RO Membrane Autopsy

Membrane autopsy can be used as a routine operating tool for membrane
plant operators to help assess the performance of their membranes. The
objective of a membrane autopsy is to identify if there is any damage at
the surface of the membrane, to identify foreign compounds on the membrane
surface, and to assess how these compounds affect the membrane operation.
The autopsy results can be used to make an informed decision about how
best to:

1. Rehabilitate membranes
2. Improve pre-treatment
3. Optimise anti-scale or biocide chemistry
4. Improve the cleaning regimes used by the plant
5. Adjust plant operating conditions

Reasons to perform autopsy

Membrane processes all experience performance degradation throughout the
life of the membranes. Operating parameters provide an indication of
membrane damage, scale or fouling which is causing the performance
degredation. Operating parameters, which may change, include feed
pressure, normalised pressure drops, normalised permeate flows and
permeate quality. There are many mechanisms which cause declined membrane
performance including membrane surface and structural damage, ineffective
pre-treatment, changes in feedwater quality, inadequate plant design or
unsuitable cleaning of the membrane surface. Membrane autopsy is used to
determine the specific mechanism that is causing the change in membrane
performance so that changes can be made to the process.

Analytical Methods:

Open and Examine

LOI: Loss On Ignition test. Differentiates between organic and inorganic nature of the foulant.

ICP-AES

TOC

Tensile Testing - for membranes:

If membrane failure has occurred tensile testing can be used to assess the
physical property of the membrane material. Chemical damage can change the
strength of hollow fiber membrane material causing them to break. Also,
precipitation of compounds in membrane fibers can cause the membrane
properties to change. Tensile testing is used to assess these changes.

Stereo Microscopy: can identify certain types of crystal shapes associated with certain types of inorganic scale

SEM-EDS

Fujiwara

Microbiology

FEEM - flruorecense excitation emission matrix. analysis of certain types
of organic cmpds such as humics and fulvics

DYE TEST: This is performed to expose and highlight damaged membrane
surfaces.

FTIR

NMR

LC-OCD

CHROMATIC ELEMENTAL IMAGING: a breakthrough technology called Chromatic
Elemental Imaging. CEI offers not only vivid, three dimensional color
images that identify the specific elemental foulant constituents and
concentrations but also their spatial locations on a membrane surface.

AFM (atomic force microscopy)

Reference:

http://membranefutures.com/Membrane-Autopsy

http://www.avistatech.com/Services/membrane_autopsy.htm#

Compiled by Rami E. Kremesti M.Sc.