Why is permeate flow reduced as I increase pressure?

[maple marc]

Deer Run EZ 125 RO in fifth season of use. Has seen 6000 gallons of sap through it. This RO has one 4x40 post. Well cared for, with hot water rinse after each run and acid and soap wash at the end of each season.

Weird behavior this year: Each run starts out well. Today with warm sap I was removing nearly 50 gallons of permeate per hour at 160 psi. After about 100 gallons of permeate my rate dropped so I increased pressure. But as I increased pressure the permeate flow actually dropped, as did the concentrate flow. This has happened during each run this run--unlike normal behavior other years.

What is going on? Permeate flow should increase as pressure increases, right?

Thanks for any ideas from you RO gurus.

[Bricklayer]

Only 2 things it could be.
1. Your membrane is fouled and needs a really good wash. I typically rinse my membranes after every use with 100-300 gallons of perm. Then a soap wash and let it sit in the soap untill the next day. If I’m not boiling within 2 days I’ll complete the wash and rinse with 200-300 gallons of permeate. Your membrane could be finished as well and un-saveable. It does happen. They do have a shelf life. Sometimes a professional from one of the big maple manufacturers can bring them back.

2. Your RO pumps are not performing as per spec. Usually with pumps the GPM falls off the higher psi they have to pump.
Check your flows perm flow + concentrate flow. They should match what your pump can pump according to its specs for the certain pressure.

[BAP]

Good recommendations from Bricklayer. Unfortunately, your maintenance routine is not necessarily “well cared for”. You need to do more than 1 soap wash per a season. Also, how hot of a water are you using to rinse? Membranes don’t want the water to be too hot. You really should be rinsing with permeate that is whatever the ambient temperature is.

[TomorrowRiverMapler]

That certainly does not make sense but I have to concur with BAP on RO care. I have a Leader Micro II (2 post 4x40). The manual says after every use to do a permeate rinse of 125 gallons, then caustic soap wash till temperature reaches 118 degrees followed by a 125 gallon permeate rinse. It's also critical to know what your permeate benchmark flow is. For Leader's Micro it is measured new using 70 degree water at 150 psi and is about 2 gpm per post. This test is then done after every use after a rinse/wash/rinse and then compared to the benchmark. That way you know when your membrane is getting plugged. If the drop is greater than 15% an acid rinse is the first step to unplug. Post back what you found out the problem was.

[SeanD]

Marc, you've gotten good advice here. Deer Run recommends processing at 275 PSI. Are you using the recirculation valve or just the large HP valve? I think the #1 thing to do is a soap wash. I think you'll see immediate results. I soap wash almost every day/run bigger than 500 gal and and definitely every time when the weather warms and the sap quality decreases. I do 2 passes, so that's 4+ hours of run time.

I've never tried letting the membrane soak in soap, but I have used 50:50 washes and rinses for the last couple of years. I picked that tip up somewhere here. It seems like it has helped keep the membranes in good condition.

Keep us updated.

[maple flats]

Another possible issue is the raw sap filter, it has a 2.5x20 filter , is it fouled? I change to a new one every day, in late season sometimes 2x a day.
Also, run a soap wash according to EZ RO's instructions, you might also need an acid wash if the soap wash doesn't get you back to proper functioning. I always run a permeate rinse daily, at times more often, then at day's end I run a perm rinse then a soap wash, then a perm rinse and then a filter change.
With a 125 RO you want to run about 125 gal of permeate rinse.

[dcast99]

I do a rinse, soap wash, rinse and acid wash every day(actually let the acid sit overnight) then another rinse. Don't like taking a chance the RO will act up when I have 700 to 1000 gal of sap to process.