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Reverse Osmosis System Basics

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Reverse Osmosis System Basics

  1. 1. Reverse Osmosis Basics<br />Overview:<br /><ul><li> Osmosis
  2. 2. Reverse Osmosis Definition
  3. 3. RO Fundamentals
  4. 4. Reverse Osmosis Membrane
  5. 5. Parameters Affecting RO Systems
  6. 6. Air Gap Faucets
  7. 7. RO Maintenance
  8. 8. Quick ConnectFittings
  9. 9. Troubleshooting</li></li></ul><li>Reverse Osmosis Basics<br />Osmosis:<br /><ul><li> Osmosis is a natural phenomenon that provides water to all animal and vegetable cells to support life
  10. 10. Water moves from a high concentration of water (less sugar/salt dissolved in it) to a low concentration of water (more salt/sugar dissolved in it) across a semi-permeable membrane
  11. 11. This means that water can cross a selectively permeable membrane from a dilute solution (less dissolved in it) to a concentrated solution (more dissolved in it)</li></li></ul><li>Reverse Osmosis Basics<br />Osmosis: What is it?<br />Reference: //<br /><ul><li> A semi-permeable membrane is a membrane which will allow only certain molecules or ions to pass through
  12. 12. Osmosis is very important in biology as it provides the primary means by which water is transported in and out of cells</li></ul>Net Movement of Water Molecules<br />
  13. 13. Reverse Osmosis Basics<br />Reverse Osmosis: What is it?<br /><ul><li> RO is a form of filtration using osmosis in reverse
  14. 14. Water passes from a more concentrated solution to a less concentrated solution
  15. 15. To accomplish this a force or pressure MUST be applied
  16. 16. RO requires 1 psi of pressure for every 100 ppm of TDS
  17. 17. RO is used to remove dissolved solids from water but it can also improve taste, odor & color of water
  18. 18. RO membranes have the capability to remove particles as small as ions i.e. magnesium ions or sodium ions
  19. 19. RO membrane will reject most compounds based largely on size
  20. 20. Dissolved ions, such as salts, carry an electric charge and will also be rejected by membrane</li></li></ul><li>Reverse Osmosis Basics<br />Osmosis: How does it work?<br /><ul><li> Feed water flows into RO unit with the force of line pressure
  21. 21. Water is forced through membrane by cross flow filtration
  22. 22. Cross flow filtration is most commonly used in RO as it allows membrane to continually clean itself
  23. 23. Membrane then either rejects or repels contaminants
  24. 24. Two exit streams generated: waste & product stream
  25. 25. Waste stream consists of: A concentrate (reject) stream which carries contaminants (compounds too large to pass through membrane)
  26. 26. Permeate stream consists of: Product water which has been forced through the membrane & is virtually free of TDS</li></li></ul><li>Reverse Osmosis Basics<br />Reverse Osmosis Schematic<br />
  27. 27. Reverse Osmosis Basics<br />RO Membrane:<br />
  28. 28. Reverse Osmosis Basics<br />Reverse Osmosis Fundamentals:<br />FEED WATER: Main flow of impure water to be treated; <br />PRODUCT WATER: Portion of feed water which passes through membrane as permeate<br />REJECT WATER: Portion of feed water which did not pass through membrane; carries impurities to drain<br />MODULE: Combination of spiral round membrane element & <br /> pressure vessel<br />
  29. 29. Reverse Osmosis Basics<br />Spiral Wound Membrane:<br /><ul><li>RO membrane is a method of fine filtration but much smaller
  30. 30. Membrane consists of tiny pores which are approximately 0.0005 microns in size
  31. 31. THEREFORE reverse osmosis membranes are capable of rejecting contaminants as small as 0.0001 to 0.00001 microns</li></ul>Thin Film Composite Membrane (TFC)<br />
  32. 32. Reverse Osmosis Basics<br />RO Membrane:<br /><ul><li> Membrane is the work-horse of an reverse osmosis system
  33. 33. When choosing an RO system you must do so wisely – taking into account water quality is very important
  34. 34. Three main types of membranes:</li></ul>CTA membrane: Cellulose acetate/triacetate blend<br /><ul><li> Provides lowest cost per gallon of water
  35. 35. Resists chlorine but has a lower flow rate limit in applications of high water consumption</li></ul>TFC membrane: Thin film/thin layer composite<br /><ul><li> Can handle high flow, has a high rejection rate & can handle high water consumption
  36. 36. Cannot handle chlorine concentrations; water must be carbon pre-filtered</li></li></ul><li>Reverse Osmosis Basics<br />Membrane Comparison:<br />
  37. 37. Reverse Osmosis Basics<br />TFC Membrane:<br /><ul><li> TFC membranes are intolerant to chlorine – will cause deterioration of membrane
  38. 38. Must use a carbon pre-filter for TFC membranes
  39. 39. TFC membranes have a much higher rejection rate of many chemicals than CTA membranes
  40. 40. Carbon pre filters are vital in the life of this membrane & must be changed regularly</li></li></ul><li>Reverse Osmosis Basics<br />Parameters that affect RO:<br />Water Temperature: RO system ratings are based on 770F/ 250C water temperature<br />i.e. : RO system rated at 20 GPD (gallons per day) at 340F/10C will only produce 6 GPD<br />Feed Water Pressure: A lack in water pressure (less than 40 PSI) will reduce product water; this can be helped with the aid of a booster pump<br />Contaminants in Feed Water: Large particles, iron concentration or high levels of hardness in feed water can cause clogging of the membrane<br /> Clogging of the membrane can decrease its life<br />Microorganisms: RO membranes can filter out bacteria, depending on the bacteria size, however this may cause fouling of the membrane as bacteria can begin to grow through pores of membrane causing BACTERIA CREEP – RO systems should not be installed on non-potable water<br />
  41. 41. Reverse Osmosis Basics<br />RO Production Rate vs. Feed Water Conditions:<br />
  42. 42. Reverse Osmosis Basics<br />RO Systems can remove the following contaminants:<br /><ul><li> Dissolved solids = TDS (salts & minerals) – UP TO 2000 ppm
  43. 43. Most Heavy metals (lead, mercury, silver)
  44. 44. Most radioactive elements
  45. 45. RO systems may not be capable of removing nitrates to recommended levels</li></li></ul><li>Reverse Osmosis Basics<br />Typical Rejection Ranges of Contaminants:<br />
  46. 46. Reverse Osmosis Basics<br />RO Treated Water:<br /><ul><li> RO systems will remove up to 97% (depending on parameters) of salts in water bringing it closer to a level of ‘pure water’
  47. 47. The purer the water, the more aggressive it will be with materials it comes in contact with
  48. 48. THEREFORE RO can be slightly corrosive
  49. 49. It’s recommended NEVER to use copper piping on RO water </li></li></ul><li>Reverse Osmosis Basics<br />Typical Consumer RO System:<br />POSTFILTER<br />RO membrane<br />AIR GAP FAUCET<br />PREFILTER<br />TANK<br />To<br />Drain<br />
  50. 50. Reverse Osmosis Basics<br />Under-the-counter RO System:<br />
  51. 51. Reverse Osmosis Basics<br />Air-Gap Faucets:<br /><ul><li> ‘Air gap’ faucet is a plumbing device designed to provide a siphon break for an under-sink reverse osmosis unit
  52. 52. It is a valve used to isolate one part of a water system from the drain
  53. 53. Air gaps are designed to prevent backflow by incorporating a “backflow prevention” method called an ‘air gap’
  54. 54. Purpose of an air gap faucet is to assure that no water from a stopped-up sink can possibly be forced backward into your reverse osmosis system unit via its drain connection
  55. 55. Some plumbing codes do enforce the use of an Air Gap faucet</li></li></ul><li>Reverse Osmosis Basics<br />RO System Maintenance:<br />When to Replace Pre-filters:<br />When to Replace Post-filters:<br /><ul><li>Every 6 months for normal installations.
  56. 56. After a Boil Water Advisory (BWA)</li></ul>Every 6 months, depending on water conditions.<br />Noticeable decrease in water production indicates that the prefilter should be changed.<br />After microbiological contamination, such as in a Boil Water Advisory (BWA)<br />
  57. 57. Reverse Osmosis Basics<br />RO System Maintenance:<br />When to Replace the Membrane<br /><ul><li> Typically, every 18 months to 3 years
  58. 58. Test using a TDS (total dissolved solids) meter. Replace a membrane below 80% TDS reduction.
  59. 59. This will depend on influent water quality, usage, pre & post filter maintenance
  60. 60. Maintain filters, lengthen life of membrane!!!</li></li></ul><li>Reverse Osmosis Basics<br />Troubleshooting:<br />Q: I have an RO system & there is water coming out the back of the faucet. What’s wrong?<br />A:You probably have an air gap style faucet. What is most likely happening is there may be a clog or kink in the RO drain line causing water to come through the hole at the back of the faucet<br />Q:What if my hardness level is more than 7 gpg?<br />A:The hardness level of your water will tend to foul the membrane of the system.<br />Q:Is it true that RO systems waste a lot of water? <br />A:With some RO systems it take as much as 10 gallons of water to produce one gallon. This is an extreme case but most ‘high quality’ systems will have a 3:1 ratio<br />Q:Should you use copper tubing with RO systems?<br />A:NO. RO systems reduce up to 97% of TDS in water. The aggressiveness of the purified water toward materials it comes in contact with is a function of its purity. The better the purity the higher its aggressiveness.<br />
  61. 61. Reverse Osmosis Basics<br />Troubleshooting:<br />Q: My RO continues to run. What is wrong?<br />A: Shut off valve could be defective OR<br />A: Check the storage tank; it might not have enough air in it. The tank should have 7 lbs of air in it when empty. Too much air will cause an RO to shut off permanently <br />Q: I have installed my RO but am not getting much water from faucet. I do hear water running. What is wrong?<br />A: For a residential system it takes a long time to product RO water. Faucet needs to be in ‘off’ position & then the tank will fill slowly. If a system is rated at 30 USGPM then it will take one full day to produce that 30 USGPM. The water you hear running is the reject stream going to drain.<br />Q: My RO system seems to work but when I want to get 3 gallons of water at once I can’t get anything. Is this normal?<br />A: Most RO systems come with a 3-4 gallon storage tank. <br />
  62. 62. Reverse Osmosis Basics<br />Troubleshooting:<br />No Permeate Water<br /><ul><li>Membrane Fouling
  63. 63. Prefilter Fouling
  64. 64. Inadequate Pressure</li></ul>Slow Flow at the Faucet<br /><ul><li>Air Charge
  65. 65. Tank not filling
  66. 66. Installation of tank, tubing length
  67. 67. Inadequate Pressure</li></li></ul><li>Reverse Osmosis Basics<br />Quick Connect Fittings:<br /><ul><li> RO systems cannot be installed using copper piping as product water is slightly aggressive
  68. 68. Plastic tubing is most commonly used in RO installations
  69. 69. Pipe connections are accomplished using Quick Connect Fittings
  70. 70. Quick Connect fittingsdo NOT need any additional special tools
  71. 71. Simply cut tube square & insert into QCfitting to accomplish a secure connection</li></li></ul><li>Reverse Osmosis Basics<br />Quick Connect Fittings:<br />Prepare the connection: cut pipe square<br /> ensuring that it is free from score marks<br />DO NOT USE A HACKSAW<br />To avoid damage to o-ring of QCfitting, make<br />sure burrs & sharp edges are removed<br />