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

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

3. Table of contents
Profile 4
Physical remediation 6
Biological remediation 9
Chemical remediation 14
Test facilities 19
Purification installations 21
Want to know more? 23
3

4. ‘Where traditional methods are inadequate or
too costly, HMVT tackles soil challenges
with specialist in-situ remediation’
4

5. Profile
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.
In-situ techniques • chemical degradation of pollutants
In-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 technology
scale plume areas are more accessible and there is no need to that requires no active/physical remediation. This remediation
demolish buildings. Soil remediation no longer stands in the way of method will not be discussed in this document
constructing new buildings or infrastructure. We can deploy various
in-situ techniques depending on the type and magnitude of the For optimum results, we combine various remediation techniques
pollution. where necessary within our remediation solutions. Our R & D team is
continually researching innovations that can deal with contamination
Why 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 experience
remediation 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 waste
abroad since 1988, ranging from soil surveys to pilot projects, from water treatment systems, but also has available a very broad range
complex decontaminations to after-care programmes, both small of measuring tools and purification equipment.
and massive. We have applied virtually every method and we have
experience of almost every pollution scenario. Not only do we The following pages give a detailed explanation of the various
implement projects but we also offer advice and design. remediation techniques and other services which HMVT can offer.
Our company
HMVT employs experienced environmental scientists and
technicians. On average, our employees have been working in this
field for ten years. Quality and safety are at the core of our company
strategy. 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
are 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 techniques
HMVT is an all-round, in-situ soil remediator which uses the following
treatment methods:
• physical removal of pollutants
• biological degradation of pollutants HMVT innovative and effective in-situ remediation
5

6. ‘Contamination is extracted from
the subsoil and treated above ground
using various technologies’
6

7. 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. soil vapour extraction (bioventing)
2. various types of groundwater extraction
- dewatering by vacuum drainage
- gravity drainage
- deep well drainage
- re-infiltration by percolation
3. Multi Phase Extraction (MPE)
Figure 1: Bioventing system
1. Soil vapour extraction Applicability
Soil vapour extraction (SVE) is a technology that takes out air in the For a large part, the porosity of the subsoil will determine the
subsoil from the unsaturated area by means of vertical extraction applicability of bioventing. Bioventing can be applied in naturally
filters 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 practice
give 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. 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 oildepot
8

9. Figure 6: Different forms of substance transport
This is expressed in the distribution coefficient Kd. It is essential to Referentie HMVT
factor 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 air
more 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. ‘Biological degradation is stimulated by
optimising the conditions under which
degradation occurs’
10

11. Biological remediations
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.
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 largescale
substrate injection
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
degradation is such that monitoring is sufficient.
We apply the following methods:
1. Aerobic degradation: injection of donor oxygen
2. Anaerobic degradation: injection of carbon source
Figure 8: principal biosparging and influence
Our experts can find out whether contamination can be degraded
by aerobic or anaerobic means. Biological techniques can offer an
affordable 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 is
1. 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. 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. • 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 ENNA
mixed on site and consists of an emulsion with extremely small
particles (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 an
extended period (slow release). This enables the bacteria to break
down the contamination in the soil over a period of a few years up
to a maximum of five years, depending on the other characteristics
of the soil. This is biological attenuation. The technology can be
applied to both the source and the plume area. ENNA can also be
used as a biological screen to contain contamination. Compared to
other 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 small
particles (2 tot 10 µm) easily spread and penetrate into the soil Professional practice
matrix. 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 the
therefore 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-lasting
simultaneously 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. ‘A technology that has proven itself in
recent years is chemical oxidation’
14

15. Chemical remediations
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.
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 certain
solution 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 in
reaction 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 are
Figure 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 does
1. Chemical oxidation not entirely deposit as iron oxide or hydroxide under the aerobic
During 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 the
soil 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. One
which 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 or
the 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. 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. 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 sulphide
of contamination, for example purified product in the source areas that will be reduced.
of the contamination.
Professional practice
Professional 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, which
made stimulated biological breakdown possible. Following the
remediation, the location was declared suitable for the development
of new apartments.
3. Bergermeer, The Netherlands (project value EUR 15,000):
Chemical oxidation of volatile aromatics and mineral oils with an
effectiveness of more than 90%.
2. Chemical reduction
In locations where other in-situ remediation technologies are not
able 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 in
particular which come under this heading, i.e. stabilisation when Figure 14: Nano iron in a drop of oil
heavy 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 chemical
remediation 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 iron
macro-chemical conditions such as redox at less than -150mV and particles are extremely small, i.e. so-called nano particles between
acidity 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 relative
force 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 subsequently
step 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 2
Fe3+ + 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 with
step 3 0-value iron and ENNA for applications under the name of ‘FENNA’.
SO42− + carbon source → HS−/H2S- + CO2 + H2O
reduction of sulphate
step 4
Fe2+/Zn2+ + SO42- + carbon source → FeS/ZnS + H2O
zinc deposit (ISMP)
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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’
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19. 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
sufficiently complete for proposing the optimum in-situ remediation
technology. 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.
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 laboratories
Figure 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 heading
or soil is taken and analysed in several tests under laboratory ‘Professional practice’.
conditions. The following is a list of experiments and tests:
Professional practice
For 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 biological
For 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 soil
For chemical oxidation:
• Contaminant analysis
• Determine the buffering capacity
• Determine the matrix requirement
• Attenuation test
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20. ‘HMVT has multiple technologies available which
it builds in-house for purifying various
contaminated air and water flows’
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21. Purification plant
It 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 for
purifying 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 exchange
Air 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
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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 area
of in-situ remediation? Our consultants are always willing to answer
your queries and provide you with more information. Also visit
www.hmvt.eu for more information on our specific products and
services.
Hannover Milieu- en Veiligheidstechniek B.V.
P.O. Box 174
6710 BD Ede
T NL + 31 (0)318 - 624 624
T BE + 32 (0)3 - 609 55 30
E info@hmvt.nl
www.hmvt.nl
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