I am going to perform a membrane autopsy of a reverse osmosis membrane to investigate fouling. I know how to do it based on research papers that i have read but I need a standard procedure describing the steps to be followed.
Attaching here a link :
https://www.uswaterservices.com/the-splash/reverse-osmosis-ro-membrane-autopsy-what-you-need-to-know
Hope this will be helpful to you.
A membrane autopsy is a good description of the analysis that can be performed on a fouled membrane. It can also be the key to determining how to prevent fouling of new membranes and to maximize the efficiency of this key piece of water treatment equipment. U.S. Water Services performs this analysis in-house at our location in Cambridge, Minnesota, and then issues a comprehensive seven page report of the results. The test is destructive, and the membrane element is not returned.
The procedure begins with a physical examination of the intact element. We start by looking for physical damage to various parts of the element, including the brine seal, outer casing, permeate tube and any evidence of telescoping of the membrane. We next look for evidence of gross fouling on the leading edges of the rolled membrane in the end cap. Fouling in this area can restrict water flow through the element, and the elements behind it in the array tube. If a system is experiencing leading edge fouling, it usually occurs on the first element in each array of the first bank.
The fouling is principally a result of dissolved organic material, or fine suspended solids that have made it past the pre-filter system. Next, the element is taken apart by removal of the end caps, and the membrane is unrolled. This allows a series of specific tests to determine what has happened to this particular system. Samples of the membrane will be subjected to dye testing. The dyes are chosen due to the size of their molecules, which prevent the dye from passing through normal membranes. The dyes will pass through damaged membrane sheets, and will stain the underside of the membrane composite material.
This membrane barrier damage is often caused by exposure to halogens (chlorine and bromine compounds). We use another test, called the Fujiwara analysis, to determine if halogens have reacted with the membrane's polymer structure. Membranes that have been damaged by other oxidants, such as permanganate, ozone, or hydrogen peroxide, will not react to this test, so it's possible to determine what type of chemical is causing the damage.
The next step is to collect foulant off of the membrane sheet, and analyze it for chemical composition. The foulant is tested for Loss On Ignitions (LOI) to determine how much is organic material. The sample is then analyzed by X-Ray Fluorescence and X-Ray Diffraction, which provides information about the relative concentrations of specific ions, such as iron, calcium, silicon, phosphorous, or barium. An example of this type of analysis is shown below:
Silicon, SiO2…………………………….. 9.88%
Iron, Feo3………………………………… 22.20%
Calcium, CaO……………………………. 6.28%
Phosphorous, P2OS……………………. 11.50%
Barium, BaO………………………………. 9.60%
Magnesium, MgO………………………… 1.00%
Sulfur………………………………………… 2.24%
Strantium, mg/l…………………………….. 2.19%
Barite, BaSO4……………………………… 16%
Amorphous (non Crystalline)……………. >80%
Unidentified………………………………….
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