..........................................................................................................................................................
Aluminum
in Drinking Water
Although aluminum is readily removed from water by cation
exchange resins such as those used in water softeners, aluminum is not readily
removed back off the resin by normal salt regeneration - periodic acid
treatment is required to exchange accumulated aluminum off the resin, therefore
self-regenerating cation exchange systems are not practical for residential use
The Water Quality Association
Aluminum is an extremely abundant metal
in the earth’s crust. It is a health risk associated with dialysis patients.
Aluminum can leach from rock
and soil to enter any water source.
It can be found as aluminum
hydroxide, which is a residual from the municipal feeding of aluminum
sulfate.
It can also be present as
sodium aluminate from a process known as clarification or precipitation
softening.
Contaminant
|
In Water As
|
Secondary Maximum Contaminant
Level
|
Aluminum (Al)
|
Al3+
Al(OH)3 |
US EPA:
SMCL* = 0.05 to 0.2 mg/L WHO† Guideline: 0.1 to 0.2 mg/L Health Canada OG** = 0.1 to 0.2 mg/L |
Sources of Contaminant
|
Rock and soil leaching
|
|
Potential Health Effects
|
High risk associated with dialysis patients
|
|
Treatment Methods
Point-of-Entry (POE)
Point-of-Use (POU) |
Portable Cation Exchange***
Distillation Reverse Osmosis |
.
*Secondary Maximum
Contaminant Levels (SMCLs), or National Secondary Drinking Water Regulations
(NSDWRs), are non-enforceable guidelines regulating contaminants that may
cause cosmetic effects (such as skin or tooth discoloration) or aesthetic
effects (such as taste, odor, or color) in drinking water. EPA recommends
secondary standards to water systems but does not require systems to comply.
However, states may choose to adopt them as enforceable standards.
**Operational Guidance Value
(OG) established by Health Canada based on operational considerations.
***Cation exchange is not a
preferred method for fully automatic home treatment systems due to the need
for periodic acid regeneration. If this method is used, a tank exchange
program is recommended so regeneration is handled by trained and qualified
personnel at a central facility.
WHO† - World Health Organization
|
HEALTH
EFFECTS
Aluminum
is regulated in public drinking water with a recommended Secondary Maximum
Contaminant Level (SMCL).
In
this case, the EPA and WHO agree that aluminum above 0.1 ppm may impact color
but recognize that level may not be appropriate for all water supplies.
US
EPA encourages utilities to maintain levels below 0.05 ppm, but recognizes the
need to be flexible in this case because of the usefulness of Aluminum salts in
the coagulation process.
WHO’s
guideline of no more than 0.2 ppm is based on the importance of Aluminum as a
coagulant and that all municipal systems should be able to keep treated water
below this value.
Studies
linking Aluminum in drinking water to human health issues have been
inconclusive.
.
Although aluminum is readily removed from water by cation exchange resins such as those used in water softeners, aluminum is not readily removed back off the resin by normal salt regeneration.
.
Although aluminum is readily removed from water by cation exchange resins such as those used in water softeners, aluminum is not readily removed back off the resin by normal salt regeneration.
Periodic
acid treatment is required to exchange accumulated aluminum off the resin,
therefore self-regenerating cation exchange systems are not practical for
residential use.
Point-of-use
methods (POU) such as reverse osmosis (>98% reduction) or distillation
(>99% reduction) should be considered.
When
alum (Al2(SO4)3 · 14.3H2O) is used in coagulation in municipal water treatment,
it can, under certain pH conditions, precipitate as a result of the
concentration effects in the reject waters of either reverse osmosis or
distillation systems.
Aluminum
floc, depending on equipment design and pH, can foul reverse osmosis membranes.
The
treatment methods listed herein are generally recognized as techniques that can
effectively reduce the listed contaminants sufficiently to meet the SMCL.
However,
this list does not reflect the fact that point-of-use/point-of-entry (POU/POE)
devices and systems currently on the market may differ widely in their
effectiveness in treating specific contaminants, and performance may vary from
application to application.
Therefore,
selection of a particular device or system for specific contaminant reduction
should be made only after careful investigation of its performance capabilities
based on results from competent equipment validation testing for the specific
contaminant to be reduced.
As
part of point-of-entry treatment system installation procedures, system
performance characteristics should be verified by tests conducted under
established test procedures and water analysis.
Thereafter,
the resulting water should be monitored periodically to verify continued
performance.
The
application of the water treatment equipment must be controlled diligently to
ensure that acceptable feed water conditions and equipment capacity are not
exceeded.
Visit
WQA.org to locate water professionals in your area. Note that Certified Water
Specialists have passed the water treatment educational program with the Water
Quality Association and continue their education with recertification every 3
years.
REGULATIONS
The US EPA sets unregulated Secondary Maximum Contaminant Levels (SMCLs) for
contaminants that affect the aesthetics of drinking water but do not pose a
risk to human health.
Because
SMCLs are federally non-enforceable, public water treatment facilities are not
required to monitor them unless regulations at the state level require it.
The
federal SMCL for aluminum is between 0.05 to 0.2 mg/L or ppm, which means at or
above these levels certain aesthetic effects, specifically the coloration of
water, could occur.
The Water Quality
Association publishes this Technical Application Bulletin as a service to
its members and the interested public. Information contained herein is based
upon the most recent public data known as of the publication date and cannot
take into account relevant data published thereafter. The Water Quality
Association makes no recommendations for the selection of a treatment system,
and expressly disclaims any responsibility for the results of the use of any
treatment method or device to reduce or remove a particular contaminant.
No comments:
Post a Comment