The MBR Blog

Misc Simon Judd 2

Simon Judd

Professor Simon Judd has over 20 years’ experience in teaching the fundamentals of water and wastewater technologies and is author of The MBR Book, Watermaths, and Industrial MBRs. Contact Simon at

Membrane ageing − a hard life?

The lifespan of a membrane is of key concern in determining operating expenditure (OPEX). Extending the replacement frequency from five to ten years can reduce the overall OPEX by almost 20% for an immersed hollow fibre MBR (Judd, 2017), and more so for a flat sheet system.

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The origins of ragging in MBRs − a story of cotton wool

Ragging in MBRs is almost certainly caused by cotton wool or similar cellulosic textile fibres. Only very short lengths of tiny filaments must break through the 1–3 mm fine screens, which suggests that they are originally dispersed. But they soon get together again to form those long rags.

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Footprint − the factors governing size in an MBR

It's their compactness that is one of the beauties of MBRs and often leads to their selection as the preferred technology. Crucially, MBRs permit a higher MLSS concentration than a conventional CAS process, and this means proportionately smaller biological process tanks. 

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