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Lysophos® – P-Recovery at WWTP's instead of Mining

a patented process for Phosphorus recovery prior to anaerobic digestion

The Challenge

Recovering limited resources

Next to nitrogen, phosphorus is the most important nutrient element for plants and animals, and for us humans. It is essential for all life and as such cannot be replaced. Although phosphorus is abundant in the earth's crust, there are few ways to extract it on earth. Much of the production is concentrated in China, USA and Western Sahara, so there is a heavy dependence on these few countries. Most of the phosphates mined go into fertiliser production. The limited phosphorus deposits are also contaminated with uranium and cadmium. Mining reduces the deposits irretrievably, which is not sustainable.

CNP's Solution

Lysophos® – P-Recovery with thermal hydolysis

Thermal hydrolysis before aaerobic digestion enables the polyphosphate bound by Bio-P to be dissolved back as far as possible. The hydrolysed sludge is dewatered so that most of the redissolved phosphate is in the centrate. With the addition of ammonium in the form of e.g. centrate water from the dewatering after digestion, the precipitation of the ortho-phosphate as struvite takes place.

After separation of the struvite, the phosphate-depleted centrate is partially or completely remixed with the pre-dewatered sludge and fed to the digestion. The hydraulic load on the digester can be reduced by increasing the TR in the influent if the sludge is only partially remixed with centrate.

Advantages

High-efficiency P-recovery and digester protection

  • Patented process
  • Centrate serves as ammonium source for struvite crystallisation
  • Higher P yield due to centrate recycling
  • P recycling with yields >50% achievable
  • Significant reduction of the struvite problem in the digester
  • Increased performance capacity of the digestion plant due to higher DS
  • Simple and proven technology
  • Recovery of high-quality struvite