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GeoInsighter Spring
2003 Newsletter
A Primer On Small Water
Treatment Methods
Point-of-Entry and Point-of-Use Systems Part One Return to the Newsletter
Index
Where impurities within an
aquifer are widespread (i.e., treatment of a particular area to remove
the impurity is not feasible) and already well understood, water may be
treated by a full-scale municipal or moderate-scale community treatment
plant prior to distribution to the public. In other cases, remedial
activities are performed to target and cleanup a specific area of an
aquifer that has been degraded by an identified problem. However, both
of these scenarios may not address all impurities present nor provide a
benefit to private wells, and, therefore, the quality of water obtained
at the tap of your home or business may require treatment.
The topic of water quality is gaining priority in many circles and is
now a regular consideration during property transactions. Treatment may
be warranted because of natural or human-caused impurities that are
nuisance problems, such as odor or staining, or more serious problems
such as health effects. While the source of these materials may be
completely out of your control, small water treatment systems are a
relatively common solution to water quality problems.
Treatment of water may be achieved as a point-of-entry (POE) system,
where a device or series of devices improves the quality of water where
it enters a home or business, such that the higher quality is then
available throughout the building. A point-of-use (POU) system is a
device, or series of devices, that improves water quality only for a
specific location, such as under a counter for kitchen use or in a
hospital operating room for medical use. The future will likely bring us
more split water systems where a lower level of water quality may be
diverted to flush toilets and outside spigots and a higher level to
sinks and showers. Currently, this is not common practice in the
northeast, but a close example includes a water softener in the basement
(POE) to minimize iron staining and a carbon filter on the kitchen
faucet (POU) to improve taste.
The decision to use a water treatment system or device is usually
derived from knowledge of impurities in your water based upon taste,
odor, visual characteristics, or laboratory analytical results. Once the
impurities are known, an evaluation can be made regarding what the
source might be (i.e., whether they are naturally occurring or the
result of human activities). Sources may be unnatural, such as impacted
runoff from urban areas, runoff from agricultural areas, pollution
carried by precipitation, industrial discharges, and uncontrollable
releases from buried fuel tanks and surface spills. Sources may also be
natural, related to normal minerals in soil and bedrock, decay of
natural materials (e.g., tannins and lignins), and gas released from
bedrock into ground water (e.g., radon). If the source cannot be
treated, then an individual system often makes sense.
Examples of impurities that can be addressed by POE or POU systems
include: sediment (i.e., rock particles), color (turbidity), odor (i.e.,
hydrogen sulfide), taste (i.e., chlorine), a stain causing condition
(i.e., iron and manganese), natural elements (i.e., arsenic), natural
gas (i.e., radon), and chemicals (i.e., gasoline compounds, pesticides,
or herbicides).
A system is typically selected to achieve a particular goal, such as
meeting an applicable public drinking water standard or preventing
staining of laundry.
The type of system selected will be based upon the following
considerations:
raw water concentration of the impurity;
specific chemical characteristic of the impurity (i.e., chromium
species);
other chemical parameters of the raw water (i.e., pH, dissolved
oxygen, and hardness);
anticipated rate of water use, which affects system maintenance,
performance, and estimated life span;
desired end quality results;
economics (some systems differ greatly in cost, but only slightly in
treatment efficiency);
maintenance requirements (some systems are totally automated, while
others require regular owner or contractor service); and
potentially applicable regulations, such as where discharge of waste
by-products from the treatment are not allowed to be discharged on your
property.
Multiple sampling events are typically performed to characterize the
nature of the impurity in the raw water to evaluate possible
concentration fluctuations. In some cases, the magnitude of the
concentration may have significant implications on the treatment system
selected, so additional testing is performed to confirm initial results.
System reliability will be important, particularly when minimizing
adverse health effects is the objective of system operation. By products
and/or wastes produced by the system and how they will be managed will
also factor into the selection. Many off-the-shelf systems are
available for POE and POU implementation that are relatively
standardized or easily modified for a particular application, especially
with regard to residential or other small volume uses. Specialty
contractors are usually used to install the system components in a
manner compatible with the existing water system and provide at least
initial confirmatory testing to document that the system is performing
as expected.
In the next edition of the GeoInsighter, a discussion of different types
of treatment systems and their advantages and disadvantages will be
presented. Michael C.
Penney, P.E., L.S.P.
mcpenney@geoinc.com
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