Reverse Osmosis: Design Challenge

A few years back we installed an APEC RO90 and it has worked flawlessly. We moved out to the country, installed another RO90 on the "city" water and it again performed great.

Now we want to take it up a notch and try to go self sufficient and get away from all the chemicals/downside of public water. We drilled a well, but sulfur was too high consider treatment.

We have a large spring on the property and a water test showed clean from industrial chemicals (as you would expect out in the country). The two negatives we have is that the water is a typically hard for limestone country at 121 mg/L (CaCO3) and the tests for E.coli/Coliform came back positive. Water from the "city" source is similarly hard, so my only real problem is the pathogens. (Chlorinating puts me back in the starting position with getting rid of chemicals and UV's maintenance/longevity issues rule that option out for us.)

From what I have read, a good RO membrane can take out these pathogens. (In fact, recurring bouts of intestinal ailments got me to install the original RO90 system at the first house ... and that worked wonders for me ... and lowered my confidence in "big city" water noticeably. Especially after I found out that the city water intake was just downstream from the city dump leachate treatment plant. :^(

I have researched Dow Filmtec/Axeon/other membrane manufacturers and they make membranes that range upwards of 2500 to 10,000 gallons per day. Pricey, but not impossible with a little savings/elbow grease.

I have looked at a number of "commercial" plug and play systems in the range to deliver 5 gal per minute that use these larger RO cartridges, but they are loaded with pumps/controllers/instrumentation that moves the price to the stratosphere.

Our need here is to come up with the most straight forward design that a 50 year DIY guy with time on my hands can build from off the shelf membranes/housings/etc.

Would be interested to hear from anyone that might suggest practical design resources or may have done a similar project.

Thanks!

M

 

That is well beyond the normal home sink tap! You are now into industrial territory!

 

What are you trying to filter? Whole house?

 

Gents,
Thanks for the replies!

I know this might seem like overkill, but the wife has a tough family history of cancer and I just recovered from cancer surgery that gives me an 80% shot at five years. (I'll take it.) We are really focused on getting into all natural food/etc. Dumping everything that even looks borderline has made a noticeable difference in how we feel. We thought about doing it before ... and we sure wish we had.

Water is also on the table to take control of.

In reality, 2500 gal/day is way more than we would use. I just want to build in some margin of safety ... as it might be affordable.

I see two potential ways to accomplish the end. First, a large RO/NF membrane setup and a couple medium sized bladder storage tanks. Second, a smaller RO/NF setup that runs continuously into a large 500-1000 gallon atmospheric tank with a second pump system to feed out. Not a small space and maintenance addition.

I know the membrane manufacturers want them to be operated continuously, but since this is a non-industrial system that would be seriously de-rated over what they are usually exposed to ... maybe I could find an operating point that would meet the need without requiring an industrial level control system.

All of the resources I have found on the net are targeted at the muni/industrial folks as would make sense. I am just looking to find someone that might understand what might be possible about operating these on a derated basis. Someone that works with them and could say 'try this' or otherwise give me the 'why' I am entirely barking up the wrong tree in trying to do this at all.

I appreciate your time and thoughts!

M

 

Im an apec advocate. Im a health guru too. Make juices and the like. Follow the Gersen therapy to rid your body of toxins that may cause cancer. Its mostly by what we eat.

But thats a whole other topic.

The apecs use dow membranes. Im a plumber and its all I install. I have the ro 90 with a 14 gallon tank. Im on a well. Its way more then enough water for my family of 4. It makes water so rapidly.

We cook with it, drink it, and make ice with it.

Unless you want RO water coming out of your shower there should be nothing you would need bigger IMO.

You want a softener placed before any RO system. They work best that way.

IMO I would keep the RO 90. Get two 14 gal tanks. Run off city water. Install a whole house softener and backwashable carbon filter to remove the chlorine.

Chlorine is the killer of RO systems.

 

1. First of all you would need a water softener to remove the hardness. 5 gal/min output means you need at least 10 gal/min through the softener. Go with a 12x52 pressure vessel and a touch screen controller that has auxiliary relays for ro control. When the softener regenerates, the ro should stop.
2. Next, you would need to chlorinate or at least ozonate. There is no getting around this since you tested positive for microbiological contamination. You would need a chlorine injection pump and a large holding tank. Grundfos pressure booster pump should apply pressure from here on.
3. Chlorinated water needs to be de-chlorinated before the ro system, since chlorine tolerance on most industrial membranes is 0.1 ppm. This would require a granular activated carbon filter. In/out type with no controller should be enough. However if you are willing to spend a little money, get a backwashing head to avoid channeling over time.
4. At this point, check your water pressure. Axeon's HF5 ultra low energy membranes work at 80 PSI supply pressure. A big blue sediment filter connected in series with membranes will do the job of a complex ro system. You can also wire in additional solenoids and pressure sensors to protect the membranes. http://www.axeonwater.com/skin/commo...SPEC_SHEET.pdf
5. Check the water at this stage for contaminants and pH. If the water has high silica or any other contaminants, you would need additional treatment upstream of the ro in order to protect membranes from premature fouling. A properly designed treatment system should allow the membranes to last 2-4 years. https://www.wecofilters.com/blog/pos...-water-testing
6. If pH is below 7, you would need a calcium carbonate vessel to add minerals and neutralize the water before it reaches your copper plumbing lines.