Hands in the mud! Ecoval Sudoe completes work on pilot plant for the production of volatile fatty acids

One of the objectives of the Ecoval Sudoe project is to demonstrate the technical feasibility of producing volatile fatty acids (VFA) from urban sludge. To do this, at the Ourense Wastewater Treatment Plant (WWTP), Cetaqua has set up different tests to optimise the generation of acids such as acetic, propionic, or butyric acid from sewage sludge.

In order to determine the most suitable operating conditions for the pilot VFA production plant, different laboratory-scale tests were first carried out, such as batch tests on a 0.5L scale and the operation of semi-continuous reactors of 5L volume, which demonstrated the suitability of sewage sludge as a substrate with high potential for the production of high added value bioproducts with VFA.

The information provided at the laboratory scale has helped Cetaqua technicians to have a first approximation of the VFA production yields that can be obtained from sludge with and without pre-treatment. They were also able to analyse the effect of operating parameters such as pH, feed/microorganism ratio, hydraulic residence time, etc.

On a pilot scale, the technicians have optimised the fermentation process for the production of VFA, obtaining a stream that has to undergo solid-liquid separation, a unitary operation that has had to be perfected thanks to “jar tests” that have made it possible to determine the optimum doses of coagulant and flocculant for the division of the solid and liquid fractions. Thus, the objective of producing a liquid current rich in VFA for the partner NEREUS to study its clarification and concentration and a high-dryness solid cake that INSA will recover energetically has been achieved.

Following these tests, work is now continuing on the pilot plant which, after a start-up phase marked by hydraulic difficulties in operation and the necessary adjustments, is now operating more robustly. It will soon begin to be fed with biowaste.

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Biogroup and INSA Toulouse meet to plan joint tasks of ECOVAL

Within the framework of ECOVAL Sudoe, a meeting to discuss the impact and replicability of the project was held at the National Institute of Applied Sciences of Toulouse (Institut National des Sciences Appliquées de Toulouse) between the 13th and the 16th of July. Almudena Hospido, in representation of BioGroup (CRETUS) met with peers Mathilde Besson and Etienne Paul, on behalf of INSA Toulouse and the Toulouse Biotechnology Institute.

The main object of discussion was the work planning for joint tasks of the ECOVAL project and the activities related to the comprehensive urban organic waste management model and measurement of its social and legal impact; and the replicability and transfer of the business model and its environmental and economic assessment.

The city model of Toulouse, where the meeting was held, was also a case of study for the attendees because of its implementation of the bio-waste collection since 2019. Chloé Maisanno, head of the “Observatoire Régional des Déchets et de l’Economie Circulaire en Occitanie – ORDECO” (Regional Observatory of Waste and Circular Economy in Occitania) showed her interest in the development of the project and participated at the last session on Friday morning.

The participants concluded that the meetings were a success in achieving their objectives and took the opportunity to exchange results and approaches taken in each of the laboratories. A follow-up reunion will take place in October.