Features

Ragging in immersed hollow fibre membrane bioreactors

While most scientific articles about MBR systems suggest membrane surface fouling as being the main operational limitation for the technology, it is widely recognised by practitioners that clogging phenomena – possibly related to inefficient pre-treatment – are at least as important. It is also recognised that clogging takes different forms...

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Membrane operation

A decade of simultaneous nitrification and denitrification experience in MBR applications

Biological nitrogen removal from wastewater typically happens through aerobic nitrification (from ammonia to nitrate) and anoxic denitrification (nitrate to nitrogen gas). This is usually carried out in two separate process tanks other than in a sequencing batch reactors (SBRs). However, it is more energetically efficient to convert ammonia directly to nitrogen gas, since it requires less oxygen.

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Process biology

Sludge viscosity − the thick of it

The non-Newtonian nature of sewage sludge means that its measured viscosity µs varies with shear rate due to the shear-dependent deformation of the flocculant solids (Yang et al, 2009). Viscosity affects the shear at the membrane interface, shear being a key parameter in promoting flux, and the dependency of apparent viscosity on temperature may then also be significant in determining flux.

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Process biology