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Treating and Testing: An Engineer’s Take On Water Quality

Water Missions International - Ebola Response,  Monrovia, Liberia 2014

At Water Missions International, our aim is to be a best in class Christian engineering ministry that transforms lives through sustainable safe water solutions. We understand the importance in clean, safe water, which is why we’ve put in place the best possible practices to filter and treat the water in the communities we’ve worked with. A clear glass of water can be deceptive, which is why we always test for the dangerous contaminants the human eye cannot see.

Collecting Water Samples
Our founder George Greene III collects a raw water sample for testing.

There are three different types of water contaminants: suspended solids, dissolved solids, and microbial contamination. Suspended solids are usually dirt and debris, and they are the reason that the water might appear cloudy or look dirty. This type of contaminant is commonly found in surface water sources like river and lakes. We filter out these types of contaminants at the beginning of our water treatment process since dirt can complicate the disinfection process. Dissolved solids refer to salt and minerals, possibly also chemical, contaminants—things that dissolve in water, such as salt, lead, or arsenic.

The final type of contaminates are microbial. These are always the most significant health problem and our primary concern. We find them almost always in surface water sources. They’re less likely to be found in ground water—water from boreholes or wells—but if the well was constructed incorrectly or if a disaster occurs, these sources can still be contaminated.

There are three types of microbial contaminates. The first are protozoa. These small organisms enter the water as cysts, or eggs. They move into our bodies when we drink contaminated water. The cysts end up in our intestines, where the organisms make their home. A common example of protozoa is Giardia. Fortunately, protozoa are big enough that they can easily be removed by proper filtration.

Bacteria, the second type of microbial contaminants, can’t be completely removed by filtration. They’re too small to get stopped by that process, so we need to kill them by treating the water. Fortunately, when we treat the water with chlorine it’s easy to kill life-threatening bacteria like Cholera and rend the water safe. Chlorine also has the power to inactivate the third type of microbial contaminant—viruses like Ebola.

Ensuring Water Quality
We use different strip tests to monitor chlorine levels and check for contaminants.

Once we’ve filtered and treated the water, we always test it to make sure it’s safe. Our technicians and engineers are familiar with the best ways to check that the water is safe, and they teach these methods to safe water system operators in every community to make sure that the water is checked regularly.

We use a variety of equipment to test the safeness of the water that comes out of our systems. We take a small sample of water and run it through a turbidity meter, which checks for suspended solids by scattering light through the water to check for dirt. We check for the dissolved solids with a series of paper strip tests. We dip these strips into the water and, based on if the strip changes color, we can tell what minerals are present. We can perform the same test with a colorimeter test meter, which our staff will also use, by adding different reagents to water samples and checking to see if the water changes color. The final way we check for dissolved solids is to use a conductivity meter to test whether or not the water can conduct electricity, allowing us to know if the water is too salty for human consumption.

Water Missions International - Ebola Response,  Monrovia, Liberia 2014

The simplest way to check for microbiological contaminants is to check our chlorine levels. By regularly checking our chlorine levels, we can know with confidence that the water is free from bacteria.

The best way to reassure safe water recipients that their water is now safe is with a membrane filter test. One of our staff will collect a sample of the water and place it in a sterile container. Back at our in-country program office, they will run a 100 ml sample through a .45 micron filter. They’ll put this sample in a petri dish with M-Coliblue, a food source for bacteria, and then incubate the petri dish for 24 hours at 35 degrees Celsius. If there were bacteria in the water sample, they will have grown enough that our staff can visually see it when they check the dish later.

Petri Dishes
The petri dish on the left shows the bacteria present in the untreated water. The culture on the right shows a lack of bacteria in the treated water.

We test for total coliform bacteria, commonly found in all water, and E-Coli. The presence of total coliform bacteria in the water after it’s gone through the system immediately alerts our staff that there is not enough chlorine being added to the water.  We can monitor chlorine levels by using strip tests on the water, and we can also use the red color wheel test you may have seen your lifeguard perform at your swimming pool. We check for E-Coli because this is a big red flag for fecal contamination. We test for both of these at the same time.

When you compare the petri dishes of a community’s untreated water with the water from their safe water solution, it’s easily for community members to see the difference. They don’t want the petri dish with things growing on it. They want the clear one, and that’s the water they deserve—clean, safe, and healthy.

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