Washington Water Treatment, Testing, and Sampling
“A
little learning is a dangerous thing;
drink
deep, or taste not the Pierian spring:
there
shallow draughts intoxicate the brain,
and
drinking largely sobers us again.”
–Alexander Pope
Our experience managing water systems has provided us with the
opportunity to see a wide range of treatment systems, which operate
with varying degrees of success. Most components in water
requiring removal can be treated with one of three entirely
different methods. Our goal is to work with you to help you
choose the treatment method that will best serve your needs.
What is the Approval
Process?
The first step is to determine the treatment goals and level of
service. Next, enough water samples need to be collected to
have an adequate understanding of the water chemistry. Nearly
every treatment process depends on impurities or characteristics in
the water that are not directly a problem; however, they cause an
indirect interference with the treatment process. Alkalinity,
tannins, and pH are common examples.
Once the water quality sample results have been assembled, the
most reasonable treatment strategy can be determined. Once a
treatment technology has been selected, whether or not to run a
pilot project needs to be determined. In some cases, such as
with surface water treatment, larger treatment plants, or treatment
plants with a large number of unique parameters, a small-scale
pilot study is absolutely required before the design is
started.
In other cases, with well established technologies, smaller flow
rates, and where public health is not at risk, a formal pilot
study often costs more than the treatment plant itself.
Therefore, if the treatment plant is small and/or we have a high
degree of confidence in the success of the approach, we may
recommend installing a “full-scale” pilot treatment plant, which
when successful, becomes the final installation.
In either case, it is wise to work with the WSDOH to establish
the appropriate type of pilot study and the parameters that need to
be considered.
The pilot study (either a true pilot, or full-scale pilot) is
designed, submitted and approved. Then the equipment can be
installed. Once finished and samples have been taken, the
full scale treatment plant can either be certified as complete
(full scale approach), or the main treatment plant designed (small
pilot approach).
Sometimes, the installed treatement plant requires additions or
adjustments to optimize performance.
One unique analysis we perform with every treatment plant is to
consider the cost of treating the water at full-flow vs. treating
at a lower rate with the utilization of storage. Often times
it is less expensive to add storage than to maximize the rate of
water treatment.
Arsenic Testing and Treatment
Arsenic is a primary contaminant that can cause problems in the
digestive system, skin, and is a known carcinogen. It is
regulated in water with a concentration above 0.0104 mg/L.
Arsenic can be difficult to treat, depending on the other
constituents in the water. We work with you to determine your
water quality goals, and then develop a treatment strategy to meet
your needs. For more information see our Arsenic Treatment
Technical Article.
Chlorination
Chlorination is usually installed for disinfection.
However, it can also be used for improving Taste and Odors, or as
an oxidant for iron removal.
There are several different methods of chlorinating drinking
water (chlorine gas, Calcium Hypochlorite, on-site generation from
a salt brine, or bleach). For small systems, injecting bleach
(sodium hypochlorite) is the most simple, reliable, and
cost-effective method.
We design chlorine injection systems that are easy to install,
operate, and maintain. While we will specify diaphragm pump
injectors, if that is your preference, we believe that the cost,
flexibility and ease of maintenance for the peristaltic pumps is
hard to beat.
Our primary advantage in the chlorination designs we develop is
that we make every effort to minimize the cost of providing
effective contact time. While it is easy to design long
serpentines or large reservoirs, these solutions are often very
costly. We customize the contact time solution for each and
every situation to minimize the construction cost.
Color
There are two primary causes of color in water: “Red water”
(oxidized) iron, and tannins. As suggested by the name, red
water iron is red. Tannins can be yellow, brown, or
green. Other contaminants can cause staining, but color
refers to the color of the water itself.
Red water iron is typically removed by coagulation and then
filtration. Depending on the pH and other water chemistry
parameters this process can either be very simple, or very
complex.
Tannins are a class of large, complex organic molecules that
come from the decay of vegetation. They can be removed by
either ion-exchange or oxidation. Tannins are usually very
difficult to remove. While we can be 100% successful in
treating tannins, they require a “guess and check”
methodology. Sometimes we are successful with our first,
educated guess, but sometimes they require two or three tries.
Corrosion Control
Lead and Copper in your water is a result of corrosive water
dissolving copper plumbing, brass fittings, or lead solder from the
inside out. In severe cases, it can cause blue or green
staining on plumbing fixtures. Lead is a well-known health
concern. Some people are sensitive to copper. In some
cases, corrosive water can lead to a catastrophic premature failure
of a house’s plumbing.
Lead and copper are only rarely found in the drinking water
source. Therefore, the presence of these contaminants at the
tap is almost always a result of corrosive, not contaminated,
source water.
The most important step in corrosion control is to determine the
cause of the corrosivity and the most effective method of
treatment. We have developed some very simple and inexpensive
field tests to help determine the best treatment methods. We
have found that “by the book” treatment does not always work and
that it is important to combine both the theoretical treatment
methods with findings on-site. This results in a little extra
expense up-front, but results in huge savings during the
construction and follow-up phases.
Corrosion Control Approval Process
Corrosion control begins with sampling. If lead and copper
is detected above the action limits, then additional samples for
conductivity, hardness and alkalinity need to be sent to a
lab. pH must also be measured on-site as it can change with
time. Ideally, two sets of these samples should be taken
three to six months apart.
Once the samples are collected, then a corrosion control
strategy recommendation must be made. This can either be done
by DOH (for a fee) or by a consulting engineer (likely also for a
fee). Once the approach has been selected by the waterr
system and approved by DOH, then the design of the
treatment plant can be developed and submitted. Usually, the
design is either presented as a small or full-scale pilot.
From there the design is reviewed, approved, and constructed.
Disinfection
Chlorination is the most common method of disinfection.
Other methods that can be used independantly, or in concert
with each other include UV light, ozone, and hydrogen
peroxide. UV light is especially popular with private homes
or businesses requiring disinfection treatment for interrnal
processes.
Filtration
Filtration is a physical process whereby particles are removed
from water. These particals may be sand, silt, clay,
bacteria, or organics. The size of the particle determines
the most appropriate filter. At times, multi-step filters are
appropriate to prevent filters designed to remove the smallest
particles from being clogged with the larger ones. Filtration
methods include: multi-media beds, centrifuges, woven filters (bags
or cartridges), and membranes. The most important aspect
of a filtration design is to thoroghly undsterstand the
characteristics of the particles to be filtered. Not
surprisingly, the smaller particles tend ot be the most
difficult. Indeed, extremely small particles (colloidal iron,
clay, etc) are sometimes most successfully treated by understanding
and taking advantage of their chemical rather than physical
properties.
Hardness
While hardness is more common in the Midwest and South, there
are pockets of hard water in the west as well. For small
water systems, ion exchange (water softener) is the most effective
treatment technology. This is one technology that is very
well established and is almost always a simple and straightforward
project. While hardness is not a regulated contaminant, some
systems choose to treat for hardness to protect their pipes and the
plumbing systems of each home. If the community members
conduct a significant amount of outdoor watering, it may be better
for individuals to treat water at their homes, so irrigation water
does not need to be treated.
Iron
Groundwater containing iron also commonly has manganese.
Iron causes red-orange staining. The presence of manganese
results in brown to even black stains.
Iron is usually treated by one of two methods: ion exchange or
oxidation filtration. We match the best technology with your
water use patterns, operational preferences, water chemistry, and
budget. Iron and Manganese are usually easy to treat;
although, the presence of tannins, or an extreme pH can require a
multi-step approach.
Iron Bacteria
Iron Bacteria are easy to remove from a water system with a
shock chlorination; however, they are very, very difficult to
remove from a well and/or aquifer. If a well has become
fouled with iron bacteria, we are able to assist you with
developing a plan for eliminating, or controlling the problem.
Beware of anyone who simply proposes shock chlorination of a
well to control iron bacteria. While this may cause an
initial kill of bacteria with an impressive flushing of gooey
sludge, it more often than not makes the long term condition of the
well worse rather than better. An understanding of
microbiology, hydrogeology, and well construction is essential to
successfully controlling iron reducing bacteria.
Manganese
Manganese is a naturally occurring mineral in some
groundwater. It is not health concern, but causes dark brown
to black staining. It is often found in association with
iron. Manganese is treated by the same oxidation-filtration
or ion exchange processes. Manganese can be a little more
difficult to remove because it oxidizes very slowly without the
presence of a catalyst such as Manganese dioxide.
Nitrates
Nitrates can be found naturally in groundwater, but are usually
the result of contamination. Manure piles, drainfields, and
heavy fertilizer application are common sources of nitrate
contamination. When possible, the source of contamination
should be identified and eliminated, if possible.
Nitrate is a primary contaminant and can cause methemoglobinemia
(blue baby syndrome) at concentrations above 10 ppm. The only
practical method of removal for a small public water system is
through ion exchange. Private homeowners can also consider
reverse osmosis as a viable alternative.
Ion exchange for nitrate removal requires very careful operation
and maintenance of the treatment plant. If the plant is not
properly regenerated on the required schedule, nitrate dumping can
occur, resulting in higher nitrate levels after the treatment plant
than in the natural source water. We recognize these factors
and work carefully with the communities requiring treatment to take
their responsibility for maintaining the treatment plant very
seriously.
Odor
The most common odor in public water systems is the “rotten egg
gas”, hydrogen sulfide. This gas is often found in parallel
with iron and manganese. Hydrogen sulfide comes out of water
very easily as a gas. Therefore, in systems with a reservoir,
simply spraying the water across the top of the reservoir with
adequate venting is often enough to remove all smell. If a
reservoir is not available or practical, injection of an oxidant
(chlorine, ozone, hydrogen peroxide) is often the best
solution.
While tannins are more commonly associated with color, they can
also cause “fishy” odors. See the section on Tannins for more
information.
Strong chlorine or chemically odors are sometimes presence on
chlorinated systems. Ironically, sometimes the solution to
these taste and odor problems is to increase the concentration of
chlorine in the water. Flushing or other operational controls
are the answers in other situations. Rarely does the strong
chlorine odor require expensive treatment techniques. Private
homes often desire to install activated carbon filters to remove
all chlorine before it enters the house.
In every odor situation we believe that the first and most
important step is to identify where the odor is coming from and
then resolve the odor problem based upon the water chemistry.
Sand/Sediment
As with other water quality issues, the first and most important
step is to identify what the contaminant is and why it is a
problem. Sand and sediment are generally easy to resolve;
however, it is extremely important to understand the nature of the
problem.
If you have sand because your well is failing or was improperly
constructed, then installing a simple sand filter might fix the
problem of sand in your lines, but it will mask the root of the
problem: a well that needs attention. Beware of cheap
solutions today that cause tens of thousands of dollars in expense
a few years down the road.
Taste
Taste and Odor are inseparably linked. See Odor.
Tannins
Tannins are a class of large organic molecules. Each water
source has a different “blend” of tannins. Some water has
undetectable levels of tannins. Other water has relatively
high concentrations of tannins, but they have no color/taste/odor
properties and don’t interfere with other treatment
processes. Other tannin blends are very difficult to remove
and require a complicated multi-step treatment process and regular
maintenance and on-going expenses.
The two primary methods of removing tannins are ion exchange and
oxidation-filtration. Since tannins have an overall negative
charge, specialized anion exchange resins are required. There
are two primary classes of these resins, each with two
sub-catagories. Each water has a different soup that may
require different media, or a combination thereof.
Oxidation-filtration requires the use of a strong oxidant such
as hypochlorite (chlorine), potassium permanganate, or ozone.
A coagulant is often times also required. Once oxidized and
coagulated into a filterable floc, the actual filtration media is
often less important. In this situation, the filtration
process is strictly physical.
Other . . .
Everything found in water can be treated; however, each source
of water is different. What works on one water system may
fail miserably on another. We have a strong background in
chemistry. We believe that the only way to successfully treat
water is to understand why we choose various processes, media, and
approaches. Rather than simply rely on cut sheets and
manufacturer’s claims, we insist on understanding our treatment
designs from the fundamental principals of chemistry and
physics.
We believe in being up front and honest when it comes to water
treatment. There are never any guarantees. We can run
pilot plants and do extensive water quality testing, but we cannot
and will not guarantee that a treatment plant will work
perfectly.
We believe that any engineering firm or contractor that makes
the claim that their treatment is guaranteed to work, is not being
realistic. All treatment designs must be based upon the best
information available and understanding of chemistry, but in the
end, there is no way to be certain of absolutely everything that is
in the water that could effect the treatmen outcome.
Loading...
