UV reaction with nitrate, creates nitrite. Any info for its effects in home aquaria?

MilitantPotato

Candiru
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Jul 19, 2006
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So my fiance is working on a waste water project that processes water to be injected into ground water. I overheard her mention that for her project there was concern that the UV sterilization will convert the nitrate in the system to nitrite and my ears perked up.
I did a quick google, and there's plenty to read about. I was wondering if there is any impact in the home aquarium from this reaction? I realize the scale is completely different, and most UV setups don't sterilize the water due to contact time and intensity issues. Also, I'm assuming since it's a closed loop the filter will likely process this nitrite quickly, eliminating a build-up?
 

rodger

Polypterus
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Apr 29, 2008
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So my fiance is working on a waste water project that processes water to be injected into ground water. I overheard her mention that for her project there was concern that the UV sterilization will convert the nitrate in the system to nitrite and my ears perked up.
I did a quick google, and there's plenty to read about. I was wondering if there is any impact in the home aquarium from this reaction? I realize the scale is completely different, and most UV setups don't sterilize the water due to contact time and intensity issues. Also, I'm assuming since it's a closed loop the filter will likely process this nitrite quickly, eliminating a build-up?
Not sure I understand how that would work. I have been researching denitration reactors and UV steralization as seperate functions and they never cross. Changing nitrate back into nitrite is an incomplete function of turning it into nitrogen gas. At least that is my understanding.

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Bud8Fan

Fire Eel
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Nov 15, 2006
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From: http://reefkeeping.com/issues/2005-06/rhf/index.php

In addition to the standard nitrogen cycle, there are other ways that nitrite can be produced. One of these ways is by photolysis of nitrate. That is, nitrate can break apart when exposed to UV light, producing nitrite and hydroxyl radical (OH).6,7

NO3- + H2O + UV à NO2- + 2 OH


Many other articles available as well but this one directly deals with our hobby.
Do a search for "UV Nitrate Nitrite"
 

pacu mom

Goliath Tigerfish
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Jun 8, 2006
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Seems like that would be more incentive for water changes to keep the nitrates low. I've never had a nitrite reading since we cycled our tank.
 

Bud8Fan

Fire Eel
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Nov 15, 2006
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I'm betting in our hobby the tiny amount converted is either not detectable or quickly reconverted through the nitrogen cycle by bacteria. This is more concerning for very large industrial applications using a lot more power than we would ever dream of using.
 

Drstrangelove

Potamotrygon
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Oct 21, 2012
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So my fiance is working on a waste water project that processes water to be injected into ground water. I overheard her mention that for her project there was concern that the UV sterilization will convert the nitrate in the system to nitrite and my ears perked up.
I did a quick google, and there's plenty to read about. I was wondering if there is any impact in the home aquarium from this reaction? I realize the scale is completely different, and most UV setups don't sterilize the water due to contact time and intensity issues. Also, I'm assuming since it's a closed loop the filter will likely process this nitrite quickly, eliminating a build-up?
This can be true for medium pressure UV lamps. It has not been found (at least in several studies I saw) in low pressure lamps. I think most people would have a low pressure lamp UV. They run cooler, provide a lower range of radiation more targeted to aquariums, cost less to operate and last longer.

Medium pressure UV radiation occurs more commonly in waste treatment----which is what your fiance is working on.

That doesn't mean that there aren't medium pressure UV lamps out there, but that they are on the "not recommended list" if one looks around.
 

Bud8Fan

Fire Eel
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Nov 15, 2006
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This can be true for medium pressure UV lamps. It has not been found (at least in several studies I saw) in low pressure lamps.
Just googled "low pressure uv nitrite nitrate" and found otherwise. All are pointed at industrial systems so I'm still guessing our tiny uv systems are not going to produce noticible levels of nitrites.
 

Drstrangelove

Potamotrygon
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Oct 21, 2012
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Just googled "low pressure uv nitrite nitrate" and found otherwise. All are pointed at industrial systems so I'm still guessing our tiny uv systems are not going to produce noticible levels of nitrites.
Maybe we are in agreement, but just in case.


Nitrate can be converted into nitrite by UV waves in the 200-240 and 300-325 nm wavelengths.

http://www.sciencedirect.com/science/article/pii/S0043135412004800
http://www.sciencedirect.com/science/article/pii/B9780124116450000109


Low pressure UV (LPUV) lamps operate primarily at 253.7 nm. Medium pressure UV (MPUV) lamps operate at a broad range of 200-400 nm.

A shortwave UV lamp can be made using a fluorescent lamp tube with no phosphor coating. These lamps emit ultraviolet light with two peaks in the UVC band at 253.7 nm and 185 nm due to the mercury within the lamp. Eighty-five to 90% of the UV produced by these lamps is at 253.7 nm, whereas only five to ten percent is at 185 nm. The fused quartz glass tube passes the 253 nm radiation but blocks the 185 nm wavelength. Such tubes have two or three times the UVC power of a regular fluorescent lamp tube. These low-pressure lamps have a typical efficiency of approximately thirty to forty percent, meaning that for every 100 watts of electricity consumed by the lamp, they will produce approximately 30–40 watts of total UV output. These "germicidal" lamps are used extensively for disinfection of surfaces in laboratories and food processing industries, and for disinfecting water supplies.

Mercury at low vapour pressure produces essentially monochromatic (single wavelength) UV light at 253,7 nm, so-called low-pressure UV lamps. At higher vapour pressures, the frequency of collisions between mercury atoms increases, producing UV light over a broad spectrum. (i.e., 200-400 nm.)


https://en.wikipedia.org/wiki/Ultraviolet
https://www.crystec.com/senlampe.htm
http://www.bestuv.com/about-uv/lamp-technology
http://www.bestuv.com/about-uv/uv-vs-chemicals

LPUV tubes don't create the proper wavelength to impact nitrate stability. MPUV tubes do.


That is one reason why it's very difficult for a low pressure UV tube to be a problem in aquariums. Unless people are using MPUV tubes, it's a non issue afaik. Since MPUV tubes are more costly, consume a lot more power, have a much shorter lamp life and create up to 10x as much heat, it's not a choice that would seem to be a common one for aquarium owners.
 
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