hodorskib's Small Scale RO Build

eustis22
Performance depends on several factors. Temperature is one. How many membranes and their flow rate is another. I only have 3 of the 150gpd membranes and get lower performance that what you reported. I usually see 2% sap go to 5%. At the end of the season I saw 1.75% go to 4%. Mine is processing about 8 gallons of sap an hour, giving me 4 gallons of concentrate. I tried once to squeeze the sap a bit more (66% permeate to 33% concentrate) but it was really slow, I let it run overnight for 6 hours and it was only processing 5gph of sap. It took the 2% sap up to 6% though.

next year I'll buy 2 more membranes since that seems to increase processing rates.

also, about the RO soap. I did it a few times during the season when the trees froze up and I knew the RO was going to sit. If I go more than 2-3 days between using it, it starts to smell. The pail of RO soap is going to last me forever so I don't mind using it during the season.

I have 4 of the 150 GPD membranes in series. Would upgrading my membranes increase my concentrate %?

Measure. Measure how?

Over the past two years I have been running 6 membranes in series and have found that I am able to get an 8% concentrate starting from 1.5% sap in a single pass. If the sap is cold in the 30s about 8 gallons and hour through the system and above 40 8-10 gallons per hour. After each run I do a soap wash for about an hour- an hour and a half. This is has kept the system clean and running great. I just finished processing 2,000 gallons so far this season. Keep them clean and they will perform.

Hi Hodorskib and all for sharing 22 pages of great info here. I just read through it all and Hodorskib's website. I have two questions and if they have already been answered please point me to the post, thx!

1. Temperature: I am north of Hodorskib in Colebrook, CT where it stays real cold. My sap is stored in my unheated garage. It seems the ideal temp for ROing sap is 40F. My sap is usually colder than that. Should i use a heater of some sort (an aquarium heater, inline heater, or stock tank heater might work) to raise the temp of the sap going through the RO to about 40F, or just deal with the reduced gal/hour with cold sap?

(I'm aware you don't want to heat up the sap too much due to mold growth)

2. New to all this, I bought 100GPD membranes instead of 150GPD membranes. I collect maybe 60 gallons per run, so I don't need to process large quantities overnight. Will the 100GPD membranes be OK? Will I be able to raise the sugar content as much as if I used 150GPD membranes?

Many thanks, Eric.

Thank you Hodorskib. I built my 5 cartridge 150GPD series system over the winter and tried running it today. Was hoping to boil concentrate this afternoon. My raw sap is coming in at 4%. I adjusted the pressure until I had about 50/50 coming from both outputs and then measured my permeate and concentrate with a calibrated refractometer. It showed quite a bit of sugar from my permeate line. I verified the plumbing and then tried again, this time lowering the pressure to allow about 4:1 concentrate to permeate. Doubled checked the calibration of the refractometer and measured raw sap again at 4%. Sap from the concentrate line is at 4.2% and sap form the permeate line is at 3.8%.

When I received the cartridges I noticed that they had packed the membranes inside of the cartridges. They were pushed into the bottom of the cartridge and plastic packaging had folded around the o-rings. I just checked the o-rings on all 5 membranes and the o-rings look okay when they're wet but when I spin the membrane I can feel that some of the o-rings aren't perfectly smooth. I'm going to replace all 10 o-rings tomorrow.

Any other ideas?

deitzd-

Sounds like a plumbing issue or a bad membrane in the mix. I suppose it could be the o-rings and thats a pretty quick/easy fix if it is, but in the mean time, can you post a photo of your plumbing? I know you said you checked it, but it wouldn't be hard to accidentally plumb one of the lines wrong. Others have noted it on here before. Sometimes a second set of eyes helps.

Here it is.
Attachment 19901

Looks good as far as I can see. You could try bypassing the 4 additional membranes and add them back into series one at a time to see if one of them is bad. If you narrow it down to one that starts letting the sugar pass, check and see if It could also be a crack in the housing some how letting the two sides mix. I've had 3 housings blow pinholes in the bottom where it comes off the machine that forms them. I end up "welding" the hole with a red hot screw driver to plug it.

Thanks much Msboucha. I'll replace the o-rings tomorrow and then try bypassing each membrane if necessary.

It might be easier to run a separate permeate line from each ro housing. Test each permeate separately and isolate the contaminated one(s). It could be a poorly wound cartridge, or even a cracked housing.

I would suspect that your readings are within an acceptable margin of error for the instrument (meaning your permeate and concentrate are the same sugar concentration). Do you get any flow out of the permeate line BEFORE you apply any restriction? With those readings, I would think that a membrane is missing entirely, or a housing has a large internal crack. If one membrane is leaking you should still have a considerably higher concentrate sugar % than permeate.

Can you get the system to 100psi?