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Building Principles: Water Systems — The Next Installment
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.
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.
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
Sampling and testing
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.
Iron, manganese and metallic taste
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.
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).
Pressure and volume
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.
Rick Stryker is a professional engineer with Camp Facilities Consulting providing study, design, permitting, and construction consultation services to the camp and conference center community. Camp personnel may contact him at 570-296-2765 or by e-mail at email@example.com.
Originally published in the 2002 November/December issue of Camping Magazine.