Are the effects of UV sterilizer cumulative?

[a.t.t.r]

Contact time being the primary factor in whether or not a cell dies/is damaged I was wondering. Since our tanks are closed systems does each pass into the UV accumulate ontop of the last? If something takes x amount of a dose to die but each pass hits it with 1/10th of x and it passes the uv 10 times (let’s say within an hour to 12hours) would the be doing the same amount of damage?

Reason I ask is I am currently limited to a 5w uv on a 20 gallon tank with a flow rate of apx 100gph and a very low volume contact chamber. I only intend to run this for a few (fighting Dino’s) weeks so I am trying not to invest in a larger unit.

 

[ThePlummer]

You'll be fine... I only use UV when I have a algae/dino/cyano bloom.

 

[bzuca87]

Contact time being the primary factor in whether or not a cell dies/is damaged I was wondering. Since our tanks are closed systems does each pass into the UV accumulate ontop of the last? If something takes x amount of a dose to die but each pass hits it with 1/10th of x and it passes the uv 10 times (let’s say within an hour to 12hours) would the be doing the same amount of damage?

Reason I ask is I am currently limited to a 5w uv on a 20 gallon tank with a flow rate of apx 100gph and a very low volume contact chamber. I only intend to run this for a few (fighting Dino’s) weeks so I am trying not to invest in a larger unit.

Get the green killing machine if you’re looking 4 cheap and temporary at petco

 

[Malcontent]

Yes, cell repairs require energy and stages of ich that aren't feeding have a finite energy supply.

Most studies of UV disinfection assume a single pass because that's almost always how they're used in drinking water treatment.

If you think about it, you trade exposure time for turnover rate and get the same result unless flow rate is too low and a single pass results in a dose more than sufficient to inactivate.

The only setting where multiple passes are used are in food sterilization and those studies came to the conclusion you would expect: there's a flow rate below which inactivation is lower but above that it's basically the same.

 

[a.t.t.r]

Yes, cell repairs require energy and stages of ich that aren't feeding have a finite energy supply.

Most studies of UV disinfection assume a single pass because that's almost always how they're used in drinking water treatment.

If you think about it, you trade exposure time for turnover rate and get the same result unless flow rate is too low and a single pass results in a dose more than sufficient to inactivate.

The only setting where multiple passes are used are in food sterilization and those studies came to the conclusion you would expect: there's a flow rate below which inactivation is lower but above that it's basically the same.

Am I reading this right that more passes at a higher flow rate but less energy delivered per pass resulted in greater reduction? Be interested to know the total volume of that test. Like yea it passes more times or less times but what was the idle time between each pass.

 

[Malcontent]

Am I reading this right that more passes at a higher flow rate but less energy delivered per pass resulted in greater reduction? Be interested to know the total volume of that test. Like yea it passes more times or less times but what was the idle time between each pass.

Yes, faster is better.

Imagine an organism and the UV system are perfectly balanced so that one pass delivers exactly enough UV to kill it. Double the flow rate and it still receives the same total dose. Same with tripling it, etc.

Then halve it. Half as much water passes through the UV but you don't derive any benefit from killing the organism twice.

 

[AJsReef]

Yes, faster is better.

Imagine an organism and the UV system are perfectly balanced so that one pass delivers exactly enough UV to kill it. Double the flow rate and it still receives the same total dose. Same with tripling it, etc.

Then halve it. Half as much water passes through the UV but you don't derive any benefit from killing the organism twice.

UV doesn’t kill, it sterilizes. The increased UV dosage through contact time could sterilize the organism quicker than multiple passes. Assuming you’re guaranteeing turnover.

Hypothetically speaking, if an organism needed a .5 second time under dosage to sterilize and had a contact time of .5 seconds it would be sterilized . If you replaced the unit with one that had a lower contact time of .25 seconds then it would have to go through the UV twice. Even in a closed system it could take some time for this to happen vs sterilizing it the first time round.

Obviously real would cases aren’t as straight forward. But just gives food to thought when it comes to sizing. Technically you can’t guarantee the time between passes even in a closed system which is exactly why turnover rates in systems are heavily debated. That’s why most UVs design for aquatic hobbyists have set dosage and flow rates based on total system volume.

 

[ProxyAquarist]

Contact time being the primary factor in whether or not a cell dies/is damaged I was wondering. .... Since our tanks are closed systems does each pass into the UV accumulate on top of the last? .... If something takes x amount of a dose to die would the be doing the same amount of damage?

Short answers first:

Q: "Are the effects of UV sterilizer cumulative?"
A: Yes, DNA and RNA damage is essentially permanent in this species. In humans, like us, and some other species, there are repair enzymes.

Q: "Contact time being the primary factor?"
A: Yes

Q: "Since our tanks are closed systems does each pass into the UV accumulate on top of the last? "
A: Yes, the effects off each pass accumulate

Q: "If something takes x amount of a dose to die would the be doing the same amount of damage?"
A: Yes

Q: "I am currently limited to a 5w uv on a 20 gallon tank with a flow rate of apx 100gph ..."
A: That should do fine. My son an 8W on a 20 Long with a similar flow, and all is well if the bulb is changed yearly with a cleaning.

Malcontent's comment were on point. I will spare you the equations; equations similar to this primary photon dose rate equation are why I did not specialize in radiology or oncology:

The principles here are fairly straight forward however:

a. UV light causes changes in the RNA and DNA genetic code.
b. The common change is a CC to TT mutation.
c. The change likely affects the product made from that RNA and DNA negatively.
c. The change uses a strong bond which is essentially permanent in this species.
d. From then on the cell produces a defective product which may be incompatible with life.
e. More UV equals more permanent mutations.
f. Eventually there are so many permanent mutations that the cell dies.

All that matters is that a UV photon hit a CC DNA or RNA molecule. The "exposure" discussion is important because it determines if that UV photon gets you at hit.

Consider this analogy:

- Photon = bullet
- UV frequency = bullet speed/energy
- Area in UV sterilizer = the amount of time the target is visible
- Flow rate = the number of times the target pops up
- Wattage = the number of bullets that leave the firearm every time one pulls the trigger
- Contact Time = Is how long you are shooting on the target range.

if you have more a slow big target, powerful bullets, more shots, and more time on the range, you are likely to get a hit.

You may only need to hit that single cell once. Changing these values just changes the odds of a hit.

When we buy a UV sterilizer we can choose the wattage (bullet speed/energy), Area in UV sterilizer (the amount of time the target is visible) and Wattage (number of bullets that leave the firearm every time one pulls the trigger). If you purchase the monster UV unit, you can be Rambo with the 50 cal. and bandoleers of bullets with 90 minutes of screen time.

Once we get the UV home, we are limited to flow rate to get the contact time; but the tank inhabitants do not want to live in the flow of propeller wash or tidal wave proportions. Thus we make accommodations, and that usually means picking a flow rate with the best chance of a hit that out tank inhabitants can live with.

A slight caveat, you want to hit the target before it multiplies. Thus fast multiplying species need higher flow rates. i.e. algae versus parasites

All that said, you should be fine if you change that bulb yearly.

So a.t.t.r., you get to be their "worst nightmare” and "get to win this time."

May you be your tank's superhero,
Jim

 

[a.t.t.r]

Short answers first:

Q: "Are the effects of UV sterilizer cumulative?"
A: Yes, DNA and RNA damage is essentially permanent in this species. In humans, like us, and some other species, there are repair enzymes.

Q: "Contact time being the primary factor?"
A: Yes

Q: "Since our tanks are closed systems does each pass into the UV accumulate on top of the last? "
A: Yes, the effects off each pass accumulate

Q: "If something takes x amount of a dose to die would the be doing the same amount of damage?"
A: Yes

Q: "I am currently limited to a 5w uv on a 20 gallon tank with a flow rate of apx 100gph ..."
A: That should do fine. My son an 8W on a 20 Long with a similar flow, and all is well if the bulb is changed yearly with a cleaning.

Malcontent's comment were on point. I will spare you the equations; equations similar to this primary photon dose rate equation are why I did not specialize in radiology or oncology:

The principles here are fairly straight forward however:

a. UV light causes changes in the RNA and DNA genetic code.
b. The common change is a CC to TT mutation.
c. The change likely affects the product made from that RNA and DNA negatively.
c. The change uses a strong bond which is essentially permanent in this species.
d. From then on the algae produce a defective product which may be incompatible with life.
e. More UV equals more permanent mutations.
f. Eventually there are so many permanent mutations that the cell dies.

All that matters is that a UV photon hit a CC DNA or RNA molecule. The "exposure" discussion is important because it determines if that UV photon gets you at hit.

Consider this analogy:

- Photon = bullet
- UV frequency = bullet speed/energy
- Area in UV sterilizer = the amount of time the target is visible
- Flow rate = the number of times the target pops up
- Wattage = the number of bullets that leave the firearm every time one pulls the trigger
- Contact Time = Is how long you are shooting on the target range.

if you have more a slow and big target with bullets, more shots, and more time on the range, you are likely to get a hit.

You may only need to hit that single cell algae once. Changing these values just changes the odds of a hit.

When we buy a UV sterilizer we can choose the wattage (bullet speed/energy), Area in UV sterilizer (the amount of time the target is visible) and Wattage (number of bullets that leave the firearm every time one pulls the trigger). If you purchase the monster UV unit, you can be Rambo with the 50 cal. and bandoleers of bullets with 90 minutes of screen time.

Once we get the UV home, we are limited to flow rate to get the contact time; but the tank inhabitants do not want to live in the flow of propeller wash or tidal wave proportions. Thus we make accommodations, and that usually means picking a flow rate with the best chance of a hit that out tank inhabitants can live with.

A slight caveat, you want to hit the target before it multiplies. Thus fast multiplying species need higher flow rates. i.e. algae versus parasites

All that said, you should be fine if you change that bulb yearly.

So a.t.t.r., you get to be their "worst nightmare” and "get to win this time."

May you be your tank's superhero,
Jim

so does a single photon cause a pair to become damaged or does it take multiple repeated hits to the same pair? Dumb question I know and Google has turned up very little.

 

[ProxyAquarist]

so does a single photon cause a pair to become damaged or does it take multiple repeated hits to the same pair? Dumb question I know and Google has turned up very little.

Not "dumb" at all.

Q: " ... does a single photon cause a pair to become damaged ..."
A: Yes, a single pair forma a bond that the cells enzymes have trouble with. This results in a error at the site and a deformed product.

Q: " ... does it take multiple repeated hits to the same pair? "
A: Unlikely, however all reactions are a probability. At certain parameters, one can predict the percentage of conversion. For our purposes, it is almost 100% in this case.

We used UV in our lab to randomly mutate cells. Some cells mutations were deadly on one hit. Some single hits were compatible with life but gave new results. These could be a new shape, new color, new function, .... Some single mutations were beneficial. Example resistance to disease, poisons, antibiotics, ...

However, your UV is unlikely to create a super-algae or super-parasite. We'd have to mutate thousands or billions of cells to get a positive change.

A few examples of why your question is a good one:

a. HIV : The reason the HIV virus causes AIDS is where it splices into the patient immune gene. This hit, disables the gene and causes the syndrome known as AIDS. On hit was enough. A photon at the same point could exhibit the same effect.

b. Unfortunately, the whole world knows COVID and its variants, those variants exemplify your second point. Each variant has mutations. Most only know the alpha (original), delta, omicron variants. With the exception of a few letters in the Greek alphabet skipped for political reasons, the rest of the variants are less known because the mutations made them less harmful. Mutations are both "harmful" and "beneficial." These variants often have multiple hits.

Yours in molecular biology,
Jim

 

[Idech]

If you’re fighting dinos, I am right at the end of the battle (fingers crossed), using a UV. The thing is, the UV will only take care of what's in the water column, in my experience, and if you have a similar type as I did.

So you need to stir the sand as often as you can, to get the dinos into the UV.

Also, in my tank, after 5 days with UV 24/7 the dinos had a 50% reduction, but then stopped decreasing.

Another member gave me a method to follow with H2O2 (3% hydrogen peroxyde), and with the peroxyde and UV, it took 3 days to obtain a 100% reduction. So 8 days total.

Something to think about.

Here is my thread if you’re interested.

How long to win the battle when using UV for dinos ?

I’ve been using a Aqua UV 2000+ (15 watts) on my 75 gallons tank. It’s been 4 days and I’m still not sure it’s really working. It seems like there is less dinos than before. No long flagellates and not as much deep accumulation. But it’s just as much spread out as before. So I am wondering...

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