The limit PT concentration of the runoff is 100 µg/l to reduce the cost on one hand and to keep it as simple as possible a natural water treatment without a pump and without adding of chemicals was preferred.

Polyplan created a flow and TP model according to the local situation. This modelling was the basic for the pre - design of the water treatment.

This calculation is working with a gravity working water treatment by bio filters in the bottom of each basin.

Polyplan develloped a biological water treatment in order to keep the Total Phosphourous concentration lower than 100 µg/l. for the dimension we used a 2 Box modell as well as a the fluent modell Mike 13.

The design has been The calculation shows also that during high inflow periods the Concentration of TP can get close to the guideline value of 100 µg/l.

To ensure this limit during the live time of the constructed wetland an additional adsorber shaft behind the last treatment step is recommend. The adsorber could be connected in that way that it just get water during the high water level period inside basin 5.