Yvan Wyart

Chemical cleaning/disinfection and ageing of organic UF membranes: A review

Membrane separation processes have become a basic unit operation for process design and product development. These processes are used in a variety of separation and concentration steps, but in all cases, the membranes must be cleaned regularly to remove both organic and inorganic material deposited on the surface and/or into the membrane bulk. Cleaning/disinfection is a vital step in maintaining the permeability and selectivity of the membrane in order to get the plant to its original capacity, to minimize risks of bacteriological contamination, and to make acceptable products. For this purpose, a large number of chemical cleaning/disinfection agents are commercially available. In general, these cleaning/disinfection agents have to improve the membrane flux to a certain extent. However, they can also cause irreversible damages in membrane properties and performances over the long term. Until now, there is considerably less literature dedicated to membrane ageing than to cleaning/disinfection. The knowledge in cleaning/disinfection efficiency has recently been improved. But in order to develop optimized cleaning/disinfection protocols there still remains a challenge to better understand membrane ageing. In order to compensate for the lack of correlated cleaning/disinfection and ageing data from the literature, this paper investigates cleaning/disinfection efficiencies and ageing damages of organic ultrafiltration membranes. The final aim is to provide less detrimental cleaning/disinfection procedures and to propose some guidelines which should have been taken into consideration in term of membrane ageing studies. To carry out this study, this article will detail the background of cleaning/disinfection and aging membrane topics in a first introductive part. In a second part, key factors and endpoints of cleaning/disinfection and aging membranes will be discussed deeply: the membrane role and the cleaning parameters roles, such as water quality, storing conditions, cleaning/disinfection/aging agents/conditions/protocols. The third and last part will be developed the parameters, methods and ways of characterization at our disposal and commonly used to develop and implement membrane cleaning and/or ageing studies.

An overview of solid/liquid separation methods and size fractionation techniques for engineered nanomaterials in aquatic environment

The increasing use of engineered nanomaterials (ENMs) will inevitably result in their release into natural environment and thereby lead to the exposure of living organisms. Hence, a new concern has arisen for the risk assessment of these emerging contaminants in the natural environment, especially in aquatic systems as an important sink and exposure source. Reducing the release of nanomaterials into water could contribute significantly to reducing exposure. Thus it is vital to consider how to manage wastewater containing such ultrafine nano-objects. This review provides an overview of technologies (classical and innovative) for nanomaterials separation/removal, which are discussed in terms of their advantages and disadvantages, as well as parameters affecting removal efficiency. To investigate the occurrence and fate of ENMs in the aquatic environment, the development of appropriate approaches for their separation prior to analysis is needed urgently. Finally, a brief summary of techniques for sample preparation and fractionation of ENMs in the natural aquatic environment is presented.

Drinking water ultrafiltration: state of the art and experimental designs approach

Abstract During cleaning steps, ultrafiltration membranes are mechanically and chemically stressed. This can result in membrane degradations, failures, and be shut down for membrane replacement and therefore affect the production rate of the process and its sustainability. These phenomena raise the problem of necessary optimization of the cleaning procedures that have to tackle simultaneously, the best cleaning efficiency and the less detrimental procedures for the membranes. Despite the fact that aging is becoming a major issue between end-users, membrane manufacturers, and chemical product suppliers, there is considerably less literature dedicated to membrane aging than to cleaning. First, this study briefly reviews articles dedicated to aging damages involved by NaOCl and commercial detergents (especially on polysulfone ultrafiltration membrane). Then, the present study details the innovative way setup: “Designs of experiments” is used to provide additional data that help with a thorough understanding ...

Application of membrane processes in fractionation of elements in river water

The influence of wastewater treatment plant (WWTP) effluents from one microelectronic industrial zone on element concentrations and partitioning in river water was investigated. The stepwise membrane filtration is used to distinguish different size fractions including large particulate (>18 μm), particulate (0.2-18 μm), colloidal/nanoparticle (10 kDa-0.2 μm) and truly dissolved fractions (<10 kDa) in river water samples and WWTP effluents. Results demonstrated that anthropogenic inputs (WWTP effluents and industrial area) had an important influence on concentrations and partitioning of some elements in river water. Mass balance results showed that membrane filtration processes could realize a good fractionation for many elements (good recoveries) in water samples. Flux decline during 0.2 μm and 10 kDa filtrations were analyzed, and corresponding fouling mechanisms are discussed.

Magnetic nanoparticles for UF membrane integrity: industrial scale

An alternative ultrafiltration membrane integrity test was already developed in laboratory scale. It is based on the use of magnetic nanoparticles (Fe3O4) and measurement of magnetic susceptibility. The mean size of nanoparticles used is around 35 nm and they show a good disparity between 20 and 100 nm. In this paper, validation of this membrane integrity monitoring method was achieved by industrialscale tests. Two holes with 0.6 mm internal diameter in a module containing 10 000 fibers (35 m2 surface area) was efficiently detected by injecting 750 mL of 1.7 g.L−1 nanoparticle solution during 2s when the test was operated at low TMP (0.096 bar, corresponding to a flux of 2.2 m3.h−1). In addition, it has been demonstrated that within the detectable range, this membrane integrity test with magnetic nanoparticles has a very rapid response time. The response time depends on the permeate flux and the dead-volume of the pilot. This membrane integrity test, with the advantages of on-line operation, high detection sensitivity, detection specificity and very low influence on membrane fouling, seems to be suitable for large scale drinking water plants.

Development of a new method for measuring the abrasive potential of water: risk of membrane failure in water treatment plants

The objectives of this study were to develop an analytical method to distinguish feed water used to produce drinking water, with varying concentrations of suspended solids, in terms of abrasiveness and to define an index that can assess the abrasive potential of the feed water coming in contact with a polymeric membrane. For such process configurations, membrane abrasion has been identified as one of the most recurring and major concerns in operation because the polymeric materials used in treatment plants are relatively sensitive to abrasion. Five different types of apparatus were benchmarked and were evaluated on their ability to be adapted to particles commonly found in most drinking water treatment plants at low concentrations. After comparing 10 criteria, the MCR302 with a tribological cell of Anton Paar was identified as the most relevant device. For the selected tool (MCR302), a statistical approach was used to provide a safe and robust ranking of the abrasive potential of the different types of water. An analysis of variance allowed the origin of the result variability to be explained. The newly developed methodology enables quantification of the abrasive potential of natural waters used for membrane filtration with a relevance of ranking higher than 90%.

Size fractionation of elements and nanoparticles in natural water by both dead-end and tangential flow filtration

The influence of membrane filtration modes on the estimation of size distribution for natural elements in water was investigated. The stepwise membrane filtration is used to distinguish different size fractions including large particulate (>18 μm), particulate (0.2–18 μm), colloidal/nanoparticle (10 kDa–0.2 μm), and truly dissolved fractions (<10 kDa) in river water samples and wastewater treatment plants effluents. Dead-end and tangential flow filtrations were compared during fractionation process. For most elements, concentrations in different size fractions obtained by two filtration modes were generally similar. The obvious difference was only found in acid fractions for some elements, which might be related to the cake grown at membrane surfaces between two filtration modes. In case of elemental partitioning, the influence of filtration modes was normally negligible, when the membranes used and operational factors were exactly the same.