Wash frequency - 1st year RO

[tgormley358]

Hi, I’m looking for input on how often you run a Wash of your RO membranes with soap that is.

I have a small system 50 gph water removal, single membrane. Purchase from a small vendor,
Paul Family Maple. He has been very helpful and the system ran great. I rinsed after every boil per instructions, but his suggestion is to wash only when needed as performance degrades, plus end of season of course. So I haven’t washed yet. But a good and More Experienced friend said he washes after every boil, and I saw someone else here yesterday post and say the same thing. So this is part survey and part a request for advise. Is washing every boil necessary?

For me, more background - 125 taps, and I only hope to concentrate to maybe 5% and run the RO for 1 hour daily at a time to achieve that. The pump runs at 180 gph and that’s about the max I collect per day.

Tom

[DrTimPerkins]

There are two schools of thought on membrane washing.

1. Keep track of flow rates (permeate + concentrate). After adjusting for sap temperature (RO processing is very temperature dependent...colder = slower), do a soap wash (with the appropriate RO soap for the time/temps suggested by the manufacturer) if the flow rates drop by 20-25%. This approach is required of organic maple producers in Quebec, and several others use it also.

2. Wash/rinse after EVERY concentration cycle.

Washing, done correctly, won't harm the membranes...it just takes time. At UVM PMRC, we always wash after concentrating...always have as far as I know. Our flow rates stay high that way, and we are never caught with a huge amount of sap just at the time our flow rates drop.

[mol1jb]

This was my first year on RO. I have a similar sized operation (150 tap) and similar capacity RO (120 gph) as you. I did not wash at all throughout this season as I too was not sure when was a good time or how much performance drop off is too much. Looking back I should have washed once a week, keeping in mind we were processing around 1000 gallons sap per week at the peak of the season. That would have kept my performance drop off minimal and my flow rates in better shape for what I needed.

Its kind of a balance of what you need. For us smaller operations, a little drop off in performance is not going to hurt our production much. But large producers I can see why they would want to wash after every run.

[Russell Lampron]

I used to do a soap wash after every concentration cycle but don't anymore. I added a second membrane to my RO and don't run it as long as I used to have to. I do a hot permeate wash after every concentration cycle and do a soap wash after every third concentration cycle.

[maple flats]

I alternate, a hot permeate wash one day and a soap wash the next time I use the RO, I always do a soap wash after the season. I used to just do a hot permeate wash every day unless I noticed a drop in performance. That proved to not be the best, I was just going by the apparent reading on the flow meters and as such I was missing small drops in performance, that's when I started alternating the wash methods.

[SeanD]

I used to do single heavy passes and I would have to wash pretty often. I started doing second passes for the first time this year and decided to watch rates to know when to wash. I do a hot recirculation every time I run it and I backwash often - almost every boil. Between that and splitting the work over two passes made a big difference.

I saw a 15% drop right when I hit 2000 gallons of raw sap or 13 passes. After the wash things were back to normal until the very last day when I was pushing some funky sap through 11 passes or 1800 gallons later. It dropped about 15% again, but it was the last time running the RO for the season so I just let it finish and did my final wash of the season when I was done. That was the least amount of washes I've done and the most amount of sap I've put through it. Doing two passes made a huge difference in the efficiency of the RO.

[Hop Kiln Road]

I switched from recirculation to two pass a couple of years ago. Enormous increase in RO efficiency. First pass 2:1 permeate/concentrate; second pass 1:1. H20 calls for rinse and wash after every 3 hours of operation and I can run my protocol for 9 hours with no change in pressures. I do rinse and wash after every use. However H2O specs only call for a 50 gal rinse, wash, 50 rinse on a 200 gal / two 4" membrane RO. More interestingly, not only are my operating pressures lower, my sugar flush while recirculating used to take 30+ gallons and now it doesn't take even 5 gallons. I also think my grade and favor have noticeably improved, but that is subjective.

[wnybassman]

I have a small 50 gph water removal machine also. Bought it last year halfway through the season. Never soap washed it last year, just did the warm water recircs and cold water rinses to specs. Didn't noticed any real ill effects of how I did it. Had the soap, just didn't know how to use it. This year I decided to use the soap. I do it after every third use or so, or whenever it will sit for a few days or more. A few times this year we had enough sap in one day where I had to do a warm water recirc with cold water rinse midway. The second session is never efficient as the first. I think what helps mine the best is sitting overnight in the fresh permeate after the cold water rinse. Not sure if it dissolves minerals or what, but it always seems to be back to 100% after sitting all night. I have a ton of permeate left now that the season is done, so every couple days I am going to send 25 gallons or so through it then after a week do my preservative to put it up.

[tgormley358]

Lots to learn here, thank you all for sharing your experience. I think I’m going to move to a more regular wash next season but not every cycle since I don’t run mine as intensively as others. I’m assuming but will double check with the vendor that I’m following all of the membrane Mfr’s specs. For instance I picked up on the fact that I’ve never heard of a warm water recirc as part of the cycle, and I’m not sure how I’d get warm water for this? Since I’ve been only running the RO for an hour I only get 50 gal of permeate which I use up completely in the rinse. So I don’t have extra permeate.

I also don’t have any flow meters to monitor flow, only pressure meters. What do you use for flow meters? Easy enough to find I assume at a plumbing supply store? I did check sugar content and 0% in my permeate after 5-6 cycles so I took that as no degradation.

A lesson learned for me, to share with others thinking about RO for next year - I recirculate concentrate back into my sap head tank which feeds my evaporator. I found an odor developing in the tank I’d never had before like a bacteria smell. As a result I started to clean or at least rinse the head tank after every RO cycle. I know the higher sugar content is what likely caused this but I just had not needed to clean the tank more than once or twice per season these past few years. It might be that a more frequent wash could also help reduce this issue.

[wiam]

I have a water heater element in my wash tank. The RO soap does not do a lot of good until it gets over 100°. Most membranes recommend not to go over 113. I think mine works better since I went to a first pass tank instead of recirculating. I pressure wash all tanks at sugarhouse each time they are empty. Adding extra valves for drain is very helpful for this.