Structure
There is so much to tell about the construction of constructed wetlands...
The structure of the most applied type
The construction of a Constructed Wetland
The structure of constructed wetlands is basically a sand or gravel filled body that works as a filter and is planted with macrophytes or helophytes; another word for bog plants, plants that grow in shallow water, rooting in the soil and protruding above the water with stem and inflorescence. Examples of helophytes are: reed, bulrush, rushes, sedge, yellow flag, etc.
Reed is usually used in our constructed wetlands, because this plant is resistant to heavy or varying (chemical) loads. In addition, reed plants root very deeply.
Step-by-step
During construction, an area of a few square meters will be excavated to over 1.2 meters deep.
An area of 3 to 5 square meters is required per person (for domestic waste water).
The excavated part is sealed from below and sideways with a special strong foil.
The next steps are:
- laying drainage pipes,
- filling this layer with gravel,
- laying root cloth,
- fill with our carefully formulated mix of sand, straw, limestone and iron particles,
- making the infiltration system,
- finish with gravel.
- Finally, the system can be planted with young reed plants.
In principle, a constructed wetland for wastewater purification is always preceded by settling wells. One for the toilet water, also called the black water, this is the septic tank. Another well is for the soapy water, usually called gray water. This pit is called the grease trap. After these two wells, the waste streams come together in the pumping station.
From there, by means of a pump, the reed bed is irrigated with wastewater twice a day, in just a few minutes at a time.
The drainage of the constructed wetland flows into a control pit, so that the quality of the purified water can be assessed, visually or by means of a chemical analysis.
The water can be drained from the control pit to a ditch or into the ground. Or to a pumping station so that the purified water can be reused. Because the water is clean, clear and odorless, it can, for example, be used for flushing the toilet. In this way, almost a third of total water consumption can be saved annually. The purified water can also be reused for other purposes, such as scrubbing water or for spraying the garden.
It is very difficult to give a price indication of a helophyte filter. This is highly dependent on the situation on site. Factors that influence the construction costs are for example:
- The distance from the house to the reed field
- The size of the household / amount of waste water
- The nature of the wastewater
- The presence of a (good) septic tank / grease trap
- The nature of the substrate
- The height of the groundwater level
- It doesn't necessarily have to be Turn Key…
At ECOFYT it is possible that you only ask us to make a design - or to supply a kit - and possibly receive guidance during construction.
We can also realize the most critical parts of the system (filling the filter bed, electronics for the pump, or the irrigation system), taking care of the rest of the work for you.