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Wastewater treatment plants can become sustainable biorefineries

In the future, wastewater treatment plants can have a broader function by being converted into biorefineries. Researchers in Resource Recovery at the University of Borås, Sweden have plans to validate a new concept in which they produce and extract fatty acids using membrane bioreactors, which in turn are used to produce the substances acetic acid and hydrogen.

The “Tuvan” municipal wastewater treatment plant (WWTP) in Skellefteå, Sweden has also a co-located dedicated food waste biogas plant. The shared facilities, all post-digestion, include biogas storage, upgrading, compression, and flare.

All of the world’s wastewater treatment plants (WWTP) produce large quantities of sewage sludge, that along with food waste is often used to produce biogas via anaerobic digestion (AD). However, in many cases biogas competes with other renewable energy types, such as wind and solar power, which can make the production of biogas alone a limiting factor for a WWTP.

But with our technology, we can develop a platform so that the treatment plants can be transformed into refineries where different chemical substances can be extracted and used to produce different types of materials. Fatty acids are a kind of intermediate product, explained Mohammad Taherzadeh, Professor in Bioprocess Technology, who heads the project.

At the University of Borås, different kinds of membranes are being developed. Their function in the bioreactor is to allow various chemical substances to pass through and at the same time ensure that the microbes used in the processes are retained in the bioreactor and not flushed away.

In the future, WWTPs can have a broader function by being converted into biorefineries for the production of everything from biogas to different new materials.

Fatty acids can be further processed

Researchers in Resource Recovery at the University of Borås, Sweden have plans to validate a new concept in which they produce and extract fatty acids using membrane bioreactors, which in turn are used to produce the substances acetic acid and hydrogen.

Fatty acids have a function similar to that of sugar in various petrochemical and biological processes, namely, as sustenance for the microbes used in the processes. The successful production and extraction of fatty acids allow for further processing of these substances to other products, such as bioplastics or butanol.

The amount of sewage sludge remaining in the process can be used as a substrate in a biorefinery.

Another feature of the method is that carbon contained in the sludge can be extracted, and therefore there can be a circular process in which the carbon is used to remove nitrogen and phosphorus from the wastewater to avoid eutrophication in recipients. Today, treatment plants purchase large quantities of carbon for this process.

The project is ongoing until the end of Ma, 2019, and is being financed by Sweden’s innovation agency, Vinnova. It is being carried out in collaboration with the waste management and wastewater treatment companies Gryaab and Renova AB. In Sweden, there are about 400 WWTPs.

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