ESR05 -Claver Numviyimana- My experiences at Training School II


As part of Horizon 2020-European training Network Maria Sklodowoska-Curie Action in the project of phosphorus recovery for fertilizers from dairy processing wastes (H2020-ETN-REFLOW, grant agreement number 814258), I was part of both a project meeting and summer school at Central University of Catalonia (U-VIC) especially in its BETA-Technological center for a period of two weeks. This was from October 4 to 15, 2021 in VIC, near Barcelona in Spain.

The activity gathered people from all around Europe, including Early-Stage Researchers (ESRs),  their supervisors, the project coordinator, management committee, and lecturers of the organized summer school. The project members came from the University of Limerick (lead university, Ireland), U-VIC (training lead university, Spain), and other high learning universities including Wrocław University of Science and Technology (my host, Poland), UniLaSalle (France), Wageningen University (The Netherlands), Aarhus University (Danmark), and Chalmers University of Technology (Sweden);  European Land Owners (ELO, Belgium). Partner fertilizer and research institutions such as Grupa Azoty (Poland) and PRAYON (Belgium) were also present. All along the training and meeting, the COVID-19 pandemic regulations were observed.

Photo: Our clouded visit to Beta Technological center.

Dairy Wastes Phosphorus Recovery- A Training in Action

As this was the first physical meeting, the general introduction was presented by the Coordinator, Prof JJ Leahy from the University of Limerick, Ireland, who described the techno- scientific basis and concept of the project.

The underline was put on the use of  cheap process to accumulate phosphorus in P-rich sludge from dairy wastewater using polyphosphate accumulating (micro)organisms (POAs) and go further with anaerobic digestion coupled with the membrane filtration to have a P rich effluent usable in production of struvite, a slow nutrient release phosphorus fertilizer.

The alternative approaches of processing the P rich sludge involves their hydrothermal carbonization (HTC) and obtaining a carbon and energy dense material (Hydrochar) and a P rich liquor usable for struvite production.

In the third scenario, the P rich sludge should be dewatered, dried, and incinerated in a fluidized bed incinerator to produce a P rich ash usable in production of phosphoric acid and struvite as well. Both biosolids, ash and struvite, will make a set of biobased fertilizers from the REFLOW project. The products will be produced and studied from different work packages (WP) of the research network, where I, ESR5, belong to WP1 producing fertilizers.

Photo: Prof JJ Leahy, the project Coordinator presenting the WP1 research network

Presentation on Struvite Precipitation from Dairy Wastes. 

At the turn of ESR5, I had to present the aspect of phosphorus recovery by struvite precipitation, a presentation that reviewed existing technologies and the REFLOW novelty. While most of the technologies make a coupling of anaerobic digestion and struvite precipitation from sludge, the highlight here, are the additional technologies in REFLOW that in addition to anaerobic digestion membrane bio-reactor, we do hydrothermal processing of organic wastes with double production: A hydrochar that can serve as an energy and carbon dense material and a nutrient rich liquor that we used for struvite production.

Both final products (Hydrochar and struvite) are the major components of STRUBIAS (struvite, biochar, or ash) fertilizer. In this section, the ESR5 progress was blamestomed where the first work was to assess and minimize the effect of interfering potential inhibitors. This previously published work was presented to the audience and can be checked via (

In further steps, the sludge produced chemically was discussed for their involvement in nutrients recycling, including phosphorus and iron recycling. While there was no or limited awareness on struvite production from chemically produced sludge, we presented a case of coupling thermochemical treatment of chemically accumulated sludge to produce hydrochar and precipitate struvite from the liquor after adequate chemical extraction.

The valorization of these chemical sludge gives an optimistic image of contribution to solving the problem caused by iron based sludge. The validated research output for microelement enriched struvite from this sludge can be accessed here (

Photo: Claver Numviyiman, REFLOW-ESR5’ presenting on technological aspect of struvite precipitation.

Another research output’s release which coincided with the stay in Spain was the study of usability of clinoptilolite zeolitic material in struvite precipitation combined with ammonium sorption. This presents an interesting case of precipitation, thermodynamics, phosphorus speciation, and ammonium sorption. It can be found here (

A Visit to Beta Tech and Associated Research Sites.

A well established research center in U-Vic working on the theory into real technological practices, looked as dedicated for novelties of research in engineering on biowaste management and bioressources technologies. The move to this area was to witness the practical aspects of the science with cutting-edge installations for investigation of new possibilities of waste treatment, valorization, energy, material, and resources recovery and recycling from wastes.

Photo: A visit to a system of anaerobic membrane bio-reactor (AnMBR) for dairy waste treatment (a lab scale) featuring ESR 13

Within this, ESR2 is investigating optimum conditions for anaerobic digestion and membrane filtration to produce a freeze-dried biosolid and a P rich permeate. The P rich permeate is intended to be used for struvite production. In fact, the AnMBR process involves the breakdown of organic bound phosphorus to orthophosphate that is recuperated in a P rich effluent which, upon proper salt dosage, produces struvite.

An incredible pilot scale was found on the field site of the homologous project “FERTIMANURE”. The pilot site is located a few kilometers from Vic city, and treats swine manure by microbial digestion followed by membrane bio-reaction and filtration. Under these processes, nutrients such as ammonium are recovered under the form of ammonium sulfate, a bio-dried biosolid and clean permeates are obtained. The process conditions were optimized to recover both ammonia and phosphate under an extremely alkaline pH.


Photos: Fertimanure AnMBR pilot plant for swine manure treatment and valorization

Photos: Reflow ESRs, project manager and project Coordinator at FERTIMANURE Pilot plant

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