4x150 - are my membranes shot?

[82cabby]

Hi all-

I have a homemade RO running four 150 GPD membranes in series with an aquatec 8852 pump. My sap has been running a very low sugar content this year, around 1.1%. One pass through the RO takes it to 2.4%. Currently it is raining so I am taking a second pass and getting 2.4% to 3.6%. I know that will darken the syrup but I am desperate to get this processed today given tomorrow’s forecast and I have a LOT of sap.

My question is shouldn’t I be getting higher concentration levels from the RO? I’m pushing 110 psi just to get what I’m getting. I’m starting to think some of the membranes are clogging. I rinse with diluted hydrogen peroxide and then permeate after every long run but it seems like the numbers should be better.

Any thoughts?

[ecolbeck]

I believe that membranes are only worn out if they are passing sugar. This can be monitored by testing permeate with an inexpensive Total Dissolved Solids tester (TDS). In your case, it is more likely that the membranes are plugged with bacteria and minerals and need to be washed. Wash solutions are available from your local maple supply house.

[82cabby]

Thanks for the suggestion! I have RO soap I usually use at the end of the season. Next break I get from boiling I’ll give it a rinse with RO soap instead of hydrogen peroxide and see if that helps.