Uv faq

Discussion in 'Protein Skimmers, Mechanical Filtration' started by dallasg, 15 May 2014.

  1. dallasg

    dallasg Moderator MASA Contributor

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    [FONT=Arial,Helvetica,sans-serif]Some Top Tips

    Q.
    [/FONT]
    [FONT=Arial,Helvetica,sans-serif] How do ultraviolet ("UV") sterilizers work?
    A. UV sterilizers work by exposing water to powerful germicidal ultraviolet light. DNA and protein links in bacteria are destroyed by exposure to this light.

    [/FONT][FONT=Arial,Helvetica,sans-serif]Q. What if the water flows faster than is allowed through the system?
    A. If the flow rate exceeds the design flow rate of the UV sterilizer, then there is a possibility that the water will not be properly disinfected. It is important to use a flow restrictor so that the flow rate cannot be exceeded.
    [/FONT]

    [FONT=Arial,Helvetica,sans-serif]Q. How long does the lamp last?
    A. The lamps last approximately 9,000 hours, check with the manufacturer. Thats a replacement approximately every 12 - 14 months of continuous operation. After this period, the lamp itself becomes solarized and blocks the rays form entering the water

    [/FONT]Q. My water is sometimes cloudy. Is that a problem?
    A. Yes. The water that enters the ultraviolet sterilizer must be absolutely clear and have a turbidity of less than 1 NTU. If your water is cloudy, then it must be pretreated.

    its a start :)
     
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  3. Nemos Janitor

    Nemos Janitor

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    Q. What is the power required to kill white spot.
    A. A radiation density of 33000 microwatt's/sec/sq.cm is sufficient to kill most common pathogens in our aquariums.
     
  4. carlosdeandrade

    carlosdeandrade

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    Let's start over at the beginning ...
    UV is an abbreviation for Ultraviolet light, which is a spectrum of light just below the range visible to the human eye. That is to say UV light is below the blue spectrum of visible light. So UV light cannot be seen by the human eye, and for that reason is often called UV energy.

    UV light is divided into four groups as measured by wavelength: (1) Vacuum UV with wavelengths from 100 to 200 nanometers, (2) UV-C at 200 to 280 nanometers, (3) UV-B at 280 to 315 nanometers, and (4) UV-A at 315 to 400 nanometers.

    The UV-C spectrum (200 to 280 nanometers) is the most lethal wavelength for microorganisms, because it disrupts the bonds in the between the atoms in the chemicals in microorganisms. This range of wavelengths, with 264 nanometers being the peak germicidal wavelength, is known as the Germicidal Spectrum.

    When you understand UV light and how it destroys microorganisms, you can properly select the appropriate UV light source and design your UV's water containment vessel around the lamp, or lamps in the case of a multi-lamp unit.


    The UV Lamp is the Source of UV-C Light.
    There are two primary types of UV light, low-pressure lamps and medium/high-pressure lamps. Low-pressure lamps produce virtually all of their UV output at a wavelength of 254 nanometers, which is very close to the peak germicidal wavelength of 264 nanometers.

    These lamps generally convert up to 40% of their input watts into usable UV-C watts, much higher than other classes of lamps. For example, a 150-watt low-pressure lamp will produce approximately 58-watts of UV-C power.

    Low-pressure lamps typically run on low-input power currents of 200 to 1,500 milliamps and operate at temperatures between 100 and 200 degrees Fahrenheit. They have a useful life of 8,000 to 12,000 hours, depending on the operating current of the lamp. Low-pressure lamps are the best lamps for aquatic UV sterilizers.

    Medium/high-pressure lamps produce a very wide range of wavelengths, from 100 nanometers to greater than 700 nanometers, well into the visible light spectrum. These lamps are very poor producers of usable germicidal wavelengths; they generally convert a maximum of 7% of their input watts into usable UV-C watts. For example, a 175-watt medium-pressure lamp will have approximately 12-watts of UV-C power.

    The remaining 163-watts are converted into heat and visible light. Medium/high-pressure lamps typically run on high-input power currents of 2,000 to 10,000 milliamps and operate at temperatures between 932 and 1,112 degrees Fahrenheit. They have a useful life of only 1,000 to 2,000 hours, depending on the lamp's operating current.

    The length of the lamp being used.
    Low-pressure UV lamps come in many different styles and lengths. As a general rule, the longer the lamp, the greater amount of UV the water will receive because it will be exposed to the UV source for a longer period of time.

    UV Design
    The physical design of the UV's water exposure chamber. This element is completely overlooked by some manufacturers, but is key to successful operation.

    Key Design Criteria:

    Lamp Positioning
    Make sure the UV lamp is positioned between the water inlet and outlet ports of the unit's water containment vessel. Any portion of the UV lamp that is not located between the water ports is rendered useless. Furthermore, when calculating the UV’s performance data only the ARC length located between the water ports can be applied to the calculation, thus reducing its capabilities.

    Vessel Diameter
    Select a unit with the largest diameter water containment vessel in the wattage you are considering. A unit with a larger diameter will always have a greater contact time. For example, a 25-watt model with a 3" diameter housing will flow more water than a 2" housing model.

    Quartz Sleeve
    Make sure the unit you are considering uses a quartz sleeve. The quartz sleeve is needed to isolate the UV lamp from the water to avoid a short circuit path for the lamp's electrical power and to allow the lamp to operate at its optimum temperature by acting as an insulator.

    Water Flow Rates

    Do manufacturers list water flow rates at the end of a lamp's life or the beginning? Most UV manufacturers give a water flow rate, but do not indicate whether it applies to a new lamp or one that is at the end of its useful life. Try to find a manufacturer that includes the water flow rate in the unit's end of lamp life rating. The end of lamp life rating takes into account the lamp losing UV-C output due to age and therefore is a more realistic projection of how the unit will perform.

    Transmissible light
    Do the manufacturer's water flow rates account for the reduced effectiveness UV light has when treating green water? This information should be listed as some type of percent transmissibility rate or absorption coefficient (decimal value). Units that account for this will have lower water flow rates.

    UV Transmittance
    The condition of the water to be treated. This also largely overlooked factor is one of the most critical in determining the ability of a UV sterilizer to treat a given volume of water. Regardless of the type of UV light source used, any body of water with impurities will adsorb UV energy.

    The impurities of interest are algae, waterborne microorganisms and bacteria, and organic waste. Green water, as water plagued by algae and microorganisms is known, will absorb the UV energy emitted by our UV light source in proportion to its density (or how green the water is).

    The greater the amount of impurities in the water, the greater the reduction in percent transmittance. Percent transmittance is the ability of a body of water to be effectively treated by a UV light source. This value indicates the quality of the water to be treated.

    The higher the percent transmittance, the easier the UV sterilizer will be able to treat the water at a given flow rate. A reduction in percent transmittance means the UV sterilizer will be less effective in dealing with the algae problem. If the sterilizer's water flow rates have not been calculated with a reduced percent transmittance rate, the unit will have considerable trouble dealing with an algal bloom.

    Water Flow Rate through the UV
    The basic criteria for a sound UV sterilizer design revolves around a careful selection of lamp type, lamp length, lamp position, and body diameter. These factors, together with the intended water flow rate, percent transmittance of the water to be treated, and UV dose rate needed to destroy the targeted microorganism or pathogen, should be the basis of your decision when purchasing a unit for your pond or aquarium.

    Multiple UV Lamp Use
    When considering the use of multiple UV lamps there are two proper ways to approach the design. Firstly, one can use a single body exposure chamber with multiple lamps evenly spaced to provide a consistent UV field. This design is very effective provided the UV lamps are properly spaced.

    Secondly, one can use a double body exposure chamber which effectively reduces the total flow rate through each exposure chamber. The flow is reduced to 50% of the total flow through each chamber.

    A Common Mistakes
    One can continue to add UV's in series and receive higher kill rates. This is not the case. When adding UV's in a series, you are passing the same flow rate through the same intensity lamp, repeatedly.

    UV Exposure is not Cumulative!
    In order to effectively implement a multi body UV unit one must operate the lamps in parallel. For example, if I am operating two 40-watt lamps in parallel I effectively have an 80 watt UV. If I am operating two 40-watt lamps in series then I effectively have two 40-watt lamps each providing the same intensity which is not cumulative.

    All UV's are not created equal!
    When researching which type of UV to purchase, remember the criteria laid out in this article, read the manufacturer's literature, ask questions, and most of all ask yourself, does this information provided make sense to me? If not, consider another UV manufacturer.

    Source: UV Aquarium Sterilizers - UltraViolet.
     
  5. carlosdeandrade

    carlosdeandrade

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    This is the flow through the UV light.
     
  6. carlosdeandrade

    carlosdeandrade

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  7. RiaanP

    RiaanP Moderator

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    Is that not in a series?
     
  8. carlosdeandrade

    carlosdeandrade

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    Yes, you're correct. Gonna have to fix that. Don't think it's possible. Bugger!
     
    Last edited: 15 May 2014
  9. Nemos Janitor

    Nemos Janitor

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    It is the amount of radiation supplied for the volume of water.

    Yes flow will affect the amount of radiation.
     
  10. RiaanP

    RiaanP Moderator

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    And the sleeves needs to be cleaned regularly. A bit of extra work.
     
  11. TheWaterboy

    TheWaterboy Sponsor

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    correct .....if this is not done the uv light looses up to 80 percent efficiency
    quartz sleeves are very important...a good uv sterilizer will have a quartz sleeve...there are many out there with the water making contact with globe direct

    and thats no cut and paste .....thats from the horses mouth;)
     
  12. carlosdeandrade

    carlosdeandrade

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    I'm prepared for that.
     
  13. RiaanP

    RiaanP Moderator

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    To those that uses UV units.
    How often do you have to clean the sleeves?
     
  14. dallasg

    dallasg Thread Starter Moderator MASA Contributor

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    i do it monthly, i use zeiss lens cleaners so i dont get scratches etc
     
  15. TheWaterboy

    TheWaterboy Sponsor

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    thats really clever thinking dallas,
    and doing it religiously like that is a bonus, youll get excellent results
     
  16. carlosdeandrade

    carlosdeandrade

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  17. Snoek

    Snoek

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    I understand that uv kills bacteria however what will the effect be on the good bacteria? Surely it can't be good for long term use. Does it effect any of the bacteria that's in liverock or the bacteria that comes off cubes?
     
  18. carlosdeandrade

    carlosdeandrade

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    Not in the slightest. This is a common misconception. Bacteria that are waterborne are affected but bacteria are mostly found attached to all surfaces in your tank.
     
  19. Zandy

    Zandy

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    Mmm thanks for this carlos..but we are still waiting for the post on ozone too.... lol.....your posts I find very informative. ..Thanks
     
  20. jclaas

    jclaas

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    (beneficial bacteria) right?
     
  21. carlosdeandrade

    carlosdeandrade

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    Thanks. Yes, need to get that going too. I have tons of info on O3. Just need to consolidate it.
     
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