Irreversible RO Fouling

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Hi everyone, I just came on board with a team of engineers who are currently designing and will be constructing a Water Treatment Plant, and one of the treatment process that is currently been considered is the use of RO in place of some other conventional process, however, during the 1st pilot study, they found out that the fouling on RO became irreversible. So a 2nd pilot study is on the way, and our goal is to determine what is causing this irreversible fouling and how we caneffectively prevent it. If I may add we currently pulling from the Red river and Red Lake river. I was wondering if anyone one of you gentlemen and ladies can share with me the best way to approach todesign this study and what parameters I should be measuring during this study. Our current plan is to setup 4 parallel RO skids and try different pretreatment processes on the feed water before it goes through the RO. Less I forget, a UF will beplaced upstream. Thank you very much for your time.

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  1. The phenomena of colloidal and bacteriological fouling of RO spiral wound brackish water membranes is reviewed in this article here. Generalizations from the literature about the mechanism of action of fouling are described. The monitoring methods used to measure colloidal and biofouling potential of feedwater is reviewed. The action of disinfectants and chemical cleaning agents on an established fouling layer is discussed. The need for extensive addition research is apparent. See this article here it may help you. http://www.swcc.gov.sa/files%5Cassets%5CResearch%5CTechnical%20Papers%5CReverse%20Osmosis/REVERSE%20OSMOSIS%20MEMBRANE%20FOULING%20-%20THE%20FINAL%20FRONTIER....1.pdf

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  2. Hi Raphael, Apologies, I'm coming into this conversation late. The autopsy is very thorough and clearly shows the fouling is caused by high amount of organics and silicate clays (that appear to have caused mechanical abrasion damage to the membranes). These foulants would have resulted in very high permeate conductivity and increased feed to the array (and differential pressure across the array). I wouldn't consider either Silicate Clays nor Organic fouling (nor the other minor foulants detailed in the autopsy) as irreversible foulants - they can be effectively removed (if cleaned early and cleaned effectively). However the damage they have caused (in this case) makes the membrane used irrecoverable. This damage is a concern - mechanical abrasion damage requires the presence of something hard (such as Silica), but also movement within the RO membrane (perhaps the test rig has strong water hammer/ high frequency of start-up & shutdown). In any case this is a concern and shoild be investigated. For future trials you need to use effective pre-treatment (of the same style to be used in full scale plant), to get realistic and effective results. The membrane also shows some evidence of Silica scale & Manganese (possibly sulfate). This indicates the membrane is operating at a recovery where the solubility of these ions is exceeded (causing them to precipitate). Suggest reviewing the trial recovery & antiscalant projections. I hope this helps, feel free to post further questions / results. Kind Regards, Anthony

  6. Let me begin by saying thank you ladies and gentlemen for your contributions thus far and your future contributions to come, however, I have only attached the autopsy results to this discussion and i will soon upload the other data you've all requested.

  7. Dear Raphael, You are going to treat surface water. Here the main culprits are colloidal particles, organic matter and colloidal silica. What pretreatment have you considered for your pilot studies? Get test done for colloidal silica too. For your second trial consider using Uf as pretreatment. In case of colloidal silica ,go for 10K MWCO uf module. Also what are the parameters for your pilot studies. What SDI has been considered for your plant design ant what is the sdi of your feed water to ro? what is the flow, array and recovery considered? You may write to me at ashwin@aquafilsep.com or may post your results and observation in the discussion. Regards Ashwin Doshi

  8. Raphael, pl share some details like BOD and COD percentage etc. You may just add that small details here.

  10. Dear Mr. Raphael Afonja if you dont mind please can you provide us the RAW water chemical analysis report should include BOD,COD and Oil & Grease parameters. I can give you the accurate RO design. You can run the plant with out any disturbances. Regards- Prasad Yerra.