hodorskib's Small Scale RO Build

[eustis22]

Just water. I boliled the tap water to get rid of the chlorine. Might go 5 gals distilled water after I fix my olives.

[hodorskib]

That is normal with just water. Once you put sap through it the pressure will build.

[eustis22]

once I've rinsed out my new membranes, then what? I can just let em sit for a few days til I get sap again?

[hodorskib]

Give them a quick rinse (5-10 min) every other day until your sap start flowing. Then give a good rinse - 30 minutes before you put sap through it.

[eustis22]

rinse with what? all I have is tap water

[metalhead62]

eustis22 you save the permeate from what u ran though it the time before

[eustis22]

yeah I just used distilled water to clean the membranes. I assumed the permeat was full of membrane stuff and pitched it. no worries...Ima grab some spring water up north this w/e

[wobbletop]

I've been seeing designs with the aquatec pump between the filter and the first membrane. I've always had my filter after the pump.

Is the pump able to draw enough through the 5u filter? I imagine this would gain some extra pressure across the membrane.

[jwith]

I've been seeing designs with the aquatec pump between the filter and the first membrane. I've always had my filter after the pump.

Is the pump able to draw enough through the 5u filter? I imagine this would gain some extra pressure across the membrane.

That's a great question. I just called Aquatec today and spoke with one of their techs about the 8800 series. He said they don't spec the in feed vacuum or suction capability but should have around 6 feet of head. I will be doing a gravity feed system and want the filter before for two reasons, first most of the 5u filters are not designed for 125-160psi, and secondly I didn't want to place a strainer in front of the pump to protect it. His advised testing it to see if it would work. Has anyone else here tested with the 8851/8852?

I've seen a lot of questions regarding parallel vs series and the results are all over the place. The RO Bucket kit seems to be using 400GPD in parallel, while only reducing sap by 50% water in a single pass. This would put 1.5% sugar to 3% sugar. I'd rather a system run longer and increase to 6-8%. I assume series is essentially like making multiple passes through the RO, except the pressure will drop across each membrane.

What pump would be suggested for the parallel system? What does the RO bucket (RB15-KIT) use for a pump? The 8800 is too small.


Is the series better for the membranes and concentration? Is the only negative slower flow rate?

[hags]

I've seen a lot of questions regarding parallel vs series and the results are all over the place. The RO Bucket kit seems to be using 400GPD in parallel, while only reducing sap by 50% water in a single pass. This would put 1.5% sugar to 3% sugar. I'd rather a system run longer and increase to 6-8%. I assume series is essentially like making multiple passes through the RO, except the pressure will drop across each membrane.

Looking at the math:

Using the 150 GPD membrane your average permeate flow is .104 GPM. 150 GPD / 24 Hours / 60 Minutes = .104 GPM
Since hodorskib is pressurizing the system to produce 10 GPH permeate or .167 GPM, he's above the membrane's .104 GPM permeate flow, so some membrane fouling will occur.
The membrane would be better off if the permeate flow was matched to the membrane's average flow, or if output was closer to 6 gallons of permeate per hour.
.104 GPM x 60 minutes = 6.24 GPH. So to lengthen the life of the membrane pressure should be adjusted to match the membrane's average permeate flow.

The other issue with pressurizing the system is membrane recovery. Membrane recovery is the ratio of permeate flow to feed flow.
The membrane should retain a 10-15% recovery to avoid fouling.
So hodorskib runs 12 GPH via the pressurized system which is .2 GPM and his 150 GPD membrane have an average flow of .104 GPM
.104 GPM / .2 GPM = .52, or 52% membrane recovery. This high recovery%, due to the pump only being able to supply 12 GPH when pressurized, leads to membrane fouling.

In theory, running the system as hodorskib has, you should use a 250 GPD membrane at minimum since it's permeate flow is .174 GPM and above the .167 GPM the system is outputting. This of course makes the recovery percentage go up, which can only be corrected by using a pump that can deliver a higher feed rate.

A 50 GPD membrane would correct the high recovery percentage of the system since it's average flow is .035 GPM.
.035 GPM / .2 GPM = .175 or 17.5% membrane recovery. A bit above the recommended 15% recovery, but maybe tolerable.
The downfall of course is .035 GPM is only 2.1 GPH of permeate and 9.9 GPH concentrate which is a complete reverse of his results.

Using the 4 or 5 membranes in series as designed and flushing / cleaning the system relatively often compared to the gallons processed is likely the reasons the membranes have survived.

When you look at the series vs. parallel setups you want to keep this in mind. The 150 GPD membrane has an average permeate flow of .104 GPM. The 150 GPD membranes in series stay at .104 GPM, since you're just adding more surface area via the series and feeding the next membrane from the previous one. In parallel, the added membranes increase the average GPM flow because each membrane is separate from the others, so four 150 GPD membranes in parallel equal 4 x .104 GPM or .416 GPM. You can see that using the system in parallel and not increasing the pumps output is highly detrimental to the recovery% .416 / .2 = 2.08 or 208% recovery. So I'm not sure how long those (3) 400 GPD membranes are going to last in the ROBucket parallel setup. 400 GPD membrane is .278 GPM average permeate flow X 3 membranes in parallel is .834 GPM average. Since they run 20 GPH or .334 GPM their recovery% is .834 / .334 = 2.50 or 250% recovery!! It should be interesting to see how long those membranes last.

hags