Reverse Osmosis Water Filtration

Discussion in 'Water Parameters and Additives' started by SchyffS, 11 Jul 2010.

  1. SchyffS

    SchyffS Reef Aquarist

    Joined:
    26 Jan 2008
    Posts:
    588
    Likes Received:
    12
    Location:
    Cape Town
    I am starting this thread in the interest of understanding reverse osmosis, the function of each filter as it leaves the tap until it ends up in the RO drum, and making the purest water available all the time every time.


    Quoted from The Reef Aquarium; Science, Art and Technology, Vol 3 by J.Charles Delbeek and Julian Sprung.

    Background
    While the quality of the salt mix you use is important, the quality of freshwater you use to make saltwater is equally, if not more important. Contact your local water works department to ask for a print out of what is in the tap water in your area. Examine the levels of ammonia, nitrite, nitrate, phosphate, iron, silicate, calcium, magnesium, pH, alkalanity and organics. They should be within the normal accepted ranges for reef aquariums. Many treatment plants add chemicals to the water to sterilise it as well as to cut down on the amount of hard water scale that can develop in the pipes. These usually consist of compounds containing chlorine, chloramines, ammonia and phosphate. In most cases, you have to treat the water to remove these compounds before it can be used in our reef aquaria.
    There are several ways 9of treating tap water, however the most common and effective method is to use a combination of reverse osmosis and deionisation filters.

    The functioning of reverse osmosis and deionisation filters
    Reverse osmosis units use a porous membrane that allows small molecules, such as water to pass through but blocks the passage of larger molecules such as phosphate. ;)
    These blocked molecules then pass out of the filter along with the rejected water :biggrin:
    Reverse osmosis filters block up to 95% :p of many compounds but for every 3.8 litres of pure water produced about 30 litres of rejected water(waste water) is released. This can be somewhat improved by increasing the pressure of the incoming water, which is done with booster pumps and and recirculation loops on more effecient units that can achieve much closer to a 1:1 product to rejection ration. :)

    Deionisation resins consists of tiney beads that function to adsorb certain types of compounds. Due to this ability, deionisation columns can be filled with a variety of resin types or can be custom designed to target one type of compound for removal. Passing the reverse osmosis water through a deionisation column(filter) further purifies the water and produces extremely pure freshwater.

    Ultimately the produced water must have a 0 Total Dissolved Solids (TDS) value. This is an indication of the amount of solids/compounds in the water.

    The question is, how do we achieve 0 TDS.

    PLEASE ADD TO THIS THREAD OF YOUR KNOWLEDGE OF THE PREFILTERS, TDS METER, FLOW PATTERN, OPERATION OF THE UNIT AND MAINTENANCE OF THE UNIT.
     
  2. AdS Guest




    to hide all adverts.
  3. SchyffS

    SchyffS Thread Starter Reef Aquarist

    Joined:
    26 Jan 2008
    Posts:
    588
    Likes Received:
    12
    Location:
    Cape Town
    Just to add that the reason for my post is because i tested my RO water with 0 TDS and found phosphate >2.0 mg/l. I then tested my tap water and found the same problem. My RO unit seems to do nothing for phosphate removal and thus i intend adding a phosphate resin filter to my unit and hope for the best.
    Its not a Waterboy unit ans not a drinking water unit either.

    Any comments?
    Has anyone in the cape tested their RO and tap water for phosphate?
     
  4. Perky Pets

    Perky Pets Sponsor

    Joined:
    24 Jun 2010
    Posts:
    2,807
    Likes Received:
    116
    Location:
    Cape Town
    Hi , tap water not tested, but ive heard a rumour that , if carbon is not replaced timiosly it may release or even generate phosphate ?
    Do some reserch ?
     
  5. viper357

    viper357 Admin MASA Contributor

    Joined:
    4 May 2007
    Posts:
    27,990
    Likes Received:
    782
    I achieve 0 TDS by changing my pre-filters every 6 months (the sediment filter and carbon filter), also change the DI resin as soon as my TDS reading gets to 2 or 3, and I make sure I flush and then run my RO unit for 20 minutes before I start collecting the water.

    I would also assume that the make of membrane may play a part, apparently the Filmtech membranes are one of the best to use.
     
  6. lIghty

    lIghty

    Joined:
    3 Nov 2007
    Posts:
    5,053
    Likes Received:
    52
    Location:
    Westville, Durban
    I really doubt that the RO water would have a PO4 of 2mg/L, there are 2 things that I think might be happening: 1 - Test kit not designed to test Freshwater (especially RO) or 2 - the kit is faulty?

    I have just replaced my RO member with a Filmtech from Waterboy, And I'm getting a TDS of 1, IMO more that good enough for our tanks.
     
  7. SchyffS

    SchyffS Thread Starter Reef Aquarist

    Joined:
    26 Jan 2008
    Posts:
    588
    Likes Received:
    12
    Location:
    Cape Town
    What is the purpose of your DI resin, is it an indicator only or does it filter as well. My tds is 0, the problem is that my tap water has high phosphate and my RO doesn't do much to remove any of it. Can an additonal resin be added to remove phosphate. Is the filmtec membrane the only membrane that removes phosphate.
    Posted via Mobile Device
     
  8. SchyffS

    SchyffS Thread Starter Reef Aquarist

    Joined:
    26 Jan 2008
    Posts:
    588
    Likes Received:
    12
    Location:
    Cape Town
    Can you test your tap water and ro water for phosphate. I use the sera test kit, its designed for both freshwater and saltwater. I tested both, the reading is consistent. Test kit is good. Next solution?
    Posted via Mobile Device
     
  9. lIghty

    lIghty

    Joined:
    3 Nov 2007
    Posts:
    5,053
    Likes Received:
    52
    Location:
    Westville, Durban
    AFAIK the DI resin removes any remaining ions from the water, it only has a limited amount of "reaction" and therefore the water that enters this filter must be prefilterred (IE RO water with low TDS) otherwise it will become exhausted quickly. I'm not sure on the types/makes of membrane, I just know the filmtech is know to be the best, but there are many types/models so you have to make sure you get the correct one for our application.

    Unfortunately I though my PO4 test kit away as it was expired, and was also in-acurate. From what I can remember, the Sera kits are too inacurate!

    Perhaps Marco could clear this up for us, as he is the guru!
     
  10. SchyffS

    SchyffS Thread Starter Reef Aquarist

    Joined:
    26 Jan 2008
    Posts:
    588
    Likes Received:
    12
    Location:
    Cape Town
    Yes, the test kit debate....for this instance i dont need the 0.001 accuracy. The test results are in the 1.0 decimal range. I would use a more accurate test kit if i was talking about 0.001 ranges.

    Yes, DI resin, usually removes the last bit of chlorine, thats what i was told as well.
    Teh carbon block and sediment has its job, its more of a prefilter to prolong the ro membrane life and also to make it work less as hard. Changing these prefilters 3-6 monthly is best practice, no doubt.

    Carbon doesnt absorb phosphate so it cant ever leach it.....so that argument doesnt make any sense.

    I agree, hoping to hear from the Marco.
    Will it be possible that any of you can test your tap water and RO water for phosphate. In the meantime, i will contact the water affairs department and try and get their water chemistry parameters.
    My conclusion up to this point is that permanent antiphos is required on the main system or the RO unit as the council water has high levels of phosphate.

    GO SPAIN :)
     
  11. lIghty

    lIghty

    Joined:
    3 Nov 2007
    Posts:
    5,053
    Likes Received:
    52
    Location:
    Westville, Durban
    :censored: Spain!
     
  12. SchyffS

    SchyffS Thread Starter Reef Aquarist

    Joined:
    26 Jan 2008
    Posts:
    588
    Likes Received:
    12
    Location:
    Cape Town
    mmm, so RO water is too pure and is unstable when tested due to contamination issues. Okay, i get it. That leaves a bit of a loop hole as we cant really test the RO water without the risk of contaminating the water sample and prove that the RO membrane actually removes phosphate.

    Carbon, im not convinced about the carbons ability to adsorb any phosphate, gonna use my one phone call on this one. Marco! LOL, help us out on the details :)

    Okay, lekker debate. Gonna do more research on carbons actual ability and its wish list of abilities as my tap water still has a high level of phosphate and thus its just not being processed by the RO unit which has a unexpired carbon block.
     
  13. Manic

    Manic Moderator

    Joined:
    12 Mar 2009
    Posts:
    3,313
    Likes Received:
    58
    Location:
    Johannesburg, Edenvale
    I hate spain. Primarily because every Portuguese person is supporting spain and because they knocked out my team (Germany), it's all paul the octopus' fault.
     
  14. IMarine

    IMarine

    Joined:
    20 Oct 2007
    Posts:
    1,512
    Likes Received:
    16
    Location:
    walmer estate capetown
    yo bra you can use phos remover from seachem in your ro unit but you need to fit a inclosed plastic filter with a sponge on top and that should sort problems out or if i am not mistaken i think you do get a phosphate filter for ro units
     
    SchyffS likes this.
  15. SchyffS

    SchyffS Thread Starter Reef Aquarist

    Joined:
    26 Jan 2008
    Posts:
    588
    Likes Received:
    12
    Location:
    Cape Town
    @ Imarine, so the water that exists the RO unit that has the 0 TDS value then goes into a PO4 filter before its ready for use. It will be a treat if there is a neat purpose made piece that attaches to the existing RO filters to be utilised a PO4 filter.

    Thanks for the advise.
     
  16. IMarine

    IMarine

    Joined:
    20 Oct 2007
    Posts:
    1,512
    Likes Received:
    16
    Location:
    walmer estate capetown
    there is and i can get no prob
     
  17. lIghty

    lIghty

    Joined:
    3 Nov 2007
    Posts:
    5,053
    Likes Received:
    52
    Location:
    Westville, Durban

    Gotta give that Octopus (wanted to leave a space in that name) credit, but do you know what else he is good with.................... Chips!
     
  18. SchyffS

    SchyffS Thread Starter Reef Aquarist

    Joined:
    26 Jan 2008
    Posts:
    588
    Likes Received:
    12
    Location:
    Cape Town
    LOL, octopus and chips...i cant say that is a normal combo special, but octupus tail on my hook will catch me a lekker big kabeljou to go with the chips.

    I did some reading on the Randy Holmes Farley papers...inorganic phosphate is best adsorbed by iron oxide hydroxide [Fe(OH)3] also known as Granular Ferric Oxide (GFO). Supplier names such as Antiphos, Rowaphos etc
    Granular Activated Carbon (GAC) is best suited for the adsorbtion of dissolved organics....phosphate is in the organic state could possibly be adsorbed by the GAC. The test kits only measure inorganic phosphate.
    I cant find a discussion on the properties of carbon and specifically its leeching of organic phosphate. But i can see how the carbon just allows phosphate to pass through without being adsorbed.

    Any one know where Marco is?
     
  19. TheWaterboy

    TheWaterboy Sponsor

    Joined:
    6 May 2007
    Posts:
    2,117
    Likes Received:
    79
    Location:
    Durban
    hey dude.....

    just read this now....sorry been in pretoria for a few days installing this......




    3000 litre per hour r.o.unit......

    [​IMG]
    going to a meeting now....will reply this evening
     
    Last edited: 12 Jul 2010
  20. SchyffS

    SchyffS Thread Starter Reef Aquarist

    Joined:
    26 Jan 2008
    Posts:
    588
    Likes Received:
    12
    Location:
    Cape Town
    Hi Marco, thats a room dedicated for a RO unit....nice :)
    Looking forward to get some RO 101 lesson from you.
     
  21. SIMS

    SIMS

    Joined:
    6 May 2007
    Posts:
    3,008
    Likes Received:
    17
    Location:
    Empangeni
    well I have tested with a hanna meter and my RO unit seems to take out ALL the PO4
     
Recent Posts

Loading...
Similar Threads - Reverse Osmosis Water Forum Date
Reverse Osmosis Special!!! Sponsor Specials 29 Mar 2016
Find Anything Reverse Osmosis at Reef Aquatics Reef Aquatics 3 Jul 2014
Reverse Osmosis Units Test Kits, Controllers, Reactors and Dosers 28 Aug 2013
Reverse Osmosis System General Discussions and Advice 19 Nov 2012
reverse osmosis Beginner Discussions 24 Aug 2012
Reverse Osmosis General Discussions and Advice 24 Jul 2012
A brief guide to how RO (Reverse Osmosis) Works Water Parameters and Additives 18 Nov 2010