Filtration of Sea Water with DMF

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Deal All,

I'd like to know that the Dual Media Filter is able to meet SDI15 < 3 generally. 

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5 Answers

  1. In case of raw seawater SDI=5, then conventional pre-treatment system (Disinfection.....Coagulation & Flocculation.....DMF .... 5 micron cartridge filter will enable you to get SDI less 3. but what about the seasonal change, is it highly causing a physical disturbance in the inlet raw water? Also, you have to keep a focus on the pre-treatment design such optimum filtration velocity, the lower the filtration velocity, the optimum the filtration (10-20 m/h is the recommended filtration velocity through DMF but I consider the optimum filtration velocity is 10-14 m/h), frequency of DMF backwash, optimization chemical pre-treatment (Coagulant dose rate), ...... 

  2. Hi  Jo Oh Hyeok

    The SWRO Plant where I operate now uses DMF Vessels. When the Sea Water Quality is good (SW SDI-5: 9 min - 11 min) and the Ferric Chloride dosing is 4mg/l to 4.5mg/l, we could get SDI15: less then 3.0. On average we are currently getting 2.5 to 2.9 SDI.

    The SDI depend largely on the Sea Water Quality and how effective the Plant Coagulation System is.

    Last April when our plant was hit by Algae Bloom, the DMF Outlet SDI reached 3.5 to 4.0 (Without continuous Sodium Hypo Dosing at the Intake) and 4.0 to 5.0 (with continuous Sodium Hypo Dosing at the Sea Water Intake).

    The effectiveness of the Backwash Regime to clean the DMF is also play big part in improving the SDI of the DMF Permeate Water.

    If I remember it right, prior to the Plant T&C we did face SDI always on the high side (Above 4), and then we did some adjustment to the Backwash sequence to make it more effective and after we implement the modified BW regime and with better chemical dosing, we manage to improve the SDI. 

    I hope my explanation help you understand the DMF System more.

     

    The Plant I Operate is a 191 MLD SWRO. Plant Configuration - DAF-DMF-CF-1st Pass RO-Post Treatment-Pumping Station.

     

    Best Regards.

    1 Comment

    1. Thank you for your kindly explanation. We applied plant configuration as pre-treatment (DAF-DMF-CF) for Morocco desalination plant. If i get a chance, i'd like to learn your potable water plant experience.

      im engineering potable water plant firstly this year.

  3. As others have said, you can get SDI15 < 3 from a dual media filter but I wouldn't say DMFs can achieve this "generally" - you would need a clean source and good chemical dosing. If you need to achieve SDI15

  5. let me be brave and trustful. The reason that you need SDI 15 < 3 is to feed  hollow fiber reverse osmosis systems, if you were asking, can I desalinate water with less energy, with far less pre-filtration and another technique that is not R.O., I would say....yes you can.

    Go for Laminar flow in magnetic labyrinth, the new technology for water desalination, where you care about the water, and not the membranes. 

    See attached document.