Citation:
D.F. Ayala, V. Ferre, S.J. Judd., Membrane life estimation in full-scale immersed membrane bioreactors. Journal of Membrane Science, Volume 378, Issues 1–2, 15 August 2011, Pages 95-100
Abstract:
Limited quantitative available information exists regarding the robustness of
membranes used in immersed membrane bioreactor (iMBR) applications, and no
information on the relative contribution of the two main membrane failure modes
of permeability and integrity loss. Such information is crucial given the
significance of membrane replacement costs to the viability and sustainability
of iMBRs. Measurements of membrane permeability and integrity have been made on
flat sheet (FS) membrane cartridges sampled from six existing full-scale iMBRs.
The recovered membrane permeability (i.e. the permeability recorded following
chemical cleaning) revealed all plants operating for less than six years to have
a clean water flux greater than that of the virgin membrane cartridge. A lower
permeability was recorded only for the oldest plant (eight years of operation),
and this was attributed to high levels of phosphate scale fouling. Assigning a
linear trend between membrane permeability loss and operation time indicated the
recovered membrane permeability to reach a threshold minimum value for virgin
membrane cartridge after ∼7 years of operation. The membrane cartridge
integrity, as measured by the strength of the weld at its perimeter, correlated
with the total volume of water permeated per cartridge, the total weight of
NaOCl cleaning reagent to which the panel has been exposed, and the mean volume
of water permeated per cartridge between chemical cleans. In this case, the
linear trend indicated a membrane life equating to ∼900m3 per panel or exposure
to a total of 1.3kg NaOCl before the threshold minimum welding strength for
membrane cartridge was reached. As with the permeability data, only for the
oldest plant was the measured mean membrane integrity below the threshold. The
data indicate membrane life for FS iMBRs to exceed six years, on the basis of
both permeability and integrity, and may ultimately be limited only by the
irreversible deposition of inorganic scale, rather than operation t