LIFE PureAgroH2O – Pilot operation of innovative photocatalytic nanofiltration technology for pollutant removal and water reuse of agro-industrial effluents.
The agro-food industry is the main manufacturing industry in Europe, representing 14% of the total turnover, more than 836,000 million euros. Most processing operations steps in agro-industry are water-based with the food and drink industry accounting for approximately 1.8% of Europe’s total water use and ranked third in water consumption rates between industries. The absence of wastewater management in the agro-industry can lead to potential ecological ramifications including environmental pollution, water quality deterioration and resource depletion. Amongst the primary areas of concern is the existence of micropollutants, especially pesticides, in the spent process wastewater. Micropollutants (industrial chemicals, pharmaceuticals, endocrine disruptors, biocides, pesticides, hormones) have emerged as a new class of bioactive and persistent contaminants, that cannot be fully eliminated in conventional wastewater treatment plants (WWTPs). Novel end-of-pipe solutions that remove micropollutants before wastewater effluents reach a WWTP and simultaneously allowing for on-site water reuse are needed.
To address this challenge the LIFE PureAgroH2O project (LIFE17 ENV/GR/000387) aims to develop and demonstrate, at industrial scale, a novel purification system for the sustainable management of wastewater effluents generated in the Fruit and Vegetable industry, the prevention of losses of various inorganic and organic contaminants to the environment and the recycling and reuse of the purified water. To achieve these objectives, a close-to-market, patented water purification system with the ability to effectively recycle 15 m3 per day of Agro-wastewater will be developed, demonstrated and commercialised in Greece. Installed at a Greek Fruit and Vegetable processing industry for pesticides removal in Greece, the system will also be tested at a second case study site in Spain.
The LIFE PureAgroH2O Technology
The innovative technology developed in this project integrates synergistically the most effective micropollutant abatement technologies, photocatalysis and nanofiltration, in one smartly designed membrane reactor module.
Treatment principles of the Photocatalytic Nanofiltration Reactor (PNFR)
The PNFR includes advanced photocatalytic monoliths and porous polymeric fibres- TiO2 based photocatalysts (VLA) – which have been verified to effectively eliminate organic substances from wastewater.
The highly innovative aspect of the reactor design is that it achieves remote irradiation of the monolith’s shell and lumen photocatalytic surfaces while conducting the tangential flow nanofiltration process. Advanced optical technologies such as bundles of side glowing optical fibres coupled with arrays of high-power LEDs and Fresnel lenses effectuate the photocatalytic action. Further enhancement of the photocatalytic effect is achieved by incorporating additional flow channels in the shell side of the monoliths and hosting and effectively irradiating polymeric fibres with TiO2 powder embedded into their matrix (TiO2 based mixed matrix fibres (Ti-MMFs).
The novelty of the PNFR reactor is to be found in the synergetic effect of photocatalysis and nanofiltration (NF) in a combined reactor with photocatalysis improving the NF effectiveness and operation capabilities, whilst nanofiltration enhances the photocatalytic effect. Indeed, one of the main disadvantage of nanofiltration (NF) is the generation of a retentate effluent that is always more concentrated in micropollutants than the feed. As NF must be operated at constant pressure (flow and concentration), the retentate cannot be recycled back to the feed. This means that about 50% of the treated water cannot be reused and more importantly must be disposed-off with special and costly approaches due to the potential toxicity of micropollutant they contain. The PNFR technology overcomes this issue since rejected pollutants are subject to oxidative degradation on the multiple photocatalytic surfaces. Consequently, the retentate effluent becomes less concentrated and can be recycled back to the feed stream. Under these conditions of continuous recycling about 95% of the feed water can be cleaned and reused. In addition, small micropollutant molecules that pass through the pores of the NF membrane are oxidatively degraded on the photocatalytic surface at its lumen side. Therefore, with the synergetic action of photocatalysis, the micropollutant abatement capacity of the NF process is enhanced, covering a broader range of small compounds.
The deposition of TiO2 thin coatings on the monolith’s surface also increases the membrane permeability due to photoinduced hydrophilicity effects. Part of this photocatalytic coating is implanted into a short depth inside the large pores of the substrate acting as turbulent flow promoter. While water and small micropollutants cross the membrane, the flow of water becomes turbulent, causing a better mixing with the micropollutant that enhances the photocatalytic effect.It should also be noted that the reactors configuration limit membrane fouling limited since most of the fouling prone substances are photocatalytically degraded upon their attachment on the membrane surface.
Prospects for future applications of the PNFR technology.
Photocatalysis is much more efficient than ozonation, offering a very high surface area for micropollutants to be adsorbed and subjected to sequential oxidative degradation stages and results with a lower THMFP (trihalomethanes) formation potential compared to the ozonation process. Granular activated carbon (GAC) ﬁltration and powdered activated carbon (PAC) adsorption have showed a mitigated efﬁciency depending on the micropollutant and the frequency of regeneration/replacement. Therefore, WWTPs can be retrofitted with the PNFR, providing an advanced treatment method, which does not depend on the type of micropollutant to treat, does not require frequent regeneration, operates in continuous flow mode, does not need intensive post treatments for the abatement of by-products and has the capacity to recover the 95% of the wastewater effluent for reuse. Since the PNFR technology operates primarily as a nanofiltration (NF) process, one of the main challenge is to control membrane fouling by selecting the best pre-treatment methods based on the industrial wastewater characteristics. Having established the pre-treatment requirements (a combination of coagulation- flocculation – sedimentation and PAC), additional applications could include treatment of wastewater from the washing of the spraying machinery, phytosanitary treatments equipment and containers of agricultural chemicals; greywater from hotels, public building and houses; taste and odour abatement in drinking water and treatment of effluent of anaerobic fermentation in biogas production and recycle the water.
Benefits for the Industry
Key benefits of the PNFR technology for industrial end-users includes for example:
- No wastewater handling costs (e.g. tankering)
- Reduction of carbon emissions (and the incurred costs) as a result of improved wastewater management.
- Significant reduction of the annual cost for freshwater usage.
- Better water quality resulting in an improved product quality .
- Multiple benefits for industries that make sustainability a key consideration in the delivery of their goods and services and strive to minimize the production of harmful chemicals, excess materials, and waste.
- Socio-economic benefits in the region where the industrial end-user is situated.
- Development of new job opportunities including high-quality researchers/staff in new work positions in the sectors of water industry and environmental technologies.
- Promotion of the strategy in investing on new technologies, proving that the targets of quality, competitiveness and environmental protection are in line with the EU policies for the environment.
- The Benaki Phytopathological Institute, coordinator
- National Centre for Scientific Research “Demokritos” (NCSR Demokritos)
- Agricultural Cooperative of Zagora-Pilio (Zagorin)
- Universidad de Almeria /CIESOL
Company collaborating with Universidad de Almeria:
- Citricos del andarax, s.a.
The LIFE PureAgroH2O project is undertaken “With Contribution of the LIFE Programme of the European Union”
For further information on the LIFE PureAgroH2O project:
Dr George Romanos
Research Director at NCSR “Demokritos”, Athens, Greece.