It's been years since we talked about potable water systems in Building Principles, and with opening camp just around the corner, this seems like an ideal time to revisit some of the key points that your county sanitarian expects you to know to run a safe, healthy water system at camp. So, let's look at some basic whys and hows of disinfection.
"Don't put that in your mouth!" It seems that most parents of small children spend most of their daily waking hours saying that. It is an especially important truth when we're talking about surface water of any kind. Although municipal water systems often rely on lakes, reservoirs, rivers, and streams, it's because of the sheer available volume and access. Treatment of surface water to achieve acceptable standards is tricky, involving a series of complex mechanical and chemical processes. Big public water suppliers can achieve consistent and cost-effective results because their systems are designed to be adaptable for specific changes in the inlet or raw water quality, and their certified operators are highly trained in the art and science of making drinkable water from the "soup" at the inlet. Even at its best and clearest natural condition, that "soup" likely contains suspended particles from the size of a grain of sand down to microbes that will make a healthy person violently ill. Those same contaminants could be life-threatening to anyone with an impaired immune system, including small children, the aged, and the medically compromised. As very few camps have a surface water treatment system, you may be wondering why it's even worth mentioning. Because surface water contaminants are usually the primary cause for waterborne illnesses, even with systems supplied by groundwater wells, like camps.
Your imagination is the only limit to the number of ways that surface contaminants can impair well water. Here's one common situation: Stable staff is filling horse water troughs. They put the end of the hose in the trough and open the faucet. After a few minutes the trough is full, and they turn it off at the spigot. Unfortunately, that's the perfect situation for the trough water (with its load of horse mouth bacteria, straw, dirt, and other things) to be invisibly siphoned back into the distribution system. That's right, even with the faucet off, it is common for a vacuum to draw on the hose and spigot, pulling contaminants back into the system. Ideally, the barn has its own water well system and the hose is connected to an Underwriters Laboratories-rated, self-draining, nonfreeze yard hydrant. Though it still draws a siphon when the faucet is closed, the water drawn back is discharged below the frost line to a pit of gravel, where it drains back into the ground and not into the water system. So, while this does nothing about the livestock germs that have been sucked into the hose, spigot, and pipe, those germs don't get into the distribution piping for the rest of camp. This situation is so common that it's worth keeping in mind and posting signs at the barn that the water is not for drinking or handwashing.
Here's another example of how surface contaminants get into the water supply. Over time, the ground has settled around your well head (that big ugly pipe that sticks up above the well). Rain and runoff puddles in that low spot around the pipe. Water stands there until it evaporates and/or runs into the groundwater down along the outside of the well head. Without the filtering soil, surface microbes run into the well water waiting to be pumped into your system for drinking. So, inspect your well head and its casing. Look for signs that water ponds near the well head, mounding and compacting topsoil around it to redirect runoff elsewhere. Stop planting flowers around the well head too. Fertilizer and such are running right into the well. If the well head is really a visual problem, paint it brown or green. The well head itself should be watertight in every way, with rubber o rings inside a bolted-on cap with all the bolts in place. No, a five-gallon bucket on top will not suffice.
Here's just one more example that may surprise you. The miles of black poly water line that snake along the ground around camp with sections held together by barbed fittings and hose clamps are a common source of injury and system contamination. That sort of water line should be joined with fused, threaded fittings, which requires equipment that no camp has in the maintenance garage. Hose clamps (not even two on each side of the fitting) have no place in a water system. But that hose clamp and barbed fitting arrangement is not watertight, as we always see the puddles at the joints. Much like the compromised well casing that's exposed to surface contaminants, the connection points are places where dirt and microbes enter the pipe. A vacuum, caused by the Venturi effect — the reduction in fluid pressure that results when a fluid flows through a constricted section of a pipe (Wikipedia, 2020) — will draw water from the puddle at the joint into the pipe whenever the velocity of the water in the pipe increases or changes direction.
These are just a few of the ways that your water supply can admit surface contaminants, and there are many more. But since you can't be everywhere at once, what can be done to reliably and automatically reduce the risk of waterborne illness? The answer is to disinfect the water system when camp is opened, and then keep disinfecting it all season long.
The idea here is that if you can kill the microbes before they get to the faucet, you have made giant strides to preventing illness. Usually, that's accomplished with compounds called "oxidizers," with chlorine compounds being the most common. While that all sounds simple, the chemistry is more complicated than it appears, and "doing it wrong" is often as big a problem as not doing it at all. Here are some things you need to know:
- Use chlorine intended for use in potable water systems. While HTH from the pool house, or Clorox from the laundry can do in a pinch, neither of these is exactly right for the job. Your base chemical should bear a seal from the National Sanitation Foundation (NSF) indicating its specific use in potable water systems.
- For your safety, and to get the most from your chemical budget, follow the mixing instructions very carefully. More is not better, because too much can cause other problems with corrosion, taste, odor, and disinfection by-products. By introducing the right amount of chemical at the right concentration, you will provide a killing dose to microbes in your source water, while a residual dose will be carried forward to oxidize bugs that get in much farther downstream.
- Chlorine can be delivered in several different ways, but the most common at camp is through a powder dissolved in water and stored in a tank called a "carboy" or a "day tank." A small pump draws the solution out of the day tank and injects it into the water inside the pipe. Most injection pumps (and there are several designs from which to choose, including peristaltic and diaphragm) have adjustment knobs to allow the operator to vary the amount of chemical being moved. Without complex electronics and programmable controls, they will deliver the same volume of chemical with every pump cycle.
- If the day tank solution concentration is low or weak, there may not be enough disinfectant injected to kill the microbes. Even stored perfectly, the day tank liquid loses strength over time. In warm weather that happens faster. I have visited more than one camp where the operator mixed the chlorine once a week and never checked on it otherwise. The amount of oxidizer and its effect on bugs is surely lower on day six than it was on day one. Like caring for the livestock, water system operation is a chore for every day when there are people in camp using the water. Check the free chlorine concentration daily, and then freshen as needed to maintain the necessary oxidizing power. Mixing a week's worth at a time is a waste of money and a pretty sure road to unreliable disinfection.
- Without getting into too much detail, I usually recommend that camps use a peristaltic injection pump instead of a diaphragm unit. This can be a hard sell because peristaltic units often cost a little more than their counterparts. This has never made sense to me because peristaltic is simpler to operate and has fewer moving parts. With either configuration, though, soft, rubbery parts and springs will wear out. Be prepared to replace those before they fail and buy a new parts kit each spring. Put the new one on the shelf when it arrives, and install the kit you bought last year, even if the old one isn't broken. That way you always have a fresh one in the queue and a relatively fresh one in the pump. The soft, replaceable parts — including seals, diaphragms, and tubing — need to be compatible with the solution that you're pumping. Make sure you select repair kits made from the right material, and don't buy them from the catalog based on price, either trying to save a dollar or trying to go first class by buying the most expensive. Both solutions may be incompatible with your chemistry and could fail equally fast. Talk to your trained and knowledgeable supplier (not necessarily your buddy at the supply house counter) and get their help in selecting the right kit for your system.
"Oxidation" is a chemistry term that applies to all sorts of things in your water, and not just the microbes you're trying to kill. Chlorine compounds will also react to some dissolved metals in your water. Several years ago, a school district near my home was having a tough time as the water at the faucet was suddenly a pressing topic at public board meetings. It turned out that the District had recently hired a new operator. Not really understanding that the disinfection day tank and pump were only for disinfecting the pipes annually, he turned the equipment on and began to chlorinate all the water coming into the system from their wells. The source water had high levels of dissolved iron and manganese (neither of which were even visible nor imparted a taste in the source water). The chlorine oxidized both of those metals, discoloring the water at the tap and giving it a metallic taste. Instead of getting help, he added another chemical trying to bind up the iron and manganese, only to have the cafeteria staff complain about the hot water; it was now pink (from the added chemical) and contained iron and manganese specs. The new addition was not stable in the hot water heating system. In the end, the best solution was to simply stop adding the chlorine solution, and everything went back to how it had been for the prior 20 years. The takeaway is that water chemistry can be very complicated, and a small change in how it's handled can have unintended consequences.
Some other technologies can also help camp deliver good, clean water; one of those is ultraviolet (UV) light. It works by exposing the microscopic bugs to a certain wavelength of light as the water flows past a special bulb inside a canister or cylinder. The units generally can run continuously for a whole 365 days on a single lamp (which can be expensive), and because there's no chemicals to be added, there's never a worry about day tanks or chemical taste or precipitation of dissolved metals. However, as with anything else, you should be aware of the drawbacks. First, it may surprise you to learn that UV doesn't kill the microbes by dissolving them, but instead disrupts the DNA so they don't reproduce. Samples sent to the lab will come back "positive" because the technician can see things swimming around in the microscope. A very different test is required to confirm that the water is indeed safe to consume. Also, "spontaneous repair" of DNA has been well documented, particularly in systems where the water is stored for a while prior to consumption. So, while the UV lamp did its job early on, the microbes sometimes heal themselves and again can reproduce. And as there is no disinfectant left in the water, there is nothing to kill the healed bugs or microbes that get into the system downstream of the UV lamp. UV is only approved for disinfection at "point of use" and not for distribution systems. Finally, the dissolved water chemistry is an important consideration for UV. Clarity of the source water, dissolved minerals, and metals can all affect whether the light can fully penetrate the water and inactivate the microbes. But if you have a remote site on camp with its own well that produces very clear, low-dissolved mineral water, and want or need to disinfect it, a point-of-use UV system might be a great way to get that job done.
Health departments usually require that the source water be analyzed at startup, but as we've seen, it may be worth the extra few dollars to run a more extensive analysis to head off other problems if disinfection is required later. Disinfecting drinking water is not an impossible task, but the effort demands the attention of a skilled (and usually certified) operator to ensure that what runs from the tap is all right for everyone to drink, bathe in, and enjoy.
- Wikipedia. (2020). Venturi effect. Retrieved from en.wikipedia.org/wiki/Venturi_effect
Rick Stryker is a professional engineer who is passionate about camps and the opportunities that they provide. He's always delighted to answer email questions at firstname.lastname@example.org.