RODI filter 0 PPM Problem

[lapin]

Before I tried a new restrictor, I would see about a booster pump. Membranes work better at higher pressures. In the USA houses are restricted to 80psi. If you do get a booster try to plumb it inbetween the filters and the RO. This way the canisters will not be exposed to too much pressure.

 

[Water Dog]

Awesome news! I think 97% is a pretty good rejection rate for a 150 gpd membrane. In the states, the two reputable RODI dealers Spectrapure and Buckeye Hydro, sell their units with capillary flow restrictors that we trim ourselves to get the optimally efficient 4:1 waste to product water ratio based on our unique source water situations. You could try to get a 550ml fixed flow restrictor to see if you can get improved efficiency if you’d like.

As far as resin life, at 433 tds source water, more frequent resin replacement will be a fact of life. You may be able to get gains by running a triple canister DI system, employing cation, anion and mixed bed resins.

Another solid way to improve DI resin life is to employ a 3 way valve after the RO membrane... this is commonly referred to as a DI bypass.

 

[Buckeye Hydro]

Not sure what flow restrictor to use?

Realize that flow restrictors are specified by their flow rate - that is, what flow will they allow. Just to confuse the issue a bit, that flow is specified in ml/min. So... let's walk through the logic of selecting a flow restrictor that will yield something near the desired ratio of 4 parts concentrate to 1 part permeate. Let's say you have a 75 gpd membrane. 75 gpd=197 ml/min. If we want 4 times that in concentrate flow, then 197 ml/min x 4 = 788 ml/min. We're in luck as there are 800 ml/min flow restrictors available. Easy peazy, right? If you install that 800 ml/min flow restrictor on your system that has a 75 gpd flow restrictor, you'll find you're much higher than a 4:1. What gives?
Like so many other things, its just not easy. Let's back up a little. That math we did above... anyone see any problems with it?
Remember that the flow of permeate (RO water) from a membrane is significantly affected by your water pressure and your water temperature. That Filmtec 75 gpd membrane is factory spec'ed at 50 psi with 77 degree water. Let's say you have 45 psi and your water temperature is 58 F. Geez. Way off of factory specs. How much water will that 75 membrane actually produce under those conditions??? One way to find out - use the calculator on our website: https://www.buckeyehydro.com/calculator/
If you plug in those conditions you'll see you can expect only 46 gpd! So let's run through that math again. 46 gpd=121 ml/min. If we want 4 times that in concentrate flow, then 121 ml/min x 4 = 484 ml/min. Commonly available flow restrictors include two that are near that flow - 368 ml/min and 525 ml/min.
So the take home message:
1. Use a flow restrictor that gives you something near that proverbial 4:1. 2. Don't expect vendors to automatically send you the ideal flow restrictor with a new system, as the vendor has no way of knowing your water temperature and your water pressure.
3. Consider having two flow restrictors on hand - one for colder winter water temperatures, and one for warmer summer water temperatures.

Make sense?

Russ

 

[Andre Duarte]

Awesome news! I think 97% is a pretty good rejection rate for a 150 gpd membrane. In the states, the two reputable RODI dealers Spectrapure and Buckeye Hydro, sell their units with capillary flow restrictors that we trim ourselves to get the optimally efficient 4:1 waste to product water ratio based on our unique source water situations. You could try to get a 550ml fixed flow restrictor to see if you can get improved efficiency if you’d like.

As far as resin life, at 433 tds source water, more frequent resin replacement will be a fact of life. You may be able to get gains by running a triple canister DI system, employing cation, anion and mixed bed resins.

Another solid way to improve DI resin life is to employ a 3 way valve after the RO membrane... this is commonly referred to as a DI bypass.

I think you meant a 1500ml restrictor. I went from 300 to 800ml. Now that I have a ratio 2-1 I should go to hight to try to get 4-1 right?

The best thing I can get my hands on here in Europe to manually adjust the ratio is the Vertex Precision Needle Valve that I am not sure that can be used for this.

Regarding the resin, I was able to buy a vertical canister, just like the ones sold on BRS for resin. This took all the resin I had on my two "european style" RO canisters... I am currently using Fauna Marine MB20 resin which is quite expensive to the amount of water I can get with it. I can try other brands but I am not confident that others will last longer.

As soon as I see the PPM output start to rise, should I just replace the resin? How can I tell I need to flush the membrane and replace the sediment/carbon filters?

 

[Buckeye Hydro]

From our FAQ's https://www.buckeyehydro.com/faq/:
A good rule of thumb is to replace your sediment filter and carbon block after six months. A more precise way to maximize the usable life of these two filters is to use a pressure gauge to identify when pressure reaching the membrane starts to decline. This is your indication one or more of the prefilters (all the filters that touch the water before it reaches the RO membrane) is beginning to clog.

Also be cognizant of the chlorine capacity of the carbon block. A good 0.5 micron carbon block for example will remove much of the chlorine from 20,000 gallons of tap water presented at 1 gpm. Some original equipment suppliers commonly provide carbon cartridges rated at 2,000 to 6,000 gallons. Remember that all the water you process, both waste water and purified water, goes through the carbon block.

Regarding your RO membrane and DI resin, use your total dissolved solids (TDS) meter to measure, record, and track the TDS (expressed in parts per million [ppm]) in three places: 1) tap water, 2) after the RO but before the DI, and 3) after the DI.

The TDS in your tap water will likely range from about 50 ppm to upwards of 1000 ppm. Common readings are 100 to 400 ppm. So for sake of discussion, let's say your tap water reads 400 ppm. That means that for every million parts of water, you have 400 parts of dissolved solids. How do we go about getting that TDS reading down to somewhere near zero?

If you do some experimenting with your TDS meter, you'll note that your sediment filter and carbon block do very little to remove dissolved solids. So with your tap water at 400 ppm, you can measure the water at the “in” port on your RO membrane housing and you'll see it is still approximately 400 ppm.

The RO membrane is really the workhorse of the system. It removes most of the TDS, some membranes to a greater extent than others. For instance, 100 gpd Filmtec membranes have a rejection rate of 96% (i.e., they reject 96% of the dissolved solids in the feed water). So the purified water coming from your 100 gpd membrane would be about 16 ppm (a 96% reduction). Filmtec 75 gpd (and below) membranes produce purified water (a.k.a. “permeate”) more slowly, but have a higher rejection rate (96 to 99%). The lifespan of an RO membrane is dependent upon how much water you run through it, and how “dirty” the water is. Membranes can function well for a year, two years, or more. To test the membrane, measure the TDS in the water coming into the membrane, and in the purified water (permeate) produced by the membrane. Compare that to the membrane’s advertised rejection rate, and to the same reading you recorded when the membrane was new. Membranes also commonly produce purified water more slowly as their function declines.

After the RO membrane, water will flow to your DI housing. DI resin in good condition will reduce the TDS in the RO water down to 0 or 1 ppm. When the DI output starts creeping up from 0 or 1 ppm, your resin needs to be replaced. Sometimes you'll hear people complain that their DI resin didn't last very long. Often the culprit is a malfunctioning RO membrane sending the DI resin high TDS water. This will exhaust the resin quicker than would otherwise have been the case. Sometimes the problem is poor quality resin – remember that all resins are not created equal.

Additionally, don’t forget to sanitize the entire system at least once per year, and wash and lube your housing o-rings with food-grade silicone grease every filter change.

 

[Andre Duarte]

From our FAQ's https://www.buckeyehydro.com/faq/:
A good rule of thumb is to replace your sediment filter and carbon block after six months. A more precise way to maximize the usable life of these two filters is to use a pressure gauge to identify when pressure reaching the membrane starts to decline. This is your indication one or more of the prefilters (all the filters that touch the water before it reaches the RO membrane) is beginning to clog.

Also be cognizant of the chlorine capacity of the carbon block. A good 0.5 micron carbon block for example will remove much of the chlorine from 20,000 gallons of tap water presented at 1 gpm. Some original equipment suppliers commonly provide carbon cartridges rated at 2,000 to 6,000 gallons. Remember that all the water you process, both waste water and purified water, goes through the carbon block.

Regarding your RO membrane and DI resin, use your total dissolved solids (TDS) meter to measure, record, and track the TDS (expressed in parts per million [ppm]) in three places: 1) tap water, 2) after the RO but before the DI, and 3) after the DI.

The TDS in your tap water will likely range from about 50 ppm to upwards of 1000 ppm. Common readings are 100 to 400 ppm. So for sake of discussion, let's say your tap water reads 400 ppm. That means that for every million parts of water, you have 400 parts of dissolved solids. How do we go about getting that TDS reading down to somewhere near zero?

If you do some experimenting with your TDS meter, you'll note that your sediment filter and carbon block do very little to remove dissolved solids. So with your tap water at 400 ppm, you can measure the water at the “in” port on your RO membrane housing and you'll see it is still approximately 400 ppm.

The RO membrane is really the workhorse of the system. It removes most of the TDS, some membranes to a greater extent than others. For instance, 100 gpd Filmtec membranes have a rejection rate of 96% (i.e., they reject 96% of the dissolved solids in the feed water). So the purified water coming from your 100 gpd membrane would be about 16 ppm (a 96% reduction). Filmtec 75 gpd (and below) membranes produce purified water (a.k.a. “permeate”) more slowly, but have a higher rejection rate (96 to 99%). The lifespan of an RO membrane is dependent upon how much water you run through it, and how “dirty” the water is. Membranes can function well for a year, two years, or more. To test the membrane, measure the TDS in the water coming into the membrane, and in the purified water (permeate) produced by the membrane. Compare that to the membrane’s advertised rejection rate, and to the same reading you recorded when the membrane was new. Membranes also commonly produce purified water more slowly as their function declines.

After the RO membrane, water will flow to your DI housing. DI resin in good condition will reduce the TDS in the RO water down to 0 or 1 ppm. When the DI output starts creeping up from 0 or 1 ppm, your resin needs to be replaced. Sometimes you'll hear people complain that their DI resin didn't last very long. Often the culprit is a malfunctioning RO membrane sending the DI resin high TDS water. This will exhaust the resin quicker than would otherwise have been the case. Sometimes the problem is poor quality resin – remember that all resins are not created equal.

Additionally, don’t forget to sanitize the entire system at least once per year, and wash and lube your housing o-rings with food-grade silicone grease every filter change.

Thank you for your very good and fast explanation.

 

[Andre Duarte]

Awesome news! I think 97% is a pretty good rejection rate for a 150 gpd membrane. In the states, the two reputable RODI dealers Spectrapure and Buckeye Hydro, sell their units with capillary flow restrictors that we trim ourselves to get the optimally efficient 4:1 waste to product water ratio based on our unique source water situations. You could try to get a 550ml fixed flow restrictor to see if you can get improved efficiency if you’d like.

As far as resin life, at 433 tds source water, more frequent resin replacement will be a fact of life. You may be able to get gains by running a triple canister DI system, employing cation, anion and mixed bed resins.

Another solid way to improve DI resin life is to employ a 3 way valve after the RO membrane... this is commonly referred to as a DI bypass.

I was finally able to get an adjustable flow valve to get that 4 to 1 ratio (wast - filtered) water. However I continue to struggle to get 0ppm output.
Now with the 4-1 ratio I am getting 333ppm in, and 10ppm out just before the RO. Resulting in a 97% efficiency on my membrane. This 10ppm are going into my RO resin from FaunaMarine and I am getting 2ppm out. Is my resin depleted by now or what else could I do to get 0ppm out?
What ppm can be considered acceptable before the resin?

 

[homer1475]

10 before the DI is fine. If your not getting 0 after the DI stage, then your DI is depleted.

 

[Andre Duarte]

10 before the DI is fine. If your not getting 0 after the DI stage, then your DI is depleted.

Right, I will replace my RO once again and see how long it lasts.
Thank you for your help.

 

[homer1475]

DI not the RO. The Prefilters and RO clean up 97% of your water, the DI cleans up the last few PPM of TDS.

 

[homer1475]

RO = Reverse Osmosis, or the main membrane in your unit(the one that typically doesn't need to be replaced for a very long time).

DI = De-ionization, or the little beads that clean up the last few PPM of TDS to give you 0 TDS water(typically needs to be replaced every couple hundred gallons made depending on the incoming TDS).

 

[Andre Duarte]

RO = Reverse Osmosis, or the main membrane in your unit(the one that typically doesn't need to be replaced for a very long time).

DI = De-ionization, or the little beads that clean up the last few PPM of TDS to give you 0 TDS water(typically needs to be replaced every couple hundred gallons made depending on the incoming TDS).

My mistake. I mean to replace the DI resin and to see for how long it will last.
Thank you for all the help and support.

 

[Buckeye Hydro]

Before you replace the DI resin, check to see if the mixed bed DI cartridge was not packed tightly and the anion and cation beads have separated.

Russ