UV or not UV

[crsublette]

1) Just a quick search, I came up with this product page for Aqua Ultraviolet Classic 57 watt UV, they list specific flow rates, UV exposure rates at those flow rates, and pond volumes for their unit, for different functions (eg clarifier vs sterilizer), also it goes on to say "A sterilizer will eliminate green water and control bacteria. The Classic 57 Watt, will sterilize up to 3,000 gallons of fresh water or 355 gallons of salt water." I'm sure I read other manufacturers in the past with similar claims and specs, and that how I made my educated guess that my UV unit is functioning as a sterilizer at the flow rates, and pond size I have. That is, when I turn it on anyway.

The link you provided talks about several things, including UV wavelength, and reduced effectiveness of the UV due to dirty quarts sleeve and water turbidity. These are of course things that can effect any UV unit, no mater what the wattage or price the unit it. It also goes on to say "We suggest oversizing the UV sterilizer by at least 40 percent to be sure of getting the killing power required when the lamp has aged". This is something I agree with wholeheartedly, and one of the reasons I advocate spending the money on a more powerful cheaper unit, as opposed to buying a more expensive lower watt unit.
2) I must admit though, I'm a bit confused by the UV exposure rates sited on the link you provided. (The required UV exposure rate to irradiate common bacteria is 15,000 µWs/cm² , while the required UV exposure for waterborne algae is 22,000 µWs/cm² .) It seems to be saying that it takes less UV rays to kill (irradiate) bacteria then it does to to kill waterborne bacteria???

2) I must admit though, I'm a bit confused by the UV exposure rates sited on the link you provided. (The required UV exposure rate to irradiate common bacteria is 15,000 µWs/cm² , while the required UV exposure for waterborne algae is 22,000 µWs/cm² .) It seems to be saying that it takes less UV rays to kill (irradiate) bacteria then it does to to kill waterborne [algae]???

Not for sure what you're asking here.

I believe the source for those numbers came from the Aquacultural Engineering book, which unfortunately I do not have the funds to purchase and to verify the table data. It would be interesting to know of other sources out there that list the µWs/cm² for an appopriate kill by a UV.


1) Just a quick search, I came up with this product page for Aqua Ultraviolet Classic 57 watt UV, they list specific flow rates, UV exposure rates at those flow rates, and pond volumes for their unit, for different functions (eg clarifier vs sterilizer), also it goes on to say "A sterilizer will eliminate green water and control bacteria. The Classic 57 Watt, will sterilize up to 3,000 gallons of fresh water or 355 gallons of salt water." I'm sure I read other manufacturers in the past with similar claims and specs, and that how I made my educated guess that my UV unit is functioning as a sterilizer at the flow rates, and pond size I have. That is, when I turn it on anyway.

Yeah, unfortunately, certain data points we simply just have to rely on the company or their hand chosen independent laboratories.

Rather than taking the company's word for it, lets evaluate their data points by what we know now. Sterilize what exactly?? Unfortunately, this is how companies like to play word games with their consumers in conflating the words clarifying and sterilizing..

What's their definition of " to sterilize " ?? Well, to figure this, one would have to find the appropriate resources to know what µWs/cm² is required for a good UV kill.


As mentioned in their hyperlink, for the Classic 57 watt, the estimated sterilization at 3,200gph is 30,0000µWs/cm² and, with the same device, the estimated sterilization at 1,066gph is 90,000µWs/cm².

At 30,0000µWs/cm², ya get a kill of most of the common bacteria, common pathogens, some spores, and floating algae.

At 90,000µWs/cm², that is half the Classic57's flow rate, ya get the above kill plus some anaerobic bacteria, common fungus, egg fungus, mold, another pathogen, possibly nematode eggs, and finally a parasite (that is trichodina)

Then, you can go even higher than this, cut the Classic57's flow rate to somewhere around 355gph and you will get a 270,000µWs/cm², which this would kill all of the above plus more parasites, a protozoa, and an actual virus.


According to Aquatic Eco-Systems (AES) and the devices µWs/cm² emission, the Classic 57 watt would be a clarifier when the flow rate is a little higher than 3,200gph and a sterilizer at 1,066gph.

I suppose it depends on one's definition of sterilizer. My definition of sterilizer would be a UV device that actually starts killing the stuff that is tough to kill, that is if it is floating in the water and passing through the UV device.

Now, according to their statement, a pond turn over rate of 0.35 per hour is quite fine, which this I would like to see to be high simply due to personal belief. It would be nice if they could give an explanation to the low pond turn over rate recommendation for the Classic 57 device to work fine as a sterilizer.


When I think sterilizer, then I am thinking of something with a kill rate of 90,000µWs/cm²~270,000µWs/cm², which would mean a flow rate of around 355gph~1,066gph from the Classic57 watt.


So, unfortunately since how folk like to play word games, then it gets a bit aggravating.

For a hobbiest, meh, all this is quite irrelevant, but I think it is quite interesting to know for folk interested in knowing if all this UV stuff actually matters.

 

[Cdsdave]

Well I'm happy so far with my "high priced unit". Skagitek.com has a comparison sheet for AquaUV ,Emperor, and W. lim. AquaUV uses a medium pressure lamp where as Emperor and W lim use low pressure. As for the 1.5 inlets on mine, I would say that's better then a 2 in since the flow needs to be slowed down anyway. The chamber on mine is 3 in diameter where Aqua UV is 2 in. Which to me means slower flow rate entering with greater volume in the chamber. Emperors UV light has 100% of its lamp exposed to the water where Aqua UV's is 75% approx.

My plumbing scheme has 3 ball valves ( pic attached). The two on the inlet/outlet valves allow me to shut the UV unit down to winterize if I desire. One valve wouldn't allow me to do that.

It's interesting to hear all the different opinions out there. It's true that high priced doesn't always mean higher or better quality. However I've found in my woodworking hobby that when it comes to tools you get what you pay for. I'm sure that's also true for lots of items including pond equipment.

Great discussion going on here

 

[crsublette]

Very nice man. :afro: :banana: :claphands:


I have heard the worst part is removing the bulb. Ya really gotta be able to move the device to a work bench so to avoid cracking the fragile quartz sleeve.

The positioning of it looks a bit confined.

 

[crsublette]

The positioning of it looks a bit confined. Have ya thought about how you would take it out to replace the bulb or to clean the quartz?? Did ya get the one with the wiper option??

You could probably add a couple unions there between the valves and the device so to make it easier to disconnect the device.

Bah!!! NEVERMIND!!

Taking a closer look at the Emperor and the quick disconnect unions and wiper are already there.

 

[crsublette]

Just a quick tip that I found as I have been reading most of the day.


If your UV device, regardless what brand, has the wiper, then be sure to use it. Don't forget about it. If it gets stuck or tough to move, then do not force it or the quartz sleeve will bust. At this point, I have read you have to disconnect the device, remove the quartze sleeve, and then do it manually.

 

[Cdsdave]

My unit doesn't have a wiper.

The pics a bit awkward, but there is plenty of room to access the UV and a very direct route to access the critical bulb/quartz sleeve. The location was excavated from the existing waterfall/spoils site of the pond dig.

My thought towards the wiper was, it's just one more potential problem.

 

[Mucky_Waters]

My unit doesn't have a wiper.

My thought towards the wiper was, it's just one more potential problem.

My feelings exactly. The seal where the wiper slides in and out seems like it would eventually be a potential spot for a leak, especially if you are using it frequently like you are suppose to. I think the best thing to do is take it apart yearly and inspect, and clean the quarts sleeve manually.

 

[Waterbug]

At 30,0000µWs/cm², ya get a kill of most of the common bacteria, common pathogens, some spores, and floating algae.

At 90,000µWs/cm², that is half the Classic57's flow rate, ya get the above kill plus some anaerobic bacteria, common fungus, egg fungus, mold, another pathogen, possibly nematode eggs, and finally a parasite (that is trichodina)

I don't think this is true at all. The way I read the AquaUV and other UV sites is the 30-90mJ/cm2 range are only giving tested power levels for different flow rates. This doesn't mean even 90mJ will kill anything. There are 3 factors. UV power, flow rate and water clarity (transmittance). A manufacturer can only know 2 of those factors, and that's what they publish. The lower the water clarity the lower the kill rate. Any clouding of the glass would be the same affect as water clarity.

Plus the EPA guidelines for killing bacteria and virus with UV is way, way less then these levels. But UV has the same issues in water treatment because it's really hard, may impossible, for them to be certain 100% kill rate due to the same issues in ponds.

However, neither AquaUV or Emperor gave numbers in "per second". I don't know why. Some day I'll have to crunch the numbers better. Maybe they have it buried some place. Many of these units, even from the same company, the bulb lengths vary a lot. Perhaps that would bring the Emperor back up and on par with AquaUV or even better.

Update after some more reading...
The low-pressure bulbs are indeed better for our needs. They convert about 40% of watts into spectrum we carry about.

The med/high-pressure bulbs only convert about 7%. These bulbs also run very hot, heat instead of UV, and therefore have a much shorter life. However Emperor says the life of their (med-pressure) bulbs are the same as low-pressure bulbs. Maybe the water flow keeps the temp down and that helps the bulb's life, don't know.

Everything I've researched keeps pointing back to the bulb type and does corroborate that a UV filter can use 1/2 as much electric for the same UV output. However, bulb length is still an unknown factor for me.

I'm not pushing AquaUV, I assume lots of other manufacturers use low-pressure bulbs too. Like I said, I've used AquaUV only because they publish a lot of info I need to size units. Complete surprise their units may be much more efficient. Worth checking into next time I have to buy a UV.

 

[crsublette]

I don't think this is true at all. The way I read the AquaUV and other UV sites is the 30-90mJ/cm2 range are only giving tested power levels for different flow rates. This doesn't mean even 90mJ will kill anything. There are 3 factors. UV power, flow rate and water clarity (transmittance). A manufacturer can only know 2 of those factors, and that's what they publish. The lower the water clarity the lower the kill rate. Any clouding of the glass would be the same affect as water clarity.

Plus the EPA guidelines for killing bacteria and virus with UV is way, way less then these levels. But UV has the same issues in water treatment because it's really hard, may impossible, for them to be certain 100% kill rate due to the same issues in ponds

However, neither AquaUV or Emperor gave numbers in "per second". I don't know why. Some day I'll have to crunch the numbers better. Maybe they have it buried some place. Many of these units, even from the same company, the bulb lengths vary a lot. Perhaps that would bring the Emperor back up and on par with AquaUV or even better.

Are you suggesting the chart in the Aquatic Eco-System (AES) article is incorrect ?? ... Which I suspect is a reference out of their Aquaculture Engineering book, since they reference this book in the article.


You are actually repeating what the the AES artcle has already stated, that is the µWs/cm² is nm wavelength in microwattseconds per square centimeter and the other variables that impact it.

So, when the flow rate is slowed down and assuming optimal water clarity and other variables clean, then the µWs/cm² will be increased due to the wavelength able to better penetrate the cell walls of particular entities. When the light properly penetrates the cell walls, then the entities cell walls are fused together or their nucleus is zapped causing the entity to die.

As the article mentions, a proper kill is dependent on the duration of penetration and intensity, as measured in µWs/cm², which many variables affect this, of a particular spectral wavelength and different entities take longer to penetrate..

I believe the duration of seconds is notated in the microwattseconds measurement.


My guess is that AquaUV, Emperor, and the other UV companies give their emission capabilities in microwattseconds since this is the standard used in the Aquaculture industry. I will have to look this up to verify.

 

[crsublette]

DecRen Water Consult article about UV disinfection verifies the AES's article's chart stating the µWs/cm² to kill particular entities.

It does appear that mJ/cm2 is the more common notation rather than µWs/cm², which 1 mJ/cm2 = 103 μWs/cm2 (which this is also an interesting article). Not for sure why one notation is more commonly used by UV device companies than the other notation.

 

[Waterbug]

Are you suggesting the chart in the Aquatic Eco-System (AES) article is incorrect ?? ...

No. What I'm saying is want I said.

You are actually repeating what the the AES artcle has already stated, that is the µWs/cm² is nm wavelength in microwattseconds per square centimeter and the other variables that impact it.

Then I'm in good company. Groovy.

 

[crsublette]

Then I'm in good company. Groovy.

Yep yep. :afro: :claphands:


Actually, unfortunately something I overlooked, you are correct the kill rate would not be 100%. It is actually more like 99.999% due to water contaminants and UV maintenance as we previously described. I would suspect that, since pond water is quite dirtier than filtered water, then the water flow would have to be reduced even further to obtain a 99.999% kill rate, which I suspect the UV pond device companies takes this into consideration when determining their GPH flow rate for their devices.

 

[Waterbug]

UV systems in water treatment plants are speced to kill 99.999%...that's extremely clear water going in. For most (all) ponds the water is much less clear. Impossible to tell what the kill rate is in any pond but if I were betting cash I'd put it all on some percentage way below 99.999%. Or to put it another way...I sure wouldn't drink water coming out of a pond UV.

 

[crsublette]

UV systems in water treatment plants are speced to kill 99.999%...that's extremely clear water going in. For most (all) ponds the water is much less clear. Impossible to tell what the kill rate is in any pond but if I were betting cash I'd put it all on some percentage way below 99.999%. Or to put it another way...I sure wouldn't drink water coming out of a pond UV.

Fair enough, yet the quite weak UV devices are good enough to have a noticeable kill on floating algae, whether be it 99.999% or 70% or 30%. Due to this anecdotal observation, then I believe a stronger UV, such as the sterilizers mentioned by the aforementioned brands, giving better penetration, would most definitely have an equal impact on other bacteria and organisms.

Since now we are talking belief....

What anecdotal observation can YOU provide to suggest, with common conventional filtration found with avid koi hobbyists, that suggests one of the high quality actual UV sterilizers can NOT have a significant impact on the kill rate of organisms mentioned above ???

Showed you mine now show yours... that is applicable in OUR context aquaculture. We are not talking about water treatment plants to create safe drinking water.

 

[crsublette]

1) Fair enough, yet the quite weak UV devices are good enough to have a noticeable kill on floating algae, whether be it 99.999% or 70% or 30%. Due to this anecdotal observation, then I believe a stronger UV, such as the sterilizers mentioned by the aforementioned brands, giving better penetration, would most definitely have an equal impact on other bacteria and organisms.

1) Fair enough, yet the quite weak UV devices are good enough to have a noticeable kill on floating algae, whether be it 99.999% or 70% or 30%.

This actually is exactly the point. Obviously, none of us can reliably assume the effective kill rate of an entity with a level of accuracy to state the kill rate is effective.

If water and fliter pads was taken to a microscope, even with string algae still present in the water or on a waterfall with the accumulation of allelopathic chemicals, if I was betting cash, then I bet there would still be, viable algae still floating in the water or on the filter pads although in a much lower population for us to care about. Again, this is exactly the point. The point is to lower the population well enough so these entities have the absolute minimal impact on the water and aquatic wildlife.

One moment. Got a few studies that further elaborates this in regards to the idiom of pollutant equilibrium and effective and ineffective outcomes of UV sterilization.


With even a 99.999% UV sterilization, absolutely nobody is suggesting in this thread that the water would still be clean enough to be safe for drinking water.