Session 37 - Water treatment

TiO2 photocatalysis offers an attractive alternative to conventional water treatment technologies leading directly to the degradation of organic pollutants, compared to transferring them from one phase to another as in the case of membranes or activated carbon. There is an increasing interest on using photocatalysis for water treatment, rendering reliable evaluation of performance of the catalytic materials necessary. Methods for testing photocatalysts used in water treatment are generally not harmonized. Two ISO standards are available for assessing the photocatalytic activity of surfaces with regards to water purification, which are based on the photo-bleaching of methylene blue and the oxidation of DMSO, respectively. A new European standard for assessing the photocatalytic activity of materials has been developed and is under publication by the European Committee for Standardization, CEN TC386/WG3. Evaluation of the performance of photocatalytic materials in water purification is based on measurement of phenol degradation with UV irradiation under controlled conditions. The proposed standard method is applicable to materials in the form of powders (suspensions in water, slurries). İn this study, the new CEN standard test will be presented, while its differentiation from the existing ones, its applicability and the process followed for its validation, will be discussed.

Session: 37, Room: A, at Sat, 09/07/2019 - 10:00 to 10:15
Oral presentation in Water treatment

Homogeneous photocatalytic processes are receiving increased interest with regards to drinking water treatment for emerging pollutants. Especially the UV/Cl2 technique has a potential for real large-scale applications as it can combine disinfection with chemical oxidation using processes that are more familiar and widely applied by water supplies. However, more research is needed to understand the complex mechanisms involved, including formation of hydroxyl and chlorine radicals among others, as well as overall performance against various groups of emerging pollutants, such as the less-studied water taste and odor compounds (T&O). We present results on the UV/Cl2 degradation of β-cyclocitral as a model of common cyanobacterial nor-carotenoid T&O in water. The study was conducted using a novel photoreactor set-up with custom-made UV-LED arrays, precise control of irradiance, continuous spectrophotometric – GC/MS monitoring and sensory evaluation of the process. Effects of key process parameters i.e. irradiance, concentration of Cl2 and β-cyclocitral, water matrix (ultrapure and typical drinking water) on the kinetics as well as key degradation products and proposed pathways are presented. Effectiveness, efficiency and prospects of real applications of UV/Cl2 for removal of hazardous T&O from drinking water are discussed.

Session: 37, Room: A, at Sat, 09/07/2019 - 10:15 to 10:30
Oral presentation in Water treatment

We describe the deployment of a novel water purification technology, which was initially conceptualized in the context of a readily successful FP7 project (CLEAN WATER, Grant Agreement no 227017, 2009-2012) and is now in the progress of been upgraded and upscaled thanks to the grants awarded by a LIFE Environment and Resource Efficiency project (LIFE PureAgroH2O, LIFE17 ENV/GR/000387, 2018-2021). The technology is currently recognizable with the term “Photocatalytic Nanofiltration Reactor” (PNFR) and combines in a synergetic way the processes of nanofiltration (NF) and photocatalysis in a single-stage, targeting to the complete elimination of pesticides and other organic and inorganic (heavy metals) pollutants from the wastewater of the Fruits & Vegetables Industry (F&VI) and to the reuse of 15 m3 of treated water on a daily basis.

Session: 37, Room: A, at Sat, 09/07/2019 - 09:30 to 09:45
Oral presentation in Water treatment

Novel ternary catalysts TiO2/CoFe2O4/Ag with variable ferrite content were synthesized, characterized and used for the photocatalytic reduction of Cr+6 pollutant, under UV and visible light illumination. Both TiO2 and CoFe2O4 were synthesized using the sol-gel method followed by hydrothermal treatment to prepare TiO2/CoFe2O4 (TCF) composite. Silver nanoparticles were successfully loaded on the surface of TCF to get three different composites, named as Ag/TCF. The crystal structure of the composites was analyzed by application of physicochemical characterization techniques. The presence of pure anatase phase TiO2, cubic CoFe2O4, and silver nanoparticles was indicated in both XRD patterns and Raman spectra. It was found that the addition of silver nanoparticles has a great contribution to the photocatalytic reduction of Cr+6 species. The photocatalytic reaction mechanism was studied by applying scavenging reaction process, revealing that electrons were strongly supported for the photocatalytic reduction of Cr+6. After the photocatalytic experiments, the composite catalyst can be easily separated from the reaction solution by external magnetic bar and re-used.

Session: 37, Room: A, at Sat, 09/07/2019 - 09:45 to 10:00
Oral presentation in Water treatment
[CEST2019_00437] Susceptibility of Algal Toxins to Advanced Oxidation Processes
by Dionysiou D., Duan X., Kong M.

Harmful algal blooms (HABs) occur more frequently and severely in recent years due to the climate change and increasing nutrient inputs, causing higher potential for the algal toxins to enter drinking water supplies. When HABs formation is intensive, conventional water treatment is insufficient to remove those toxins, so that further advanced technologies are necessary to be added. In this presentation, Professor Dionysiou will give an overview of recent progress in the destruction of several algal toxins, such as microcystin variants (MCs) and cylindrospermopsin, using light-based advanced oxidation processes (AOPs). The discussion will focus on the kinetics and transformation pathways of the destruction by hydroxyl radical, sulfate radical, chlorine related radicals, and other reactive species generated in various AOPs. The role of the specific amino acids in the reactivity of the MCs will be emphasized. The effect of solution co-contaminants in field water samples will be presented with the focus on identifying parameters that play important roles in process performance and oxidation pathways. Finally, coupling of AOPs with conventional technologies for the removal of algal toxins will be showcased, considering also potential application of some of these technologies in a treatment plan.

Session: 37, Room: A, at Sat, 09/07/2019 - 09:00 to 09:30
Oral presentation in Water treatment