New RO Membrane Troubleshooting

[Buckeye_Hydro]

We use the high capacity pump on systems up to 400 gpd @ 100 psi.

 

[The_Bishop]

Right now it's a 100GPD. Item 0218, from you.

 

[ajdelange]

I understand that, I just didn't know if a needle valve would have the fine resolution of control necessary to really fine tune the flow.

Yes, definitely but you will want some flow and pressure gauges in order to be able to see what the system is doing.

My system's a bit of a hot-rodded frankenstein setup, with a booster pump, a permeate pump, and two 75 GPD membranes in series being fed at 90 PSI. It'll generate roughly 200 GPD at 4-5 TDS, with about a 2:1 recovery ratio.

I run a similar system. The heart is a skid with prefilters and a pump capable of 150 psig, flow meters and needle valve. I run it between 2:1 and 1:1. I kluged up pressure tank, atmospheric tank, pressure pump, float and pressure switches and a control box. The brewery and lab are plumbed (with plastic pipe). Fed with softened water this system delivers a little over 1 lpm and I have run it for over 5 years with softened water feed and have had no failures, except for the pressure gauge, in that time. I have not had to change filters nor membranes and still get 4 -5 ppm tds (about 97% rejection). The surprising thing to me is that my silica is at 28 mg/L and I thought that would gum things up by now but it hasn't (touch wood).

I'm able to get away with this because the feedwater to the system is dead soft from my home water softener. It's been about a year so far and no problems.

There shouldn't be any problems. It's easy enough to calculate your brine salt concentrations from your feed water chemistry and rejection data. Increase the concentrations by about 50% to allow for 'polarization' (ion concentration in the channel is higher close to the membrane) and, I'm sure, you will find that the critical salt is well below saturation at 2:1 recovery.

Given that you have pretty much put this together your self you could try adding a second needle valve and plumbing its output back to the input to the pump. You'd want a flow gauge on this line too. By doing this you can increase recovery even further which may be of interest since you obviously like to tinker. It might be possible to get a water that meets some brewing need at 60 or 70% recovery (though you would obviously need to supplement calcium).

It's a bit overkill but it not only provides brewing water but household drinking water and ice via an 11 gallon capacity pressurized storage tank.

In addition to brewing I have found that having 50 gal (or more - I can set how high the system fills the atmospheric tank) RO water on hand beneficial for things other than brewing.
•Brewing water for me
•Brewing water for anyone who wants to bring jugs
•Brewery Rinse water
•Feed for lab DI water maching
•Lab faucet for glassware pre-rinse
•SO's CPAP machine
•Source of water for cooking, drinking, toilet flushing... when plumber or well guys shut off house supply

Most recently when the HVAC installer said he needed 70 gal pure water to mix with glycol for a new geo heat pump system my response was "Got a hose?"

Also, I hate waiting for water when I want to brew.

That, in a nutshell, is why I put the system in. I've had more that one brew day dawn on which I realized that calculations were done, grain was ground and ready to roll but that I had forgotten to collect water (used to take me a couple of days with my old 10 gpd system). This realization was followed by trips to clean out the entire stock of DI water from several drug stores.

And putting the system together was a fun project.

 

[The_Bishop]

Thanks for the pointers, AJ.

What are you using for a non-pressurized storage tank? I've been considering a non-pressurized storage tank and using a delivery pump to feed the 'household' end of things. The main reason I haven't is I'm not sure if there'd be an issue with the storage tank going 'stagnant' if the water sits too long.

I've got pre and post filter gauges to see if there's any restriction from the filters and a pressure gauge tee'd into the pressurized feed going into the first membrane housing. I should consider some flow gauges... Right now measuring flow consists of a graduated beaker and a stopwatch.

 

[ajdelange]

I found some company (I'd say which if I remembered) in California that make semi custom plastic tanks - semi custom in the sense that they have several stock sizes (round and rectangular) but will spin-weld fittings onto them anywhere you want them. I ordered a 100 gal rectangular (50 would have been plenty) with cover. The cover is vented through a fine mesh screen to keep bugs from being able to get in. There are two pairs of NPT ports on one end for high and low float switches which shut off, respectively, the RO unit (prevents overflow) and the pressure pump (if it runs the atmospheric tank dry trying to fill the pressure tank). I also have a level sensor on the outside which I can position at 1/4 full or 1/2 full by means of two brackets which I welded on myself. Most of the time the tank is kept 1/4 full which is why I said 50 gal would be plenty.

I, too, worried about stagnation and so I had them put a fitting on the bottom which connects, through a valve (plastic) to a line that runs to a drain. We go away for the summer and I do drain the atmospheric tank before we go. I've had the system since before we started coming up here for the summer (so I guess it's actually more like 7 years I've had it) and never had any problem with stagnation but then when I was there year round I would be draining it for brewing from time to time. I'd guess that if you are using it for brewing and drinking water you would probably be similarly safe. Atmospheric tanks are, AFAIK, a common part of whole house systems.

I'll also relate that in my youth a friend decided to have a party and serve punch from the crock that was part of the Sparklets water dispenser. What we found in there when we opened it up was most impressive and thoroughly disgusting but everyone had been drinking from this thing for years with no noticeable bad taste nor smell.

 

[Buckeye_Hydro]

Right now it's a 100GPD. Item 0218, from you.

The Aquatec 8800 is spec'ed for use with up to 120 gpd membrane. You can make it work with the 150 gpd membrane if you go with a 100 gpd restrictor.

If you want more pump yet, then the High Capacity Pump is the next step up. Much less expensive than a motor and pump like we put on commercial RO's.

Russ

 

[Buckeye_Hydro]

When we install storage tanks for RO in commercial applications, say a 500 g or 1000 g tank, we often install a UV and pump to recirc the tank water.

 

[The_Bishop]

Thanks, Russ. Doing a bit of planning now.

 

[schematix]

I received a replacement membrane earlier this week and gave it a whirl. It's putting out about 50% more TDS than the last one, nearly 30ppm! That's a rejection of less than 90%.

I'm out of ideas here.

 

[Buckeye_Hydro]

Assuming you bought a good membrane brand, I suspect: Internal crack in the RO membrane housing. Not visible when you look inside - only opens when membrane is seated.

Russ

 

[schematix]

I was afraid you were going to say that.

Your picture didn't show... can you repost?

 

[Buckeye_Hydro]

Hmm. I see the pic in my post just fine.

No worries - a new housing is ~$10.

 

[schematix]

Hmmm this is what i see...



Do you know the difference between the Filmtec TW30-1812-100 and TW30-1812-100HR? I ordered the standard -100, but i've received one of each now...

 

[day_trippr]

Hmm. I see the pic in my post just fine. [...]

That's because of your image hosting site account.
The rest of us see a placeholder, because your hosting site wants to charge you money to hot-link your images...

Cheers!

 

[Buckeye_Hydro]

Well, isn't that special! We'll have to find a work-around to exclude photobucket from the process.

 

[day_trippr]

You can always directly upload pics in the edit panel.
Click the paperclip icon to start...

Cheers!

 

[schematix]

Russ any thoughts on Filmtec TW30-1812-100 vs TW30-1812-100HR?

 

[Buckeye_Hydro]

Ah-ha!

 

[Buckeye_Hydro]

Russ any thoughts on Filmtec TW30-1812-100 vs TW30-1812-100HR?

Yes - go for the HR (High Rejection) version. http://www.buckeyehydro.com/residential-ro-membranes/

It's spec'ed at 98% rejection. The other version is spec'ed at 90%.

We haven't sold the other (old) version in years, since the HR came out.

So that may be the answer to your dilemma - did someone sell you an old low (90%) rejection TW30-1812-100??

 

[schematix]

I received the -100HR the first time and it was the one starting at 97% then creeping down to 93%.

The 'replacement' is a standard -100 and is hitting spec at ~90% and has been steady after the first 2-3 minutes.

I'm leaning towards the housing being fine, the replacement -100 being fine, but the first -100HR just not quite being up to spec.

 

[Buckeye_Hydro]

So the new membrane (why in the world would someone sell you the old low rejection model???) hits 90% and stays at 90%. That's all that you can ask of the membrane you bought. Your housing is fine. Next time, might want to buy your membrane from a known trusted source... oh I don't know, maybe a site SPONSOR for instance.

 

[ajdelange]

So just put a second one in series!

That comment was made tongue in cheek but maybe it isn't such a crazy idea after all.

 

[day_trippr]

Would there be enough pressure at the output of one membrane to drive the second?

Cheers!

 

[ajdelange]

Based on the fact that most of these systems can fill a little bladder tank I'd think so but I'd also think that there would be flow rate implications. Plus I think he's got a booster pump in front of the existing cartridge.

 

[Buckeye_Hydro]

Let's avoid the membranes plumbed in series on these little low pressure residential units!

 

[ajdelange]

Two nines rejection! But seriously, I wasn't terribly serious.

 

[schematix]

I had the same thought last night now that I have 2 membranes, but i dismissed the idea.

By the time i dealt with having 2 waste streams (even though the 2nd one would probably have like 0.1:1 waste: permeate), i don't think i'd get that high of output. Not to mention additional complexity. If anything i'd do a parallel system to double the output so it doesn't take all evening to make brewing water.

It looks like the 50 GPD membranes are rated at 98% rejection, so that route would probably accomplish nearly the same thing.

 

[Buckeye_Hydro]

Filmtec 24, 36, 50, and 100 are spec'ed at 98% rejection.

If you buy from a vendor who knows what they're doing, the Filmtec 75's are spec'ed at 99%.

Under "typical" conditions (hard water and no scaling analysis done), they all should be run at about a 4:1 concentrate to permeate ratio.

Russ

 

[The_Bishop]

I'll be 'that guy' and confess that I have two membranes in series. But not like you think.

I have the brine from the primary membrane feeding into a second membrane. With 75 GPD high rejection membranes in both housings, and a booster pump keeping them at 85-90 PSI, I produce a touch more than 200 GPD of permeate. Since the system is being fed softened water, I can pull off a 2:1 brine to permeate ratio and still produce permeate with 4-5 TDS with source water in the 365 TDS range.

That being said I tinker with everything and have a mental disorder about optimizing and getting high efficiency/performance out of whatever I'm tinkering with.

 

[daveMN]

Does anyone have a diagram of their setup with the pumps? I'm looking at a RO system after my water softener and trying to figure out where the pumps fit in other than increased pressure to the membrane, or is it just that simple?
Apologies in advance for the thread tangent. Cheers!