Can a double pass RO system be made with residential ro membrane?

[Renzo]

I have an idea how to do it, but more importantly, would a BW60-1812-75 membrane be suitable for this job?

What i am most curious about is whether the water produced by the first membrane will be suitable for the working range of the second membrane. For example the bw60 works with 2-11ph water but i could not find a value called min tds. Another point I think about is the dissolution of the second membrane or any substance in the system and mixing with water. Is there such an obstacle in front of me to make a double pass system.

To be used for aquarium or drinking water (using mineral filter)


Thank you for your answers.

 

[ditttohead]

Yes but why? We build mini double pass RO's, they are basically a waste of time and effort compared to simply doing a DI filter after the membrane. For double pass, you would typically do a 150 GPD membrane then have a booster for the second 100 GPD membrane since your recovery rate will be significantly higher (typically 85+%)… a small DI tank is a lot simpler, less problematic, and will give you better quality water. Double pass ro usually takes some pH correction as well for the second membrane to really do much more than minimal rejection...

 

[Sponsor]

 

[Renzo]

I knew mixbed resin was used for this job and it was difficult and to maintain. After your comment, I did some more research, there are separate applications as cationic and anionic, I will investigate, thank you. Just out of curiosity, what should keep the PH level for the second membrane? (if not a trade secret

Finally, isn't it true that pure water that produce at home cannot be purified enough to dissolve and incorporate plastic parts into its structure? Maybe some metal can be dissolved, I guess polypropylene is the most cost-effective and reliable raw material in this regard.

 

[ditttohead]

The question about the plastic is unanswerable, what level of absorption are you talking. You can purify water at home to the same degree you can in a commercial facility.

Mixed bed DI is common for aquarium use, simple, cheap, easy to maintain.

A simple example, a 1 cubic tank of DI being fed with 10 PPM RO water will get you about 10,000 gallons of high purity water <1 ppm.

As to the pH, there are many variables but we usually like to see 8+...

 

[Renzo]

I may have misinformation about pure water in my mind. My concern was this; I will produce pure water, the water passing through the pipes will rip substance from the pipes, it will poison me in the long run.
I knew that ultra purified water had a solvent effect especially on metals. But the waters that I call are absolute h2o produced in the laboratory environment, this has little to do with our topic anyway.

I will disturb you one last time,

I do not trust my mains water so i decided to go for such a method, do you think it is correct to use an extra purification process by passing through di resin for drinking water? Some experts do not recommend low-mineral water. However, I will use a mineral filter.

Thank you for giving a time.

 

[ditttohead]

You are definitely overthinking it. A simple high quality RO (not a POS from Amaz**) and a remineralizing filter will give you great drinking water. In general, a properly designed RO will reduce contaminants in excess of 95%. A double pass RO is typically done to avoid having to use DI, or to extend the life of DI resin in high use applications.

 

[Tobias.d]

Yes but why? We build mini double pass RO's, they are basically a waste of time and effort compared to simply doing a DI filter after the membrane. For double pass, you would typically do a 150 GPD membrane then have a booster for the second 100 GPD membrane since your recovery rate will be significantly higher (typically 85+%)… a small DI tank is a lot simpler, less problematic, and will give you better quality water. Double pass ro usually takes some pH correction as well for the second membrane to really do much more than minimal rejection...

Hello there. I came across this thread while doing a search on the internet. Which substance should be used between the two membranes in the system mentioned in the subject? As far as i understand caustic is used for this job, but from what i researched, it is not a very safe substance (at least for a home user) and it is difficult to dose. I'm thinking of increasing the ph with corosex instead, is that possible? Is corosex a safe chemical in drink water? (if there are some leaks)
If i keep the water between the two membranes between 8-8.5, will the second membrane really provide a higher rejection? (It's not a professional job, I just want to do better this way, so there's no need to comment on the point of perfection. If you could help me, I'd appreciate it. Thank you very much.

 

[ditttohead]

Corosex will increase the TDS substantially and can cause scaling of the membrane. It is very safe but I would not recommend it for this application. Sodium Hydroxide is typically used, you could also use soda ash.

 

[Tobias.d]

Corosex will increase the TDS substantially and can cause scaling of the membrane. It is very safe but I would not recommend it for this application. Sodium Hydroxide is typically used, you could also use soda ash.

These chemicals appear dangerous in my hand. If it is effective in purification, I can risk it and use corosex. If the membrane can remain durable as 1-2 years (It will produce drinking water for 3 people)
The TDS level of the product water of the second membrane does not matter (no bad effect of magnesium ions to drinking water) will use a mineral filter afterwards.
So how will I set the dosage? Should I fill the filter cartridge until catch the required pH level?

Thanks for your help.