Engineering students consider using the sun to clean contaminated drinking water in Tanzania


Dartmouth, Africa, waterEditor's Note: Students from Dartmouth's Thayer School of Engineering are working in Tanzania to help improve sanitation and energy technologies in local villages. This series chronicles work being done by the student-led group, known as Humanitarian Engineering Leadership Projects (HELP), to design "rocket stoves" in the village of Mwamgongo and top-light updraft design (TLUD) gasification stoves in the village of Kalinzi. The goal is to create a healthier, more energy-efficient cooking apparatus that these villagers will accept and use. HELP students are filing these dispatches from the field during their trip. This blog post, their 13th for Scientific American, addresses water and sanitation systems.

Along with the work I was doing with Zach and Wendy on the stove project in Mwamgongo, I also worked on the water and sanitation projects with Aaron and Mitch, two medical school students who were doing a close study of the water and tap systems in villages of Mwamgongo and Kalinzi.

The tap system in Mwamgongo is a gravity-fed system that originates at a protected spring high in the mountains that surround Mwamgongo. In contrast, the water system in Kalinzi is centered around the plethora of protected springs in the area. Earlier groups of HELP had determined that there was both fecal coliform and Escherichia coli (E.coli) contamination in both the springs and the tap system. Bacterial growth tests that we performed out in the field had also proved that both types of bacteria were able to survive and grow in temperatures exceeding 98.6 degrees Fahrenheit. This means that both types of bacteria found in the water were fully capable of growing within the human body.

Unfortunately, in both villages there seems to be a relative lack of concern about the tap system. Because I was based in Mwamgongo, I can speak in much more detail about the Mwamgongo tap system. The system was installed by an NGO group with the intent of creating a healthier, cleaner water source that could be sustainable. This was especially important in Mwamgongo, where the major water supply (before the installation of the taps) was the river that ran through the village. This river also comes down from the mountain but is contaminated with trash, fecal matter and schistosomiasis. Schistosomiasis is a parasite that, although rarely fatal, can cause massive organ damage over time, and can cause anemia and impair cognitive development in children. Even with the tap system, schistosomiasis is still a major problem in Mwamgongo, which has around 90 percent of village children infected with the disease.

While in Mwamgongo, I tested the tap system again to check and see whether there was still contamination in the tap system, and my results confirmed earlier tests. There were still high levels of fecal coliform contamination and low levels of E.coli contamination still in the taps. I also performed a SODIS (solar water disinfection) test on the water. SODIS is a technique that tries to kill bacteria in water with the ultraviolet rays emitted by the sun. It is an incredibly simple water purification system that HELP is still exploring the effectiveness of. Basically, bottles of water are left on corrugated metal to sit in direct sunlight for at least eight hours (incredibly easy to do in a country that straddles the equator like Tanzania). The UV rays from the sun are supposed to kill the majority of the bacteria in the bottle. Unfortunately, my initial results did not really show a huge difference in bacteria count before and after my SODIS test.

In order to double check my results, I brought fresh samples of water from Mwamgongo to Jose Antonio and Javier, two members of ISF (Ingenieros Sin Fronteras) I had gotten to know rather well, in order to have them perform SODIS as well and compare our results. ISF is the Spanish equivalent of Engineers Without Borders. They were also working on several water projects in the Kigoma region, and we decided to exchange and test each other's water samples. Unfortunately, the results from ISF's water test are still pending, but the possibility of using SODIS to effectively purify the drinking water of the village is a very exciting project that HELP is excited to continue working on.

Image courtesy of Kanika Searvance

The views expressed are those of the author and are not necessarily those of Scientific American.

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