# UV Filter Recommendation



## John S (6 May 2013)

For years I have run a Hozelock Titan 5500 with a Bioforce 9000 UV filter. The set up has always worked well for me and helped produce reasonably clear water. A seal failure on the filter has let water into the quartz tube. The tube has gone brown and will not clean and the electronics are probably shot. In short it’s not worth repairing. They don’t make the 9000 anymore so can anybody recommend another filter? It doesn’t have to be Hozelock, there new revolution range are out of my price range.

Cheers,
John


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## John S (9 May 2013)

Anybody got any thoughts?

APS do some that look like clones of the Bioforce ones, has anybody used them?


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## mi casa (13 May 2013)

Hi dude my Hozelock filter the uv part did the same so i cut the power cable off and got a separate uv off Amazon £34  it's the Jebao 11w and it as been spot on as there was nothing wrong with the filter part it was just the uv. The hozelock was only 5w and this is 11 they go up to 55w. thats one way of doing it


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## John S (13 May 2013)

Thanks for the info. My hose size is 38mm and the fittings on these units look a lot smaller but I will search for something similar.


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## mi casa (13 May 2013)

yes its 20 all the way up to 50mm they look small in the photo but there not


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## mi casa (13 May 2013)

you just cut the clear plastic to the size you want


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## John S (13 May 2013)

That looks just the job. Thanks for posting the picture


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## mi casa (20 May 2013)

Hi mate any joy getting a uv for your pond


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## John S (20 May 2013)

Not yet. Car needs taxing this month so will be when I get paid next. I'm looking at getting a stand alone unit like yours.


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## GSDF&F (21 Sep 2013)

Hi mi casa, that looks a pretty good set-up. My filter looks the same as yours, but as I've just taken over the property, I'm starting from scratch with the pond. (My thread's in the "Pond" section for the info) The 5w UV tube was blown & the glass surround was heavily stained, as was the plastic outer cover for the glass tube. There were no sponge filters inside either, so I'll need to get those as well. But your reason for the "add on" has got me wondering if the seal has also gone on mine, which buying another UV lamp would be pointless, though I suppose I could easily seal the er! seal if you get my drift. Any advice most welcome.?


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## GSDF&F (21 Sep 2013)

Am I right in saying the UV unit is pump fed first, then through the original filter & finally back to the pond. Er! what's the screw cap for on the top.


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## foxfish (21 Sep 2013)

It doesn't really matter where the uv is placed, lots of people have strong views on this but not so many have experience, the screw cap is sealing an alternative outlet.


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## Yo-han (21 Sep 2013)

It does stay clean longer when placed after the filter


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## foxfish (21 Sep 2013)

There you go...


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## martin-green (21 Sep 2013)

GSDF&F said:


> Am I right in saying the UV unit is pump fed first, then through the original filter & finally back to the pond.


 


foxfish said:


> It doesn't really matter where the uv is placed, lots of people have strong views on this but not so many have experience.


 
I don't want to start an argument, but I always have pump first, then UV then bio filter. The reasoning is that a UV is supposed to cause the micro organisms (that are green) to flocculate (clump together) and these get trapped in the bio filter, if you have the UV after the bio filter you are dumping the "clumped" organisms back in the pond.


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## foxfish (21 Sep 2013)

Yes you are right that UV light will damage the free floating algae spores & cause them to clump together this will then be filtered out by the mechanical filter medium.

Why does this fact imply the UV has to be sited in front of the filter?

If the filter is sized correctly, then anything big enough to be trapped will be, as the continuous flow throughout the water column will eventually send any such particles into the filter.

It can be agued that placing the UV after the filter will keep the quartz glass surrounding the UV tube much clearer & therefor increase the UV efficiency?

However... as long as the system is correctly matched to the volume of water being treated it makes no 'real life' difference were the UV is placed!

As with planted tanks - a lot depends on the success of the system via the understanding of how it works but, equally, the amount of effort you are prepared to put into it. 
So if you maintain a well balanced set up that has been thoughtfully put together, is makes not a bit of difference where the UV is placed.
I have found that generally speaking, folk expect an awful lot from a tiny filter compared to the size of the pond!


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## ceg4048 (22 Sep 2013)

martin-green said:


> The reasoning is that a UV is supposed to cause the micro organisms (that are green) to flocculate (clump together) and these get trapped in the bio filter, if you have the UV after the bio filter you are dumping the "clumped" organisms back in the pond.


This is not the mechanism by which UV disinfection occurs. UV has nothing to do with clumping and cannot affect pathogens in this manner.

Disinfection occurs when the DNA and RNA molecules of the pathogen absorbs UV photons. The most effective frequency is in the neighborhood of 250 nanometers.

The photon bombardment and absorption of the radiation energy affects the "Base Pairs" of the DNA.
Here is a schematic of a typical DNA molecule showing the famous "Double Helix" shape. The Base Pairs are the horizontal ladder steps having the symbols A, T, C, G:





All of what we are or what we will become, physically and chemically, is encoded by the sequence that the base pairs occur in. When a cell needs to reproduce or to perform a function the information on how to accomplish that function must be decoded by reading the sequence of Base Pairs, then replicating that sequence, and finally, carrying out the instructions given by that segment of the sequence.

In schematic above can be seen a molecule called "Thymine" (the purple T). It usually bonds with another molecule called "Adenine" (light grey A), thus forming an "Adenine-Thymine Base Pair."

Because the molecules are tightly packed together, absorption of UV into the DNA causes two adjacent Thymine molecules to fuse together, creating something called a "Thymine Dimer". This new molecule changes the sequence of the Base Pairs, thus causing a mutation. This new mutated set of instructions usually disrupts the function of the cell and prevents reproduction or replication of cells because the coded sequence of "how to be", "what to look like" and "what to do" become completely nonsensical, so the organism dies, or at best, cannot reproduce.

In fact, clumping is a mechanism used by microorganism to evade the effects of UV radiation because they can hide from the photon bombardment.

Theoretically, therefore, it makes much more sense to mount the UV bulb in the area of least turbid water possible which ensures maximum exposure and dwell time of the radiation upon the microorganism. There is no way any mechanical filter will remove microorganisms.

Cheers,


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## Ian Holdich (22 Sep 2013)

Damn, you beat me to it again Clive!


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## foxfish (22 Sep 2013)

I really don't understand that at all & I am not sure what you are trying to say apart from contradicting me!

I am not sure how many years of experience you have had with the installation of UV filters but I have had about 30 & I can only offer my personal advice.

It makes no difference if you place the UV in front or after the pump, in front or after the filter or anywhere along the line, what makes a difference is how often you maintain your equipment, how well it is installed & how well it is sized to the pond!

More often than not, space is at a premium inside the allocated filter space, it might not be possible to choose the ultimate position of the UV ... don't worry about that.. put the UV where it avoids acute pipe bends & is easily  accessible to maintain & clean the quartz.

That of course is a real word fact & not some technical fact.


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## martin-green (23 Sep 2013)

ceg4048, that's easy for you to say, but could you put it in simple terms, as I for one do not understand it  

As far as I can understand it, you seem to be saying I am  wrong, but I would point out that another person seems to agree with me, so we can not all be right can we? 

I also wonder is what you say about a UV steriliser not a UV clarifier ?

I have taken them to be very similar, just that the steriliser is way more powerful, and not what is used in a pond.


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## ceg4048 (23 Sep 2013)

Hmm, well, yes, the long and the short of it is that the clumping of microorganisms is not a valid explanation. There is no link between lethal dosage of UV and physical or mechanical clumping. Irradiating germs with UV does not initiate any mechanical merging of the germs. It either kills them outright, or it prevents them from reproducing. If germs clump together it has no bearing on how the radiation works and would be a downstream, or indirect consequence. So my point is that UV kills things outright. It cannot be an adjunct to mechanical filtration. You cannot get rid of germs that way unless your filter media is made of micro-pores such as in an RO filter. That unit mechanically removes germs because the pore size is the size of a water molecule.



foxfish said:


> I am not sure how many years of experience you have had with the installation of UV filters but I have had about 30 & I can only offer my personal advice.


Well, here are some more annoying technical facts:
Germs have been around for about 4,000,000,000 years
Ultraviolet Radiation has been around for about 13,500,000,000 years.

So, for 4,000,000,000 years, UV has been killing germs in the manner described in post #17 whether you like it or not, or whether you understand it or not. UV has never killed germs by clumping. So 30 years is a mere pittance by comparison. 

Cheers,


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## foxfish (23 Sep 2013)

Yep that is very annoying ... my point is I am here to help folk, that is what I enjoy doing... not to just have the last word.
 However If you think you know so much about pond building & construction then I will leave to answer any future question relating to this subject


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## ceg4048 (23 Sep 2013)

I don't know anything about building and constructing ponds. I'm not even sure what your problem is. I wasn't addressing your post at all. I was addressing Martin's post. If you say that in practice, location doesn't matter with regard to the UV unit, then I believe you. I never argued that point, so your annoyance is self inflicted. It has nothing to do with me.

UV does not work by clumping. That is my argument. No idea whatsoever why you should feel offended.

Also, we are immune to blackmail. If you choose abstention over reason then that is a product of your own free will. Congratulations.

Cheers,


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## ian_m (23 Sep 2013)

The instructions I had with my pond UV clarifier stated "to be installed after the pump & filter" so that less dirt would collect on the UV unit internal glasswork. I used mine with a water feature to keep water clean, which it did admirably until after a year or two the UV tube looses its effectiveness.


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## martin-green (23 Sep 2013)

ceg4048, I understood that one, would have been easier if you had said that in the first place. 

The fact I don't believe it is neither here nor there.

But as I first said, I don't want to start (or cause) an argument.


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## foxfish (23 Sep 2013)

Well the problem is as I understand it that UV filters do not work on their own to remove green water from ponds, they require a mechanical filter to remove the dead algae.
As an example. a  person has read that uv light will rid his pond from green water & installs a UV unit but he does not have a mechanical filter & the green water remain. Said customer then does more revision & installs a mechanical filter & in combination of the two the pond clears.
You may well be right in what you say & maybe the matrix has an influence but it is documented to a huge extent that UV light has the effect of killing free floating algae spores which then clump together allowing the filter to remove the particles.
I own a portable UV filter unit that is rented out on occasion manly in the spring, the unit comprises of a twin 55w UV light & a back flushable sand filter.
If a pond has green water I can usually clear the pond in a day or two with my potable unit, I cant really try the experiment until I find an infected pond but I am prepared to bet money the pond will not clear with UV alone.

I have a UV in front of me here, the literature states .....

" When water, pumped from your pond passes in front of the Ultraviolet rays of the UV bulb, the cells of the algae divide. When they divide, they die causing them to clump together into larger masses of algae. These larger dead algae can now be filtered out by your mechanical - bio-filter system. Now when your system is back washed, the pads cleaned or other media washed off, this flushes the algae from the system never to be seen again."

Whether true or not that is what you will read everywhere on the net or on UV literature found within the packaging & for what ever reason, from my experience you need a combination of UV light & mechanical filtration to clear green water from a pond.


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## martin-green (23 Sep 2013)

I have the answer.



ceg4048 said:


> ...... UV has never killed germs by clumping.


 
You are the one who said germs and took it down that route, which is why no one agrees with you.




martin-green said:


> ……….. the micro organisms (that are green


(Not a mention of germs in that is there)




foxfish said:


> …………free floating algae spores


(Not a mention of germs in that is there)


But just for a nano second, we will assume what you said is right.

Below is what you said.


ceg4048 said:


> It either kills them outright, or it prevents them from reproducing. If germs clump together it has no bearing on how the radiation works and would be a downstream, or indirect consequence. So my point is that UV kills things outright. It cannot be an adjunct to mechanical filtration. You cannot get rid of germs that way unless your filter media is made of micro-pores such as in an RO filter. That unit mechanically removes germs because the pore size is the size of a water molecule.


 
You say it kills the germs outright, or stops them from reproducing, and that a pond bio-filter will not catch them (But a Reverse Osmosis filter will)


Let me ask you this. Where have they gone then? (Rhetorical question)


Did you also not say


ceg4048 said:


> I don't know anything about building and constructing ponds


So, would it be fair to say, that you have never seen inside a working pond bio-filter, or even if you have, why is it that it is always full of green stuff after a while? It can't be from the pond because you said the UV doesn't cause stuff to clump together.

I suggest, that you have gone too deeply into the subject and missed the point.

Lets all stay friends. After all, its only opinions.


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## ceg4048 (24 Sep 2013)

Hi Martin,
				 I think you're missing the point entirely. Free floating algae counts as germs. The UV radiation disrupts the DNA and RNA in exactly the same way as it disrupts the DNA/RNA of the free floating algae, and kills or sterilizes them in the same way. You never need to remove dead algae cells. If they are dead or cannot reproduce then it doesn't matter whether you remove them or not. They will sink to the bottom with the rest of the random detritus, where clumping of detritus particles then has relevance. If the radiation does not kill them outright then it reners them as good as dead because they cannot produce spores, so, they live their short lives out and are finished. If they pass by the UV again, multiple times then they get zapped more often and then it's all over. The reason the water is green when you have a green water attack is because they are swimming freely in the water column. If they are dead then their bodies decay like everything else that decays in water. That's where they go. They basically turn into dirt.

Furthermore there is a HUGE difference between a pond filter and an RO filter membrane. An RO filter membrane has a pore size just about as large as a water molecule. Under pressure, the water molecules squeeze through the pores. Water molecules are one of the smallest molecules because they are constructed of a single Oxygen and two Hydrogen (which is the smallest atom). A water molecule is very much smaller than a virus or any microorganism. So there is no way any microorganism can pass through an RO membrane. You cannot compare an RO membrane with your pond filter. I don't care what bran of bio-filter you name it cannot be as effective at removing particles from water. If it could, Martin, then you would be able to use your bio-filter to rid the water of hardness, bacteria and everything else that RO filters are known for, right?

I suggest that you do not go deeply enough, and that's why you are susceptible to propaganda.




foxfish said:


> " When water, pumped from your pond passes in front of the Ultraviolet rays of the UV bulb, the cells of the algae divide. When they divide, they die causing them to clump together into larger masses of algae. These larger dead algae can now be filtered out by your mechanical - bio-filter system. Now when your system is back washed, the pads cleaned or other media washed off, this flushes the algae from the system never to be seen again."


Mate, please. Try to have another look at my post #17. This is really important because people find it easier to buy fantasy just because someone is selling it. The truth is free, but it's often too complicated, so folks give up too easily. Your heart beats because it is made of cells that beat rhythmically. Even if you were to scrape some of those heart cells off and put them in a Petrie dish they would still beat. The way they are constructed and their characteristics propensity to beat is determined by a set of instructions from your DNA that specifies exactly what yjey should be made of and how they should behave. There is a wiring diagram, an architectural plan and an operational program encoded in the DNA. Look at the picture closely. Can see how there is an "A-T", followed by a "C-G", followed by another "A-T"? Well there are millions of combinations, and the sequence in which they appear is  like a Morse Code. The sequence of how those pairs are arranged defines how you are built. When your hand is cut and new skin is required, somewhere in that sequence are instructions of how to build your skin. Other cells copy that piece of code and carry out the instructions to build new skin.

If someone changes the sequence by inserting things that weren't there before, or by taking some of those pieces away, it changes the code. This is referred to as Mutation. This actually happens a lot, but the organisms have backup copies of the code or can repair damaged codes. Does this remind you of a computer program?  Well that's exactly what the DNA is. It's the hard drive where the data is stored. Imagine taking a magnet and swiping it across your hard drive. That will scramble the sequence that the information appears in and will render your computer useless. That's what happens with UV. The DNA absorbs the energy and that energy fuses some of the pieces together changing the code. So, as an analogy, heart cells will be built that do not know how to beat. Skin will not know how to repair itself, or ruptures easily. This is what happens to the microorganisms. They either die outright or they mutate into something unimaginable.

Try going to your pond or tank and swirl the substrate around. What happens? That kicks up a lot of dirt and the water becomes cloudy right? Well, those dirt particles are not alive, so some just sink back to the bottom while others are sucked into the filter. Either way, in a few hours, the water clears. I'm not telling you anything new. That's just dirt. And when you kill algae cells, then dead cells turn into dirt. Does dirt clump together? Sometimes yes, and sometimes no. It's random due to electrostatic charges and so forth, but that's a different and subsequent mechanism. It is not the primary mechanism.

If you spend too much time in the sun the same thing happens to the DNA in your skin. Repeated lethal and sub-lethal UV dosages causes some cells to die (causing sun burn and peeling) or it causes mutation. That mutation and code changes causes cells to have a different behavior, such as tumors and other mutated forms. That's a type of skin cancer. The bodies response to excessive UV is to produce more Melanin (which is a genetic response and is a coded sequence hidden in the main DNA sequence of A-T, C-G and so forth).

Cheers,


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## foxfish (25 Sep 2013)

OK so just to clarify your opinion....
A pond in the spring, that is suffering from a free floating algae bloom causing dense green water, can be cleared with a standard size (pond rated) UV unit without the use of a mechanical filter?
It is impossible for the algae cell to clump together?
The dead or damaged cells can not be physically removed by a small particle filter - IE a pressurised sand filter - as commonly use in swimming pools & koi ponds?


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## ceg4048 (25 Sep 2013)

Hi mate,
			  Well, remember that when we say "free floating", this may not be accurate either. In fact, that phrase might actually be the source of the confusion.

Check out this image. This is a Scanning Electron Microscope (SEM) image of a type of green water algae called _Haematococcus pluvialis_. It's not necessarily the same as the one in our ponds and tanks (because there are thousands of different types), but it is representative. Can you see the two antenna looking appendages? Well those are NOT antennae. They are called flagella. The algae whip the flagella around and that motion provides propulsion. Even though this is a plant, it behaves like a protozoan because it can move. So it would be better to use the expression "free swimming" algae. To reiterate; they swim, they don't just float. that's why they can populate every cubic centimeter of the pond or aquarium or 55 gallon drum. Other types of algae, like diatoms that do not have propulsion sink to the bottom and may drift. By chance, they happen to land on a plant or hardscape and then they bloom when water conditions have deteriorated. That's why you see those algal types on the bottom, because they cannot swim. Green water algae are not restricted to hardscape or plants because their propulsive capability allow them to move. If you think that a plant cannot move then just think about a Venus Flytrap, which opens and closes to feed itself.




Photo courtesy of Dennis Kunkel Microscopy.

Here is another SEM image of a species called _Chlamydomonas_. Wen you have a GWA attack, there can be many different species appearing together. Some have flagella and others do not.




When they are killed by the UV radiation, they obviously can no longer swim, so they drift to the bottom, or drift around the pond and then, yes, just like other dirt, the bodies may clump to other detritus. We see detritus clumping together all the time. That's how detritus behaves in water. If they don't make it into the filter then the bodies will simply decay like any other organic matter. So the water clears because the cells are dead and drift down due to gravity or due to whatever buoyant forces are acting upon them. The green chlorophyll decays and turns into Nitrogen compounds or whatever other products of decay occur. So green color disappears.

UV does not magically force algae cells together just so that they become a bigger target for filters. That is a fairy tale, but yet, it's exactly as you say; the UV works regardless of where it is mounted.

Now, as far as the question of whether you can clear the pond without a filter, well, you need some way of bringing the water in contact with the algae, so it might be more accurate to say that you can kill the algae without having any filter media. Does that mean the water changes color from green to brown, or from green to clear? Uncertain, because that's a filtration issue, not a killing issue. That's why I mentioned in an earlier post that clumping is a different issue, because when previously free swimming organisms turn into dead dirt, well, then it's a lottery. I'm not saying that clumping does not happen. I'm saying that clumping doesn't have to happen for the UV to be effective at killing GWA.

Cheers,


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## foxfish (25 Sep 2013)

ceg4048 said:


> , It cannot be an adjunct to mechanical filtration. You cannot get rid of germs that way unless your filter media is made of micro-pores such as in an RO filter. That unit mechanically removes germs because the pore size is the size of a water molecule.


Hmm well I am listening but, far from convinced so far... I did not think that the free swimming algae, that are so common in high flow koi ponds, were that tiny - I did not think they were microscopic?
I certainly would not expect any dead algae to lye on the bottom of a Koi pond as in most cases the water is drawn from a central bottom drain into the filter & there will be considerable water movement from both pumps & large fish, so most particle will be in suspension.


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## ceg4048 (25 Sep 2013)

Well, I guess the only way to tell is to take a sample of the green water and look at it under a microscope.



As I said, after they are dead then they follow the rules of detritus. Whatever happens to regular dirt happens to them.

Cheers,


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## foxfish (26 Sep 2013)

What do you make of this stament ...

If water passes through the unit too fast, that is above the manufactures limit; it will be useless at killing any microorganisms at all and algae will only be flocculated. The flocculation process involves the optimization of the electric charge of the algae and bringing floc particles (Flake of precipitate that comes out of solution during the process of flocculation.) together to form larger particles that can easily settle in a sedimentation chamber in the filter or get caught up in the pre-filter filtration mats themselves. Be careful in the UV units you buy because sales wording of the unit may indicate that the UV unit is not meant to eradicate bacteria or algae but only floc it. These floc UV units are usually cheaper and go under the name as UV clarifiers than UV units that can eradicate pathogens go under the name UV sterilizers. Most manufactures will state what their UV units are for.


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## ian_m (26 Sep 2013)

UV Sterilization for Aquarium & Pond | How to use UVC Sterilizer | Information


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## ceg4048 (26 Sep 2013)

Yeah, that whole flocculation argument makes no sense to me. As mentioned, it's all about dwell time and intensity.

The degree to which the destruction or inactivation of microorganisms occurs by UV radiation is directly related to the parameter "UV dose." The UV dosage is calculated as:

D = I*t

Where D is the calculated UV dose.

"I" is the intensity of the radiation.

"t" is the exposure time.

So the dose is a product of how strong the radiation is and to how long the target is exposed to that strength.

Either the target is zapped with a lethal dose, or an inactivation dose. That will be the only difference between a "clarifier"  and a "sterilizer".

Different organisms have different resistances and so require different dosages. The clarifier may be strong enough to zap algae cells but may not provide a lethal dosage to some pathogens such as protozoans, which require a much stronger dose than bacteria, for example. So either one will work for killing algae but one may have to be more selective if the intent is to kill protozoans.

As mentioned if the flow rate is too high then the target is not exposed to the radiation for long enough, so the variable "t" is a small number and so the multiplication results in a small number, or, a lower dosage. To compensate, the wattage needs to be higher.

Cheers,


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