Time To Clean or Just Cold... Low Flow!

[bryankloos]

Hey All,

My 4x150 series unit has been chugging along this first season. I have 3 rounds on it with maybe 700 gallons of sap concentrated.
After each run I open the needle valve on the concentrate line, flush with permeate, recirculate with warm permeate for 1 hour, change the 5uM filter and then fluch again with fresh permeate for a few min before storage.

Yesterday I noticed my flows were starting to slow down, and I'm wondering if its time to a real NaOH clean or if its just the temps.

I ran through about 80 gallons of sap in maybe 8 hours... So 10gph of sap with resulting in about 3.0ish gph concentrate. outside temp was 28F. I try for about 2:1 running my system at about 125 psi.

Is this to be expected? I seem to think my first run was much faster (250 gal Sap in maybe 17 hours).

Questions:

1. Should I rotate my membranes between runs?
2. When is it time to do a NaOH cleaning?
3. When is it time to do a H2O2 cleaning?
4. When is it time for me to stop overthinking things?

All help is appreciated.

Thanks!

Bryan

[maple flats]

For sure the sap temperature (more than the air temp) has a big impact on the performance of any RO. I won't try to address how you have "cleaned" it in the past because I'm only familiar with my RO, but cleaning might be a portion of the reason it slowed down.
I suggest you check out The Bucket RO and see how the manufacturer suggests it be cleaned. That might help.

[SeanD]

I'll add on even though like Dave I have a Deer Run and don't know the specifics for your RO.

On the Deer Run, it's time for a soap wash when you notice a 15% drop in flow rate. So for me on a 125, when I drop to 106 gph then I wash. you can calculate your flow rate by adding your concentrate and permeate gpMs and multiplying by 60. That will give you your gpH. You can prolong the time between washes by regularly flushing and backwashing after a boil - although I've read some people here wash every time.

For the Deer Run, a typical end of boil/run flush is to recirculate with 120 deg water for 10 min (I do 20) then flush with cold permeate for 10 min. Your recirculation line should be closed and your high pressure valve should be wide open to get the highest flow over the membrane. It sounds like you are doing that already, but...

After 4-6 hours of run time, it's time for a backwash. Every time I run the RO, it's for more than 4 hours, so I backwash every time. For a backwash, recirculate with hot water and then flush with cold permeate for 125 gallons per membrane. Again, the valve should be wide open for the highest flow.

The numbers are likely different for your setup, but the philosophy is probably similar.

[blissville maples]

Should run a 115 degree soap wash at least every other use. Otherwise your membranes will accumulate biofilm due to sitting uncleaned. Especially longer than a couple of days.

Not sure what you mean by n2o2 and all that jargon. You either rinse, soap wash or acid wash those are your three options, no need to change the lingo!! Just good when everyone speaks in same terms.

A warm rinse helps with sugar but doesn't do anything for the fatty acids/ yeasts.

The other thing you must do is acid wash when performance drops significantly. That's the only way to address the minerals being packed into the vessels of the membrane. I usually do about 2/3 way thru season. I soap wash almost every night, my membranes performance remains good following this regimen.

As far as flow rates just watch the gallons per minute on your permeate flow that shows what's actually passing through the membrane as far as water. As this figure starts dropping that means your membrane is getting dirtier. Of course temperature plays a factor but for me it doesn't change a whole lot until the end of the season, by then sugar is dropping off anyway.

[blissville maples]

Sometimes if I want to concentrate an additional amount of sap without washing I will open my permeate tank valve yeah close my sap tank valve this makes you concentrate water. In doing so the turbulence will remove some of the sugars on the outside of the membrane and you can watch your flow rates go up infront of your eyes within a few minutes

[bryankloos]

Sorry guys... I'm a scientist my trade.

NaOH is sodium hydroxide, or Lye, or RO Soap.
H2O2 is Hydrogen Peroxide
C6H8O7 is Citric Acid.

i'll do a soap wash today and see how things work the next go around.

Thanks All.

[30AcreWoods]

I'll just add that if your sap was anywhere close to that 28 degrees air temp you noted, that is as good a reason as any for reduced performance (assuming you've cleaned/rinsed as discussed). I rinse and clean frequently, and have noticed temperature to be the biggest variable in performance with all other things being equal (clean).

[bryankloos]

Thanks All,

My money is on the temps. It was by far the coldest day I've used the RO. Ive done regular warm permeate flush after each use. I did the Soap (NaOH) wash yesterday with a good permeate flush afterwards. I'll calibrate my digital handheld pH/TDS meter today and confirm all the soap has been flushed before I run again... Waiting for the trees at this point.

[iby]

Should run a 115 degree soap wash at least every other use. Otherwise your membranes will accumulate biofilm due to sitting uncleaned. Especially longer than a couple of days.

I'm surprised to hear so many people saying that you should heat your solution before cleaning the membranes. since Sodium Hydroxide is one of the main components in cleaning soaps, I thought that as the solution warmed, it lets off some type of nitrogen gas that can explode.. that's why you're told to never dispose of it down the drain without neutralizing it... I could be completely off base and obviously I'm the minority since everyone seems to do it this way... maybe some of the other components in there neutralize that condition... for those that just buy straight sodium hydroxide though... I''d make sure to understand the chemical properties of what you're using... I'll continue using cold water though for my washes...

[Super Sapper]

There should be no issue with a warm wash. A cold wash with NaOH greatly reduces it's cleaning properties. In industry it would not be allowed as it would not clean as well.