Settlement as struvite

One of the methods used to remove phosphate from the waste water is to allow the phosphate to settle as struvite (MgNH4PO4, also known as Magnesium-Ammonium-Phosphate) with magnesium and nitrogen. This requires the addition of magnesium salt. Struvite can be used to produce fertiliser.

The advantage of this method is that struvite is fairly easy to shape. However, there are also disadvantages. Struvite is frequently contaminated, particularly with metals and medicines. The method is also quite costly. The required installation is expensive and the addition of magnesium costs money. The income, on the other hand, is relatively small. Approximately 25 to 50% of the phosphate is still lost. The proportion of nitrogen-phosphate in the fertiliser that is eventually produced is fixed. This made it more difficult to sell because farmers want to alter these proportions depending on the soil and the crops for which the artificial fertiliser is used.