Piloting phosphorus recovery by RAVITA process

RAVITA is an innovative phosphorus recovery method for producing phosphoric acid from wastewater directly. Although the method is still in product development stage, a 1 000 PE technical scale pilot has been built in Viikinmäki WWTP in Helsinki.

In the RAVITA process Bio-P is not needed, as phosphorus is extracted from the chemical precipitation sludge. As the sludge is dissolved into a metal phosphate solution from which phosphoric acid produced, the precipitation chemicals are also regenerated and can be used circularly. The process is not dependant of the WWTP size and offers excellent scalability. The product, intermediates and co-products have all been analysed to measure heavy metal and organic micropollutant concentrations, which generally are significantly lower than in many other recovered phosphorus streams.

Results and next steps

In 2018 new process units were added to take the development of RAVITA process from laboratory scale to pilot scale. A large thickener with slow mixing was built and a new decanter centrifuge (Alda laval ALDEC 10) with the capacity of 1 000 L/h was acquired. The trial run of the pilot facility in Viikinmäki started in the beginning of 2020, the main emphasis on quantifying important data such as chemical and energy consumption, mass balances, costs and the quality of product and side streams. The first results of the pilot scale testing show more than 80% of phosphorus in the chemical sludge stream as recoverable, most of it is in the sludge as AlPO4 and Al(OH)3. The total recoverable phosphorus compared to incoming wastewater is around 55-60%.

Potential applications in the BSR

As the European Union moves toward a circular economy recovering materials from waste streams becomes increasingly important. EU relies heavily on imported phosphorus, wide-scale P-recovery in the WWTPs could cover 10-20% of the total need. RAVITA is one of the highly promising new solutions developed in the region with great potential for application throughout the BSR. As with most P-recovery solutions, it all comes down to financial feasibility, which can be estimated with the pilot scale testing.

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