Membrane Autopsy

AWC can perform membrane autopsies to determine the presence of specific foulants and scalants on the membrane surface.

Tests performed:

• SEM: Scanning Electronic Microscopy: SEM analysis is used to determine topography, morphology and crystallographic orientation of a sample.  The SEM shows very detailed 3-dimensional images at much higher magnifications than what is possible with an optical microscope.
• EDS: Energy Dispersive Spectroscopy: EDS analysis is a standard procedure for identifying and quantifying elemental composition of sample areas as small as a few cubic micrometers. The sample material is bombarded with electrons from an SEM and the X-rays produced are measured by an X-ray dispersive spectrometer. Every element has its own characteristic wavelength and can be identified accordingly.
• FTIR: Fourier Transform Infrared spectrometer: FTIR is a powerful tool for identifying types of chemical bonds (functional groups). The wavelength of light absorbed is characteristic of the chemical bond. The spectrum of an unknown material can be identified by comparison to a library of known compounds.
• XRD: X-Ray Diffraction: XRD can be used to differentiate between amorphous and crystalline materials and identify the crystal type/structure of the latter. It provides further insight on the scalant or foulant that might be present in the membrane element.
• BART: Biological Activity Reaction Test: This is an effective method for monitoring the population size and/or activity of specific groups of bacteria; particularly, Iron Related Bacteria (IRB), Sulfate Reducing Bacteria (SRB) and Heterotrophic Aerobic Bacteria (HAB) - the three most important agents involved in biofouling. In this test, a group of bacteria from a water sample is cultured in a media of controlled growth parameters. These cultures are monitored twice a day for fifteen days for visible growth, turbidity, color changes and gas formation. The bacterial population and activity levels can then be determined based on the length of time required for initial changes in the appearance of the culture medium.
• Visual Inspection: This test is conducted by our membrane experts to locate defects along the seals, anti-telescoping device, o-rings, membrane envelope, spacer and glue line.
• Weight Measurement: Scaled membranes are heavier than clean membranes. Weight measurement provides insight as to the severity of scaling and potential structural damage to the membrane.
• Bubble Test: The membrane is merged in storage solution and slightly pressurized with air from the permeate side. If leakage is present, air bubbles will escape from the leaking point and give a clear indication of the leaking location.
• Acid Test: HCl is applied to the scale or foulant collected from the membrane. When CaCO3 is present, evolution of CO2 gas will result in bubbling on the surface of the sample.
• Flat Sheet Testing Flow Rate and Rejection: During membrane autopsy, small pieces of membrane samples will be cut from the element and tested with a flat sheet setup. The flow rate and rejection will be monitored and compared to a clean membrane. The test will allow us to assess the condition of the membrane under investigation and determine the appropriate cleaning process.
• Dye Testing: A dye solution will be applied to one side of the membrane to determine whether its integrity has been compromised through mechanical or oxidative damage.
• Fujiwara Test: This test is performed to determine whether the membrane has been exposed to halogens. The test detects the presence of organically bound halogen compounds.