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

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


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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





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  1. 1. lamorpa 10:03 am 10/12/2010

    Um, isn’t the headline, "Engineering students copy the use of the sun to clean contaminated drinking water in Tanzania (as has been done many times before and in many, many places around the world)

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  2. 2. kristi276 5:02 pm 10/12/2010

    Eat your veggies, there are starving children in Africa. It always seems that the western solution to the crisis in Africa is to treat Africans like they are children. When will Africans be encouraged to come up with solutions to solve the problems of underdevelopment is Africa? There are many bright minds throughout the African continent, is there the equivalent to MIT and engineering. While the industrialized nations are looking to the moon and beyond, the non-industrialized world is still looking for clean water and their next meal. Africa is entombed in tribal and ethnic wars that have waged far to long. Maybe what is needed is a United States of Africa. Where there is a will, there is a way.

    Land, food, water, peace, development and freedom

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  3. 3. juhe49 3:35 am 10/13/2010

    Sodis is not that easy to apply as you mentioned; if there is even low turbidity, the particles can block the impact of the uv ray and you will measure the same no. of microbes after the exposure.
    You mentioned in your article " even with the tap system, schistosomiasis is still a major problem in Mwamgongo". If you know the transmission path of shistosomiasis, you know that the high infection rate comes from bathing in contaminated surface water via the skin and not via drinking water supply.

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  4. 4. bucketofsquid 2:37 pm 10/13/2010

    It seems to me that focusing the sun light would be more likely to work rather than just trying direct sunlight. At the very least, solar boilers could raise the temperature of the water and kill a fair amount of critters. On a large scale it could provide bath water too. Is there a treatment for Shistosomiasis? Could that be made available for low cost?

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  5. 5. BBKing 2:47 pm 10/13/2010

    Shame the UV thing didn’t work. But how about heating? I believe the usual advice is to boil the water, but that is probably just because it is easy to see when it is OK. What sort of time/temperature curve would knock out the worst bugs and parasites? There may be equipment that can not quite achieve 100degC, but which can be easily and cheaply made available. For instance, would 70degC for a few seconds be useful?

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  6. 6. nmsu96 6:59 pm 10/13/2010

    The solar energy program at UT El Paso (UTEP), Tx a few years ago had a solar still that works very well. It is able to deal with mineral salts and bio contaniments. The plans are free and the still is easy to build. The UTEP plans are only one of several that are out there, UC Davis also has several solar still plans that work. Desert survivial teachs that it is easy to build a solar still using a piece of plastic and a rock and a flexable plastic straw, dig a cone shaped hold in the ground and put a container in the bottom, put the straw in the container and run it up the side of the hole. Cover the hole with the plastic leaving it a little loose so that a small rock placed in the middle forms a cone, seal the edges with dirt. As the sun heats the soil it condences the moisture on the plastic and runs down to the bottom point at the rock and drips into the container, suck the water up with the straw. For more production put bad water in the hole, make sure it does not get in the fresh water container. Use the sun, the rain cycle workes.

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  7. 7. undra.quispe 2:35 pm 10/20/2010

    It remains to be seen whether a car company that has spent years and millions of advertising dollars touting the horsepower that can be gained from such improvements….
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  8. 8. uniquestar.7 5:52 am 10/28/2010

    Public health authorities in Tanzania advocate boiling for drinking water. Most locals do this because they know the consequences of ignoring the advice. Schistosomiasis treatments are available and provided free, not only to those who visit a doctor or think they need it, but as mass treatment to whole communities so as to break the cycle of transmission.

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  9. 9. shweyang 5:14 pm 05/23/2012

    Starvation is one of the worst circumstances ever faced. Why do especially for those living in such poor environment bring up many children even parents themselves cannot feed for themselves? I am not blaming them but surprised.

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