Christelle Guigui

Evaluation of membrane bioreactor on removal of pharmaceutical micropollutants: a review

Municipal wastewater reclamation and reuse has become an important solution in many places around the world to deal with water scarcity problems. Among the available treatment approaches, membrane bioreactor (MBR) has a great potential to become a key element in municipal wastewater reclamation and reuse schemes due to its significantly higher treated effluent quality as compared to the conventional activated sludge process. As great concerns have been raised to some emerging trace pollutants found in aquatic environment in the last decade, notably the pharmaceuticals, removal of pharmaceutical micropollutants by MBR or MBR-related processes should be evaluated to further understand the status of MBR in different wastewater treatment and reuse schemes. This paper gives an overview on removal of pharmaceutical micropollutants by MBR or MBR-related processes, such as activated carbon-assisted MBR and combined membrane bioreactor and reverse osmosis process.

Performance of NF/RO process for indirect potable reuse: interactions between micropollutants, micro-organisms and real MBR permeate

Micropollutants and micro-organisms are major concerns for indirect potable reuse of municipal wastewater. In this study, the retention of pesticides, polycyclic aromatic hydrocarbons (PAHs), metals and micro-organisms in real membrane bioreactor (MBR) permeate matrix and in ultrapure water matrix by nanofiltration (NF) or reverse osmosis (RO) process, and the impact of their retention on NF/RO membrane fouling, were investigated. NF 90 and ESPA2 membranes were chosen for this work. The RO membrane showed high retention for most of the molecules tested, whereas the NF membrane exhibited some variation in the retention of pesticides. The retention of pesticides and metals was enhanced by their interactions with the MBR permeate, while an almost complete retention of PAHs and micro-organisms was observed in both matrices. The presence of PAHs in the MBR permeate increased the permeability of the RO membrane, whereas no such effect was observed for pesticides, metals and micro-organisms. Also, phage leakage was detected when the NF/RO membrane was contaminated by bacteria, which may have caused a slight membrane damage. Pesticide rejection was found to be related to LogKow and molecular weight in ultrapure water at low concentrations (mu g/L level).

Fouling and its reversibility in relation to flow properties and module design in aerated hollow fibre modules for membrane bioreactors

Nowadays, most membrane bioreactors are using membranes submerged in the biomass and aeration in the concentrate compartment to limit or to control fouling. An important issue for the design of modules or membrane bundles in MBRs is to understand how the air/liquid flow is behaving and influencing fouling and its reversibility in relationship to the module properties. This paper focuses on an innovative and very specific process, in which HF membranes are put in a cartridge outside the activated sludge tank and a recycling loop is associated to the cartridge in order to decrease concentration of foulant species at the membrane surface and mass transfer resistance. Recycling operates with a very low liquid velocity in the module (a few cm.s(-1)) which constitutes a specificity of this process in terms of filtration operation. The aim of this study is to characterise two-phase flow and its effects on fouling and fouling reversibility at the scale of a semi-industrial bundle of outside/in hollow fibres, and as a function of bundle properties (packing density, fibre diameter), using specific methods to characterise the flow and fouling effects. Two modules were used showing a different packing density. Filtration was operated at constant permeate flux with clay suspension at 0.65 g.l(-1) in the same hydrodynamic conditions. Fouling kinetics and irreversibility were characterised by an adapted step method, and gas and liquid flows were characterised at global scale by residence time distribution analyses and gas hold-up. Fouling velocities are clearly influenced by gas velocity. The proportion of dead to total volume in the module is mainly affected by the liquid flow velocity and module design. The module with the higher fibre diameter and the lower packing density showed better performances in terms of fouling which was correlated with better flow properties.

Particle deposit formation during filtration characterisation using ultrasonic waves

Membranes filtration processes are widely used because of their ability to remove particles, colloidal species and micro‐organisms from different liquids feeds. However an inherent process limitation is the membrane fouling due to deposition of suspended matter during filtration. Therefore the understanding of formation and transport properties of particle deposit responsible for membrane fouling is a necessary step to optimize membrane processes. These deposits are non homogeneous, highly porous and very thin (less than 500 μm). Thus, it is necessary to obtain local information in order to analyze and model the basic mechanisms involved in deposit formation and then to further predict process operation. As local parameters such as cake thickness and porosity are hardly reachable with conventional techniques, we propose in this paper the use of an ultrasonic echographic method. In a first step this method is validated on deposits of small glass balls. We show that the porosity and thickness of the deposit...