Autopsy and failure analysis of ultrafiltration membranes from a waste-water treatment system Original Research Article

Two hollow-fibre ultrafiltration membrane modules of the waste-water treatment facilities of a cosmetics company were analysed to investigate the causes of membrane damage and rapid fouling of the membranes. This autopsy consisted of visual inspection of the membranes and the module, a bubble-point leak test, tensile strength tests and characterisation of the fouling layers on the membrane and the module, including a microbiological analysis. With the Fujiwara test it was shown that the membranes were not damaged by chlorine or other halogens. It was shown that the membrane damage was not caused by chemical agents, but by mechanical forces: high local shear forces or vibrations. High local shear forces can arise when fibres or lumps are pressed through the membrane fibres and vibrations can arise at start-up and shut-down and upon transition from clean rinsing water to viscous waste-water. These effects are larger if membranes are fouled. In order to reduce the reoccurrence of membrane damage, it was decided to reduce the use of cotton rags and paper tissue in the process area, thus reducing the amount of fibres in the waste-water. It was also decided to optimise the cleaning procedure. Moreover, ‘slow valves’ and pumps with “slow starts” and “slow stops” were installed to reduce pressure shocks. Since the implementation of these measures, the membrane plant has operated for over a year with a minimum of membrane fibre damage, thus saving its owner 10,000s of Euros in membrane replacement costs.