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HMVT: in situ remediation


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HMVT is a soil remediation company with extensive and wide-ranging experience in realizing soil remediation operations based on situ technologie (extraction, chemical, thermal and biological). We approach every soil contamination with the best possible combination of these techniques.

in situ remediation, dualphase, ISCO, airsparging, soil vapour extraction, thermal desorption, stimulated biodegradation, CORONA, water treatment, air purification

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HMVT: in situ remediation

  1. 1. Hannover Milieu- en Veiligheidstechniek B.V. An overview HMVT INNOVATIVE AND EFFECTIVE Twenty years of experience in soil, water and air remediation
  2. 2. 2
  3. 3. Table of contentsProfile 4Physical remediation 6Biological remediation 9Chemical remediation 14Test facilities 19Purification installations 21Want to know more? 23 3
  4. 4. ‘Where traditional methods are inadequate or too costly, HMVT tackles soil challenges with specialist in-situ remediation’4
  5. 5. ProfileA floating crust of diesel under a former industrial site, polluted groundwater or hydrocarbon contamination in theinner city. When contamination is complex, you want to keep the risk to humans and the environment as small aspossible. At the same time you want building development to carry on. This demands the right response. Wheretraditional 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.In-situ techniques • chemical degradation of pollutantsIn-situ remediation removes subsoil and residual contamination • monitoring the stability of degradation processes (monitoring of on site. The advantages? Profound contamination and large- natural degradation/stability is a passive remediation technologyscale plume areas are more accessible and there is no need to that requires no active/physical remediation. This remediationdemolish buildings. Soil remediation no longer stands in the way of method will not be discussed in this documentconstructing new buildings or infrastructure. We can deploy variousin-situ techniques depending on the type and magnitude of the For optimum results, we combine various remediation techniquespollution. where necessary within our remediation solutions. Our R & D team is continually researching innovations that can deal with contaminationWhy HMVT? even more efficiently. We work with students, research laboratories You are looking for an experienced remediator who can solve soil and consultancies on this.problems smartly and efficiently. A company which will tackle every soil problem individually and which uses state of the art Besides soil remediation, HMVT has also gained a lot of experienceremediation technology. Public authorities, industrial concerns, with many types of air and (waste) water treatment in the past 20 property developers and large-scale remediators know our strengths. years, both within and outside the remediation market. As a result, HMVT has been involved in hundreds of projects at home and HMVT not only has the necessary expertise to design air and wasteabroad since 1988, ranging from soil surveys to pilot projects, from water treatment systems, but also has available a very broad rangecomplex decontaminations to after-care programmes, both small of measuring tools and purification equipment.and massive. We have applied virtually every method and we haveexperience of almost every pollution scenario. Not only do we The following pages give a detailed explanation of the variousimplement projects but we also offer advice and design. remediation techniques and other services which HMVT can offer.Our companyHMVT employs experienced environmental scientists andtechnicians. On average, our employees have been working in thisfield for ten years. Quality and safety are at the core of our company strategy. We work in teams, put together on the basis of knowledgeand experience. We don’t impose sections or other barriers betweenour staff. Our staff consciously exchange practical experiences andare trained in-house in our specialised professional area.How we operateRemediation is always a custom job. Besides that, we have alsofound that the social and other costs of soil remediation should notbe excessive. That is why we aim to achieve remediation goals thatare feasible and use resources and energy as efficiently as possible. A specialist team is allocated to each project. This team draws up an action 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 followingtreatment methods:• physical removal of pollutants • biological degradation of pollutants HMVT innovative and effective in-situ remediation 5
  6. 6. ‘Contamination is extracted from the subsoil and treated above ground using various technologies’6
  7. 7. Physical remediationPhysical remediation technology is understood to consist mainly ofmethods by which contamination is extracted from the subsoil andtreated above ground. We apply the following physical techniques:1. soil vapour extraction (bioventing) 2. various types of groundwater extraction - dewatering by vacuum drainage - gravity drainage - deep well drainage - re-infiltration by percolation3. Multi Phase Extraction (MPE)Figure 1: Bioventing system1. Soil vapour extraction ApplicabilitySoil vapour extraction (SVE) is a technology that takes out air in the For a large part, the porosity of the subsoil will determine thesubsoil from the unsaturated area by means of vertical extraction applicability of bioventing. Bioventing can be applied in naturallyfilters or horizontal drains. The purpose can be both to evaporate unsaturated, moderately porous ground, fine sand and loamy soils. volatile pollutants and to stimulate biological degradation by As regards contamination, this technology can be applied to the injecting additional oxygen into the ground by means of the induced removal of volatile compounds which have a Henri coefficient air, a method known as bioventing (EPA, 1995). exceeding 0.01 or a vapour pressure exceeding approx. 0.7 mbar. Nutrients are often also injected when using this technique to Professional practicegive nature a helping hand. Figure 2 is a representation of this 1. Nijlen, Belgium (project value EUR 130,000): Combination of technology. air sparging, bioventing and groundwater extraction. Remediation resulted in a reduction of the polluting chemical cocktail (styrene, cresol, phthalates, isopropylbenzene and btex) down to below the post-remediation value. 2. Mechelen, Belgium (project value EUR 95,000): Combination of air sparging, bioventing and groundwater extraction. Remediation of MTBE, volatile aromatics and mineral oils to below the post- remediation value imposed by the authorities.Figure 2: high vacuum bioventing system 7
  8. 8. 2. Groundwater extraction Groundwater extraction is a perfect technology for extracting polluted groundwater (see figure 3). It is moreover used as an auxiliary method for biological and chemical remediations. When nutrients or oxidants are injected into the ground (reinfiltration), groundwater extraction helps to disperse these throughout the soil substrates. Groundwater extraction includes gravity drainage, vacuum drainage and/ or deep well reinfiltration. Figure 3: Gravitational pumping 3. 3. Multi phase extraction (MPE) A third method for extracting groundwater is multi phase extraction. In this method a mixture of air, water and/or oil/ oil products in the crust is extracted from the top layer of the groundwater. Figure 4 shows a diagram of MPE. It is of the utmost importance in MPE to specify the scope of the water and air purification installation properly. By carrying out an oil characterisation, it is possible to determine beforehand in which phase (air or water) the oil components can be most effectively extracted and purified. It is often also important to take additional measures because of the high concentrations of contaminants (e.g. LEL meter). Figure 4: Multiple phase extraction Applicability Top 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 the heterogeneity of an area of ground. A high degree of heterogeneity negatively impacts the effectiveness of the transport flow. The air or groundwater often flows through the layers with higher porosity, whereas these can hardly flow through the less 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 into the soil matrix (including clay minerals and organic substances). This results in a certain equilibrium between the contamination that is dissolved in the groundwater and the pollution adsorbed into the soil matrix. Figure 5: impression photo remediation installation at a large oildepot8
  9. 9. Figure 6: Different forms of substance transportThis is expressed in the distribution coefficient Kd. It is essential to Referentie HMVTfactor in both when calculating the load. Because bodies of water 1. Antwerp, Belgium (project value > EUR 2,000,000): Crust layer are usually in motion, there are two processes taking place, namely remediation on a large scale with more than 600 remediation filters. adsorption where pollution transforms from the water phase to A floating crust of more than 1,500 m3 was removed.the adsorbed state (often at the front) and retardation where the pollution transforms from the adsorbed state to the water phase. 2. Antwerp, Belgium (project value EUR 280,000): Combination of This latter phenomenon makes the front of the concentration move crust remediation with groundwater extraction, bioventing and airmore slowly than the actual water body. This is also known as sparging. The floating crust was completely removed.delayed flow. 3. Dendermonde, Belgium (project value EUR 92,000): Removal of floating crust with Multi Phase Extraction. Crust was completely removed thus achieving the remediation objectives. 9
  10. 10. ‘Biological degradation is stimulated by optimising the conditions under which degradation occurs’10
  11. 11. Biological remediationsBiological remediation stimulates the degradation of contaminants. Biological degradation is stimulated by optimisingthe 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 electronacceptors and helps to reduce the contamination. If there is too little natural substrate for reductive degrading to takeplace, inserting additional substrate is the logical measure to take in this case. In the case of aerobic degradation, forinstance in the degradation of BTEX and oil, oxygen will be added. This can be done by injecting air or pure oxygen orinjecting substances which increase the level of oxygen. Any further stimulation is done by optimising the managementof nutrients. 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 placing a grid of filters (covering the surface) below the water table level. This technique is used to evaporate the contamination from the groundwater (in-situ stripping) and to introduce oxygen into the polluted groundwater. This stimulates the naturally occurring aerobic degrading process.Figure 7: manifold with 20 connections for largescalesubstrate injectionHMVT has technologies at its disposal which stimulate both aerobicand anaerobic degradation. Designing and monitoring degradationprocesses forms part of our activities. In some cases naturaldegradation is such that monitoring is sufficient. We apply the following methods:1. Aerobic degradation: injection of donor oxygen2. Anaerobic degradation: injection of carbon source Figure 8: principal biosparging and influenceOur experts can find out whether contamination can be degraded by aerobic or anaerobic means. Biological techniques can offer anaffordable option as a biological protective screen in large plume The distance between the filters to be emplaced depends largely on areas. the impact area of the injected air. A reasonable primary estimate of this distance can be made by applying the principle that is1. Aerobic degradation illustrated in figure 8. However, specific soil characteristics such as Stimulated aerobic degradation is performed by introducing the type of subsoil and its porosity will influence the impact area oxygen and/or nutrients. This can be done with methods that use to a great extent. We advise that a trial is carried out first before a compressed air injection (CAI) or sparging, soil vapour extraction full-scale system is installed. The necessary parameters can then be(SVE) and/or direct injection. determined during the trials. 11
  12. 12. Applicability Applicability Sparging is suitable for the treatment of a saturated area, during Contamination which is aerobically and biologically degradable which the unsaturated area is treated at the same time. When can be remediated with the help of this technology. It has to be applying sparging for stripping, the released air is always captured in said that oil pollution with a chain length exceeding C30 is very the unsaturated area and removed under controlled conditions. The difficult to remediate using this technology. Any NAPL strata must most crucial parameters that determine whether sparging is feasible be removed prior to the remediation because these will prevent any are the porosity of the subsoil, the ground strata structure and the remediation. extent of the volatility of the contamination. Heterogeneous soil structures can have a negative impact on the Professional practice remediation period and the result of the remediation because 1. Vilvoorde, Belgium (project value EUR 800,000): Combination of less permeable layers do not permit an efficient flow of air. Multi Phase Extraction, sparging and bioventing. Chlorohydrocarbon Heterogeneity could also change the impact area to a large contamination was remediated by means of air sparging down to extent. A field trial will provide more certainty in this regard. The below the value imposed by the Belgian authorities. Bioventing permeability of a homogeneous soil stratum with poor porosity could ensured that the vapours released in the sparging process were potentially be increased with the application of a fracturing process. extracted. 2. Oosterhout, The Netherlands (project value EUR 200,000): Professional practice Combination of chemical oxidation with bioventing and air sparging. 1. Antwerp, Belgium (project value EUR 200,000): A combination The volatile aromatics and mineral oil contamination present in of technologies arrived at values below the post-remediation value the plume area were reduced to below the post-remediation value for volatile aromatics and mineral oils. Zero contamination has by means of sparging. The combination of chemical oxidation and now been measured at several spots. The biological degradation sparging resulted in reduction of the load by more than 90%. conditions were at an optimum. 2. Bilthoven, The Netherlands (project value EUR 205,000): Bioventing (soil vapour extraction) Combination of air sparging with nutrient injection. The mineral oil The method of extracting air from the soil known as bioventing and BTEX contamination found in the groundwater was remediated treats the unsaturated zone by creating a vacuum in the subsoil. and certified by the competent authorities. This causes air in the soil to be refreshed with the ambient air. 3. Amsterdam, The Netherlands (project value EUR 95,000): Air This change of air introduces oxygen into the soil which stimulates sparging for the biological degrading of volatile aromatics and the biological aerobic activities of the micro-organisms. If there mineral oil contamination. 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 2. Anaerobic degradation by the quantity and degradability of the substance. The vacuum Contamination can also be degraded under anaerobic conditions by required will be determined by the permeability of the substrate. means of reductive processes. In contrast to oxidative degradation by means of bioventing and air sparging, the primary method is not Subsoil air can be extracted via vertical filters. If there are any the application of an electron acceptor but the application of an buildings present, drains can be installed with the help of a electron donor (substrate) using the injection method. There are directional rotary well-sinking drill or high pressure drillings at an many different ways to introduce substrates into the soil and there angle underneath the buildings in order to enable the directional are many organic substances that are suitable as a substrate. extraction of air. Biological degrading of VOCl contaminants (including the degreasing substances tetrachloroethene (PCE) and trichloroethene (TCE) is possible in the right redox conditions and in the presence of substrate (DOC). A micro-organism uses a different substance (the substrate) as food and breaks down the chlorated hydrocarbons in the 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. Figure 10 shows this process. ENNA injection (shock load) HMVT selects the substrate on the basis of the specific site situation. We frequently inject slow-release soya-based electron donor, which was developed by our own R&D section. ENNA(Enhanced Natural Attenuation). With the ENNA method, a durable substrate is injected into the ground as shock-load. When using more common substrates Figure 9: subsoil tubing for bioventing system such as molasses, several injection booster sessions will be required for sustained stimulation of degradation. The ENNA substrate is 12
  13. 13. • We are able to inject large quantities – on average 20 to 40 m3 per day – with our newly developed ‘biostimulator’. Figure 11 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. Applicability Stimulated 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 and chlorobenzene. The redox conditions in the groundwater provide an important precondition for the success of stimulated reductive dechlorination. Under anaerobic conditions where a 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.Figure 10: principal biological degradation with ENNAmixed on site and consists of an emulsion with extremely smallparticles (2 to 10 µm) which can be pressed into the pores of the subsoils. The substrate is a mixture of soya and various agents,which ensures that the nutrients will be released slowly over anextended period (slow release). This enables the bacteria to break down the contamination in the soil over a period of a few years upto a maximum of five years, depending on the other characteristics of the soil. This is biological attenuation. The technology can beapplied to both the source and the plume area. ENNA can also be used as a biological screen to contain contamination. Compared toother substrates that are often used such as lactates, protamylasses,nutrolases and molasses, ENNA offers the following advantages: Figure 11: the biostimulator• A fine emulsion is prepared which closely resembles milk. This can be easily injected to a considerable depth in the ground. The smallparticles (2 tot 10 µm) easily spread and penetrate into the soil Professional practicematrix. 1. Dordrecht, The Netherlands (project value EUR 73,000): • Over time, the substrate reverts gradually to a biological state; groundwater extraction and infiltration of groundwater • A huge amount of substrate is injected all at the same time, with biological stimulants: By pumping groundwater to thetherefore one single injection is sufficient in principle; surface, providing a substrate and reinfiltrating this mixture, • ENNA is relatively inexpensive; we successfully remediated a large plume area by means of• There is hardly any acidification with ENNA such as occurs with, anaerobic breakdown.for example, lactates and molasses. A low pH as a consequence of 2. Zwolle, The Netherlands (project value EUR 700,000): acidification has a negative impact on biological breakdown; chemical oxidation in combination with stimulated breakdown.• Because of the slow-release effect, the conditions for biological Chemical oxidation removed a large part of the VOCl source.activity remain very favourable and constant for a long time. Biological breakdown followed successful stimulation after the• Contaminants lose their mobility: VOCl contaminants dissolve injection of ENNA, developed by ourselves. Save for 1 level better in soya oil than in groundwater by a factor of 1200 times. indicator, the concentrations dwindled to below the post-A shift takes place: the contaminants dissolve into the substrate remediation value.during the water and soil phases. The degree of contamination in the 3. Veghel, The Netherlands (project value EUR 350,000): groundwater decreases very quickly at the location of the substrate stimulated breakdown of VOCl contamination with ENNA. injection because the pollutants dissolve into the substrate. This Emplacement of bio-screen with injection of long-lastingsimultaneously creates an optimum mixture of the substrate and the ENNA carbon source. The pollutants in the plume area, which pollutant. This effect is particularly apparent in residual and purified extends a few hundred metres, were stopped by three bio-products. screens. 13
  14. 14. ‘A technology that has proven itself in recent years is chemical oxidation’14
  15. 15. Chemical remediationsThere 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 veryhigh efficiencies in a short period of time. This technique is often applied particularly to core areas with high pollutantconcentrations. Depending on the local contamination situation, HMVT applies the following chemical oxidationtehniques:- chemical oxidation using hydrogen peroxide (Fenton’s reagent)- chemical oxidation using ‘Enhanced’ Fenton’s- chemical oxidation using permanganate- chemical oxidation using activated persulphateThe correct application depends on the local circumstances and also on the applicability in combination with otherremediation methods.It may happen that the risk of mobile pollutants spreading (e.g. A large number of pollutants can be broken down using ISCO, heavy metals) cannot be reversed or is very hard to stem by using depending on which pollutants the oxidising agent can deal with.extractive, biological or other chemical remediation techniques. One Table 1 gives a summary of which oxidation agents can remove certainsolution can be to immobilise the contamination, a technique also pollutants. Chemicals have been arranged from vigorous (top) to less known as ‘stabilisation’. These techniques come under the heading active (bottom). Less frequently occurring contaminations which of ‘chemical remediations’ because stabilisation is a (bio)chemical could potentially be remediated by ISCO have not been included inreaction where the contamination reacts with a substrate that is the overview. A feasibility test by the HMVT specialist test laboratory introduced, rendering it immobile. You can read more about this could resolve this question.under the heading ‘2. Chemical reduction’. Fenton’s reagent HMVT applies traditional Fenton’s Reagent. Fenton’s Reagent consists of hydrogen peroxide as oxidator and iron (2+) as catalyst. If applied correctly, this forms the extremely reactive hydroxyl radical (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 areFigure 12: injectorhead 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 is at 4 to 5 because Fe2+ remains stable at low pH levels and does1. Chemical oxidation not entirely deposit as iron oxide or hydroxide under the aerobicDuring in-situ chemical oxidation (ISCO), a strong oxidation agent in conditions created.the form of a solid substance is diluted in water or injected into thesoil together with air. When the oxidation agent comes into contact The ground is first made ‘oxidation ready’in the process used by HMVT. with the contamination in the ground, the pollutants are broken This is done by lowering the pH of the soil to between 3.5 and 4 while down by a chemical route - oxidisation – into harmless compounds at the same time introducing iron in the form of iron sulphate. Onewhich include water and carbon dioxide. Several oxidation agents problem in this process can be the large buffer capacity of the ground,are used in the soil remediation sector, where the contamination for example because of a high calcium content.breaks down indirectly via very highly oxidising small particles orthe contamination breaks down directly with the oxidation agents, After the ground has been prepared for oxidation, the hydrogen depending on the oxidation agent. peroxide is injected into the ground. The hydrogen peroxide is injected 15
  16. 16. Oxidant Pollution situation Can be applied to Cannot be applied to Fenton’s reagent and Enhanced source area - may or may (chloro)ethenes, weathered/heavy fraction Fenton’s reagent not contain pure product, (chloro)ethanes, mineral oil, higher alkanes, high groundwater levels BTEX, light fraction mineral heavy fraction PAH, PCB, oil and PAH, free and complex cyanides, phenols, phthalates, MTBE, THF Ozone/peroxide source area - may or may (chloro)ethenes, heavy fraction PAH2, not contain pure product1, (chloro)alkanes, PCB 2), complex cyanides high groundwater levels in mineral oil, BTEX, the plume area lighter fraction PAH, free cyanides, phenols, phtha-lates, MTBE Persulfate source area - may or may (chloro)ethenes, heavy fraction PAH, PCB not contain pure product, (chloro)alkanes, high groundwater levels BTEX, lighter fraction PAH, phenols, phthalates, MTBE Ozone source area - may or may (chloro)ethenes, mineral oil3, (chloro)alkanes, heavy not contain pure product, BTEX, lighter fraction PAH, free fraction PAH, PCB, complex high groundwater levels in cyanides, phenols, phthalates, cyanides plume area MTBE Permanganate source area - may or may chloroethenes, TEX4, phenols benzene, (chloro)alkanes, not contain pure product, mineral oil, PAH, PCB, cyanides high groundwater levels Table 1: Overview table 1 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). in concentrations of between 5 and 15% peroxide. During the injection • the pH is not reduced; this is advantageous if the next step involves of the hydrogen peroxide the concentrations of hydrogen peroxide, the biological breakdown; temperature, pH, Ec, oxygen level, iron II, pressures, yield per filter and • this can also be used for soils with a high buffering capacity, such as redox are all measured on the ground. Everything is aimed at keeping the chalky soils; process under control. • the iron becomes available gradually; the Fenton reaction therefore happens 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. Applicability ISCO 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 of the contamination in the ground, whether there is any purified product, 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 oxidation agents that can be used in a given situation. A number of oxidation agents are used for remediating soil contamination. Figure 13: The mobile injection unit (ISCO) 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 Enhanced Fenton’s substances (OS) and/or reduced inorganic compounds such as Fe2+ can HMVT also makes use of Enhanced Fenton’s Reagent. The catalyst iron dramatically increase the quantity of oxidants required: the so-called chelate is applied instead of acid and iron sulph ate in the Enhanced matrix requirement of the soil. Fenton procedure. This makes it unnecessary to lower the pH level to 3.5. Compared to traditional Fenton’s Reagent, this has the following The application of permanganate should be avoided for soils with poor advantages: drainage. Manganese oxide (MnO2¬) is created in the reaction with 16
  17. 17. permanganate, which is difficult to dissolve and forms a deposit. This The carbon source (soya oil) that is being oxidised releases electrons; can cause blockages in the soil pores if there are high concentrations oxidation of the carbon source with sulphate results in a sulphideof contamination, for example purified product in the source areas that will be reduced.of the contamination. Professional practiceProfessional practice Pilot in Nederweert, The Netherlands (project value EUR 80,000): 1. Ermelo, The Netherlands (project value EUR 107,000): Chemical Injection with carbon source (‘pump & treat’) in combination oxidation in combination with Multi Phase Extraction to remove with groundwater extraction of heavy metals, including zinc aircraft fuel. Combining these techniques caused a drop in contamination. Further dispersion of zinc in the groundwater was concentrations, which was certified by the competent authorities. stopped completely thanks to successfully stabilising the zinc.2. Doetinchem, The Netherlands (project value EUR 700,000): Chemical oxidation in combination with biological stimulation(ENNA): remediation of VOCl contamination with chemical oxidation led to a dramatic decline in the source concentrations, whichmade stimulated biological breakdown possible. Following theremediation, the location was declared suitable for the developmentof new apartments.3. Bergermeer, The Netherlands (project value EUR 15,000): Chemical oxidation of volatile aromatics and mineral oils with aneffectiveness of more than 90%.2. Chemical reductionIn locations where other in-situ remediation technologies are notable either to break down contamination (biological stimulation and chemical oxidation) or to extract contamination from the soil, there is a third option for tackling the risks of mobile contaminations,namely chemical reduction. HMVT applies two technologies inparticular which come under this heading, i.e. stabilisation when Figure 14: Nano iron in a drop of oilheavy metals are present and injection of ‘FENNA’ for chemically pure products, including VOCl).Stabilisation ‘FENNA’A frequently occurring contamination for which the above in-situ Chemical reduction is applied to locations where pure chemicalremediation technologies are inadequate, are heavy metals. For products are found. By reducing Fe to Fe2+ under strongly reduced example, zinc can be stabilised by means of sulphide. Sulphide makes conditions (Redox 300), PCE can be converted to harmless ethene via a deposit with zinc in the form of zinc sulphide (ZnS). The prevailing TRI, CIS and VC. However, this technology is only effective if the ironmacro-chemical conditions such as redox at less than -150mV and particles are extremely small, i.e. so-called nano particles betweenacidity level at pH 6 or lower, are also significant. The microbiology 100 and 200 nm. This reaction will only occur on the surface of at the location is also important because bacteria are the driving the iron particle. The smaller the particle, the larger the relativeforce behind the reduction of sulphate to sulphide. The following is a surface. This technique is known in the United States as ‘Nanoscale phased plan for the reduction processes that occur in the soil and on Zero Valent Iron’ or NZVI for short.which the stabilisation of zinc is based. These reactions take place in the groundwater under anaerobic environmental conditions. The pollutants PCE and TRI dissolve considerably better in oily substances than in water. In this application the iron 0 nano particles are dissolved in a vegetable based soya oil. This oil is subsequentlystep 1 injected as an emulsion (small oil droplets measuring just a few µm). NO3- + H+ + carbon source → N2 + H2O + CO2 After the oil is injected into the ground, the contaminants will be reduction of nitrate (NO3-) concentrated in the oil droplets. The pollutant will then react with the iron 0 nano particles in the oil droplets. step 2Fe3+ + H+ + carbon source → Fe2+ + H2O + CO2 After the iron reaction is exhausted, the biological breakdown will reduction of iron (3+) (Fe3+) take over and then the vegetable based soya oil will be used as the DOC source. HMVT uses the combination of chemical reduction withstep 3 0-value iron and ENNA for applications under the name of ‘FENNA’. SO42− + carbon source → HS−/H2S- + CO2 + H2O reduction of sulphatestep 4Fe2+/Zn2+ + SO42- + carbon source → FeS/ZnS + H2O zinc deposit (ISMP) 17
  18. 18. ‘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’18
  19. 19. Test facilitiesDetailed information about the soil, the groundwater and thecontamination are crucial for in-situ remediation. In some casesprevious investigations into drawing up remediation plans are notsufficiently complete for proposing the optimum in-situ remediation technology. For example, information may be missing that could givean indication of the potential biological activities on site. This couldinclude the redox conditions, the iron content and/or the sulphatecontent. If chemical oxidation is included, it will be necessary toobtain an impression of the buffer capacity to be able to calculatethe chemical quantities to be applied. Figure 16: impression photo 2 HMVT lab Besides the laboratory tests which are needed to obtain supplementary information for specific projects, the lab is also used 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 laboratoriesFigure 15: impression photo HMVT lab and by carrying out pilot field trials. Besides research into ground remediation we also carry out tests to find the most suitable HMVT has its own laboratory facilities with all the necessary purification methods for air and water. You will find a series of new equipment to carry out these tests. A field sample of water and/ technologies developed by HMVT summarised under the headingor soil is taken and analysed in several tests under laboratory ‘Professional practice’.conditions. The following is a list of experiments and tests: Professional practiceFor extractive remediations: 1. Development of new chemical oxidation techniques• Permeability test 2. Development of the sustainable substrate ENNA (ENhanced • Contaminant analysis Natural Attenuation) 3. Development of several substrate compounds for biologicalFor biological stimulation: breakdown of VOCl• Contaminant analysis 4. Feasibility tests for biological breakdown of contamination with • Buffering capacity various substrates• Attenuation test (aerobic and anaerobic) 5. Jar tests for the optimisation of water purification methods, e.g. • Laboratory analysis (iron, sulphate, DOC, etc.) iron removal 6. Dispersion behaviour of ENNA in the soilFor chemical oxidation:• Contaminant analysis• Determine the buffering capacity• Determine the matrix requirement• Attenuation test 19
  20. 20. ‘HMVT has multiple technologies available which it builds in-house for purifying various contaminated air and water flows’20
  21. 21. Purification plantIt is often necessary to purify air and water flows when extracting polluted groundwater and/or air from the soil (see section ‘Physical remediation’). This depends, among other things, on the discharge and emission standards for water and air.HMVT has several technologies available which it builds in-house forpurifying various contaminated air and water flows. A summary of these is given below.Water purification using:• Strip towers• Plate aerator• Sand filtration• Oil water separator (OWAS)• ‘Wet’ active carbon• Ion exchangeAir purification using:• Catalytic burning• ‘Dry’ active carbon• Corona pulsed plasma (industrial air cleansing)• Oxicator• Biofilter (biobed)The design and spatial assessment of the different purification installations depends very much on the flow to be treated and the extracted contamination.The photographs below show various purification installations. Figure 19: Air stripping tower Figure 17: Catalytic burning Figure 18: Sand filtration 21
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  23. 23. Want to know more?HMVT would very much like to meet the challenge of finding the optimum solution to your soil, water or air problem. Our strength?Know-how, years of experience and an innovative outlook. Would you like to know more about the possibilities we offer in the areaof in-situ remediation? Our consultants are always willing to answeryour queries and provide you with more information. Also visit for more information on our specific products and services.Hannover Milieu- en Veiligheidstechniek B.V.P.O. Box 1746710 BD Ede T NL + 31 (0)318 - 624 624T BE + 32 (0)3 - 609 55 30E 23