Does the Aquasana Countertop remove Ammonia?
I noticed the FAQs suggested it filters out Chloramines. But it does not specifically say ammonia. I could not find this from the cert and performance test also…
http://www.aquasana.com.au/certifications-and-performance-data/
Regarding Ammonia, if following the Chloramines FAQs, does this mean the filter should be replace every 5 months? Thanks.
This post was submitted by Eric Chan.
October 8th, 2008 at 12:10 am
The Aquasana Countertop(AQ-4000) and the Rhino Whole of House Filter(EQ-300) are currently being tested for chloramine removal; the AQ-4000 is about 3,000.00 a contaminant and the EQ-300 is
80,000.00 a contaminant to test. Preliminary results have been 99.9% removal but we have been experimenting with the filter media to try and remove flouride better and also sulfates with activated alumina. The results will be publishable as we become satisfied with the media ratios. We knew before that we removed it because chloramine is a chlorine compound, and it has the formula….. well here are some excerpts from a journal review.
METHODS OF TREATMENT
Distillation or evaporation does not effectively remove chloramines.
During distillation the chloramines would be volatilized and carried over to the
product water (distillate). This is especially important to keep in mind
in the pharmaceutical, power and laboratory markets due to their heavy use of
distillation technology (boilers in the power industry produce steam via
evaporation). The effects of reactive chlorinated materials on their
products are of special concern.
Chloramine removal by reverse osmosis has not been well documented.
Preliminary indications are that HR (CA) membrane will not reject
significant percentages of the monochloramine form. Much like chlorine, it
will pass through to the permeate side and thus work as a sanitizer on
downstream portions of the system. Dichloramine and trichloramine forms
would be expected to have greater rejection potential due to their larger
mass and higher ionic character, however, precise data is not available.
Even more limited is experience on PA-type RO membranes. Historically very sensitive to oxidants such as chlorine, PA membrane use has been limited
to water free of any such disinfectants. However, chloramines have a
significantly lower oxidative potential than the hypochlorite ion or
hypochlorous acid. PA-type tolerance t9 water containing chloramines would
be expected to be much greater compared to chlorine. This would certainly
be even more true for newer generation TFC membranes purported to have
greater chlorine tolerance.
We are not making any claims for continuous low level disinfection with
chloramines on PA RO systems. At this time no PA-type system should be
exposed to >0.2 ppm chloramines without R&D approval. The effects of
chloramines on PA membrane are, however, of interest to us as they may
have potential as a sanitizing agent once the development of a moderately
oxidant tolerant PA membrane has been realized. One must keep in mind that in the absence of free ammonia, a minute amount of free chlorine is in
equilibrium with chloramines.
Due to tighter pore structure, TFC membranes would be expected to reject a
higher percentage of chloramines than cellulosic membranes. Indeed, one
report of up 90% rejection of the monochloramine form has been heard of in
R&D.
For the moment it appears that RO’s utility in removing chloramines is in
removing water impurities that would otherwise be competitors or provide
interference in downstream ion exchange (IX) or activated carbon (AC)
technologies. As we will see, RO’s primary utility is removing chloramine
breakdown products as a result of AC treatment.
IX resin has a certain affinity for cations and anions. The more highly
ionized species (such as sulphates, chlorides, etc.) are preferentially
adsorbed to the resin over less strongly charged molecules such as
chloramines. With RO as pretreatment, competition for exchange sites would
be practically absent. Hence, some chloramines would be removed by “fresh”
strong base IX resin, but this is not a reliable mode of treatment.
Another portion of chloramines may decompose via oxidation in an IX system to the chloride ion as happens with Cl. Again, this is not a reliable reaction.
Feed water quality and resin characteristics are likely to provide unique
performance for each application.
Some degradation via oxidation of the cation resin could also expected.
Though not nearly as severe as with free chlorine, life of the resin would
be reduced a slight degree. While IX effect some chloramine removal, it
has limitations
Activated Carbon (AC) is proven to reduce chloramine presence from 1 to 2
ppm to less than 0.1 ppm (a USP WFI requirement). The mode is similar to
free aqueous chlorine destruction, however, with chloramines one
encounters “by-products” of ammonia, chloride and nitrogen gas. Remember that AC does not adsorb C12 or NH2Cl like organics. Bear with me as I present the generally accepted reactions:
————————————————————————–
1. NH2Cl + H2O + C* => NH3 + Cl- + H+ + CO*
2. 2NH2Cl + CO* => N2 (g) + H2O+ 2H+ + 2Cl¯+ C*
(C* and CO* represent carbon and carbon oxide surface (of activated
carbon) respectively)
————————————————————————–
Note that in the reduction of free aqueous chlorine by AC only H+and Cl¯
ions are generated:
3. C* + HOCI => CO* + H++ Cl¯
4. C* + ¯OCl => CO* + Cl¯
For USP WFI requirements, ammonia nitrogen must also be less than 0.1 ppm in the product water. AC will not remove NH3. At pH 7.5 or lower, both
cellulosic and noncellulosic RO membranes would reduce the NH3 and Cl
concentrations to less than 0.1 ppm from AC feed waters up to 2 ppm NH2Cl.
Õ Clinoptilolite, a natural-occurring ammonia selective zeolite (resign)
was not found to be effective in reducing NH3 levels to USP criteria. Strong
base cation would probably be effective in removing NH3, but only RO and
distillation are acceptable as the final form of treatment in the
production of WFI grade water.
Activated carbon is a viable method to reduce chloramines. The literature
notes some important facts in designing AC beds for chloramine removal:
1. Chloramine reacts more rapidly with finer GAC particle sizes (CECA
brand 12 x 40 mesh was found significantly better compared to Darco 12 x
40 and Witco 12 x 30 mesh).
2. Two gpm per square foot and 4 foot deep for an empty bed contact
time of 15 minutes provides over one year run time with 1-2 ppm chloramine feed with effluent of less than 0.1 ppm.
3. The removal efficiency of GAC is much greater for free chlorine
than for chloramines. Therefore, if one can first oxidize chloramines to free
chlorine and N2 the GAC bed can be sized smaller because GAC can handle
Cl2 much quicker.
Activated carbon followed by RO (or IX and RO, depending on purity required) appears to be the best non-chemical-intensive method to treat chloramines.
Your comments/questions are invited. R&D would appreciate any field
experience a data involving chloramines on especially RO. For further
information I suggest reviewing the following articles from which I drew much of the above information:
- Water Chemistry by V. Snoeyink, D. Jenkins 1980, Pages 396-399
- Proceedings of the 47th Annual IWC 1986 “Innovative Design for Chloramine
Removal…” by Jones et al, Pages 440-448
Journal AWWA - Research and Technology June 1986; “A Review of Chlorine Dioxide in Drinking Water” by E. M. Aieta and J. D. Berg, Page 70
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