RO Water Pretreatment

Yes, there are. Contact a water treatment speciality chemicals manufacturer (name withheld) for advice directly.

Consult the manufacturer of the RO equipment.

It sounds like a daft idea to me, get equipment to purify the water, but add more cr4p in before you start? Eh?
There is no substitute for lack of proper maintenance. If you don't want to maintain the equipment, just don't fit it.

Sorry if that sounds harsh and grumpy, it just sounds like someone looking for a lazy solution...

I'm happy to stand corrected and eat my words

Del

Of course the problem with adding chemicals, is you need a dosing system... just more stuff to go wrong.

Del

typically only water at a single sink is filtered RO, the rest of the house is untreated supply

Put a particle filter upstream.

And a carbon filter downstream of the particle filter.

And then you have to clean/replace them.

What you need is a pre-pre-pre treatment
Del

Replacing depth filters is cheaper than replacing RO filter membranes.

That's how we did it when we used RO filtration in wet chemical process stream.

6 depth filters in a single cannister, upstream of the RO filter.

Google reverse osmosis. Getting a better idea of the process would answer a lot of your questions. For one the resin isn't a softener.

If your running water thru an RO system it need not be treated at all. Anything you add to the water will be one more thing that has to be filtered out.

Most RO systems are added to remove the softener. Which is a sodium salt in most systems. Which doctors want people to limit their intake of. One course of action would be to change to a potassium salt. About 4 times the cost. But your body can always use potassium. And less harmful for the environment. Plants use it too.

Generally tap water purification set up comes up with 10 micron fiber filter. Activated carbon filter followed by 5 micron fiber, so that most of the suspended impurities are pre filtered & safety is ensured to the membrane.

It is note worthy that, R.O membrane it self is capable of removing total hardness & total dissolved solids [ say salts].

If your use is meant for drinking purpose, the existing set up as mentioned on top is more than enough excepting for the fact that, you need to periodically clean the 10 micron filter & do service for ACF & 5 micron filter at longer intervals.

Hardness removal using chemicals is not advisable for drinking water for the possible contamination by regeneration chemicals & TDS additions.

How ever if your feed water contains excess hardness, it is better to go for Nano filter prior to R.O along with the existing 3 pre filters. The nano filter will take care of your hardness & heavy metals removal & feed H2O & Nacl mixture for TDS removal at R.O membrane segment. Here water softening chemicals ware not warranted. Your R.O membrane can put up longer service days at the cost of Nano membranes. It should work out much cheaper than chemical dosage for water softening.

I wish to thank everyone here who expressed their opinion on this matter. Udhaya why I chose to reply your comment specifically is because from the description given you seems to have a very good idea.

We have in part of our country a serious problem of CKD (chronic kidney disease). After several research studies by WHO and 2 universities here they have come to the conclusion that CKD is due to a complex salt of Cadmium, Arsenic, Calcium, Magnesium, Fluoride and finally gly-phosphate (traces of a pesticide called round up) in drinking water. The only solution for this is simply consume RO water as RO gets rid of all these elements.

I on my part as an engineer doing my bit of community service has contributed by setting up 12 plants at village level with my own funds to run on non commercial basis. I always use a softener prior to the RO plant which incorporate prefilters Udhaya mentioned in his comment. In fact I did my own design and it is no big deal for a professional engineer. However I have seen some large scale RO plants which use chemicals to pretreat feed water in order to reduce the membrane fouling. My question to you learned crowd was whether anyone here knows generic names of those chemicals. In fact I was told one such chemical is Sodium Hydrasulfite.

My apologies for any inaccuracies in my English. It is my second language :)

Biofouling - Use ozone pre-treat.

Chemical (precipitation) fouling - pre-treat to the lowest pH to the equipment can tolerate, but then post-RO the pH back up to a comfortable Langlier value.

RO is not water treatment - it is water processing.

You mentioned fouling. Are you having bacterial growth problems? If so, a good dose of 254 nm UV light will deactivate most of the bacteria minimizing the fouling without adding additional dissolved substances to the water. Follow this up with ultrafiltration before your RO & the fouling on your membranes will be greatly reduced.

FYI, RO is nothing more than an ultrafine filtration process that can remove dissolved minerals.

The OP needs to consult with RO system supplier and find their recommendations for concentrated brine to be routed to the sewer, as a percentage of total flow.

If water hardness minerals are present, these may form scale that might be reversible with a low pH cleaning solution.

Some scale minerals are not reversible enough with these acids, and thusly, over time, loss of performance is inevtiable. Replaceing membranes more or less frequently is totally up to you.

Biofouling is a persistent issue in many RO systems, especially when they sit idle for longer periods of time that just a few hours. High and low pH cleanings will be needed. Also to help avoid that problem, some chlorine should be in the source water well upstream of the RO unit, followed by a charcoal filter to remove the oxidizer (bleach) to prevent damage to the membranes.