RODI Upgrade Questions

[benjabba]

I currently have a 4 stage 75GPD system. I have had it for years and am very happy with the system. I have kept up with the membrane and filter changes on a regular basis and always operate at 0 TDS. My question is what is the best way to get more water out of the system at a quicker rate while at the same time reduceing the amount of waste water I am getting? I am using a .5 micron sediment filter, .6 micron carbon filter, and a DI cartridge. PSI is always steady at 68. Given these specs on my existing unit is it possible to get more water out of my system more quickly?

Thanks

Ben

 

[bige]

Not sure but there is a member here that seems to know more than others. He is Az something or other. But do you have a pump? I have read that using a pump makes them more efficient. I could be wrong. But the ro systems I have looked at that have less waste are using a pump.

 

[mojo]

well an increase in psi will increase through put and efficiency. They make system that are more of a on demand type. The Merlin type RO unit can run at .5g or more per min. without any storage.

here is a link to one as a example

Merlin On-Demand Reverse Osmosis System

 

[AZDesertRat]

You cannot reduce the waste ratio below 4:1 without shortening the RO membrane life, the waste or brine is what keeps the membrane operational.
If you have 65 psi or higher you can add a piggyback membrane to what you have doubling your GPD while still maintaining the same waste ratio.
A complete piggyback kit is on sale for $55 at the bottom of the page here and includes a 90 GPD membrane, housing, brackets, additional tubing and fittings and a flow restrictor.
Untitled Document

Should only take 10-15 minutes to install and if you have sufficient pressure will double your GPD.

Another option would be to add a Aquatec booster pump to your existing system. By raising the pressure up to 90-100 psi at the membrane you increase the GPD up to around 120 GPD with your single membrane and increase the rejection rate or removal efficiency too so DI will last longer. The booster pumps kits are in the same flyer up the page a little and would run $125 to $179 depending on what how you use the RO/DI.

Personally I use a booster pump myself and do have a low waste system but its in the $800-$900 range and not in everyones budget. For me it has paid for itself over the last 3+ years though in DI and membrane savings alone.
low waste RO/DI system

The way the UHE works is it uses stored DI water to backflush the membrane via a microprocessor controller then double flushes it and stores it in DI wate rwhen it shuts off so you do not have to deal with TDS and TDS creep. Very unique in the industry and still the only system proven to work. Otehrs have tried to copy it but they didn't use DI for the flush and their units fail.

 

[benjabba]

Thanks for all of the comments everybody. What I may try to do is add a booster pump first and see what that can do for me. Any value to adding a second membrane and booster pump?

 

[AZDesertRat]

I'm not sure if the booster pump will keep up with dual membranes, you might contact Aquatec with that question. Two 75 or 90 GPD membranes would put out about 250 GPD at 90-100 psi.

 

[mojo]

on a lot of industrial units you actually run another membrane on the concerate line ( waste line ) This will help reduce waste. You will have to figure out what is more important. More efficiency or more gpd. The permeate water ( good clean ro water ) in most case is stored in a storage container untill needed. The the concerate water passes through one or two more Ro membranes. allowing for more efficient usage of the water you have. To go this route is pretty costly and I would not suggest this for any hobbiest really. I use BRS RO units. But I had the Vertex unit with the built in backflush pump. That is a great way to keep your unit running at top efficiency. Just like industrial units they will backflush the membrane to ensure that it doesnt get clogged and free of debris.

I am sure this is way more than what you need. But how many GPD are you looking for? if its just waste then try a unit with a micro processor and built in backflush. It does really make a big difference. I just cant justify it. Just remember the waste water of your ro has already been through a partical filter and a carbon filter. So your ro waste is really all that bad. One of my old employers used to use this water for a prerinse before running it down the drain.

Mojo~

 

[AZDesertRat]

The industrial and commercial units do not reduce waste. They are still have a 15% recovery or less. The way they cut the waste to what it is is they use extremely high pressures in the hundreds of psi and they have chemical clean in place capabilities unlike home owner units.
Many long time RO/DI vendors offer dual membrane system that run the brine through a second membrane, Spectrapure. Buckeye Field Supply. AWI and PurelyH2o are just a couple. None promotes reduced waste since it shortens the membranes life drastically because you are already running a much higher waste TDS through the second membrane and at a lower pressure so reducing the waste is not sensible. You still stay with 4:1 waste ratio and the system essentially gives you twice the GPD at only slightly higher final TDS, maybe a fraction of a PPM higher in some cases. Spectrapure has been selling dual membrane systems for over 25 years now with great success.

Backflushing with tap water does not work since you are now putting tap water TDS on the treated wate rside of the RO membrane which is just what you don't want to do. Vertex and a few others have tried this but its not working well and is receiving many justified complaints, they didn't do their homework.

 

[mojo]

The units I was refering too us something similar to what you are talking about using a dual membrane unit. The ones I used to work on ran at about 350g per minute and the ro was stored in a 10000g storage tank. But yes I totally agree with not wanting any tap water to backflush the RO membrane. Typically this would be done with a pump tied into the storage of RO water.

Curious though, How much water is Ben hoping to get ?

 

[Devonjevon]

I have a dual membrane system, a pressure pump, and a permeate pump. Before adding the permeate pump I averaged about 260 gallons a day. I added the permeate pump because I use a 40 gallon pressurized storage tank for both top off and water changes. For normal users I'm not sure if a permeate pump would be useful. I fill up my 38.8 gallon storage tank without permeate pump in 3 hr 48 min. With permeate I fill up in 2 hours 33 min. (95 psi 70degree temp) Disadvantage to my permeate pump. With normal operation it makes a clicking noise. Mine sounds like a grandfather clock on steroids I guess because of my pressure pump. I haven't seen much benefit in using the permeate pump without a pressurized tank. But I am by no means a expert and maybe other will chime in with comments. Advantages. No electricity to plug up in using permeate pump. I hear their is considerable less waist with it's use. I have close to a 2:1 ratio but I think that's because of my low initial tds.

 

[AZDesertRat]

The only homeowner type system that uses stored RO or RO/DI water to backflush is the Spectrapure MaxCap UHE 100 which is what I own.

A permeate pump will ONLY work with a pressure tank since it uses the backpressure in the tank to operate the pistons you hear making noise.

If you are running at 2:1, what is your tap water TDS? If its more than about 100 would recommend raising it to at least 3:1 as it is fouling the membranes, especially the downstream one.

 

[Devonjevon]

Hmm wondering if I could use my pressurized tank to flush my membrane? Make my own. Not sure if the flow rate or psi will be great enough to flush. Experiment time this weekend.

 

[AZDesertRat]

Its not quite that easy. It takes a timer or microprocessor, solenoid valves and lots of fittings. The UHE uses non pressurized DI water through the booster pump at timed intervals plus at the end of each water making cycle. Using the pressure tank would cause a ddrop in pressure which would trigger the ASOV to make water in the normal path. Lots of engineering involved and thus the cost of the UHE. The UHE also includes float switches, bulkheads, extra 3/8" tubing and a solenoid to control the level in the ATO so you always have sufficient DI for the backwash process.

 

[benjabba]

Wow guys thanks for the great information. This may sound "anti-green" in this day and age but I am looking for the ability to speed up the rate at which I make water first and reducing the amount of waste water I generate second. Don't get me wrong, reducing or re-using waste water is important to me but at the moment I only have a limited amount of time on the weekends to make about 100 gallons of water. I know that doesn't sound like much but I also have to use that water to mix salt and still have the time to work on my tanks. It really sounds like either option suggested will work for me. I like the idea of a booster pump cause I like gear. .

Here is another question. What is the maximum distance I can run my waste water line?

 

[AZDesertRat]

There really is no limit on how long the waste line can be as long as you adjust the flow restrictor accordingly. Every foot of 1/4" line adds additional head loss so the restrictor will be different according to the final head figure. A capillary tube flow restrictor would work best for this application and you would trim it to the final 4:1 waste ratio after everything is installed and operating.
Some people run the brine or waste to rain barrels or tubs to be used for irrigation of landscape and plants. With my low waste system, I am running at less than 1:1 ratio so my brine TDS is between 1200 and 1600 TDS so I send it to the sewre where it gets treated and recycled then recharged into the aquifer for reuse over and over. The TDS is too high for sensitive plants and grasses, too high to wash the car or laundry and too high to put in the swimming pool. At the normal 4:1 waste ratio the TDS will be 20 to 25% higher than the tap water so depending on your tap water TDS it may be fine to use for those purposes, my tap TDS is 630 to 850 so thats out for me.

 

[benjabba]

Do you think the booster pump in the link below will do the trick?

VX-RO-135 Premium Aquatics - VX-RO-135 Aquarium Supplies

 

[AZDesertRat]

It would work but for the extra money I would go with an Aquatec 8800 with a pressure switch, Vertex does not have a very good reputation and much of their stufff is pretty low end. With most anything RO/DI related, you really do get what you pay for.

You can get the Aquatec 8800 at Spectrapure, Buckeye Field Supply, Purelyh2o,Bulk Reef Supply, Filter Guys and many other places for around $130 with the pressure switch and power supply.

 

[Devonjevon]

It would work but for the extra money I would go with an Aquatec 8800 with a pressure switch, Vertex does not have a very good reputation and much of their stufff is pretty low end. With most anything RO/DI related, you really do get what you pay for.

You can get the Aquatec 8800 at Spectrapure, Buckeye Field Supply, Purelyh2o,Bulk Reef Supply, Filter Guys and many other places for around $130 with the pressure switch and power supply.

I have the Aquatec 8800 and it's great. I went the cheap way and bought a water general rodi unit and u really get what u pay for. The 100gpd membrane was worthless filters dismal. So I had to do something. output was so slow it was like drip acclimating a 5 gallon bucket. 15 gallon a day max. So after spending more money replacing everything with a decent filters membranes and such I shoulda got the good stuff. But in the time it took to type this I made 5 gallons. If u just want speed then try a booster pump or dual membrane or both.
AZ I agree with you.

 

[benjabba]

Thanks for the feedback guys. I will order the 8800. I was trying to get some other stuff from PA which is why I posted the link. The Vertex is the only booster pump they sell. I will post my results once I have some.