Using a UV light with an RO

[Clinkis]

Because of my setup and work schedule I usually need to store my concentrate overnight. It's usually not a problem but as the season progresses and temperature rises it becomes more of an issue. I was wondering what success (if any) people have had incorporating a UV light into their RO. In theory, it should help improve concentrate life and reduce membrane fouling. If so, where in the system do you put it?

[Bucket Head]

Sugar molecules alter the UV light rays, meaning you will never get a complete sterilization of the sap. So the more sugar you have (after RO), the harder it will be to sterilize. So looking at it like that, having the UV before the RO makes sense. With that said, how clean is your RO? No offense here- but that RO has bacteria in it- they all do. None are 100% clean. So everyone introduces a little bacteria from the RO. So looking at it that way, UV after ROing would make sense, hoping to kill the most bacteria right before storage. But it will be harder for the UV light to "travel" through the sap.

There is a user on here that stated he has less biofilm on the walls of his concentrate tank with post-RO UV treatment. I would say try it after ROing. It certainly could'nt hurt. How much concentrate are you producing? Do you have two vessels you could use for concentrate? You could RO and UV into one vessel,tank/barrel,etc. and then pump and UV the concentrate into the other vessel so its "treated" twice, which may help seeing its concentrated.

Hopefully some others here will chime in with their results, good or bad.

Steve

[Snowy Pass Maple]

Great advice from Steve above - for the reason he outlined, I put my UV on the incoming feed and run it at a much lower flowrate to achieve a higher "dose" of energy into the sap. I figure that is your best chance to have an impact - but as he notes, you can assume there is inevitably still some microbial activity that accumulates. If you have a filter, changing that is important too - I only go 2-3 days at most with my cartridge filter if we're seeing temps in the high 40s+.

I posted my $0.02 in this thread:

http://mapletrader.com/community/showthread.php?22313-UV-Light&p=241087#post241087

I have not found a good way to prove/disprove how much benefit I get with mine other than to say I went all last season never making anything darker than A-medium unless I intentionally boiled the sap longer. This tells me that we run a pretty clean operation - and while the UV is one piece of that, so many things can affect that including all other sanitation efforts, maintaining good turn-around-time, as well as intrinsic differences in the sap itself, that I can't really make any claim on the UV itself.

I asked in another thread but will ask again here - does anyone have UV absorbance curves for maple sap to help get a sense of just how much of the sap is truly getting a killing dose from the UV? I am sure Proctor or Cornell must have looked at this - if not, it would be very interesting to see. Miniature CCD based UV spectrometers are so cheap and widely available now that I'm sure it's been done. Then we could better calculate the value with these UV setups in different flow conditions.

[Clinkis]

Thanks for the feedback. The other research I've done agrees with what your both saying. I plan on putting the UV light AFTER my pre filter and BEFORE my membranes on my RO. This should be when my sap is clearest and thus most penetrated by the UV light. Also my RO is made with residential components so its very slow thus the low flow rate will mean the sap will have a long exposure time. My only concern is that the heat from the UV light, although possibly increasing flow rate through the membranes, may increase the proliferation of bacteria. Any thoughts on that?

As far as general sanitation. I have small operation and already have a strict regiment of cleaning and disinfecting thus tend to make lighter syrup already. My hope is that later in the season I can maintain this as the season progresses and the weather warms. Last year near the end of the season my syrup became very dark (although still very tasty) and it was always a race to get the concentrate boiled before it spoiled as I usually run my RO overnight and boil the next day.

Thanks again for your feedback and would gladly be interested to hear other thoughts, suggestions or experiences with UV lights