by Rick Stryker
What comes out of the faucet should never be part of the “how was camp?”
post-session quizzing between a camper and parent. All sorts of aging
infrastructure can present pressing facility issues, but with most of
the components buried or otherwise concealed, many operations consider
water supply and distribution “out-of-sight and out-of-mind.” Unfortunately
though, when the toilets don’t flush, or when there’s no water to drink
on a ninety-five-degree day, suddenly there may be a new urgency to the
water-supply situation.
In the last column (September/October 2002 issue), we discussed water
production and common ways that water systems supply pressure. In this
column, we will clarify several basic issues concerning potable water
quality including disinfection, taste and odor, and a few different configurations
of distribution systems. It is important to understand that each system
is unique — from the chemistry of the water to the topography of the land
— and as such, each system has to be studied individually. In short, there
are no one-size-fits-all solutions.
Water Disinfection
All of the supply components of the water supply system must be disinfected.
This includes the well itself, the well pump, the storage tanks, and the
inside of the distribution pipelines. Often this is done when a new component
is first installed. It’s important to note that many systems “winterize”
by draining the system to prevent damage from freezing. Under no circumstances
should the pipeline be left in a condition where debris or animals could
enter the pipe. Each time that a drained system is refilled, the inside
of the pipe should be flushed clear and then decontaminated by introducing
a concentrated chlorine solution to the pipe and letting it stand for
24 hours. Normally, the residual chlorine level (which is discussed later)
and bacteriological counts are confirmed by a lab before the system is
put into service and water used for drinking.
Chlorine
Most often, a chlorine compound is used to disinfect the water. It can
be injected into the water as a liquid or a gas. In the proper concentration,
disinfection should be complete after the water has been in contact with
the chlorine about twenty minutes. A small amount of free chlorine should
remain in the solution at the farthest reaches of the system to continue
to combat most biological pathogens that could find their way into the
water.
Note that the previous paragraph emphasizes most and does not claim to
inactivate all potential pathogens. Recently, Giardia Lamblia and cryptosporidium
have caused outbreaks of illness in public water supplies all across the
nation, spurring “boil water” and “no use” orders by the municipal supplier.
These situations have occurred because the treatment facilities through
which the raw water flowed were not prepared to expose these organisms
to lethal doses of chlorine. To inactivate Giardia cysts, the lethal chlorine
concentration is more than 10 ml /liter or 10,000 parts per million (ppm)
for more than thirty minutes. Contrast that with a typical health department
swimming pool chlorine residual requirement range between 1.5 and 5 ppm.
As you can see, chlorine is no “silver bullet.” In the case of these two
contaminants, preventing the supply from being contaminated is the best
answer.
Ultraviolet light and ozone
Although ultraviolet light and ozone can be used very effectively to disinfect
water, these alone are not typically accepted methods of distribution
system disinfection since once the water has passed the treatment units,
there is no remaining disinfecting agent in the water. Any small pinholes
or leaks in the system could allow pathogens into the pipeline where they
could multiply with impunity.
Sampling and testing
At a minimum, most camp and conference center water systems are typically
required to perform basic disinfection procedures and collect regular
samples. These are tested in a laboratory to confirm that the supply does
not contain live organic pathogens and that the most remote taps contain
sufficient residual disinfectant to be effective. Most often, the lab
provides data on “total coliforms” and “fecal coliforms.” In and of themselves,
these organisms are typically not dangerous, but are used as indicators
of the health of the water environment. If the disinfection system is
working properly, most of the organisms, which can make consumers sick,
should be neutralized.
It is important to note that the health department or state mandated
tests usually DO NOT require routine operational checks for contaminants
that could represent a health threat to consumers — such as lead or copper.
These may be required tests if there have been past occurrences of sickness
or other water standard violations. Keep in mind that groundwater conditions
change with time and that as the supplier, the camp or conference center
cannot rely on the minimum testing standards to support a legal defense
if someone gets sick. In short, a full range of tests at least yearly
will help ensure that the system is healthy.
Water Quality: Taste and Odor
Obviously, this is a very broad topic, and both the degree of problem
and the degree of acceptable solution are pretty subjective. Water Treatment
Plant Design (American Society of Civil Engineers & American Water
Works Association, 1990) describes the situation well — “Because little
is known about the exact chemical cause of a taste or odor problem, the
treatment has historically been more of an art than a science.” The book
goes on to describe two categories of treatment — chemical transformation
and removal. This column focuses more on the transformation methods since
these represent the most common small-scale treatment techniques. There
are some conditions that may have simple solutions to help make the water
more palatable. Please note that “simple” is not necessarily the same
as “easy” or “cheap.”
Many people incorrectly interchange “water softening” and “water treatment.”
Softening is actually a form of treatment. Water softening is a process
by which dissolved minerals are removed from the solution. Common household
softeners use beds of salt in a tank through which the water flows. As
it does, the electrochemical properties of the salt attract certain minerals
(most notably calcium carbonate molecules) using a process referred to
as “ion exchange.” The water that comes out the other side of the salt
bed has a mineral content much lower than the water that went in. This
makes the water feel less sticky and hence the term “softer.” As more
and more calcium carbonate builds up on the surface of the salt crystals,
the exchange rate decreases, and the unit becomes less efficient. Modern
household softeners have an automatic backwash or regeneration cycle to
clean off the salt and allow it to resume its task. Along with the mineral
content that is washed off, some of the salt goes, too, and so more must
be added occasionally.
Sulfur
Although some folks would claim that sulfur water is highly nutritive
and beneficial (I really knew someone who liked his sulfur well!), most
people find the smell and taste of sulfur generally unappealing. In most
cases, the sulfur is being dissolved and carried by water moving through
the ground on its way to the well. It can often be removed from solution
by mixing it with lots of air under pressure. This procedure, known as
“aeration,” requires some specialized equipment including automatic compressors,
storage tanks, and mixers. In addition, once the sulfur has been moved
from the solution into a gaseous form, the stinky stuff from the water
is now stinky stuff in the air. You’ve really only moved the problem.
“Mossy”
Most often, a mossy taste or odor is the result of algae somewhere in
the system. Both the algae itself and the chemicals used to control it
can be the source for unpleasant tasting water. Algae requires sunlight,
so most frequently, this is a problem when surface supplies are used for
drinking. Where there is a mossy taste but the supply is a well, it’s
likely that the well has been contaminated by surface runoff containing
algae or algae by-products. As suggested earlier, this should be a loud
signal to the operator that bacteriological testing should be done to
insure that other contaminants like Giardia and crypto haven’t entered
with the algae.
Iron, manganese and metallic taste
This condition will require a small amount of detective work to determine
the source. First, it’s critically important to determine whether the
mineral taste is inherent to the groundwater or whether it’s being generated
in the distribution system. Iron and its oxides are common in the earth’s
crust and are generally pretty soluble in water. If the groundwater you’re
pumping has iron compounds in it, they can be often removed with one of
several chemical applications. Oddly enough, just chlorinating the water
may remove enough iron from the solution to make the water much more palatable.
Remember that what was dissolved, or in solution, now settles out of solution
(precipitates). The iron particles will need to be filtered out — adding
another step to the treatment process.
Recall from basic chemistry that pH is a measure of how many hydrogen
ions are floating around looking to attract oppositely charged particles.
Lacking other particles dissolved in the water, these renegade hydrogens
may work to remove the interior coatings of the pipe itself. Elements
that can be freed from the pipe and its joints include iron, copper, and
lead. All of these elements have been identified as potential health hazards,
and the EPA has set maximum contaminant levels (MCLs) for potable water.
If the source of the taste problem is corrosive water, manipulation of
the pH is not a difficult task. But like the other treatment methods,
it entails some specialized equipment and operator knowledge in order
to achieve the desired results.
“Stale”
A stale taste of water is usually indicative of water that has been in
storage too long either in a storage tank or in the distribution system.
If the water has been in the system too long, it’s likely that the chlorine
residual is also no longer up to the required level. This problem is best
corrected by modifying the distribution network, perhaps using one of
the configurations that follow.
Distribution Systems
There are two methods of moving water from a source or storage spot to
the points of use. Their names describe what they would look like from
above — branched and looped. The chart above shows the exact same location
of demands for both systems, and illustrates how each configuration could
be used.
In a branched system, a single pipe feeds smaller pipes along the way
much like a tree trunk feeds the branches. A simple looped system has
an interconnected system of pipes that can feed water from at least two
directions. Remember that water will move according to differences in
pressure and doesn’t “know” that there is a short route and a long route
to the tap at location 1. When the user at 1 opens the faucet, water will
flow in both directions (though more will flow toward 1 than 2).
In our practice, we see branched systems in 75 percent or more of the
camp and conference center systems. This is because as new areas are developed,
a water line is extended from the main to serve the new buildings or facilities.
Although this is often the most expedient method of solving the problem,
it has significant implications in terms of service, operation, and the
quality of water delivered to the tap.
Pressure and volume
In a branched system, supply water has only one path to reach the user.
This translates into a lower net service pressure when there are multiple
demands along the trunk or main. In a looped system, water can flow through
both branches to serve a single demand or multiple simultaneous users.
Because of this, the diameter of the pipe in a looped system can usually
be smaller than a branched main.
Chlorine residual
The concentration of chlorine fed into the system at the well is typically
higher with a branched system than with a looped system. This is to compensate
for the potential for long periods of non-use at the far end of the line.
As seen previously, looped systems can rely on at least a small amount
of flow through both branches.
Maintenance
If the water main in a branched system requires work, all of the users
downstream from the point of repair will have to be shut off until the
system is reconnected. If a looped system is equipped with strategically
located valves, part of the system can be taken off line and serviced
while other portions remain live.
There are some economic issues that may seem to make the looped system
impractical or too expensive. However, if allowed to solely govern the
network selection, these issues could actually cost more in chemical costs,
service, and quality issues over the long run. When it comes to your water
supply system, your design professional should help you consider all of
the alternatives and the potential impacts of each choice.
Originally published in the 2002 November/December
issue of Camping Magazine. |
