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.
The MBR Blog
What’s the best membrane material for MBRs? If you consider all the products listed in ‘Industrial MBRs’, for example, it turns out that more than half of the 80 products represented in that book are PVDF (polyvinylidene difluoride).
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.
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.
There’s plenty of tales of the impact of poor screening on downstream unit operations in MBRs. While there is little actual proper research into the performance of screens published in the peer-reviewed literature, there are some useful guidelines produced by practitioners.