PHOSPAQ™

Phosphorus needs to be removed before industrial facilities can discharge wastewater or recycle it. Public water facilities also need a phosphate filter to transform sewage into drinking water. That’s because effluent from anaerobic reactors can still contain low levels of phosphate, BOD and ammonia. The PHOSPAQ™ post-treatment process removes biologically degradable COD, phosphate (PO43-) and ammonium (NH4+) from wastewater. It takes place in an aerated reactor, which provides optimal conditions for biological conversion of COD and quality struvite formation.

As phosphate becomes scarce, phosphorus recovery becomes more commercially interesting. PHOSPAQ™ allows facilities to harvest commercial phosphate. Struvite is an excellent slow-release, EU-approved fertilizer. Compared to e.g. dosing of iron salts, PHOSPAQ™ is a more cost-effective technology for phosphorus recovery.

The PHOSPAQ™ process takes place in an aerated reactor. Aeration provides the oxygen for the biological conversion of COD and provides optimal conditions for struvite formation. Stripping of carbon dioxide raises the pH and stimulates struvite precipitation.

Magnesium oxide is added to remove phosphate that is recovered by precipitation as struvite at a pH of 8.2 to 8.3. The PHOSPAQ™ reactor is equipped with separators that retain the struvite.

The struvite is harvested from the bottom of the reactor by means of a hydrocyclone, followed by a screw press and transferred into a container. The dry weight of the harvested struvite is around 50% and the crystals have an average size of around 0,7 mm.