Reverse osmosis

[Mr Bill]

None of my customers have noticed any change in taste since adding the RO machine and believe me they would notice.

Just my humble opinion here but I think for what you would have into it by the time you designed your own you could have bought a used one and put new membranes in it. I have said it before, sometimes the peace of mind knowing it is going to work is worth the extra dough especially when you have the problem is when the sap is running the best.

I do believe you.

I understand what you are saying. The desire to do it not simply finacial, much like sugaring. The challenge is much of the fun. Used equipment isn't exactly abundant in southern Indiana either. You may be right that constructing my own might be similar in cost to used, and if it would be, I probably won't build. But, I have figured out that I can construct vacuum pumps and filtering equipment for 10-20% the cost of new which is probably less than most decent used gear and I want to explore RO as well. I used to be an engineer and have a small machine shop so the reliabilty peace of mind isn't a particularly difficult challenge.

So, has ANYBODY constructed their own RO?

[WESTVIRGINIAMAPLER]

Bill,

I haven't but if you can build a good one cheap enough, I may be a customer!

[powerdub]

I certainly see where you have all the knowledge and tools to do the job. In that case it would be a fun project. I, in no way meant that as a discouragement. It has been my experience that my homemadestuff costs me more in the long run. Keep us posted if you do go ahead and do it. By the way, I asked a few sugaring buds that don't come here your question and no one has run into anybody that has made thier own RO machine.

[sugaring42long]

Mr Bill , There are several people in my area with homemade RO's. The ones I have seen were all made by the same guy. They are pretty basic ( pvc pressure vessels and hypro pumps ) and dont perform like company built RO's mainly because of the pumps that he used.
I was going to build an RO a few years back and even had aquired many of the parts and also had spent tons of time researching how spiral wound membranes work and which ones to use for sap. Then I found a used older model Memtek RO that was made for the maple industry and knowing what I do now it was the best thing that could have happened.
Theres so much to discuss about this subject I dont even know where to start.
Mr Bill are you familiar with spiral wound membranes? If not thats your first step, you need to do some surfing and get a handle on how they work and what size membranes you want to use -- 4" or 8". The membranes I use are Made by Filmtec which is a Dow Corning company.
You will probably want to use nanofiltration elements like the NF-270 or the NF-90. Filmtec has a nice website as well as hydranautics and Koch membrane systems.
You will need to buy or make membrane housings, end caps ,thrust rings and permeate tube adapters for each membrane. Then you will need a feed pump , a pressure pump and most likely a recirculation pump.
Other items needed:
flowmeters - one for concentrate and one for permeate.
Pressure gauges
metering valves
check valves
filter housing
controls
Time for research and patience. Good luck

[powerdub]

Too bad I didn't live a little closer. I have some of that stuff like the membrane tubes. I even have a frame from an osmonics. I have a pressure pump but it is 480v 3ph. May not be a problem for en engineering type.

[Mr Bill]

Mr. Welch,
Yes, I'm familar with spiral wound membranes. 4 or 8 inch is a no brainer -- 4 inch, I'd have trouble fitting housings for the 8 inch membranes on my lathe machining the business end for an o-ring and end cap.

Why did you suggest nanofiltration instead of RO filtration? Sugars will go through many nanofilters. I presumed, maybe incorrectly, that NF-90 and 270 were in reference nanofilters with particular molecular weight cutoffs. Wouldn't a molecular weight cutoff of 270 be rather big? Sucrose has a molecular weight of 342 and probably would mostly be retained in the concentrate but molecular shape has much affect and from what best I can tell, membrane manufacturers figure that out empirically instead of theoretically. However, dextrose/glucose and fructose are 180. I'd also think you'd want to keep most of the ionic salts in the concentrate. A MWCO of 90 would probably keep most of those in the concentrate. If you lost too many salts to the permeate, then I could see how that might affect the taste as some believe RO does.

Thanks for the suggestion to check out the Filmtec and Koch websites. Most of my reading has been on the Osmonics membranes. They recommend their Desal brand RO elements for sugar concentration. But they have a bunch of versions of Desal units.

Thanks.
Bill

[sugaring42long]

Bill.
The nanofiltration membranes have pretty much been the industry standard for sap for quite a few years. When RO's were first becoming popular in the eighties the membranes were cellulose acetate and then in the early nineties the thin film composite membranes like the filmtec "brackish water" or BW-30 which flowed much better and now the nanofiltration elements.
I read your other post about membrane pore size and you nailed it, there is a fine line between high flow and losing trace minerals in the permeate.
Having used several different types of membranes and comparing flow, fouling tendency and syrup quality I am happiest with the Nano membranes. I currently have two eight inch NF270-400's and love em. I still get tons of sugarsand in my pans and have compared syrup made with and without the RO and can not tell the difference except the non RO syrup is usually darker.
Somewhere, I believe on a canadian website for organic Maple syrup standards I read they prohibit the use of "high flow" or Nano membranes.
For a hobby operation If someone is worried about it I would go with tight membranes but be prepared to have to wash it a lot more frequently to keep the permeate flow acceptable. For a profit making adventure nano is the way to go.
Bill ,whatever arrangement you come up with, make sure you have tons of recirculation flow as this is the key to making the membranes flow and not foul as easily. Chuck

[Mr Bill]

Chuck,

Superb reply, thank you so much. You've been be far the most helpful and informative.

Just curious, do you think the darker non-RO syrup is simply because it just boiled longer, (i.e. the sugars were exposed to the high heat more)?

A couple questions that will put more of this togeather for me.
What kind of ratio of recirculation flow to concentrate outflow do you use/recommend?
What kind of ratio of permeate outflow to concentrate outflow do you typically use/recommend with your NF-240? What did you get when using the smaller pore membrane such as the NF-90?

Thanks,

[sugaring42long]

Bill, yes I do believe that the time the sap is heated is longer with straight sap than concentrated sap and that will make for darker syrup. Its the same as running your pans deeper, you will almost always make lighter syrup by running as shallow as you dare.
Another issue related to this is where in the evaporator the brix of the boiling sap becomes concentrated enough to start the carmelization process. When I boil 8% to 10% concentrate and then go through my steamaway My whole front pan is but a few % from finished syrup and it does not stay in there over the hottest part of the fire for long.

About the membranes, most of the spec sheets for modern membranes list a maximum recovery rate of 10% to 15%. Meaning that you should have 9 or 10 times the recirculation flow as you do permeate flow. This is to avoid the build-up of a boundry layer of very high concentration fluid on the membrane surface. Most also list a maximum recirculation flow(70 gpm for the nf270-400) and a maximum pressure drop across the element (15 psi for the nf270-400). You could just put a differential pressure guage across the membrane to monitor recirculation flow.
Remember when you design your pressure vessel, end caps and thrust ring to take into account the large hydraulic force that will be exerted on the down-side end cap when you have 15 psi of pressure acting on the end of the membrane. On a single 8" membrane this can be several hundred pounds of force.
Another observation about new RO's like those made by Lappiere, Airablo and CDL is that they Exceed most of the element manufacturers specs of recirc flow and recovery %. But they do get tremendous performance out of these machines and do warranty them for some time. Lappiere patented the recirc pump mounted on the vessel concept that is very common today and that is the main reason for the flow improvement. You can look up his patent on the uspto website. Later- Chuck

[Mr Bill]

Chuck,
Thank you so much for the excellent data.

I appreciate the note about loads and pressures. I built a small test chamber just this past summer for testing down to 300 feet (roughy 150 PSIG) underwater video camera units and remotely operated vehicle (ROV) subsystems that I designed for a client. This would be pretty similar. I will likely have some more questions later.

Thanks again.