Review on the management of water quality for bio-mineral swimming pools in Western Europe.

In this review, we depict the state of the art concerning the water quality management of bio-mineral bathing pools, and compare these to traditional swimming pools. Bio-mineral pools use a combination of mechanic filtration, bio-filtration, and UV-treatment to disinfect the water. Studies in test tanks have shown that bio-filtration is effective in maintaining the water quality with regard to the treatment of organic pollution. Concerning biological risks, the bio-mineral pool relies on UV-treatment to degrade bacteria. Unlike chemical disinfectant treatments, UV disinfection does not lose its effectiveness in the event of high traffic in the pool. However, as only the water taken up by the filtration system is disinfected, it is essential that all the water in the pool is filtered. If the pool has a dead zone, its water is not disinfected and there is a risk of localized pathogen development. As the development of bio-mineral pools spreads in Europe, legislation gradually follows. The health parameters measured differ slightly from one country to another, but there are constants: the measurement of Escherichia coli, Enterococci, and Pseudomonas aeruginosa. In terms of biological swimming pools, regulatory homogeneity across Europe does not exist. From these comparisons, Austrian legislation segmenting water quality into 4 categories ranging from "excellent" to "poor" represents legislation that combines health and safety with indications of possible malfunctions. Next, a study of three real sites of bio-mineral pools is presented. It appears that whatever the type of pool, bio-mineral filtration makes it possible to achieve performances comparable to those encountered in chlorinated swimming pools concerning the risks associated with fecal contamination and external pollution. On the other hand, when frequentation is high, as is the case in small pools used for aquafitness, monitoring the risks of inter-bather contamination, as illustrated by the presence of Staphylococcus aureus, reveals a recurring problem. Knowing that this parameter is not evaluated in bathing waters in the natural environment and that numerous studies show that Staphyloccocus aureus are always detected, even on beaches, we propose the definition of three thresholds: i.e., 0 CFU/100 mL (threshold value in Wallonia) for water of excellent quality, less than 20 CFU/100 mL (threshold value in France) for water of very good quality, less than 50 CFU/100 mL (contribution of bathers by simple immersion) for good quality water, and more than 50 CFU/100 mL for poor quality water. This document could therefore be converted into a manual for operators on the use and management of bio-mineral baths.

Functionalization of Mono- and Bimetallic MIL-100(Al,Fe) MOFs by Ethylenediamine: Postfunctionalization, Brønsted Acido-Basicity, and Unusual CO2 Sorption Behavior.

The metal sites of MIL-100(Fe), MIL-100(Fe,Al), and MIL-100(Al) metal-organic frameworks (MOFs) were decorated with ethylenediamine (EN). Interestingly, the Al-containing MOFs presented hierarchized porosity, and their structural integrity was maintained upon functionalization. Solution and solid-state NMR confirmed the grafting efficiency in the case of MIL-100(Al) and the presence of a free amine group. It was shown that MIL-100(Al) can be functionalized by only one EN molecule in each trimeric Al3O cluster unit, whereas the other two aluminum sites are occupied by a hydroxyl and a water molecule. The -NH2 sites of the grafted ethylenediamine can be used for further postfunctionalization through amine chemistry and are responsible for the basicity of the functionalized material as well as increased affinity for CO2. Furthermore, the presence of coordinated water molecules on the Al-MOF is responsible for simultaneous Brønsted acidity. Finally, the Al-containing MOFs show an unusual carbon dioxide sorption mechanism at high pressures that distinguishes those materials from their iron and chromium counterparts and is suspected to be due to the presence of polarized Al-OH bonds.

Advanced photocatalytic oxidation processes for micropollutant elimination from municipal and industrial water.

The objective of this study was to develop and validate an innovative technology to ensure efficient elimination of different types of micropollutants and toxic compounds in waste water. The process is a tertiary treatment process, which can be easily integrated into municipal and industrial waste water treatment plants. It is based on oxidation by ozone and subsequent photocatalytic treatment. After development and validation of this system at laboratory scale, the solution was tested at pilot scale. The first part of this work was to develop a TiO2-based film on glass substrate, characterize its physico-chemical properties and optimize its composition at laboratory scale to be photoactive on the degradation of model water containing several pollutants. The model water consisted of a mixture of 22 major micropollutants including pesticides, plasticizers, brominated compounds, and pharmaceuticals. The best photocatalyst for the degradation of the selected micropollutants was a TiO2 coating doped with 2 wt% of Ag and where 10 wt% P25 was added. Then, in order to scale up the process, its deposition on steel substrates was tested with dip and spray coating at laboratory scale. Calcination parameters were optimized to limit steel corrosion while keeping similar photoactive properties regarding the degradation of the model polluted water. The optimized solution was deposited by spray coating in a pilot scale reactor in order to assess its efficiency in a pilot water treatment plant.

Green Chemistry for the Transformation of Chlorinated Wastes: Catalytic Hydrodechlorination on Pd-Ni and Pd-Fe Bimetallic Catalysts Supported on SiO2.

Monometallic catalysts based on Fe, Ni and Pd, as well as bimetallic catalysts based on Fe-Pd and based on Ni-Pd supported on silica, were synthesized using a sol-gel cogelation process. These catalysts were tested in chlorobenzene hydrodechlorination at low conversion to consider a differential reactor. In all samples, the cogelation method allowed very small metallic nanoparticles of 2-3 nm to be dispersed inside the silica matrix. Nevertheless, the presence of some large particles of pure Pd was noted. The catalysts had specific surface areas between 100 and 400 m2/g. In view of the catalytic results obtained, the Pd-Ni catalysts are less active than the monometallic Pd catalyst (<6% of conversion) except for catalysts with a low proportion of Ni (9% of conversion) and for reaction temperatures above 240 °C. In this series of catalysts, increasing the Ni content increases the activity but leads to an amplification of the catalyst deactivation phenomenon compared to Pd alone. On the other hand, Pd-Fe catalysts are more active with a double conversion value compared to a Pd monometallic catalyst (13% vs. 6%). The difference in the results obtained for each of the catalysts in the Pd-Fe series could be explained by the greater presence of the Fe-Pd alloy in the catalyst. Fe would have a cooperative effect when associated with Pd. Although Fe is inactive alone for chlorobenzene hydrodechlorination, when Fe is coupled to another metal from the group VIIIb, such as Pd, it allows the phenomenon of Pd poisoning by HCl to be reduced.

Advanced oxidation processes for waste water treatment: from laboratory-scale model water to on-site real waste water.

A process combining three steps has been developed as a tertiary treatment for waste water in order to remove micropollutants not eliminated by a conventional waste water treatment plant (WWTP). These three processes are ozonation, photocatalysis and granulated activated carbon adsorption. This process has been developed through three scales: laboratory, pilot and pre-industrial scale. At each scale, its efficiency has been assessed on different waste waters: laboratory-made water, industrial waste water (one from a company cleaning textiles and another from a company preparing culture media, both being in continuous production mode) and municipal waste water. At laboratory scale, a TiO2-based photocatalytic coating has been produced and the combination of ozonation-UVC photocatalytic treatment has been evaluated on the laboratory-made water containing 22 micropollutants. The results showed an efficient activity leading to complete or partial degradation of all compounds and an effective carbon for residual micropollutant adsorption was highlighted. Experiments at pilot scale (100 L of water treated at 500 L/h from a tank of 200 L) corroborated the results obtained at laboratory scale. Moreover, tests on municipal waste water showed a decrease in toxicity, measured on Daphnia Magma, and a decrease in micropollutant concentration after treatment. Finally, a pre-industrial container was built and evaluated as a tertiary treatment at the WWTP Duisburg-Vierlinden. It is shown that the main parameters for the efficiency of the process are the flow rate and the light intensity. The photocatalyst plays a role by degrading the more resistant micropollutants. Adsorption permits an overall elimination >95% of all molecules detected.

Sol-gel Syntheses of Photocatalysts for the Removal of Pharmaceutical Products in Water.

A screening study on seven photocatalysts was performed to identify the best candidate for pharmaceutical products degradation in water. Photocatalysts were deposited as thin films through a sol-gel process and subsequent dip-coating on glass slides. The efficiency of each photocatalyst was assessed through the degradation of methylene blue first, and then, through the degradation of 15 different pharmaceutical products. Two main types of synthesis methods were considered: aqueous syntheses, where the reaction takes place in water, and organic syntheses, where reactions take place in an organic solvent and only a stoichiometric amount of water is added to the reaction medium. Photocatalysts synthesized via aqueous sol-gel routes showed relatively lower degradation efficiencies; however, the organic route required a calcination step at high temperature to form the photoactive crystalline phase, while the aqueous route did not. The best performances for the degradation of pharmaceuticals arose when Evonik P25 and silver nanoparticles were added to TiO2, which was synthesized using an organic solvent. In the case of methylene blue degradation, TiO2 modified with Evonik P25 and TiO2 doped with MnO2 nanoparticles were the two best candidates.

Highly Efficient Low-Temperature N-Doped TiO2 Catalysts for Visible Light Photocatalytic Applications.

In this paper, TiO2 prepared with an aqueous sol-gel synthesis by peptization process is doped with nitrogen precursor to extend its activity towards the visible region. Three N-precursors are used: urea, ethylenediamine and triethylamine. Different molar N/Ti ratios are tested and the synthesis is adapted for each dopant. For urea- and trimethylamine-doped samples, anatase-brookite TiO2 nanoparticles of 6-8 nm are formed, with a specific surface area between 200 and 275 m²·g-1. In ethylenediamine-doped samples, the formation of rutile phase is observed, and TiO2 nanoparticles of 6-8 nm with a specific surface area between 185 and 240 m²·g-1 are obtained. X-ray photoelectron spectroscopy (XPS) and diffuse reflectance measurements show the incorporation of nitrogen in TiO2 materials through Ti-O-N bonds allowing light absorption in the visible region. Photocatalytic tests on the remediation of water polluted with p-nitrophenol show a marked improvement for all doped catalysts under visible light. The optimum doping, taking into account cost, activity and ease of synthesis, is up-scaled to a volume of 5 L and compared to commercial Degussa P25 material. This up-scaled sample shows similar properties compared to the lab-scale sample, i.e., a photoactivity 4 times higher than commercial P25.