Copper Silver ionisation

[TimB]

Hi all

I'm using a product that needs to be kept really clean to work properly and its not. Its developed a biofilm as water passes through it. In use I want it to not give issues as cleaning regularly is not an possibility.

I do not want to use chemicals as its not possible. So I'm looking at copper silver ionisation. Trouble is I have no idea how to go about it. I would like to have just the electrodes as small as possible and run on 12v DC max.

Anybody do anything like this?

Cheers

Tim

[Colin G3YHV]

Could you shine UV on it  -  it keeps my pond clean.
Colin

[TimB]

"Could you shine UV on it"

Hmmm yes do not see why not and you can get UV leds would be very simple I think to implement. 

Thanks

[top204]

For that type of application you will need upper UVA or lower UVB devices. I think they now call that type of UV LED; "UVC" as well.

From what I remember when I was investigating that type of LED a few years ago, they are not readily available and have a tendancy to be rather expensive, unless they have found a simpler way of producing them in the intervening years. Standard UV LEDs used for curing or note forgery etc, cannot be used for biological cleaning.

[TimB]

From what I'm seeing now UVC leds are not very expensive. From £2 to £5 which is fine for me

I'm now trying to figure if its going to pass through 0.5mm of PTFE tube and if it will degrade it.

[trastikata]

I'm now trying to figure if its going to pass through 0.5mm of PTFE tube and if it will degrade it.

About 92% reflection for that thickness - source here.

If you are considering copper-silver ionization then you have access to the fluid, is the entire system from Teflon, could the system handle Chlorine or Ozone?

[TimB]

Unfortunately the component is not PTFE lined. My tubes to it are. The system is sealed and I cannot have consumables unless they can last for years. UV would be ok if I can irradiate the water just before the part. Ozone I think would be OK. 

Perhaps I can add a UVC transmissible section of tubing before the sensor or use the copper silver ionisation system. If I can find data on how to do it that is.

[trastikata]

Can you replace part of the PTFE tubing with glass tubing, then UV irradiation could work.

[TimB]

UVB and UVC is main blocked by glass.

Also PTFE seems to be transmissible to UVC wavelengths.

[trastikata]

UVB and UVC is main blocked by glass.
Also PTFE seems to be transmissible to UVC wavelengths.

I was referring to fused silica (quartz) glass which is good UV transmitter, whereas PTFE blocks about 90% of the UV light - check the document I posted earlier.

[TimB]

Right, quartz glass is UV transmittance. The link you listed has had a special process to make it highly UV reflective, Note the white colour. That was the aim they have a number of videos showing its reflectivity.

I note a lot of confusion on how transmissible PTFE is to UVC.
http://www.aquanetto.ch/water-treatment/fluoroplastics.html

[Yves]

To come to your initial post about copper and silver ionization, I assume it is for the swimming pool? silver is a bacteriocide and copper is an algicide and both are required to keep your swimming water clean. There is enough conductivity in ordinary water to perform some electrolysis. What I need is I used a 12 volts transformer and rectified the voltage with a full bridge rectifier. I use a NE555 to alternate the current polarity to two electrodes, one is composed of copper and the other one of silver. So what is happening each electrode was set to be either anode or cathode for about 10 seconds. There was a build-up of silver chloride forming over the silver electrode which has very low solubility in water but enough to maintain a few ppm of silver in water, particularly if place in a high flow after the sand filter. The system works well and the pool was not requiring much chemicals.

Cheers,

Yves         

[TimB]

Thanks Yves

The requirement is for a flow sensor. It is badly effected by biofilms. While my test rig positively encouraged it I'm worried that in use by the customer it may happen, so want to prevent it. The water going through is sterile, but I'm worried about what will happen when they have a shut down and its out of use for 2 weeks.

The options as I see it are
UV it will kill only the water passing through
Cu & Ag has an effect downstream however if a biofilm develops it is not removed quickly
Lastly I could have a bottle of acetic acid and periodically perform a sterilisation cycle by pumping some into the stream.

One thing to say the flow is in the low ml per min range.

BTW good point about reversing the polarity, I will do that if I use Cu/Ag.

[trastikata]

Tim,

I believe in your situation you don't need the forced ionization through electrochemical methods. If it is possible to install silver tubing or silver coated tubig immediately before and after the sensor, this should be sufficient to prevent the formation of a biofilm in the stagnant water around the sensor in case of shut down.

[TimB]

Ok thanks, sounds like a plan!