Upgrading Home built RO

[Wanabe1972]

Guys I built a single membrane RO last year that I just ran in batch mode with no recirculation. This did pretty well with about 1 gallon of concentrate a minute with about 50 to 60% reduction in a single pass. I picked up a small SS gearpump and motor I want to use as a recirculation pump. My guestion is will this style pump work? Also where do I pump into the system? I was thinking after my charge pump and prefilters but before the high pressure pump. If i run this like this will I need to install a check valve in the main feed line so not to push sap into the prefilter backwards. If this is all confusing I could draw a picture of my system. Thanks Jeff

[Flat Lander Sugaring]

I am going to pull concentrate off the out of the membrane and put it back in on the suction side of the feed pump. I will also have a ball valve in that line so I can regulate the amount.

[Wanabe1972]

So it is common to run concentrate back through the pre filters? Thats what i couldnt get my mind wrapped around. I guess the prefilter should not collect sugar. If this is the case I wont need to do anything more than crack the valve on the concentrate tank a bit. My system is set up so my sap, concentrate and permeate all feed into the same line going to the feed pump. I just open and close valves depending on what funtion the RO is performing at the time. This way my feed pump is used for RO operations and also feeds my head tank depending on valve selection. Thanks

[GeneralStark]

What exactly are you guys referring to as "recirculation"? Sure, you can recirculate your concentrate back to the feed pump to remove more water and increase brix, but if you are talking about "recirculation" in terms of creating turbulence in the membrane vessel to minimize fouling of the membrane, that is a different story.

Are you trying to turn your DIY RO into a real deal RO?

[mellondome]

You will need your "recirculation pump" inside the pressure loop. If you search, I posted up a diagram a year or so ago. You want to come off the concentrate side of the membrane and circulate back to the inlet, after the pressure pump. Of course use a tee so you can draw off concentrate. You need to be aware of the flow rates of your membrane... as too much flow across the surface will harm them. 4x40 are usually around 14-17 gpm.

[Wanabe1972]

I am just trying to strangle as much water out as i can while RO is running unattended. I work nights and sleep days So i usually collect in the morning while the ground is hardest. I start the ro running from my truck tank and when it runs out it shuts off and about 50 to 60 % of the water is removed. I would get out of bed and fire the evaporator and run the RO through a flush/wash and start over again in the morning. The only way for me to raise the concentration was to get up from bed and run it through again (3 to 4 hours of sleep and 12 hour shift at the mill a day makes me sleepy). I figured if i pulled concentrate from the tank and added to fresh sap going through the RO when it shut down i would have a higher concentration.

[mellondome]

You can always run the concentrate through multiple times. With my single 4x40 home job... I would concentrate into one of my tanks. Once it was all run through from my holding tank, I would recirculate in my concentrate tank. Pulling from one end and returning to the other. I try to keep the flow as fast as possible , usually around 6 to 1. This keeps the membrane cleaner and I still get over a gal of water per minute permeate. When I needed sap in the head tank, I would squeeze it down to 2 to 1. After head tank was full, I returned it to recirculate and opened the flow back up.
when you start boiling you may be at 6% and when you get close to finished boiling for the day, you may be feeding the head tank with 12% . It will change the boil, but anytime the ro is running.. it is saving boil time and fuel.

[BreezyHill]

Jeff what about a float switch in the tank to shut down the RO? Make it adjustable depth. You can do the math as to how many gallons of water to remove to get to your desired % sugar and then let the RO batch run.

You can get SS float switches of Ebay fairly cheap and use a section of PVC to extend into the tank and use a 2x4 with a hole for the PVC to support the switch. Hold at desired level with a cheap lock grip plier or a cheap clamp.

Ben

[Wanabe1972]

I never thought of doing it this way. I already have a float as you discribe in my concentrate tank that let's me know sap is low while I'm in the sugar house. A couple of electric valves and some creative wiring I think I can make this run automatic. I could have it run from the truck tank through the RO until the tank is empty then auto open the concentrate tank and just keep running it through until the float shuts it off. I already know how much concentrate is in the tank cause my float is marked in gallons. I will just have to test my sugar content in the truck tank and adjust float.

[BreezyHill]

Relays on ebay are really cheap.

[Wanabe1972]

No need to look at eBay due to me working for a large manufacturing company and the words preventive matenance these end up in the garbage daily. Some of these items whould not last another year in service there but may have thousands or tens of thousands of cycles left in them. I already have two multi tap relays in my RO control panel so I just need to pick the right one to tie into. I knew when I built this thing I should have used a PLC instead of relay logic. Thanks jeff