A review of in situ real-time monitoring techniques for membrane fouling in the biotechnology, biorefinery and food sectors

Abstract

Pressure-driven membrane processes are often used for the separation and purification of organic compounds originating from biomass. However, membrane fouling remains a challenge as these biobased streams have a very complex composition and comprise a high fouling tendency. Conventional, the fouling is monitored based on either a decrease in flux or an increase in pressure over time. Those conventional techniques provide no information on the location, composition or amount of fouling. As fouling is often cumulative, it will be detected as a loss of performance. Once fouling becomes irreversible, it is often not possible to clean the membrane without chemicals and the filtration/separation process has to be stopped eventually. In situ real-time monitoring of membrane fouling could provide dynamic information on the development of fouling, allowing optimization of the process. This paper reviews the state of the art in in situ monitoring techniques that could be applied to membrane processes in the biotechnology, biorefinery and food sectors and briefly reflects on the current awareness of in situ monitoring techniques among experienced industrial users of membrane processes. The physical principles as well as the strengths and weaknesses are addressed, and potentially, promising techniques are identified.

A Conductive Microfiltration Membrane for In Situ Fouling Detection: Proof‐of‐Concept Using Model Wine Solutions

“…Realtime monitoring of the progress of membrane fouling could provide a useful tool to optimize the cleaning frequency, to increase the lifespan of membranes and reduce the operational downtime. [2] Common real-time fouling monitoring for a filtration system includes in-line transmembrane flux or pressure monitoring to evaluate membrane performance. One of the shortcomings of in-line monitoring is that the membrane performance does not necessary provide information on fouling processes at and within the membrane, such as the quantity and chemical composition of fouling substances adsorbed on the membrane.…”

“…Electrochemical monitoring techniques, such as electrical impedance spectroscopy and voltammetry, could provide important information such as the charge transfer resistance increase due to the accumulation of nonconductive foulants on membrane surfaces. [2] Studies on online fouling monitoring have previously been carried out on nonconductive membranes using a 4-probe electrochemical cell. [5,6] The nonconductive membranes were included in an equivalent electrical circuit model to analyze the fouling progress on the surfaces.…”

“…However, the ongoing efficiency of cross-flow microfiltration is hindered by rapid membrane fouling, which reduces the lifespan of microfiltration membranes and increases the operational costs. [1,2] however was often complicated due to the large number of elements in the equivalent electrical circuit, when fitted with the Maxwell-Wagner model. [8] A recent work reported a layer of carbon nanotubes deposited on a polyethersulfone supporting membrane, which simplified the equivalent electrical circuit model to a three-component circuit.…”

Particle Track and Trace during Membrane Filtration by Direct Observation with a High Speed Camera

“…The mentioned models have been described theoretical and compared to filtration data in terms of permeate flux, TMP and "post mortem" analysis of membranes after filtration, e.g., SEM [5,6]. However, the development of on-line fouling monitoring techniques have added extra dimensions into understanding the mechanisms of fouling layer structure and formation [7]. Ultrasonic and laser based methods have been developed for indirect measurements of fouling layer thickness during filtration [8][9][10], while a more recent method, fluid dynamic gauging, can also estimate the cohesive strength of fouling layers [11,12].…”

Electrokinetic leakage as a tool to probe internal fouling in MF and UF membranes

“…resistance due to membrane fouling, reversibility of membrane fouling, main fouling mechanisms, filtration cake thickness and porosity, etc. However, their findings are based on estimation models themselves based on macroscopic scale parameters (flux and pressure) and can be far from the microscopic reality occurring around the membrane surface [1].…”