Does UV cause ORP to spike?

[Saltees]

Cos my ORP jumped from 170+ to 250+. It corresponds to the time I turn on the DELTEC UV 80W and my ORP probe is placed inline immediately after the UV along the return line. Is there correlation or coincidence?

 

[Jay Hemdal]

Have you tried this multiple times and gotten similar results? I can’t think of direct cause and effect, EXCEPT that UV production at a certain wavelength produces ozone (185 nm) and if your bulb is in that low range and if the chamber has air in it, some ozone could be produced and that would raise your ORP.
Jay

 

[Saltees]

Have you tried this multiple times and gotten similar results? I can’t think of direct cause and effect, EXCEPT that UV production at a certain wavelength produces ozone (185 nm) and if your bulb is in that low range and if the chamber has air in it, some ozone could be produced and that would raise your ORP.
Jay

Thanks Jay. Let me see if the trend continues for next few days with UV on and off the UV over the weekend. I’d been cycling the tank for the past 2 weeks and the ORP hovered around 150, till I turned on the UV today. All this while the UV is connected but off.

 

[piranhaman00]

Yes running UV increases the ORP.

 

[Saltees]

Yes running UV increases the ORP.

Now I have proof... their correlation. My ORP probe is placed immediately after the UV via inline probe holder.

 

[Leo Reef]

I am puzzled. I learned that UV kills all kind of organic materials and that would decrease ORP? This is also visible on my apex ORP: UV on gives aroudn 15-20 lower ORP. I do not know if this is a short term effect or a lasting one. Inreresting thread anyway.

 

[Randy Holmes-Farley]

Perhaps it depends on what is in your water, or if your UV might be producing wavelengths outside of the usual 254 nm, but these researchers found that UV disinfection did not increase ORP in raw seawater:

Disinfection of Seawater: Application of UV and Ozone
Ozone: Science & Engineering
The Journal of the International Ozone Association
Volume 35, 2013 - Issue 1

https://www.tandfonline.com/doi/abs/10.1080/01919512.2012.722050

"Table 4 summarizes average results of continuous experiments performed over a two-month duration. UV254 irradiation induced small changes in seawater organic matter. However, pH (8.05) and ORP (235 mV) do not vary after treatment. UV absorbance slightly decreases; a small part of TOC is mineralized and specific ultraviolet absorbance at 254 nm (SUVA254) is also slightly reduced that show a preferential photolysis of aromatic organic matter by UV radiation."

 

[Saltees]

Thanks for chipping in guys! Now I wonder what could be in my water to trigger this correlation, because as I turned off the Deltec UV 80W last night the ORP dropped from 240 to 190 immediately. Nothing much in my tank except for 5 (freshwater) mollies, and salt water made from Tropic Marin Classic salt. The tank is cycled BTW, just waiting for me to get aquascape right.

 

[Augus7us]

Perhaps its because your ORP probe is right after the UV and its readings are off? I would be curious what it reads while the UV is on if the probe was in a different part of the tank. Just a thought.

 

[Saltees]

Perhaps its because your ORP probe is right after the UV and its readings are off? I would be curious what it reads while the UV is on if the probe was in a different part of the tank. Just a thought.

I’m moving the chiller between the UV and the probe next month, perhaps I’ll run the test again.

 

[Saltees]

Just turned off and on the UV over last 3 days... look at the ORP dipping and rising in tandem with the UV turning off and then off.

 

[Dennis Cartier]

I noticed the same correlation when running a UV in my tank. When it was on, ORP climbed, when off, ORP fell. At least while the unit was clean. When it was dirty, no effect on ORP at all

As Randy mentioned, it may depend on what is in your water column.

OT: Hey @Saltees, do you own an Alfa? I noticed your avatar.

Dennis

 

[ReefPig]

Interestingly I had a cheapo AquaMedic UV, this boosted my ORP every time it was on, by a considerable amount.
This worked "ok", but I found after 9 months when I cleaned it, that the plastic inside was degrading, rubbing my finger on the inside produced a lot of black particles / dust.

I more recently swapped this out for a more expensive TropTronic UV, this does not increase ORP at all, but my water is much more clear and obvious I'm running a UV.

As Randy suggested, I think some UV's have a different wavelength and maybe cause the Ozone effect to be more prominent.

 

[Saltees]

I noticed the same correlation when running a UV in my tank. When it was on, ORP climbed, when off, ORP fell. At least while the unit was clean. When it was dirty, no effect on ORP at all

As Randy mentioned, it may depend on what is in your water column.

OT: Hey @Saltees, do you own an Alfa? I noticed your avatar.

Dennis

YES! ALFA GT 3.2 V6 BUSSO.

 

[MabuyaQ]

All UV bulbs produce light within a range of the Entire UV spectrum, if this includes the 160-240 range it will also produce ozone from oxygen.

 

[Saltees]

Why UV-C Cannot Produce Ozone - UV Resources

UV-C light in the 253.7nm wavelength (most common germicidal range) does not produce ozone. Most germicidal lamps, including those from UV Resources, are produced with doped quartz glass, which blocks the transmission of the 185nm ozone-producing wavelength.

www.uvresources.com

"Ironically, UV light in the 240-315nm wavelength will break this third oxygen atom attachment above and convert it back to oxygen. The peak ozone destruction occurs at the 254nm wavelength. So, a UV-C lamp at the 253.7nm wavelength will actually destroy ozone!"

 

[Dennis Cartier]

YES! ALFA GT 3.2 V6 BUSSO.

Very nice. I love my Alfa.

Now, back to our regular scheduled programming

Dennis

 

[Saltees]

Very nice. I love my Alfa.

Now, back to our regular scheduled programming

Dennis

That’s a keeper too!!!

 

[Saltees]

I’m moving the chiller between the UV and the probe next month, perhaps I’ll run the test again.

I shifted the probe 2m further down the line still after the UV on route to DT, this is what I find...it’s no longer correspond to the on/off of the UV. Next week I’m going to turn on my SANDERS OZONE 100mg/l, that should put some upswings on my ORP, I hope. My tank’s water is still yellow but clear.

 

[Isaac Alves]

So whatever happened? Did it just end up not correlating? What was causing the ORP spike?