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View Full Version : Replace Reverse Osmosis Membranes After Maple Season?



fireant911
04-27-2022, 10:49 AM
The good: This was my first season at using a Reverse Osmosis machine at processing sap. It operated relatively smoothly and yielded more than double concentrated sap (from 2.6% to 5.6%+). Being a small hobbyist, only 25 trees were tapped and after tallying all the records, it appears that approximately 260 gallons of raw sap was processed. This success can be measured by the seven gallons of sap proudly displayed in our cupboard!

The bad: I have been struggling to clean these membranes since last week! I attempted to follow the very well-written instructions on the Mattatuck Maple Madness website yet I quickly ran out of all my permeate when doing the initial RO Soap wash. Chemistries were all over the place and I experienced MUCH trouble in hitting and maintaining the target pH values for the RO Soap and Citric Acid washes. Yesterday, I purchased many gallons of distilled water to hopefully finish the cleaning of these membranes. I then saw that this new supply of flushing material quickly was diminishing so I ended up using our well water... I have invested way too many hours in trying to clean these membranes and I at the point that I will proclaim that I am defeated... easily, I have 15 hours into trying to clean the membranes... and I am not yet finished. Surely, it cannot be this difficult as many others seem to breeze over this aspect but it has become a horrible, hated chore for me. Currently, I am doubtful that my cleaning efforts this year will be even satisfactory for next season's usage.

With my failures, disappointments, and frustrations out in the open, may I ask if others have opted to purchase new reverse osmosis membranes for each season as to bypass this annual drudgery? Although the filters are not inexpensive (the 150 gpd filters are available to $26 each and I need four of them), at this point, $104 seems like it would be money well-spent and would guarantee no surprises with fouled filters for the 2023 season. Another option that may be available is to have the membranes professionally cleaned (I first read about this option here on the MapleTrader) - how does one go about finding these membrane cleaning services (I am located in Michigan's Upper Peninsula)?

Granted, Reverse Osmosis may not be the best option for everyone (me!) though I would like to continue using this approach but with less challenges. HELP!!!

wobbletop
04-27-2022, 03:08 PM
I have a similar size operation to you. I don't bother using permeate to rinse/wash the membranes. I just bring the RO into the house and use a 5 gallon bucket in the bathtub for rinse/wash/acid. I am on well water as well, with a 5u sediment filter and water softener.

I will do a 5g rinse, then a 5g soap that circulates until I turn it off. Before using the RO again I will do another 5g rinse. It doesn't take too much time since I'm not babysitting them while this is happening.

My key is to not let the RO sit for more than a day without rinsing/cleaning after processing sap.

I will test the membranes periodically with a TDS meter to make sure they are not passing any sugar. I use a digital pH meter, but they do not last (but they're cheap).

fireant911
04-28-2022, 07:03 AM
Thanks wobbletop! That was a very helpful reply. Could you elaborate about your TDS testing procedure? How frequently do you test? If you see a rise, do you stop your regular operation and perform a wash using RO Soap at that time? Do you notice any changes on your pressure gauge after doing the RO Soap wash? Sorry for my sophomoric questions but I am an extreme novice to the art of sugaring.

wobbletop
04-28-2022, 09:17 AM
I don't test TDS very often. At the start of the year to make sure my membranes weren't damaged over the summer somehow, and then not much. I would test more if I saw a problem, but I've had no issue with them. If I saw a rise, I would suspect some type of physical damage to the membranes or to a seal somewhere.

I don't notice pressure changes. The pump always seems to put out 110-120 psi. It can take a while (5 minutes) to get up to pressure when first starting the RO. I just aim for equal concentrate and permeate flow and let it go. If I try a second pass (to up the concentrate), the flow rates drop by a noticeable amount.