAH,freeandcomplexcyanides, phenols, phthalates, MTBE, THF

weathered/heavy fraction mineral oil, higher alkanes, heavyfractionPAH,PCB,

Ozone/peroxide source area - may or may not contain pure product1, high groundwater levels in the plume area

(chloro)ethenes, (chloro)alkanes,mineral oil, BTEX, lighter fraction PAH,freecyanides,phenols,phtha-lates, MTBE

heavyfractionPAH2, PCB2),complexcyanides

Persulfate source area - may or may not contain pure product, high groundwater levels

(chloro)ethenes, (chloro)alkanes,BTEX,lighterfractionPAH,phenols, phthalates, MTBE

heavyfractionPAH,PCB

Ozone source area - may or may not contain pure product, high groundwater levels in plume area

(chloro)ethenes,mineraloil3, BTEX,lighterfractionPAH,freecyanides, phenols, phthalates, MTBE

(chloro)alkanes,heavyfractionPAH,PCB,complexcyanides

Permanganate source area - may or may not contain pure product, high groundwater levels

chloroethenes, TEX4, phenols benzene,(chloro)alkanes,mineraloil,PAH,PCB,cyanides

Table 1: Overview table1 According to the patent holder, not enough projects have been completed in the Netherlands to warrant application in soil that contains pure product.2 According to the patent holder, breakdown does occur, but no practical examples from outside of the United States are known.3 Mineral oil is not fully broken down into water and carbon dioxide, but into smaller hydrocarbon chains.4 Permanganate cannot be applied in benzene contaminations, but it can be applied in the case of ethyl benzene, toluene and xylene(s).

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Figure 13: The mobile injection unit (ISCO)

permanganate,whichisdifficulttodissolveandformsadeposit.Thiscan cause blockages in the soil pores if there are high concentrations ofcontamination,forexamplepurifiedproductinthesourceareasof the contamination.

Professional practice1. Ermelo,TheNetherlands(projectvalueEUR107,000):Chemicaloxidation in combination with Multi Phase Extraction to remove aircraft fuel. Combining these techniques caused a drop in concentrations,whichwascertifiedbythecompetentauthorities.2. Doetinchem,TheNetherlands(projectvalueEUR700,000):Chemical oxidation in combination with biological stimulation (ENNA):remediationofVOClcontaminationwithchemicaloxidationled to a dramatic decline in the source concentrations, which made stimulated biological breakdown possible. Following the remediation, the location was declared suitable for the development of new apartments. 3. Bergermeer,TheNetherlands(projectvalueEUR15,000):Chemical oxidation of volatile aromatics and mineral oils with an effectivenessofmorethan90%.

2. Chemical reductionIn locations where other in-situ remediation technologies are not ableeithertobreakdowncontamination(biologicalstimulationandchemicaloxidation)ortoextractcontaminationfromthesoil,thereis a third option for tackling the risks of mobile contaminations, namely chemical reduction. HMVT applies two technologies in particular which come under this heading, i.e. stabilisation when heavymetalsarepresentandinjectionof‘FENNA’forchemicallypureproducts,includingVOCl).

StabilisationAfrequentlyoccurringcontaminationforwhichtheabovein-situremediation technologies are inadequate, are heavy metals. For example,zinccanbestabilisedbymeansofsulphide.Sulphidemakesadepositwithzincintheformofzincsulphide(ZnS).Theprevailingmacro-chemicalconditionssuchasredoxatlessthan-150mVandaciditylevelatpH6orlower,arealsosignificant.Themicrobiologyat the location is also important because bacteria are the driving force behind the reduction of sulphate to sulphide. The following is a phased plan for the reduction processes that occur in the soil and on whichthestabilisationofzincisbased.Thesereactionstakeplaceinthe groundwater under anaerobic environmental conditions.

step 1NO3-+H++carbonsource→N2+H2O+CO2 reductionofnitrate(NO3-)

step 2Fe3++H++carbonsource→Fe2++H2O+CO2 reductionofiron(3+)(Fe3+)

step 3SO42−+carbonsource→HS−/H2S-+CO2+H2Oreduction of sulphate

step 4Fe2+/Zn2++SO42-+carbonsource→FeS/ZnS+H2Ozincdeposit(ISMP)

Thecarbonsource(soyaoil)thatisbeingoxidisedreleaseselectrons;oxidation of the carbon source with sulphate results in a sulphide that will be reduced.

Professional practicePilotinNederweert,TheNetherlands(projectvalueEUR80,000):Injectionwithcarbonsource(‘pump&treat’)incombinationwithgroundwaterextractionofheavymetals,includingzinccontamination.Furtherdispersionofzincinthegroundwaterwasstoppedcompletelythankstosuccessfullystabilisingthezinc.

‘FENNA’Chemical reduction is applied to locations where pure chemical productsarefound.ByreducingFetoFe2+understronglyreducedconditions(Redox300),PCEcanbeconvertedtoharmlessetheneviaTRI, CIS and VC. However, this technology is only effective if the iron particles are extremely small, i.e. so-called nano particles between 100and200nm.Thisreactionwillonlyoccuronthesurfaceofthe iron particle. The smaller the particle, the larger the relative surface.ThistechniqueisknownintheUnitedStatesas‘NanoscaleZero Valent Iron’ or NZVI for short.

The pollutants PCE and TRI dissolve considerably better in oily substancesthaninwater.Inthisapplicationtheiron0nanoparticlesare dissolved in a vegetable based soya oil. This oil is subsequently injectedasanemulsion(smalloildropletsmeasuringjustafewµm).Aftertheoilisinjectedintotheground,thecontaminantswillbeconcentrated in the oil droplets. The pollutant will then react with theiron0nanoparticlesintheoildroplets.

Aftertheironreactionisexhausted,thebiologicalbreakdownwilltake over and then the vegetable based soya oil will be used as the DOC source. HMVT uses the combination of chemical reduction with 0-valueironandENNAforapplicationsunderthenameof‘FENNA’.

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Figure 14: Nano iron in a drop of oil

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‘Thanks to our knowledge combined with supplementary

tests, we are able to give a verdict on the remediation

method and its feasibility for almost every case of

contamination’

Test facilities

Detailed information about the soil, the groundwater and the contamination are crucial for in-situ remediation. In some cases previous investigations into drawing up remediation plans are not sufficientlycompleteforproposingtheoptimumin-situremediationtechnology. For example, information may be missing that could give an indication of the potential biological activities on site. This could include the redox conditions, the iron content and/or the sulphate content. If chemical oxidation is included, it will be necessary to obtain an impression of the buffer capacity to be able to calculate the chemical quantities to be applied.

HMVT has its own laboratory facilities with all the necessary equipmenttocarryoutthesetests.Afieldsampleofwaterand/or soil is taken and analysed in several tests under laboratory conditions. The following is a list of experiments and tests:

For extractive remediations:• Permeabilitytest• Contaminantanalysis

For biological stimulation:• Contaminantanalysis• Bufferingcapacity• Attenuationtest(aerobicandanaerobic)• Laboratoryanalysis(iron,sulphate,DOC,etc.)

For chemical oxidation:• Contaminantanalysis• Determinethebufferingcapacity• Determinethematrixrequirement• Attenuationtest

Besides the laboratory tests which are needed to obtain supplementaryinformationforspecificprojects,thelabisalsoused within HMVT’s Research & Development section. Thanks to our knowledge combined with supplementary tests, we are able to give a verdict on the remediation method and its feasibility for almost every case of contamination. New techniques are developed year on year thus carrying on the tradition of innovation at HMVT. We are able to accomplish this partly thanks to our laboratories andbycarryingoutpilotfieldtrials.Besidesresearchintogroundremediationwealsocarryoutteststofindthemostsuitablepurificationmethodsforairandwater.Youwillfindaseriesofnewtechnologies developed by HMVT summarised under the heading ‘Professionalpractice’. Professional practice1. Development of new chemical oxidation techniques2. DevelopmentofthesustainablesubstrateENNA(ENhancedNaturalAttenuation)3. Development of several substrate compounds for biological breakdown of VOCl4. Feasibilitytestsforbiologicalbreakdownofcontaminationwithvarious substrates5. Jartestsfortheoptimisationofwaterpurificationmethods,e.g.iron removal6. DispersionbehaviourofENNAinthesoil

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Figure 15: impression photo HMVT lab

Figure 16: impression photo 2 HMVT lab

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‘HMVT has multiple technologies available which

it builds in-house for purifying various

contaminated air and water flows’

Purificationplant

Itisoftennecessarytopurifyairandwaterflowswhenextractingpollutedgroundwaterand/orairfromthesoil(seesection‘Physicalremediation’).Thisdepends,amongotherthings,onthedischargeand emission standards for water and air.

HMVT has several technologies available which it builds in-house for purifyingvariouscontaminatedairandwaterflows.Asummaryofthese is given below.

Water purification using:• Striptowers• Plateaerator• Sandfiltration• Oilwaterseparator(OWAS)• ‘Wet’activecarbon• Ionexchange

Air purification using:• Catalyticburning• ‘Dry’activecarbon• Coronapulsedplasma(industrialaircleansing)• Oxicator• Biofilter(biobed)

Thedesignandspatialassessmentofthedifferentpurificationinstallationsdependsverymuchontheflowtobetreatedandtheextracted contamination.

Thephotographsbelowshowvariouspurificationinstallations.

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Figure 17: Catalytic burning

Figure 19: Air stripping tower

Figure 18: Sand filtration

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Want to know more?

HMVTwouldverymuchliketomeetthechallengeoffindingtheoptimum solution to your soil, water or air problem. Our strength? Know-how,yearsofexperienceandaninnovativeoutlook.Wouldyou like to know more about the possibilities we offer in the area of in-situ remediation? Our consultants are always willing to answer yourqueriesandprovideyouwithmoreinformation.Alsovisitwww.hmvt.euformoreinformationonourspecificproductsandservices.

Hannover Milieu- en Veiligheidstechniek B.V.P.O.Box1746710BDEdeTNL+31(0)318-624624TBE+32(0)3-6095530E info@hmvt.nlwww.hmvt.nl

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