Specialist Group on Use of Macrophytes in Water Pollution ... - IWA

And what is the best suitable solution? So – though the emphasis lies on VF – we designed
HF and SF (Surface Flow) or FEM (Floating Emergent Macrophyts) systems - as we pleased.
Or as it pleased us.
But to come back to the true item of this topic, basically, the Dutch constructed wetlands (for
waste water, that is) looks like this:
From top to bottom we have:
1. the visual part: the macrophytes (commonly reed);
2. a gravel bed in which lie the main pressure pipe with its side branches;
3. the actual substrate being fine sand (usually a D50 of a quarter millimeter); and finally
4. at the bottom, below a root cloth, a gravel layer with drains and a connection pipe ...
off to the surface water!
In this top layer of (round) gravel, in which the pressure pipes are hidden, water is injected
per every square meter… (And when the pump switches on, water is divided, over the entire
surface, through the gravel, when the pump switches off, gravity makes the water to travel
through the sandlayer). The gravel layer being thick enough to store the waste water in its
pores: no puddles, no smells ...
The actual working body consists of 1 m of fine sand ...
We may use calcium carbonate and iron (in small sparticles) to try to bind phosphorous. And
straw, as a carbon source for denitrification. Commonly we use 1 mm PE lining for water
tightness. And some have artificial water levels in their systems, others just run dry.
And in case you want to know something about the performances, I have some figures…
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14 IWA <strong>Specialist</strong> <strong>Group</strong> on Use of Macrophytes in Water Pollution Control: Newsletter No. 37