RO unit for water with chloramines

[Ben Rhau]

Hi all,

I'm in the market for an RO unit, and my tap water is very soft, but contains chloramines and NaOH. According the literature, most carbon blocks do not efficiently remove chloramine, and the vendors recommend a 5 or 6 stage RO/DI to effectively remove chloramine. My question: Is it worth adding the two additional stages to remove chloramine, or should I just get a 3-stage RO and add Prime to the output?

Thanks

 

[Ben Rhau]

One thing I'm reading is that, unless removed first, chloramines will degrade the RO membrane. The proposed mechanism is that, at high pH, the chloramine dissociates into ammonium and hypochlorite ions, and it's the ammonium ions that deteriorate the membrane. Has anyone experienced this?

 

[MacZ]

Hi all,

I'm in the market for an RO unit, and my tap water is very soft, but contains chloramines and NaOH. According the literature, most carbon blocks do not efficiently remove chloramine, and the vendors recommend a 5 or 6 stage RO/DI to effectively remove chloramine. My question: Is it worth adding the two additional stages to remove chloramine, or should I just get a 3-stage RO and add Prime to the output?

Thanks

I live in a country where chlorine and chloramine are removed at the water plant before sending the drinking water into the public system, so I don't have any in my tap, but I have helped dozens of people now getting their units set up in countries where the stuff is in the water system, all with a 3 stage (carbon, sediment, membrane) units have reported trouble free removal and tested no chloramine nor chlorine in the permeate.

One thing I'm reading is that, unless removed first, chloramines will degrade the RO membrane. The proposed mechanism is that, at high pH, the chloramine dissociates into ammonium and hypochlorite ions, and it's the ammonium ions that deteriorate the membrane. Has anyone experienced this?

As far as I know any ions with a higher reactivity (or very high concentration) have deteriorating influence on the membrane and it is not like the membrane is going to be worn out very quickly. But it raises waste water amounts significantly and reduces the lifetime of the membrane by some months.

 

[Ben Rhau]

<This study> confirms your observations, except that the DI resin appears to be necessary. Scroll all the way down to “Removing Chloramine With Activated Carbon: Does it Really Work?”

 

[MacZ]

Ok. Thanks for the additional material. I can link people to this in the future. For myself it doesn't change anything, luckily.

 

[Mike Wise]

My tap water contains chloramines and Na(OH) too. I just add a dechlorinator to the R/O water as I add it to the tank (directly into the tank actually). I've been doing this for years without problems.