UV Dose Calculation

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I need a simple way to calculate the UV-dose (mW/cm2) without the use of a failing UV-intensity meter so I can compare to a proposed effluent standard in our new permit (30.0). 

We have a very reliable transmittance meter showing a level in excess of 65% typically. 

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7 Answers

  2. Hello Derek

    I am located in CT and would be happy to discuss this issue with you.  email me at rmcintyre@enaqua.com and I will send you my contact information. I have experience in Optics/ Measurement and lamp technology and might be able to find a practical solution to you "dose" problem.

  3. Dear Derek,

    Good question but complex issue, for ​calculation of  the ​UV-dose (mW/cm2)​ or J/m2. Scientists have known for nearly a century that ultraviolet light of certain wavelengths is an effective germicidal agent. However, production of ultraviolet light in the proper range  expensive. With the development of high-intensity, long-life lamps came renewed interest in the use of ultraviolet as a disinfection agent for a variety of liquids, but primarily water.

    UV can be measured and it can be controlled. If UV is UV can be measured and it can be controlled. If UV is not measured & controlled not measured & controlled it will cause mysterious it will cause mysterious problems

    Following parameters are require

    1. Dwell Time or Belt/Line Speed Dwell Time or Belt/Line Speed
    2. Hour Meter
    3. Electrical Power (amp meter)

    E= hc/λ

    Where h= Planck Constant (6.626 x 10-34 m2 kg/s); c = speed of light in vacuum (3 x 108 m/s); λ (Lambda) = wavelength of the radiation, in this 365nm, which is equals to 3.65 x 10-7 m.

    So, E = 6.626 x 10-34 x 3 x 108)/ 3.65 x 10-7 = 6.626 x 10-34 x 3 x 108)/3.65 x 107 = 5.446 x 10-19

    Units = [(m2 kg/s) (m/s)]/(m) = (m2 kg/s x m/s) x (1/m) = m2 kg/s2 = J

    E = 5.446 x 10-19 J

    For understand problem following example may be considering

    duration: 7 x 24 x 60 x 60 = 604800 s

    E = 5.446 x 10-19 x 6.048 x 105 = 3.294 x 10-13 J (this much radiation is falling on metre square, but your source is 5 cm is away)

    Consideration of squared law as your source is.

    5 cm = 0.05 m, which means radiation only covers (0.05)2 = 0.0025 m2

    This means you have to divide the above equation by 1/0.0025 = 400 so as to make it in 1 m2 , as below

    E = 3.294 x 10-13/400 = 8.235 x 10-16 J

    ANSWER = 8.235 x 10-16 J at 365nm

    Others are

    9.953 x 10-16 J at 302nm

    1.183 10-15 J at 254nm

    1 Comment

    1. Mr. Baboo, these calculations make no sense at all. They have nothing to do with the calculation of UV dose (proper term fluence) in a UV reactor. What is needed is a fluence rate model to calculate the fluence rate distribution in the UV reactor. The the Fluence (UV dose) (mJ/cm2) is the product of the volume averaged fluence rate (mW/cm2) and the exposure time in seconds.

  4. Hi Derek. You need to know some data about technology and equipment UV  and their configuration. For example, I attach a model of calculation schedule of Trojan UV 3000 Plus. I hope that you can resolve your question. 

     

    Best Regards.

  5. Dear Derek, You may find some useful info in our Drinking-water Standards for New Zealand 2005 (revised 2008), Section 5.16: UV disinfection: treatment compliance criteria, and in Guidelines for Drinking-water Quality Management for New Zealand 2015, Section 8.4.3.3: UV light, Section 8.6.2.6: UV intensity measurement, Section 8.5.6: UV validation protocol (UV appliance challenge).    See URLs attached: http://www.health.govt.nz/publication/drinking-water-standards-new-zealand-2005-revised-2008  also  http://www.health.govt.nz/publication/guidelines-drinking-water-quality-management-new-zealand   The fluence (UV dose) / radiant exposure are referenced to as mJ/cm2 or J/m2 or mW.s/cm2 not uW.s/cm2

    1 Comment

  6. One CANNOT determine the UV dose delivered in a UV reactor with just a "UV intensity meter" (the proper term is "UV irradiance meter"). To determine the UV dose delivered, on either needs to do a complex biodosimetry test or use a fluence rate mathematical model (such as UVCalc). Send me an email at jbolton@boltonuv.com and I'll provide more details.

    1 Comment

  7. Hello ,As per UV protocol EPA/NWRI/IUVA recommended dosage is 30000uw-s/cm2 for 254NM UV lamp.BOD /TSS for effluent should be less than 10 mg/l and Total coliform 2.2 per 100ml for 7 days maximum should be maintain.

     

    2 Comments

    1. Mr. Nazeer - I see that you are still using the horrible units of uw-s/cm2. 30000 uw-s/cm2 is the same as 30000 uJ/cm2 or 30 mJ/cm2. When you state a number to 5 significant digits, it is implied that the measurement is accurate to a few parts in 30000, which is certainly not the case here. In modern scientific studies, a UV dose (proper term fluence) should be stated as 30 mJ/cm2.