Water treatment using constructed wetlands is nothing new since it has been frequently applied to treat household wastewater. The treatment of more complex contamination in Constructed Wetlands is a whole different discipline. Think of compounds such as benzene, oil, chlorinated hydrocarbons, heavy metals and emerging pollutants for example pharmaceutical residue. HMVT has unique experience in combining groundwater management systems and the treatment of contaminated water in Constructed Wetlands.

We have implemented Constructed Wetland systems at different locations to treat water naturally and have them integrated in the landscape.

Challenge us and our model

To be able to answer clients’ questions swiftly and enable us to quickly calculate the design, we have generated a model that simulates the processes in a constructed wetland. The model is almost completed and so far we have run the model with data from our own projects. There is one way to make the model even better: to run it with greater amount of data and then assess the results in order to improve the model.

Thus, we would like to challenge you: approach us with your water treatment problem! We will run our model with your site particulars and will tell you what wetland solution is possible for your specific case. We will provide an estimate for the dimensions and the expected treatment results.

We can widely improve our model – with your information.

Do you have a water stream that you want to run by our model? Contact us!

For more information: contact our Constructed Wetland experts Paul Verhaagen and Frank Pels.

Japanese knotweed was first introduced in the Netherlands by the German botanist Philip Frank Balthasar von Siebold who became famous for his research on Japanese flora and fauna. He first brought Japanese knotweed to the Netherlands between 1829 and 1841. The newly introduced species was then cultivated in Leiden and sold as an ornamental plant. Since the 1950s Japanese knotweed has begun to spread outdoors on a large scale due to the dumping of garden waste and ground excavations, amongst other sources. Well.. We have been aware of this. Meanwhile this exotic plant has spread extensively all over the Netherlands where it has taken over any space it could reach. Municipalities, water authorities, provinces and site managers are at a loss. The Japanese knotweed overgrows everything and damages foundations, roads and dikes.This ferocious plant is almost impossible to eradicate since even when a miniscule part of the plant or root remains in the soil it once again returns in full force.

The solution HMVT has come up with for this obstinate problem is the use of heat. When the soil reaches a temperature of above 55 oC the knotweed dies and with it the extensive network of underground roots. We have already successfully implemented this technique at a first project in Rotterdam and our next project is bound to be launched in Amsterdam.

This project is in collaboration with the University of Wageningen. A team of researchers determined that throughout the treated area all remains of the plant were successfully killed off. To validate this further, the soil has been spread out at the location to be monitored by Wageningen University until the end of the season. Afterwards we can be one hundred percent certain that we have defeated this harmful invasive species.

Want to know more?

Would you like to know more about our method for eradication of Japanese knotweed? In just a few weeks we will receive the control results of the last monitoring period by Wageningen University. Once all results are in we will be glad to share an update and give you a good idea of the functioning of this method. Just leave us your email via the link. We will get in touch with further information after the summer once we have received all the new results. Then we can say with 100 % certainty that with our method every last part of the plant was eradicated.

Click here to leave us your email address so we can keep you updated on the progress of Japanese knotweed eradication. It is worth it, even if all tried methods so far have failed.

For more information please contact our expert Ted Vendrig

The purpose of the pilot test is to investigate if it would be possible to clean soils that are ‘polluted’ with Japanese knotweed in piles.

There is research evidence that the root grow from the Japanese Knotweed can be stopped by heating the soil to at least 55oC and sustaining this temperature for a period of at least 3 days (Day et al, 2009). Lower temperatures can also be effective to stop the growth of Japanese Knotweed, but then the temperature should be raised above 40 oC  and sustained for at least 7 days (MacFarlane, 2011).

For the pilot test a piles of Knotweed polluted soil is created in the harbour area of the port of Rotterdam. HMVT provides the design and instalment of the heating equipment and also operates the pilot test. Wageningen University & Research (WUR) will check the treatment results on the Knotweed.

Design of the pilot test
The pilot test is being executed on approximately 500 m3 of soil containing a lot of roots from the Japanese knotweed. A pile is created by putting the soils within a modular concrete wall. In the figure below you can see a schematic overview of the pile layout. The soil is being heated by HMVT by hot air injection, a technique we also use for in-situ soil remediation. In To prevent heat losses the top of the pile is covered by an insulating liner.

In the pile we placed several temperature monitoring sensors in order to follow up continuously the temperatures in the soil. When the soil is heated enough, Wageningen University will check if the Knotweed roots are terminated successfully. When the results are positive, the pile will be maintained in place during summer time to double check also over time if the Japanese Knotweed is terminated successfully indeed.


When the pilot test proves to be successful, the heating approach can also be performed in-situ on locations where excavation is difficult, like near railway tracts.

HMVT has 5 new colleagues. It’s time to introduce them to you.

Martijn Baars
During his career, Martijn Baars took many steps as a mechanic, service engineer, execution process technologist for water treatment installations. With experience in groundwater remediation, both on the implementation and consultancy side, he is a professional in innovative water treatment solutions in a professional. As of March 1, Martijn combines advice and implementation at HMVT. He’s mainly focused on purification techniques around the wastewater industry.

Wouter Neutel
As of February 1, Wouter strengthens the team of project leaders at HMVT. He is a professional in the themes of soil and air. With years of experience in research, advice and implementation of soil, sediment and soil remediation, he really complements the team. He also worked for us eight or nine years ago. In the meantime, he has gained experience in the consultancy world.

Rik Tiemens
As of 1 February, Rik strengthens the HMVT team with work preparation. He works in the field of technical drawings, but also procurement and implementation of material management. He strengthens our team both internally in our workshop and externally with our projects.

Carl Geerlings
As of February 1, Carl is a fresh new part of the HMVT team. As a junior mechanic, he will be trained by our senior mechanics. He has knowledge and experience in Mechatronics and as a service engineer. He participates in our office and externally projects. In this way, he will see al the facets of remediation.

Yazid Siteli
Yazid is  preparing his Master Degree in Water Science at the National Institute of Scientific Research. He was involved in many projects during my stay in Canada. All those projects were lab or pilot scale. Hence, he decided to do this internship in order to have a “full scale” experience that will help him to have a complete view on water treatment process. He’s building a pilot unit for Constructed Wetland also with the modelling for a better understanding of the system. He’s currently working on a ISCO project that it’s going to be in Montpellier, where he’s doing a pilot scale test to confirm the efficiency of the treatment.

Wouter, Rik en Carl

HMVT was contacted by a client who had problems with the treatment  of chromium VI and arsenic in a waste water flow. The initial ideas involved  the use of an ion exchanger resin to capture the heavy metals in the water. HMVT proposed to look at an alternative purification technique, based on chemical reduction and precipitation.

HMVT conducted six pilot tests in their test facility. Three different ion exchanger-resins were tested in three pilot tests. Purification techniques based on chemical reduction and precipitation were tested in the three other pilot tests.

The latter tests proved that the water could be treated with chemical reduction and precipitation approach. With a limited use of chemicals and limited sludge production, the requested discharge limit could be achieved. The technology also  results in a significant cost reduction, compared to the techniques in which ion exchange resins are used.

The  tests gave us and the client insight into amount of chemicals, reaction times, the amount and composition of the sludge formed in the process and the speed at which the sludge settles. With these parameters HMVT has made a design for a cost-effective full-scale water treatment.

Preliminary testing in the lab or with a pilot on site has the following advantages for you:

  • You can try a new purification technique at low cost;
  • Different techniques can be tested in the same, so you can make a better and result-based design choice;
  • You have better insight for the full-scale implications of a technology: you gain prior insight into costs, energy consumption, waste flows released, treatment efficiency, chemicals- and carbon- consumption;
  • Possible problems are known before the start of the full scale. This can be immediately incorporated into the design for the full-scale solution. This prevents unpleasant surprises afterwards.
  • You get – in advance – a good insight into the return and costs of the techniques; this has major advantages in applying for permits and negotiating their terms.


Do you have a problem or question about water purification or air purification?. HMVT has all common air and water purification techniques available for you. Please feel free to contact our specialists.

Please contact our experts

Neem dan nu contact op met één van onze specialisten!

The corona crisis has a significant impact on how we act and operate in our business HMVT’s sole priority is on everyone’s health.. The current projects of HMVT are continuing all in line with the guidelines of our clients.

Common sense

We follow the national advice of RIVM (Dutch institute for Public Health and Environment). In practice, this means that our installations can continue to operate. We often work with one or two employees per ongoing project, in which the installation is already standing and running. As long as these employees have no health issues, the main contacts / technicians continue to go to the installations. Do they show health issues? Then we’ll send another employee. This again, in close contact with our clients. With the manpower of HMVT, we ensure that current projects can continue.

Existing appointments
In consultation with you, we look at the possibilities of having meetings conducted  by telephone or skype. In this manner, we prevent delays and we continue to work safely and efficiently. Our employees are well aware of the online possibilities for meetings. Feel free to ask them about this!

New remediation projects
HMVT is keen  to look at the possibilities to start new projects. Good communication and ideas are always key for successful projects This does not change now, we still can get things started by digital meetings. So, please contact us so that we can get started.  We are happy to share our ideas for your project !

The employees of HMVT work at home as much as possible on the advice of RIVM. We minimize the number of employees at our office in Ede. You can call us on our general telephone number or direct call to our contact persons as presented on our website.

Neem contact op met onze experts

Neem dan nu contact op met één van onze specialisten!

On Thursday November 29, Marco welcomes colleagues from the past and present in a completely renovated office. Tonight is all about recalling memories. With two jubilees (both Marco and Rein have been in service for 25 years), it is perfect to come together. The newest trainee stood comfortably alongside the founder of HMVT. “Where is HMVT now? And what was it like before?”


Working with pleasure, it is a central theme of HMVT and therefore in the career of Rein and Marco. Their jubilees deserve a golden pin and a bunch of flowers. Marco and Rein received also a personal gift: two self-made “awards” from HMVT with their own story. Jos and Joop told beautiful stories from the past. Marco continued with a short speech in which he thanked everyone for the past years. He also looks to the future: doing nothing is not an option in the coming period.

Group feeling

While enjoying food and drinks from the standing tables, there was enough to talk about. After a convivial dinner, almost the whole old and new team gathered for a group photo. It was a wonderful moment to capture and we look back on a successful reunion.


The past year HMVT successfully carried out an in-situ thermal light project in the Netherlands, removing over 6.000 kg of chlorinated solvents from a thick unsaturated zone. At this project we heated the unsaturated zone by the injection of hot air (>400 oC) towards an average temperature of 70 oC. To create a closed loop and to remove the chlorinated solvents we also extracted soil vapor via a series of extraction wells. The system was monitored by a series of temperature sensors and ran 24/7, controlled by a PLC/Telemetric system. On a regular basis soil and soil vapor concentration levels were checked.

We call this a ‘thermal light’ project since it is a relatively easy and cost-effective way to enhance a classical soil vapor extraction system. Together with our Joint-Venture TRS Europe we can also offer more robust in-situ or on-site heating technologies like electrical resistance heating, steam enhanced extraction or conductive heating.

We are now going to test if heating of soils ‘polluted’ with Japanese Knotweed can be treated with this hot air injection technology. The Japanese Knotweed is an invasive plant that is very hard to destroy, that grows very aggressive and is also capable to destroy all kind of infrastructures. It is a plant that needs to be controlled seriously. At this moment in time there is not yet a (cost) effective method to control it yet.

From experts we have learned the plant will not survive heating at ca. 60 oC for multiple days. HMVT already tested successfully if it’s hot-air injection system would be able to only heat from the surface till ca. 1,5 m bgl. This works, the next full scale testing project will be a hot-air treatment of a pile of soil, containing ca. 1.000 m³ of soil polluted with Japanese Knotweed. This test will be carried out in cooperation of the University of Wageningen and – if successful – will most probably followed by other pile or in-situ treatments.

Groundwater is a precious natural resource. However, its vulnerability is often overlooked because in Western-Europe it is easy to use, cheap and abundant. But slowly our groundwater is turning grey: even when soil remediation and groundwater quality standards are formally met, groundwater is gradually impacted by decades of industrial and agricultural activities. Consequently, at numerous water production wells, quality has dropped below acceptable levels, already. This means that additional treatment steps are required before the groundwater can be used for industrial processes or drinking water purposes; with significant -financial- consequences for users. In this session we are zooming in on the origin of the problem, parties confronted with the problem and solutions.


The origin of the problem may be easily summarized as a result of wide-spread industrial and agricultural activities. As specific sources of contamination could be mentioned:
• the use of nutrients for fertilization and pesticides by farmers,
• residues of medicines, hormones, microplastics and Teflon coating flushed via the sewage system to surface waters by consumers,
• former landfills,
• other soil contaminations which are not complete removed,
• etc.

By groundwater flow, contaminants migrate over time and cause deterioration of vast and growing volumes of groundwater. The process is facilitated by activities in the underground, like injudicious use of aquifer thermal energy storage (ATES) systems, which could perforate aquitards and enhance contaminant migration. See figure 1.
This is only one part of the story. As awareness on environmental issues evolved at the end of last century, many successful programs were carried out to protect the groundwater. Soil and groundwater remediation and emission restrictions contributed to that goal. Plans were made for smart combinations of activities such as ATES integrated with groundwater remediation. However, due to presumed enormous future costs, many actions needed were not taken. Policy changes often interfered with actual remedial and protection measures; on paper solutions were found but in reality, problems were not resolved. So, now we realize that our groundwater is going grey.

Learn more and read the whole abstract 

Take a look at all the presentations of Aqua Consoil ‘Our precious groundwater goes grey’.

During the Intersoil congress, organised by Web-Event in collaboration with several parties including Leefmilieu Brussel, the theme was soil remediation. Being the soil remediation specialist, HMVT was of course in attendance.

Klaas de Jong spoke on behalf of HMVT at the Intersoil Congress. On Tuesday 13 November, in his presentation Klaas recounted the story of the remediation of a former dry-cleaning business. This remediation was carried out using a thermal approach to an unsaturated soil zone and an oxidative approach to the groundwater.

Current developments
In the course of this congress the changes in the regulations were also discussed, as well as the responsibilities of all the parties involved in soil remediation. In addition, new techniques and methods in carrying out soil studies were explained in detail, as well as innovative techniques in soil and groundwater remediation.