Filter granulates based on iron hydroxide for further phosphate removal for small waste water treatment plants

The problem

Phosphate compounds in municipal waste water promote due to their fertilizing effect the growth of algae in water bodies and therefore lead to eutrophication.
Waste water from properties that are not connected to public waste water treatment facilities have to be cleaned in a mechanical full biological small waste water treatment plant before they are allowed to be discharged into water bodies or to be drained.
The approval criteria defined by the German Institute of Construction Technology (DIBt) for further phosphorus elimination (cleaning class “+P”) for small water treatment plants is c ≤ 2 mg P/l in the water outlet. Currently only very few decentralized small waste water treatment plants feature additional phosphorus elimination to ensure this concentration in domestic waste water.

The solution

Our product FerroSorp® AW can be used as an efficient, inexpensive solution for further phosphorus elimination in waste water treatment and can easily be retrofitted. The use of FerroSorp® AW not only minimizes the entry of phosphorus into water bodies but also provides the possibility to recycle the phosphorus for agriculture purposes and thus close the natural phosphorus cycle.

The method

Figure 1: Principle - further phosphate elimination from municipal waste water in combination with phosphorus recycling

Dissolved phosphate ions in mechanically and biologically pretreated waste water are first adsorbed to the surface of FerroSorp® AW and thus eliminated from the water. High adsorption capacity can be maintained by a subsequent chemical regeneration of the filter granules. At the same time adsorbed phosphorus is recycled and can be used as fertilizer or secondary raw material for the fertilizer industry.


With the newly developed product FerroSorp® AW phosphorus can be completely removed from the water outlet of small water treatment plants and thereby eliminate the water hazard it represents. Additionally phosphate can be recycled and made available for agricultural purpose. The application of FerroSorp® AW presents the opportunity to conserve resources and protect the environment.
The phosphorus adsorption capacity of FerroSorp® AW depends on the waste water parameters and the basic conditions of the specific treatment plant. For each specific technological design the optimal operating conditions are derived after determining the procedural technical conditions.

Examples for applications

A particular advantage of the method suggested is that, regardless of the applied technology in the small water treatment plant (SBR-plant, activated sludge treatment, fixed bed system, MBR-plant, sprinkle filter plant, etc.) phosphate can be eliminated from the biologically treated water.
From current view FerroSorp® AW can be used advantageously in the following applications:

Advantages at a glance

Brochure FerroSorp® AW for further phosphate elimination

Ordering of information material