RO systems for large volumes

Hi water dudes- I'm looking at an RO system for my 3bbl brewery. I'd love to grab a bigass system for huge GPD and quick brewdays, but budget is always tight.

What I'm thinking is that I can get a lower GPD (say, 100) system on the cheap and just let it run into my HLT the day or two before brewday. I could even hook my 3 kettles up together via a hose for ~375G of storage space, and run excess water into spare fermenters for storage for the next brewday.

How feasible is this? My water is very hard and very alkaline, so am I threatening to ruin my membranes this way? I've heard of people running water softeners before their RO Systems- does anyone do this? Again, trying to save money but if running without a softener is going to tear up my membranes, that's not really saving money. Thoughts? I can post my water if needed.

See the recent thread at https://www.homebrewtalk.com/f128/time-whole-house-ro-system-424352/. It answers many of your questions.

Yes, hard water must be softened before being presented to an RO system.

Yes, it is quite possible to collect water over a couple of days.

At the same time 1000 GPD systems (skid only but if you have a big HLT you don't need anything else) can be had for around $3K.

Any good RO machine supplier is going to want to have your tap water quality information when sizing and specifying the equipment for a large system. If you are dealing with only a 100 gpd system, then you are more into the realm of the home systems and you are on your own.

If you have the forethought and time, running a smaller flow capacity system and storing the finished water in a tank should be significantly more economical. You need to assess the average daily water demand and the demand for each brew event to size your storage tank sizing. If you were only brewing 3 bbl batches, then you might need only 100 to 120 gallon of storage to handle the brew event. Pair that with a 100 to 120 gpd RO system and you may be fine. But if you are brewing less than once a day, the sizing of the RO system could go down.

If the water is really that hard, then including a typical ion-exchange softener is wise and often used.

Check out some of the salt water reef keeping forums. You'll find a lot of guys are running a float valve in 55+ gallon plastic barrels for on-demand top off water and 0 TDS base for salt water changes. Sometimes more than 1 barrel. It is nothing to have 110+ gallons on hand at any given time.

I'd check out the float valve at BulkReefSupply.com. Anything from them comes highly recommended. If you've got room for a 3 bbl brewery, I'm guessing an RO tank with auto fill capabilities won't cramp you for space too much.

mabrungard said:

Any good RO machine supplier is going to want to have your tap water quality information when sizing and specifying the equipment for a large system. If you are dealing with only a 100 gpd system, then you are more into the realm of the home systems and you are on your own.

If you have the forethought and time, running a smaller flow capacity system and storing the finished water in a tank should be significantly more economical. You need to assess the average daily water demand and the demand for each brew event to size your storage tank sizing. If you were only brewing 3 bbl batches, then you might need only 100 to 120 gallon of storage to handle the brew event. Pair that with a 100 to 120 gpd RO system and you may be fine. But if you are brewing less than once a day, the sizing of the RO system could go down.

If the water is really that hard, then including a typical ion-exchange softener is wise and often used.

Click to expand...

We will definitely be brewing less than once a day except during the first week or two, during which time we can supplement with purchased water. I'll start talking to the vendors about how to set up for my particular needs and discuss softening options. Because I plan to blend back some city water to get the minerals back up, I'll probably only need 50-60 gallons of RO for most of my beers.

Reef Keeping RO/DI system seem popular with brewers.

I've purchased from these folks before:
http://www.airwaterice.com/c=RoIoTx9cbb3Wk8I9KWgFvsOBp/category/1/

ajdelange said:

Yes, hard water must be softened before being presented to an RO system.

Click to expand...

What are the maximum amounts before softening is needed? Is it only Ca and Mg that is of concern?

At the same time 1000 GPD systems (skid only but if you have a big HLT you don't need anything else) can be had for around $3K.

Click to expand...

Can you point me to a brand/supplier for this?

How much feed water is needed to end up with 1,000 gallons of RO water?

With larger systems, they are 'tunable' with respect to their rejection flow rate. The higher the rejection flow rate, the more water that flows tangentially along the membrane and flushes away the elevated ion concentrations at the membrane surface.

I have several RO system design programs on my computer to assist with defining that rejection flow rate and the size, number, and configuration of membrane tiers. Of course, everything is dependent upon the incoming water quality. Presoftening the incoming water will enable the system provider to tune the rejection flow rate much lower without endangering the system with scaling problems. Ca and Mg are the main concerns, however silicate is another ion of interest due to its scaling potential.

jmf143 said:

What are the maximum amounts before softening is needed? Is it only Ca and Mg that is of concern?

Click to expand...

What is of concern is the 'limiting salt' i.e. the salt that is most likely to precipitate as that is the one that limits the recovery. The more you recover the more concentrated is the 'concentrate' and the more likely the most likely to precipitate is to precipitate. It's a matter of computing the saturation at the membrane which is a function of the input chemistry, the polarization (how much more concentrated the ions are at the surface of the membrane than in the lumen of the channel) and the pH.

Calcium and magnesium carbonates are most likely to be the limiting salts as their carbonates are much less soluble than things like sodium sulfate for example. It's a pretty simple matter to compute the limits if you know the chemistry of the source, the recovery, the amount of feedback (if any) and the pH. If you take care of the calcium and magnesium then you are probably going to be able to get 50% or more recovery without a problem unless you have high silica about which there isn't much you can do except keep the recovery low and offer prayers. As an example of this I run my system at about 33% because of silica (28 mg/L). WRT to the other salts I could easily run at 50%. No fouling yet on my first set of membrane cartridges (touch wood). The membranes can be cleaned but I wouldn't know how to get silica gel off them.

If you send along your chemistry I can give you a WAG at what your maximum recovery could be.

jmf143 said:

Can you point me to a brand/supplier for this?

Click to expand...

I recommend the Titan systems because they are the only ones I know and I have had trouble free service (so far). They use the Filmtec membranes and seem pretty well put together (with the possible exception of the use of John Guest connectors for everything but none of those has given me any trouble - yet): https://www.afwfilters.com/commerci...gpd-commercial-whole-house-ro-system-244.html

If you look at the picture you will see a handle below the gauge on the upper panel. Rotating that restricts the outflow from the concentrate side and increases the pressure across the membrane. This causes the permeate flow to increase and the concentrate flow to decrease. Reading the flow meters on the right make it an easy matter to adjust the recovery to the desired value. If you want really high recovery at the expense of a bit less rejection you can order the system with a second valve and flow meter. This feeds some of the concentrate back to the input and the calculations become a bit hairier but not that bad. I can send them to you.

jmf143 said:

How much feed water is needed to end up with 1,000 gallons of RO water?

Click to expand...

For 50% recovery 1000 gal RO water would require 2000 gal feed. For 33%, 3000 gal of feed would be required. For 75%, 1333 etc.