Design & Build Your Own Constructed Wetland

By Frank van Dien
October 2017

The Author is CEO at Ecofyt in Oirschot, the Netherlands. The first company in Holland to specialize in the design and building of constructed wetlands.

The easy guide to a low-cost, non-electric wastewater treatment

This book (ISBN/EAN: 978-90-826076-1-1) was written with a select audience in mind:
Somewhere in 2016 I was asked to give a course on constructed wetlands to managers and owners of agricultural companies, in Ethiopia. Having done that a few times earlier, in Kenya, together with good friends at WWF and UNESCO-IHE, I knew there was a solid formula to that.
Let’s get together for one week for both theory and practice... really building a small, working, usefully constructed wetland during the course.
And another few dozen people would not just know about constructed wetlands, they would understand them.

The important restrictions in this case were: electricity was not a reliable commodity... and it could not be about complex, high-tech purification systems.
And I knew that a workbook for these classes would definitely help in laying a solid foundation. But this book is not just for that course and not just for Ethiopian farmers. It gives insight in wastewater purification on a natural way, in a low-cost method. It tells about cheats and tricks gathered in more than two decades of building constructed wetlands.

And the matter should concern all people, I think. Not that everyone should be able to build his/her own wetland – you might very well be, after reading this book – but I feel that awareness towards treating pollution is a necessity. And that it is not exclusively something only governments can do... This makes part of my vision at ECOFYT transferring knowledge about the problems of wastewater and, even better, the possible solutions. Raising awareness, so I’m convinced, will be to the benefit of the environment.

There are many books and publications on constructed wetlands. Some are purely scientific, explaining to us what is happening on microscopic levels, on chemical levels. This book is written from a very practical point of view. It tells you that “Not In My Back Yard” is not applicable... It also tells you that this is not too difficult matter, useful and maybe even fun to do.

Why should we treat wastewater?

We all need water. Mankind, animals, plants alike; without water there is no life. And we have specific demands for that water. Though we use it for different purposes, there will certainly be a specific amount that we need of top-quality drinking water. This drinking water may come from different sources: groundwater, surface water or rainwater, but in nearly all cases we already have to treat it in order for it to be clean enough to consume. This manual, however, is not about cleaning water to that extent. This is about cleaning the water we used, to such an extent that nature can cope with it, when we give it back.

Treating wastewater is all about water quality and responsibility. Usually we start out with water of a good or decent quality but after we have used it, it has become a polluted substance. Treating wastewater is a necessity because it is not only harmful to nature, it is also directly harmful to mankind. Many diseases are related to too low quality of water, but for sure you already know that.

The water we discharge is part of the huge cycle of water: it will become part of the groundwater or surface water – that again will be the source of our drinking water.

When do we need to treat wastewater?

To be honest, if you live with your family in a forest and there is no one else around, it’s no problem whatsoever if you do “short and long stays” behind the trees: nature will easily cope with that. So, if it is only a small amount of water – and the pollution is organic, degradable and of not too extreme concentration – there are not so many worries, as nature itself will most likely to be able to treat it.

But the reality is that most of the time we live in bigger groups: villages, towns, big cities. That is when we really need to take care of our waste, both solid waste and wastewater. As soon as the quantity grows (more people, dirtier jobs), we need to help nature and support it in order to ensure that we are not creating a downward spiral.

We have the obligation towards everybody who will be on this planet, with and after us, to make sure that we can live in an environment that is healthy. This is so all people after us can work on their prosperity, not on resolving our dirt.
As I said, it’s a matter of responsibility: the space we need for our lives is not really ours; there are future generations that will need the same space. Maybe you are in the sad position that you inhabit a place that was neglected and polluted before you got there.

But think about it: how many generations ago was that?
And how many generations before that did not inherit their ancestors’ waste problems? I believe we do not have the right to leave dirt behind...

What can we do?

In this book, we are not going to solve the problem of wastewater on a big scale. This is on the small scale, treating wastewater on location; in other words, clean it where it got dirty.
The large-scale solution – you will never hear me say that that would not be a good way because it absolutely is – calls for enormous investments, mainly in piping, concrete, energy input and big labour. And many of those investments are mainly to get the water to the communal treatment plant. That is the solution we may expect from our governments. In this book we talk about our personal responsibilities. In case you are not connected to some sewer system, what can you do yourself in order to help nature (or to help the next generations) to keep this a clean world?

One of the many possibilities we have concerning wastewater is guiding the water through a constructed wetland.
This is still mainly ’letting nature do its work’ but in an engineered environment, not in a “per hazard” discharge.
There are quite a few advantages to this system:

There are so many types of constructed wetlands! Some seventeen varieties, one might say; it is just how you look at it. But there are a few obvious main features. The most visible are the plants, whatever kind, be it swamp plants or trees, small or big. Being “planted systems” is the major connecting element of constructed wetlands.
We are not going to treat all types of constructed wetlands; on the contrary, we will only focus on one type in this manual. And that one is also defined by the fact that there is:

  1. a substrate, some sort of soil where the plants emerge from and
  2. that the water is slowly flowing through that substrate, not over it. And
  3. the fact that we will use gravity only for the water transportation.

There are also invisible main features about constructed wetlands: the mentioned vegetation has roots, to take up the nutrients that they need (and usually wastewater has plenty of that). And then there are the micro-organisms.
Most of them are way too small to see.
But they are the ones we built the wetlands for, actually: they are our invisible helpers! Many kinds of bacteria live and thrive in the soil of the constructed wetlands and they transform the pollution. That is actually the part of the water we needed to get rid of after we used it. And to be even more exact about how wetlands work, it’s the combination of chemical, physical and microbial processes.

Now you might say two things:

  1. But bacteria were among the main problems in the untreated wastewater, right? Bacteria and viruses where the ones causing illness and disease.
  2. If these micro-organisms are so powerful in degrading our waste components – and they live in the soil – why then build constructed wetlands?

I think these are good questions.
So, about a): There are so many species of micro-organisms; some are harmful to us and some are not. But they all have their function in this world. Many of the viruses and bacteria that cause diseases live and thrive in our wastewater, especially water that was in contact with faecal matter.
So these micro-organisms will enter the wetland but that’s it, then the vast majority will die there. Mostly because that is not their favourable environment and partially because other organisms like them for dinner: the pathogens will meet predators in the wetland, too.

How do we know?

There are so many scientists involved in the world of constructed wetlands, there are already over seven decades of research by, nowadays, thousands and thousands of scientists, professors and students. We have come a long way and learned a lot about what is going on in the soils.
And that brings us to b): Constructed wetlands do not provide so much new. But if you understand what nature does, or which natural processes are going on in the soil, then you can create the circumstances in which you can facilitate nature in doing what she can.
Constructed wetlands are systems that give a turbo-boost to the micro-organisms we need in the process of cleaning wastewater.
This book is for those who agree with the necessity, acknowledge their responsibility, trust the findings of the scientists and who are on the verge of saying, “Okay, I get it. What can I do?”

How are we going to do it?

With the technique that is explained here we hope to help you improve your direct environment. That is what this book is about: treating your wastewater. It tells about the most basic system, suitable for the domestic level and small company level.
And by the way, that is why it also needs to be followed up by a workbook on “Constructed Wetlands, Vertical Flow” to get a more complete view on the matter. It is my intention to write more workbooks because at my company ECOFYT we also gained experience with larger scale solutions and more complex systems. But I think it is always smart to start small.

In this workbook we are going to tell you about the Horizontal Flow Constructed Wetland (HFCW). Some people use the words Treatment Wetland instead of Constructed Wetland. It is also called a Subsurface Horizontal Flow Wetland (SSHF) to indicate that the water should not run over the surface but through the filter media (the substrate). And, more specifically, in this manual we are talking about the version that is gravity based, specifically for locations where electricity is missing, scarce or too unreliable. So this manual is about a water treatment system without the use of pumps.
In the following pages we are going to explain the process in simple, easy-to-follow steps. Any Constructed Wetland project has 6 main steps:

  1. Determine the specifics of the wastewater you want to treat
  2. Calculate and design
  3. Prepare for the construction
  4. Actual construction
  5. Aftercare
  6. Maintenance

And thus you will find these chapters in this manuscript.
Enough about the necessity now, enough about the moral. I enjoy rolling up my sleeves and getting the job done. May I invite you to enter the world of the Constructed Wetlands?

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