After passing the constructed wetland the water is (biologically) cleaned. However, this water is yet inapplicable for greenhouse horticulture. Dissolved minerals still need to be separated from this water. This can be achieved by implementing a reverse osmosis installation in the irrigation water preparation. A micro-filter assures that the osmosis membranes don't get blocked by small particles.

The reverse osmosis installation can separate the smallest particles from the water. Under high water pressure an (osmosis) membrane separates minerals (and even germs and microbes) from the water. The product of the reversed osmosis is almost pure water. The water which retains from the reverse osmosis is highly concentrated with minerals (salt) and is transported to the sewage waste water facility.

After reaeration the end product of the reversed osmosis is applicable as irrigation water.