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Thread: Loss of back pressure

  1. #1
    Join Date
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    Saratoga, NY
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    Default Loss of back pressure

    Hi,

    I've just recently assembled a small RO setup for my backyard maple syrup production this year. To my utter surprise, once I assembled everything it did actually work to produce a thin but stable stream of concentrate out of a 3 x 150GPD membrane setup in series...I plan to add a permeate pump and possibly a pressure relief valve to better regulate pressure but it did work for about half a day of sugaring.

    The issue became that I realized I was slowly but steadily losing back pressure after achieving the initial balance of about 90-100 PSI via manipulation of a check-valve on the concentrate output line. I have a couple questions for the members on this:

    - some of my sap was fairly cloudy at this point, is it possible I was just trapping too much additional "stuff" along with the sugar on the concentrate side?

    - my membrane housing kits came with a check-valve style elbow fitting for the permeate output port...could these possibly be impacting the efficiency / pressure of the system? Or, maybe a better question, do I need them on the permeate output at all? Should they go on the concentrate side instead perhaps?

    - lastly, I am using an open-top, refillable canister style filter at the front end of the line (in front of the pump) and just jammed some filter paper in there...is there anything people find works especially well in these?

    Thanks in advance...I am very, very slowly learning how all this works.
    --
    2015: 8 bucket taps (7 red, 1 sugar) on DIY barrel evaporator
    2016: 13 taps (bucket and tube) on block arch and hotel pans
    2017: SAME
    2018: 25 taps on 2x3 flat pan and resurrected barrel arch
    2019: 25 taps...same setup plus DIY 3x150gpd RO filter
    2020: 50 taps, all buckets..."new" oil tank arch setup
    2021: 100 taps (50/50 buckets/3-16 tubing) on 2x4 divided pan
    2022: 150 taps (50/100 b/t) on 2x4 pan with sap warmer pan
    2023: SAME
    2024: 150 taps, added single-post 4x40 RO system

  2. #2
    Join Date
    May 2009
    Location
    UVM Proctor Maple Research Center, Underhill Ctr, VT
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    Default

    You should always do a good job of filtering before the sap hits the membrane, especially with cloudy sap. "Jamming in" filter paper will not do it. Most likely what you are seeing is organic material (microbes) building up on the membrane surface and reducing flow. You will need to soap wash (RO soap, sodium hydroxide) and then rinse well with permeate to restore the flow rate. Larger machines incorporate recirculation to reduce the influence of (slow down) membrane fouling.
    Dr. Tim Perkins
    UVM Proctor Maple Research Ctr
    http://www.uvm.edu/~pmrc
    https://mapleresearch.org
    Timothy.Perkins@uvm.edu

  3. #3
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    Quote Originally Posted by DrTimPerkins View Post
    You should always do a good job of filtering before the sap hits the membrane, especially with cloudy sap. "Jamming in" filter paper will not do it. Most likely what you are seeing is organic material (microbes) building up on the membrane surface and reducing flow. You will need to soap wash (RO soap, sodium hydroxide) and then rinse well with permeate to restore the flow rate. Larger machines incorporate recirculation to reduce the influence of (slow down) membrane fouling.
    Thanks, that's helpful and makes sense. Based on the color of the concentrate coming out after I had "recharged" the system from a gradual pressure loss I assumed it was in fact the heavy microbial content sap I'd been running.

    Would it be fair to say I should invest in a dedicated filter housing like for a home water setup in addition to the refillable one?
    --
    2015: 8 bucket taps (7 red, 1 sugar) on DIY barrel evaporator
    2016: 13 taps (bucket and tube) on block arch and hotel pans
    2017: SAME
    2018: 25 taps on 2x3 flat pan and resurrected barrel arch
    2019: 25 taps...same setup plus DIY 3x150gpd RO filter
    2020: 50 taps, all buckets..."new" oil tank arch setup
    2021: 100 taps (50/50 buckets/3-16 tubing) on 2x4 divided pan
    2022: 150 taps (50/100 b/t) on 2x4 pan with sap warmer pan
    2023: SAME
    2024: 150 taps, added single-post 4x40 RO system

  4. #4
    Join Date
    Dec 2002
    Location
    Rock Creek, NC
    Posts
    5,807

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    Quote Originally Posted by ADK_XJ View Post
    Would it be fair to say I should invest in a dedicated filter housing like for a home water setup in addition to the refillable one?
    You should get a canister type filter and use 5 micron cartridges in it. You won't need the one that you are stuffing some paper in.
    Russ

    "Red Roof Maples" Where the term "boiling soda" was first introduced to the maple world!

    1930 Ford Model AA Doodlebug tractor
    A couple of Honda 4 wheelers
    Four chainsaws and no chickens!

  5. #5
    Join Date
    Feb 2015
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    Quote Originally Posted by Russell Lampron View Post
    You should get a canister type filter and use 5 micron cartridges in it. You won't need the one that you are stuffing some paper in.
    Got it and, at the risk of seeming daft, if it's one that slides into a standard 10x2.5 housing that I have do I run the "permeate" line from that one into the next series of membranes and expel the remainder?
    --
    2015: 8 bucket taps (7 red, 1 sugar) on DIY barrel evaporator
    2016: 13 taps (bucket and tube) on block arch and hotel pans
    2017: SAME
    2018: 25 taps on 2x3 flat pan and resurrected barrel arch
    2019: 25 taps...same setup plus DIY 3x150gpd RO filter
    2020: 50 taps, all buckets..."new" oil tank arch setup
    2021: 100 taps (50/50 buckets/3-16 tubing) on 2x4 divided pan
    2022: 150 taps (50/100 b/t) on 2x4 pan with sap warmer pan
    2023: SAME
    2024: 150 taps, added single-post 4x40 RO system

  6. #6
    Join Date
    Dec 2002
    Location
    Rock Creek, NC
    Posts
    5,807

    Default

    Quote Originally Posted by ADK_XJ View Post
    Got it and, at the risk of seeming daft, if it's one that slides into a standard 10x2.5 housing that I have do I run the "permeate" line from that one into the next series of membranes and expel the remainder?
    You plumb that in before your membranes to filter out the fine stuff that will plug your membranes. If you're using a feed pump, plumb it in after that and before the high pressure pump. If you're not using a feed pump plumb it in before the high pressure pump. Permeate doesn't need to be filtered and should be run directly into your permeate collection tank to be saved for cleaning.
    Russ

    "Red Roof Maples" Where the term "boiling soda" was first introduced to the maple world!

    1930 Ford Model AA Doodlebug tractor
    A couple of Honda 4 wheelers
    Four chainsaws and no chickens!

  7. #7
    Join Date
    Feb 2015
    Location
    Saratoga, NY
    Posts
    426

    Default

    Quote Originally Posted by Russell Lampron View Post
    You plumb that in before your membranes to filter out the fine stuff that will plug your membranes. If you're using a feed pump, plumb it in after that and before the high pressure pump. If you're not using a feed pump plumb it in before the high pressure pump. Permeate doesn't need to be filtered and should be run directly into your permeate collection tank to be saved for cleaning.
    Thanks, after replying earlier I realized it is a different / dedicated canister and not the same as my current membrane housing.
    --
    2015: 8 bucket taps (7 red, 1 sugar) on DIY barrel evaporator
    2016: 13 taps (bucket and tube) on block arch and hotel pans
    2017: SAME
    2018: 25 taps on 2x3 flat pan and resurrected barrel arch
    2019: 25 taps...same setup plus DIY 3x150gpd RO filter
    2020: 50 taps, all buckets..."new" oil tank arch setup
    2021: 100 taps (50/50 buckets/3-16 tubing) on 2x4 divided pan
    2022: 150 taps (50/100 b/t) on 2x4 pan with sap warmer pan
    2023: SAME
    2024: 150 taps, added single-post 4x40 RO system

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