Replacing Pretreatment UF with Media Filters?

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We have ultrafiltration (UF) in our water pretreatment.

Our feed water turbidity 0.54 NTU Borewell water.

We want to change the pretreatment from UF to media filtration because: 

Is there a way we can make the UF more efficient and cheaper or is it better to simply switch to media filtration?

Sorry for inconvenience 

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42 Answers

  1. Good Afternoon Mr Chaudry,

    UF is usually working very well and not a cause of issue for maintenance. With a probably nice water, it should run very smoothly.

    Your NTU is low, what about other parameters ? total suspended solid, iron, manganese etc..

    If you want to share with me what exactly you are facing with your UF, I can have look and advise you.

    Best regards,

    Olivier

  2. How about micro media filter...it might exceed requirements for its filtered water quality as pretreatment. Maybe membrane based prefiltration provides marginally higher water quality for filtrate...micro media filter achieves almost comparable performance at lower cost,with 2 backwashable particulate media layers,aptly designed

  3. Yes, the best filter media is Activated Filter Media. It has 30-80% better performance and a more reliable and consistent filtration than sand confirmed by independent testing. Biofilm and scaling will not occur and hence chemicals are not needed. The media is self-cleaning, self-charging and self-sterilising, therefore it does not need to be cleaned or changed during the lifetime of the filter. The oldest media in operation at the moment is over 20 years and it is expected to last over 30 years. 

    I am experienced in the use of this product and filtration processes in Asia and Australia. Please email me at andrew@waterandoilsolutions.com.au and I will be happy to provide case studies, referrals, and other literature on the product. 

  4. It is very valuable all comments from Mr ​Voutchkov, one of the worldwide experts in desalination and from Mr. Talavera, with huge experience in desalination too. I invite both to deep in the OPEX improvement with installing ozonization steps in front of coagulation and/or in front of filters (sand, BAC) to break -C=C- and get AOC (assimilable by bacteria) and in case of BAC extends the half-life of activated carbon. UV in front of RO is another alternative if microorganims are efficientelly removed previously.

  5. I strongly support the observations of Dr. Talavera.  I have worked on 9 SWRO desalination projects in the Middle East, where they use UF or MF system for pretreatment as a single pretreatment stage and all of them operate at 20 to 30% below their design capacity.  UF and MF filtration are excellent (but expensive) technology to remove suspended solids and pathogens but have only disadvantages in terms of reducing the biofouling potential of seawater, brackish water or wastewater.  In seawater the main type of fouling is biofouling - seawater bacteria are not pathogens for humans and they do not reduce biofouling - quite the opposite - they accelerate it.  As suggested by Dr. Talavera, if you install conventional deep gravity media filter upstream of the existing UF system, the gravity filters will gently remove the algae and bacteria, and if their total media is deeper than 1.8 meters, they will also remove dissolved organics by biofiltration in the bottom third portion of the filter.  So you existing UF system will work as expensive back washable cartridge filters and you will need it as such if your existing UF system does not have cartridge filters downstream of it. 

  7. DEAR MR ALI:

    Please take in big consideration the response from Mr Voutchkov.

    All he says is 100%  true.

    UF is not a good pre treatment for RO in the most of the cases, producing a high fouling in the RO membranes and a big chemicals and water consumption in the UF section.

    The gurus of modernity are wrong when depreciate sand filtration because is an "old system".

    I do not know any Plant fitted with UF that is working OK.

    All of them have big troubles and also a big consumption of cartridge filters (Normally 4 or 6 times higher than the ones in sand filters Plants)

    Ask to the UF makers why their warranty is SDI 2,5 or 3 and not 0,5

    Water filtered through a 0,003 microns should not deposit any matter on the Millipore SDI of 0,45 microns, but you get normally SDIs from 1,5 to 3.

    The best pre treatment is a double stage sand filtration, with a first stage of anthracite and sand and a second one with sand and garnet.

    In your case, I should keep the UF and should install the sand filtration as pre treatment of the UF.

    Perhaps in this case, a single stage of dual media filtration should be enough.

    A pilot will give you the answer

    Regards

    1 Comment

    1. Yes I agree with you.  Can you explain some more point on Water properties & pretreatment 

       

      Thanks in advance 

  9. Dear Mr. Ali,  If your water contains high organic levels - i.e., total organic carbon (TOC) concentration higher than 2 mg/L and it has algae in it, membrane pretreatment will not work well.  The problems with membrane pretreatment are not pertinent to Dow's model of UF - membranes - if your source water TOC is higher than 2 mg/L, no membrane pretreatment system available on the market will work well.  In this case, the best technology will be deep dual media gravity filter - preferably pumice and sand. 

    For more informaiton take a look at this bbok:

    https://www.elsevier.com/books/pretreatment-for-reverse-osmosis-desalination/voutchkov/978-0-12-809953-7

  10. Hi Mohegan,

    Our plant uses multi-media filters ahead of the RO trains to remove particulates and decrease turbidity. Typical turbidity values on post filter is 0.06 - 0.12 NTU. 

  11. Well moving fro UF back to media filters, sound to me like move back in time...try Amiad AMF2 filters...you can check for yourself....find all about this wonder in www.amiad.com

  12. hi, If you really want to remove the UF as pre treatment for whichever reasons, then I suggest you use AFM (Activated Glass media) from Dryden Aqua.  With correct design of the system, ie. retention time worked out correctly with their guidelines you can get down to 3 micron, which will be more than adequate to feed the RO.  I have personally used this in many small to medium sized RO applications and its works like a dream.  Let me know if you need further assistance and I would be happy to design you the correct pre filtration solution.  All the best, James Morisse.  Cellular no:  +27 82 803 1010 or E.Mail me on james@nuwaterglobal.com

  13. There is really is no benefit to be expected for the RO if you replace the UF with media filters if the goal is produce lower turbidity in the RO feed.  Dow has a 30micron pore size, and the best media filters could claim 1 to 5 micron effective pore size.  Now, your Dow UF should have

  14. Dear Mohsan,

    If turbidity is high in your RO feed then replacing the UF by a media filter will just make it worse because such filters will barely remove colloids and corresponding turbidity.

    After UF at least the turbidity (NTU) should be very low. If not, then it seems that your UF membranes are damaged and need to be replaced. I would recommend to contact Dow.

  15. Hi Mohsan. I agree with many other posters that UF can be effective at reducing much of the load and the ability to flush the UF membranes periodically is also important. If you are finding that the efficiency of the UF membranes is not where you wish to be (in terms of SDI value), you might want to consider using our own patented NanoCeram pleated filters as the final prefilter stage for protecting your RO membranes. Our filters exhibit an SDI value in the 0.5 to 1.0 range and can significantly improve the time intervals for cleaning the membranes. I've attached a file that might be helpful.

    1 Comment

  16. Hi Mohsan,

    you can substantially reduce down suspended solid load on RO plant by using lower micron pre Filtration. We can provide pre Filtration up to 10 micron through self cleaning automatic screen or disc technology. For more details you can visit www.amiadindia.com or call at +91 9370199188

    1 Comment

    1. Ok, Send me your pre treatment  Complete Design, Brief Introduction,

      01, Removal Rate, TSS, Micro, SDI expectation result after filtration, (Raw conductivity 25000)

      Email: ch_mohsan91@hotmail.com 

       

  17. Dear Mohsan,

    Coagulation-floculation in front of UF to increase the size of particle could be a solution to reduce turbidity. 

    Note that UF will not remove dissolved organic material so, Assimilable organic carbon, AOC, and others aliphatic hidrocarbon chains will pass through the membrane, besides this UF isn't a true dissinfection system (although reduce the microorganims level), it means that bio-fouling could appear on your RO membranes after UF.

    As an ozone treatment expert I think that a typical DWTP in front of RO membranes is a good solution, so, DAF (for algae removal and bloom barrier) - sand filtration and for dissolved organic material and dissinfection -  O3+BAC+UV in front of  the cartridge filter + RO.

    a Pre-oxidation step will be required for metals removal as iron.

    For any ozone and UV treatment, please, contact me: cgarcia@newlandentecheurope.com   _src="https://www.newlandentecheurope.com" href="http://www.newlandentecheurope.com">www.newlandentecheurope.com

    1 Comment

    1. Ok, Send me ​your pre ​treatment  ​Complete Design,​ Brief ​Introduction, ​

      01, Removal ​Rate, TSS, ​Micro, SDI ​expectation ​result after ​filtration, (​Raw conductivity ​25000) ​

      Email: ch_​mohsan91@​hotmail.​com  ​

  18. Hi Mohsan,

                          If you do decide to change to media filtration we manufacture filter replacement indicators that are low maintenance and cost effective.  The great way to prevent premature filter change or avoid an oversaturated filter.  The indicators change color real-time when the filter is saturated.  Attached is the indicator and our website for more information.  You can contact me if you have anymore questions.  Thanks!                                                                                                                                                                                                                                                                                         

    Acids BTI (color change).jpg

    http://chemteq.net/bti.html

    1 Comment

    1. Ok, Send me ​your pre ​treatment  ​Complete Design,​ Brief ​Introduction, ​

      01, Removal ​Rate, TSS, ​Micro, SDI ​expectation ​result after ​filtration, (​Raw conductivity ​25000) ​

      Email: ch_​mohsan91@​hotmail.​com  ​

  20. Dear Mohsan,

    We have solutions with efficient and cost effective UF in our GIGAMEM modules with easy and economic maintenance. Please contact us.

    Isabelle Duchemin i.duchemin@polymem.fr

    1 Comment

    1. Ok, Send me ​your pre ​treatment  ​Complete Design,​ Brief ​Introduction, ​

      01, Removal ​Rate, TSS, ​Micro, SDI ​expectation ​result after ​filtration, (​Raw conductivity ​25000) ​

      Email: ch_​mohsan91@​hotmail.​com  ​

  21. Coz of cost and operation media filtration is the best choice...  You can make it with sand,  green pebble and activated carbon for better results.... 

  22. Coz of cost and operation media filtration is the best choice...  You can make it with sand,  green pebble and activated carbon for better results.... 

    1 Comment

    1. Ok, Send me ​your pre ​treatment  ​Complete Design,​ Brief ​Introduction, ​

      01, Removal ​Rate, TSS, ​Micro, SDI ​expectation ​result after ​filtration, (​Raw conductivity ​25000) ​

      Email: ch_​mohsan91@​hotmail.​com  ​

  23. Dear Mohsan,

    I can't help with your UF but if you want to make the switch to media filtration then please get in touch. Our FilterClear system offers significant advantages over traditional dual media filtration: better filtrate quality, higher filtration rate and lower capital cost. This is achieved by using four media layers which re-stratify based on specific gravity after each backwash. Generally FilterClear does not require chemicals, either for flocculation or for cleaning, so operating costs are low too. We have several references for desalination applications, including a large plant at KAUST, Saudi Arabia. See http://www.bluewaterbio.com/filterclear/ for more information.

    1 Comment

    1. Please send me you Pre Treatment System Brief Introduction on 

      Email: ch_​mohsan91@​hotmail.​com  ​

      Thanks

  24. One more question, do you pre-treat the water by UF for RO? If that is the case then you cannot avoid UF membranes as SDI will be much higher to clog your RO Membranes if you bypass UF Membranes. 

     

    In addition, DOW UF has an exceptional feature which others UF membrane manufactures have, that is Air Scouring, you can increase time of Air Scouring to eliminate the suspended particles accumulation and Air Scouring is also a Scheduled Task while it goes to Backwash after 12 hrs interval. 

    3 Comments

    1. Thank Dr.

      But we want to replace UF with media filtration,

      Just let me know if you have Pre Treatment Media Filtration Design specification & Basics, 

      1 Comment reply

    2. HI

      I agree with Mr.Ahamed,

      it is very important which type of  raw water you used, if surface water and sea water is  raw water used in your system ,the UF pretreatment was suitable choice.

      1 Comment reply

      1. Borehole Water not Sea Water conductivity 25000us

  25. Hi Ali, what do you mean with maintenance costs? Do you mean frequently replacement of UF membranes/modules ? What is the application of UF? Is UF used as pre-treatment System for RO? Do you have any P&ID for review? What is the UF feed water and outlet water quality concerning turbidity, TSS & SDI? Do you have any UF projection from DOW?

    2 Comments

    1. I would recommend to check and adjust the time intervals for backwash and CEB and also the related chemicals for CEB and/or CIP. Do you use also a recommended strainer  (150 micrometer) at the UF inlet? It seams that the UF is overloaded!

    2. Thanks,

      Yes ​UF for RO...... ​But  SDI ​is also in ​normal range. ​

      only ​problem UF ​system is old & ​due not proper ​operation UF ​membrane Block, ​required whole ​ UF system ​rehabilitation. ​

  26. Hi Mohsan. Where are you located? I'll get a Dow representative to support and work through the issues. The Dow UF is exceptional at handling high TSS loads and will outperform media filtration in quality and total recovery, we just have to make sure the system is optimised and working as recommended. What TSS are you running? Presence of metals?

    please contact me at scpitts@dow.com and I can help

    2 Comments

    1. I still strongly recommend keeping with the UF - it is the standard and will have significant advantages over conventional media systems. When was the last CIP? Borehole often has high Iron and can block a UF without much improvement from backwashing. Then a CEB is necessary with Acid or if it is severe then a CIP with citric acid is highly recommended. I had a plant that hit 2.0 bar TMP from metals. 1 CIP and the TMP was back at 0.4 bar. Dow UF fibres are very chemically resistant so cleaning procedures can be harsh without long term damage to the fibres. 

    2. Thanks, 

      SDI is in normal range,  not high load of TSS Borehole water ,

      We only want to replace as all system need maintenance & UF membrane blocked 

  27. Hi Mohsan. Where are you located? I'll get a Dow representative to support and work through the issues. The Dow UF is exceptional at handling high TSS loads and will outperform media filtration in quality and total recovery, we just have to make sure the system is optimised and working as recommended. What TSS are you running? Presence of metals?

    please contact me at scpitts@dow.com and I can help

  28. You can use AMAID 100micron disc filter before your existing UF plant to reduce load on UF.

     

    Its proven technology at many sea water desalination plant. 

  30. UF can function reasonably well up to incoming turbidity of 10 NTU. Anything more & consistent, and you require pre-treatment.  There is so much hype around membrane filtration that people have started forgetting that 95% of surface drinking water is processed by conventional methods like effective media filtration.  

     

  31. Hi,

    The problem will come down to an economic analysis.

    Is the turbidity issue, a feed problem or filtrate problem?

    If turbidity is a feed problem, then pre-treatment is the only solution if you retain UF.

    If the turbidity is in the filtrate, then this is a filter maintenance problem, with failed membranes leaking.

    On the question of changing to gravity media filters from UF, you need to know what final water turbidity is acceptable.  UF will provide a better filtrate if it is maintained, but UF is a more intensive and higher maintenance process.  An advantage of UF is the land area required is significantly less.  Media filters require a large surface area.

    Media filters are simpler in terms of operation and maintenance, but are more sensitive to the chemical dosing systems.  If putting in media filters, ensure that you provide filter-to-waste after the backwash to ensure that any particles trapped in the media after backwash do not make it to the water supply.

    The decision comes down to money and other constraints.

  32. There are several options for enhancing UF performance and improving the economic situation.  If UF quality is not needed multimedia filtration may prove effective and economic in the long run.  You will not achieve the same levels of filtration with multimedia as you will with UF.  Envirogen is well versed in filtration systems of all types.  Envirogen Group has offices all over the world.  http://www.envirogengroup.com/contact-us-2/

    Regards

  33. What g.p.m. Are the UF's producing? 

  34. Are you doing any pre-treatment in front of the UF. Organics, in particular polymers will foul a UF quickly. Depending on the influent turbidity you may not have enough surface area, look to increase capacity of the UF, or perhpas add a small amount of ferric chloride to aid the filtration process.

    1 Comment

    1. Hello jacob,

      adding ferric chloride will cause iron deposit in the UF, this what we noticed in one of our plants

  36. In general, the use of ultrafiltration is an excellent method of removing turbidity.  Ultrafiltration membranes are sensitive to the presence of incoming particles, and some pre-filtration may be a solution to consider, especially if colloids or large particles are present in the source water.  I would recommend you look into a media filter in front of the UF, to protect the membrane, but keep the UF in place.  The final decision would be based on the final requirement you have for the finished water.  As many others have already stated, not enough information is presented to give a specific solution to your issue, but having a membrane UF exposed to unfiltered source material is very likely to result in excessively high maintenance costs and poor filtration performance.  Another possibility is membrane failure, leakage or incomplete sealing of the system, resulting in poor quality (turbidity) of your finished water.  sam.mason2824@gmail.com.

     

  37. Dear Moshan Ali,

    Please share

    Inlet Water Characteristics (Is it Bore Well Water, Canal/River Water, Treated Wastewater for Recycling Purpose?)

    Filtratioin Scheme you have, like what you have prior to UF (if you have pre-filtration Multimedia Filter+GAC Filter+Cartridge Filter Prior to UF?)

    If you have any Chemical Sedimentation prior to Filtration Scheme?

     

    Did you approach DOW for the Treatment Scheme or local vendor supplier provided this?

     

    Filtration Systems if properly designed are well suited and works well with proper CEB and CIP requirements.

    Your question is incomplete to recommend you any solution.

     

    1 Comment

  38. Dear mohsan

    what is your ceb & cip frequency cycle? Whats is the turbidity in the intake? Is it an open intake or a pipe intake?

     

  39. You mention that turbidity is a problem, if it is a problem in that the influent turbidity is overwhelming the UF then you will need some sort of clarifier ahead of the all technologies regardless of whether they are UF or media filters. I doubt you have turbidity in your effluent after the UF's. If so that is another issue. We do make a granular media that has 3rd party validation for performance and is the best option for media filtration to replace UF. However all media filters have a limit on the influent turbidity they can handle so we need more information. please email me detailed information at sales@wateropolis.com

  40. Dear M. Mohsan Ali,

    We are a ​​France based ​​water treatment ​​company ​​providing ​​solutions for ​​the bottling ​​industries (​​visit http://​​www.ice-water-​​treatment.com/​​en/) over the ​​world. ​
    We are ​familiar with Ultrafiltration processes as well as media filtration, but our experience on Dow UF modules is not that high. We ​could ​propose ​some ​process assesment of your water treatment and evaluate, based on your operation experience and water characteristics what are the best options for your filration needs. Feel free to ​​transmit me ​​your data, ​​which I would ​​forward to the ​​sales engineer ​​in charge with ​​your geographic ​​area. ​ ​
    I hope that we talk soon.

    Patrick ​Ballato - ​pballato@ice-​​water-​​engineering.​​com  

  41. It is important to know the nature of your source water and process.  UF is often supported by a dual media filter in different applications.  As you are leaning towards a media filter, it appears that you do not use one.  The information provided is not enough to make a correct assessment of your situation.