Y. Wyart

Low-pressure membrane integrity tests for drinking water treatment: A review.

Low-pressure membrane systems, including microfiltration (MF) and ultrafiltration (UF) membranes, are being increasingly used in drinking water treatments due to their high level of pathogen removal. However, the pathogen will pass through the membrane and contaminate the product if the membrane integrity is compromised. Therefore, an effective on-line integrity monitoring method for MF and UF membrane systems is essential to guarantee the regulatory requirements for pathogen removal. A lot of works on low-pressure membrane integrity tests have been conducted by many researchers. This paper provides a literature review about different low-pressure membrane integrity monitoring methods for the drinking water treatment, including direct methods (pressure-based tests, acoustic sensor test, liquid porosimetry, etc.) and indirect methods (particle counting, particle monitoring, turbidity monitoring, surrogate challenge tests). Additionally, some information about the operation of membrane integrity tests is presented here. It can be realized from this review that it remains urgent to develop an alternative on-line detection technique for a quick, accurate, simple, continuous and relatively inexpensive evaluation of low-pressure membrane integrity. To better satisfy regulatory requirements for drinking water treatments, the characteristic of this ideal membrane integrity test is proposed at the end of this paper.

Pressure fields in an industrial UF module: effect of backwash

In the last decade, membrane manufacturers have improved their ultrafiltration module to raise the production of drinking water in order to meet an increasing demand. The usual process used is an inside-out filtration in dead-end mode. In this configuration, the energy consumption is limited by outside-in backwashes. Raising the permeability of the membranes lead to an increase in module compactness and strongly modify the driving force in the module. This study presents a computational fluid dynamics (CFD) model to predict the pressure and velocity field in the hollow fiber network (HFN) taking into account several parameters as the geometry of the module, the inlet pressure, gravity, and temperature. For the industrial tested module configuration, results shown that hollow fibers work in a homogeneous way in filtration mode but a great heterogeneity appear during the backwash. All the results have been validated compared with experimental values.