High Output UVC Emission from a UV Bulb/Lamp; Aquarium or Pond

 

Last Updated: 3/9/2020

OVERVIEW;
Actual UVC output from your Aquarium/Pond UV Bulb/Lamp

A great point was brought up in one of our blogs specify geared to sterilizers and UV bulbs.
All the time, we hear about the wattage a bulb of any kind uses.
A standard light we use in our homes are 60 watt bulbs.
In water sterilizers, the bulb might be a 30 watt bulb.

The point made and the question now being; does a 30 watt UV-C bulb emit 30 watts of useful sterilizing watts?
And, the answer is No.
The UV-C wattage emitted is not the same wattage of a lamp.

Wattage of a bulb can be misleading. Watts used in a bulb is the power consumption of a bulb.
A 60 watt bulb used 60 watts of power. The actual output of a bulb is directly related to the wattage.
The higher the watts used, the great the power consumption.
But what is noteworthy, is that the wattage though does not actually tell us how much useful output the bulb has, or how efficient it is.
The efficiency of the bulb is the actual output of the bulb.

This efficiency is what becomes important as we look for a replacement for our UV Sterilizer/Clarifier or even a new UV Sterilizer as most of what is sold via the Internet or discounter brick & mortar stores are LOW OUTPUT medium pressure UV bulbs/lamps with as little as 25% of the UVC of the vastly better low pressure high output UV lamps sold but by a handful of high end sellers.
So please read on and beware if the price seems too good.

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Specify speaking about UV-C bulbs, they have a light energy spike at a certain wavelength of light (254nm). This light energy is what sterilizes.
With any UV-C bulb, there will be an energy spike at this lighting level as well use some of it lighting energy on other parts of the lighting spectrum.

The light emitted at the UV-C namometer of light is the useful energy or wattage used from the bulb. The other energy emitted on the lighting spectrum that is not UV-C is essentially wasted energy.
Therefore the wattage of the lamp is not the same wattage being emitted of UV-C.
A 30 watt UV bulb does not emit 30 watts of UV-C.

Take a look at this picture which shows the energy spike of a UV bulb. At this spike, light energy has sterilizing abilities.

In a premium low pressure true UV bulb, the actual UV-C emission of the bulb is about 35%. If you have a 30 watt UV bulb, it will emit 10.5 watts of germicidal UV-C.
Nail curing UV Bulbs, are commonly sold on Amazon & eBay for aquarium pond use at a lower cost (generally for retails prices of $5 to $15).
These are usually medium pressure UV bulb with a low 7-10% output of useful UV-C irradiation. These lamps have a wholesale cost of only a few $ for the smallest ones.
What buyers should also be aware of is how many hours the lamp/bulb is rated to last as true HO low pressure UV lamps burn themselves up quickly with only 4000 hours at peak performance. So if the lamp advertises 8000-10,000 hours--- AVOID IT!

The fact remains, that a true High Output "low pressure mercury" UV lamp/bulb has a distributor cost of at least $10 for even the smallest/cheapest of lamps, so if it is selling for this cost you know you are NOT get what you need to best run your UV Sterilizer or even Clarifier

As well the Halogen UV bulbs sold in some mini UV Sterilizers also have little of the peak UVC irradiation, more in the UVB range (these too are sold at discounters such as Amazon, not quality professional UV Sterilizer sellers). A good example of a UV Clarifier sold with these UV lamps is the Cobalt Aquatics Micro-UV which besides using the lower output Halogen UV lamp/bulb, it has very poor dwell time.

Both of these types of these low cost UV bulbs are marginal for clarification at best, certainly NOT level one or higher UV Sterilization unless used at very high wattages per water flow!! When combined with the lower dwell time that most of these Sterilizers that utilize these medium pressure lamps have (generally compact UVs), you are looking 1/4 the killing/sterilization/clarification power!!
An example would be comparing a TMC Vecton 15 Watt to a Jebaeo 55 watt that is commonly supplied with medium pressure UV lamps/bulbs (15 x 4 = 60).

As an example, if you have a 9 Watt UV Sterilizer (such as the Turbo Twist), and when the bulb is due for replacement you utilize one of the low cost medium pressure UV Bulbs, you will be getting 1/4 to 1/3 the output of a premium low pressure bulb. So if you have a flow rate of 200 gallons per hour on your say 50 gallon aquarium as would be a flow rate for low pressure UV Bulb, then switch to the low cost medium pressure UV Bulb, you would need a flow rate of 80 gph just to maintain Level One UV Sterilization.
The bottom line is to not be tempted by the low prices of the nail curing medium pressure UV Bulbs that many retailers either unknowingly or knowingly incorrectly market for pond or aquarium UV Sterilizer use!

Please Reference:
UV Sterilization; Basic Factors

Recommended Professional Source for Premium Low Pressure UV Bulbs:
*American Aquarium PREMIUM Low Pressure UV Bulbs; Compact Style
*American Aquarium PREMIUM Low Pressure UV Bulbs; Straight Tube Style (for Aqua Ultraviolet, TMC, more)

Normally, the actual emission of a UV bulb is something you will not need to worry about, but what you do what to make sure is you are getting a large enough sterilizer for the water quantity you are looking to sterilization.
Company’s that know what they are talking about will publish this information or keep it in mind, when giving recommendation.
If you are not sure, make sure to look for what kind of bulb/lamp the sterilizer has and how much UV-C you are actually getting.

UVC, Watts, Microwatts

 

Revised: 1/2/18

UVC, Watts, Microwatts, Joules, & Light Penetration

This article/post is intended to give some basic understanding between the relationship of watts, microwatts, joules of UVC energy and how this translates to UV Sterilizer effectiveness.

Please keep in mind that the diagram in this article is based on air penetration, so some extrapolation is necessary for use in water applications (which is the primary intention of this article, although the principles apply to UVC air sterilization devices as well)
UVC Air Sterilization Devices

What is a Watt/Microwatt?

One Joule of energy = 1,000 milliWatt seconds = 1,000,000 microWatt seconds
One joule is the amount of energy required to perform the following actions:

• The work done by a force of one newton traveling through a distance of one meter (a newton is the unit of force equal to the amount of force required to accelerate a mass of one kilogram at a rate of one meter per second per second);
• The work required to move an electric charge of one coulomb* (the amount of electric charge transported by a current of 1 ampere in 1 second) through an electrical potential difference of one volt; or one coulomb volt, with the symbol C•V;
• The work done to produce power of one watt continuously for one second; or one watt second (compare kilowatt hour), with the symbol W•s. Thus a kilowatt hour is 3,600,000 joules or 3.6 megajoules;
• The kinetic energy of a 2 kg mass moving at a velocity of 1 m/s. The energy is linear in the mass but quadratic in the velocity, being given by E = ½mv²;
we measure UV-C intensity in Micro-Watts that strike one square centimeter of surface area.
Reference: What is a coulomb?

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UVC Penetration;
A quote from an advanced sterilization article:
UV Sterilization; How a UV Sterilizer Works

"The emission or light intensity of a UVC germicidal light bulb is usually expressed in a term called "microwatts per square centimeter" (Mw/cm2). The maximum intensity provided by a single UV-C Bulb is at its surface.
So, if we calculate the surface area of the UVC lamp and only use that area which effectively emits UVC light rays, the effective area of UVC transmission will be established. Basic mathematics will show that the surface area of a cylindrical tube is ‘pie’ D L.

Next extrapolate this effective area of UVC transmission as having a screen with squares 1 centimeter in size. Each of these cm2 areas now, for measurement purposes, emits a UVC lamp intensity measured in microwatts, in other words; the term microwatts/cm2. UVC light intensity decreasingly varies as the distance from the UVC light increases.

Put more simply (a non scientific analogy); The amount of wattage will also increase penetration, as a higher watt UV-C bulb will generally have more Mw/cm2."
See this product link for high output Straight Tube UV Bulbs:
Premium HO Straight Tube UV Lamps

"In my own experiments I have used 15 watt and 25 watt UVC bulbs in exactly the same unit (both were 18”), if wattage were only considered there would be a 60% increase in effectiveness, however I only observed a about a 25% increase.
When I used a 30 Watt UVC bulb in a unit with over twice the exposure as the 15 Watt, the kill rate more than doubled. From my experience, if you increase wattage (and Mw/cm2) you need to also increase the volume of water to maximize the higher watt bulb.
Experiments can also be safely conducted with standard household light bulbs to correlate penetration. For this start with a 7 watt clear bulb (such as a Christmas bulb) and place varying thicknesses of paper/ cardboard in front of the bulb and measure when penetration stops. Continue this with higher and higher wattage bulbs."

The Diagram to the left can give a rough comparison of distance as per UVC energy as expressed by MW/cm2 in Air transmission.
The dose applied by an UV-C lamp installation is a function of the lamp output, the intensity factor, and time. As an equation; Intensity x Exposure time= microwatt seconds/cm2.

As an example, a 9 watt UVC lamp at one inch from the lamp is found by this formula:
9 x 127 = 1143 mW/cm2.
Since many bacteria such as Vibrio require a UVC exposure of 6500 mW/cm2 or more, this means an exposure time of 5.68 seconds is required to kill this pathogen


Now let me point out that even though I have published this diagram, please use this as a rough guide only, as I have found inaccuracies in it. To be more blunt; I have found the distance, wattage, and flow rate to be the MOST IMPORTANT factors in determining exposure/effectiveness. This diagram is STATIC and does NOT take into consideration the dynamics of UVC radiation penetration for which I have yet to find a good formula to demonstrate this (even in University studies).

What is often missing in any equations I have seen is the dynamics of water flow geometry, actual water flow, and wattage. The bottom line is to use this table and others you might find elsewhere with “a grain of salt” noting that these are static and even then are flawed when true output via wattage is taken into consideration.

Further Reading, References, Product Resources:

*UV Sterilization; How it works for Aquariums, Ponds, & more

*Harmful Pathogens: The Threat, mJ/cm2

*http://www.solartanic.com/index_022.htm


UV Bulb; Replacement Lamps
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