Fraunhofer Institute for Surface Engineering and Thin Films IST
Water-purification technology enabling the use of wastewater for irrigation purposes
Challenge
The provision of clean water is one of the most important global challenges and is being considerably intensified as a result of climate change. In order to be able to utilize clear water from wastewater treatment plants as an additional source of water for irrigation, it must be purified of organic micropollutants, such as pharmaceutical residues, which would otherwise accumulate in field crops or in the environment.
Solution
SERPIC tested a novel technology as a fourth purification stage with the aim of reducing micropollutants and pathogens. A nanofilter was utilized in order to generate a pollutant-free permeate stream, which was used for irrigation after being disinfected using electrolytically created ozone gas. The pollutants were then concentrated in the concentrate stream and degraded by means of UV-excited electrochemical oxidation with electrolytically generated persulphate. The oxidants ozone and persulphate were created highly efficiently in electrolyzers with the aid of diamond electrodes. A prototype plant in Ciudad Real was utilized in order to verify the irrigation suitability of the purified water on test fields.
Added value
The targets for the removal of micropollutants and pathogens were achieved to 92%. This represents a new multi-barrier technology at TRL 5 that can be utilized for the re-use of process water for irrigation in accordance with EU regulations. The electrolytic generation of ozone gas for disinfection has proven to be an energy-saving alternative to the customary generation of ozone gas from oxygen or air.
Insights into the project
SERPIC technology achieved almost all targets for the reduction of micropollutants and pathogens; VNLX: venlafaxine, DIC: diclofenac, SMX: sulfamethoxazole, IOP: iopromide, E. coli: Escherichia coli, sul1: antibiotic resistance gene, TC: total coliform.
The individual components were assembled to form the prototype plant in Ciudad Real and subsequently field-tested.
The Fraunhofer IST carried out flow simulations to optimize persulfate production in the electrolytic cell.
SERPIC process chain: Route A is used to irrigate crops, route B is released into the environment.
Funding reference
The authors would like to thank the EU and Bundesministerium für Bildung und Forschung, Germany, Ministero dell’Università e della Ricerca, Italy, Agencia Estatal de Investigación, Spain, Fundação para a Ciência e a Tecnologia, Portugal, Norges forskningsråd, Norway, Water Research Commission, South Africa for funding, in the frame of the collaborative international consortium SERPIC financed under the ERA-NET AquaticPollutants Joint Transnational Call (GA Nº 869178). This ERA-NET is an integral part of the activities developed by the Water, Oceans and AMR Joint Programming Initiatives.
