Water Disinfection for Rwanda

Rainwater Storage, Fog Catchment, and Filtration Project: Sunzu, Rwanda

We are working with the Sunzu Yacu Community Center in Sunzu, Rwanda, to design the appropriate technology for water filtration and fog catchment for the community.

Sunzu Yacu Community Center, Rwanda

An aerial view of the Sunzu Yacu Community Center, Rwanda
An aerial view of the Sunzu Yacu Community Center, Rwanda

Inside the library. The computers and books are free for the community to use.
Inside the library. The computers and books are free for the community to use.


The Sunzu Yacu Community Center was a dream conceived by Dan and Frances Klinck, two Canadians who fell in love with a village on the picturesque mountaintop between Lakes Burera and Ruhondo in the Northern Province of Rwanda. Dan worked in the energy sector in Rwanda, and Frances taught English to students and teachers at the local primary school. After creating life-long friendships with many of the villagers, they felt compelled to do more and invited friends and supporters alongside to create a space for education and play.

In 2013, the Klinck’s engaged with young architect Andrew Goodwin to design what would become a multi-purpose educational center for an under served population of women and children in the Northern Province of Rwanda. Goodwin’s company’s burgeoning humanitarian design studio, known as the RED Studio, took on the project and quickly designed a locally influenced, yet sustainable community building.

Built on a terrace overlooking the lakes of the district, the community center was oriented to receive ample daylight and ventilation throughout the year. This helped to reduce the need for any daytime lighting or fans. The shed roofs collect rainwater in cisterns, and are reused on the property for potable and non-potable needs alike. This community center was also design to leverage the knowledge and skills of local tradesman in order to infuse the struggling economy with monies and jobs. Therefore, the building was designed using local techniques of masonry and concrete framed construction, as well as hand crafted doors, windows, casework, furniture and ceilings.

Ultimately, the interiors boast welcoming and comfortable day lit areas for the children and women of the local villages to learn and meet. With an average of 25 readers per day, this center has already had an amazing effect on the community providing opportunities to learn how to read and write at no other cost but time. Now being used as a pilot building for Dan Klinck’s business, Afritech Energy, the Sunzu Yacu Community Center is the first of many new projects that will empower local villages through clean energy investment and innovation.


The Sunzu Library in Rwanda is located on a hill far from a drinkable water source. People living there must get their water either by traveling a long distance to the lake at the base of the hill or collect rain water. Neither of these sources are sanitary and no reliable water filtration option exists.

Nearest local water source is the lake in the upper right side of this photo of the Sunzu Yaco Community Center.
Nearest local water source is the lake in the upper right side of this photo of the Sunzu Yaco Community Center.



Rwanda is a developing country located in central Africa just South of the Equator. Like many developing countries Rwanda has a young population with a high birthrate. 11.6 million people live in Rwanda with a growth rate of 2.3 percent annually. Rwanda is also a very young country with a median age of 19.4 years. Literacy and education is rare in Rwanda with only 65.8% of the country being able to read. In addition, Rwanda is one of the poorest countries on Earth with an average annual income of $1170.
Rwanda like many poor developing countries struggles to provide its people with clean water. 25% of the county’s overall population, and 30% of the rural population, lack access to clean water. As a result, in 2008, 9040 children died of diarrhea in Rwanda, which is usually caused by water contaminated by cholera.
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Carly Althoff, Journeyman International Coordinator, is onsite in Rwanda working on the development of her plan for the Sunzu Yacu Community Center, pictured below. She is our main contact.

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Develop a rain water filtration system and a fog catchment system to provide potable water for the people of the Sunzu Yacu Community Center.


1. Work collaboratively with the community to determine what their most urgent need is.
2. Learn how to aid communities using development in an efficient and sustainable way.


Desired Effects:
Prevent water-born diseases and increase the quality of life in the community.
Provide short term employment for local people in the initial construction of the project.
Provide long term employment for local people in the maintenance of the project.


In April 2017, the Community Center did not have any rainwater storage system, and therefore launched a fundraising program to buy two 5,000L RotoTanks, which each cost $800. In September 2017, two tanks were donated to the Community Center through the library’s partnerships with JI and Empowering Villages.

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Video of tanks.



The technology:

  • single or double layer of mesh net supported by two posts rising from the ground; collector and conveyance system functions due to gravity
  • water droplets that collect on the mesh drop into a gutter at the bottom of the net from where they are channelled via pipes to a storage tank
  • material for net: nylon, polyethylene, or polypropylene (shade cloth) which can be produced to various densities capable of capturing different quantities of water)
  • positioned on ridge lines perpendicular to prevailing winds


  • atmospheric water is generally clean; water collected with fog harvesting technologies has been shown to meet World Health Organization standards – UNISA
  • minimal environmental impact of installing and maintaining technology
  • Construction is minimal and system requires no energy to operate
  • Capital investment low compared to other conventional sources of water supply


  • occurrence of fog unreliable. **Carly has informed us that occurrence of fog at Sunzu Yacu is consistent
  • technology might represent investment risk unless pilot project is first carried out to quantify potential water yield rate in area under consideration


  • costs vary depending on size of fog catchers, quality of and access to materials, labor, and location
  • small collectors cost $75-$200 each to build; large 40m2 collectors coast $1,000 – $1,500 and can last up to ten years
  • multiple unit systems have a lower cost per unit of water produced
  • community participation will help to reduce labor cost of building fog harvesting system

Meteorological/geographic info needed:

  • predominant wind direction
  • topographic relief
  • relief in surrounding areas
  • altitude – desirable working altitude is at 2/3 stratocumulus cloud thickness above the base, this portion of cloud will have highest liquid content

Table 1: Water collection rates from fog collectors

Project Total collecting surface (m2) Water collected (liters/day)
University of South Africa 70 3,800
Yemen 40 4,500
Cape Verde 200 4,000
Dominican Republic 40 4,000
Eritrea 1,600 12,000

Sources: UNISA, 2008; Schemenauer et al, 2004; Washtechnology; FogQuest

More information from the UNISA 2008 Research Report on fog catchment.


1. Slow sand filter. Advantages: most materials can be found locally, removes particulates and pathogens. Disadvantages: slow flow rate, purification of sand is difficult and resource intensive, requires training to use and maintain.
Slow sand filters are used in water purification for treating raw water to produce a potable product. They are typically 1 to 2 metres deep, can be rectangular or cylindrical in cross section and are used primarily to treat surface water. The length and breadth of the tanks are determined by the flow rate desired by the filters, which typically have a loading rate of 0.2 to 0.4 litres per hour (or cubic metres per square metre per hour).
Slow sand filters differ from all other filters used to treat drinking water in that they work by using a complex biological film that grows naturally on the surface of the sand. The sand itself does not perform any filtration function but simply acts as a substrate, unlike its counterparts for UV and pressurized treatments. They are often preferred technology in many developing countries because of their low energy requirements and robust performance.


2. Ceramic filter. Advantages: clay can be found locally. Can be constructed in individual homes and on site at library. Disadvantages: potentially slow flow rate. Purchase of silver coating required.
Locally manufactured ceramic filters have traditionally been used throughout the world to treat household water. To use the ceramic filters, families fill the top receptacle or the ceramic filter itself with water, which flows through the ceramic filter or filters into a storage receptacle. The treated water is then accessed via a spigot embedded within the water storage receptacle. The filters are produced locally at ceramics facilities, and then impregnated with colloidal silver to ensure complete removal of bacteria in treated water and to prevent growth of bacteria within the filter itself.
ceramicfilter.jpgfilter-receptacle.jpgENPHO School CSF, IDEASS Pot.jpg

  • Effectiveness: The effectiveness of ceramic filters at removing bacteria, viruses, and protozoa depends on the production quality of the ceramic filter. Most ceramic filters are effective at removing bacteria and the larger protozoans, but not at removing the viruses. Studies have shown adequate removal of bacterial pathogens in water filtered through high quality locally-produced or imported ceramic filters in developing countries. A 60-70% reduction in diarrhea disease incidence has been documented in users of these filters. Studies have also shown significant bacterial contamination when poor-quality locally produced filters are used, or when the receptacle is contaminated at the household level. Because there is no chlorine residual protection, it is important that users be trained to properly care for and maintain the ceramic filter and receptacle.
  • Drawbacks
    • Not as effective against viruses
    • No chlorine residual protection – can lead to recontamination
    • Variable quality control for locally produced filters
    • Filters can break over time – need for spare parts
    • A low flow rate of 1-3 liters per hour for non-turbid waters
    • Filters and receptacles must be cleaned regularly, especially after filtering turbid water
    • Ceramic filtration is most appropriate in areas where there is capacity for quality ceramics filter production, a distribution network for replacement of broken parts, and user training on how to correctly maintain and use the filter.
  • Economics: Locally manufactured ceramic PFP (precision fiber products)-design filters range in cost from $7.50-$30. Distribution, education, and community motivation can add significantly to program costs. Ceramic filter programs can achieve full cost recovery (charging the user the full cost of product, marketing, distribution, and education), partial cost recovery (charging the user only for the filter, and subsidizing program costs with donor funds), or be fully subsidized such as in emergency situations. If a family filters 20 liters of water per day (running the filter continuously) and the filter lasts 3 years then the cost per liter treated (including cost of filter only) is 0.034-0.14 US cents.

    Commercially available ceramic filter systems range in cost from tens to hundreds of US dollars, depending on where they are manufactured and purchased, and the quality of the ceramic filters. The economics and the sustainability of commercial product-based projects depend on donor funding and subsidy, as well as follow-up to ensure replacement parts are accessible to the population using the filters.

  • Colloidal silver is used to enhance the inactivation of bacteria and other germs. CSFs (course screen flushes) remove pathogens and turbidity from drinking water.

3. Solar water disinfection (SODIS): Advantages: inexpensive. Disadvantages: dependent on weather. Household water treatment option to prevent diarrhea in developing countries.
Users of SODIS fill 0.3-2.0 liter plastic soda bottles with low-turbidity water, shake them to oxygenate, and place the bottles on a roof or rack for 6 hours (if sunny) or 2 days (if cloudy). The combined effects of ultra-violet light (UV)-induced DNA damage, thermal inactivation, and photo-oxidative destruction inactivate disease-causing organisms.

  • Benefits
    • Proven reduction of viruses, bacteria, and protozoa in water
    • Proven reduction of diarrheal disease incidence
    • Simplicity of use and acceptability
    • No cost if using recycled plastic bottles
    • Minimal change in taste of the water
    • Recontamination is low because water is served and stored in the small narrow necked bottles
  • Drawbacks
    • Need to pretreat water of higher turbidity with flocculation and/or filtration
    • Limited volume of water that can be treated all at once
    • Length of time required to treat water
    • Large supply of intact, clean, suitable plastic bottles required
    • SODIS is most appropriate in areas where there is availability of bottles and community motivation and training for users on how to correctly and consistently use SODIS for treating household drinking water.
  • Economics: SODIS, as a virtually zero-cost technology, faces marketing constraints. Since 2001, local NGOs in 28 countries have disseminated SODIS through training of trainers, educating at the grassroots level, providing technical assistance to partner organizations, lobbying key players, and establishing information networks. The experiences gained have shown that SODIS is best promoted and disseminated by local institutions with experience in community health education. A long-term training approach and repeated contact with the community is needed to create awareness on the importance of treating drinking water and to establish corresponding changes in behavior. Both the Swiss Federal Institute of Aquatic Research and Technology and the SODIS Foundation provide technical assistance to NGOs implementing SODIS.
  • Turbidity is the measure of relative clarity of a liquid. It is an optical characteristic of water and is an expression of the amount of light that is scattered by material in the water when a light is shined through the water sample. The higher the intensity of scattered light, the higher the turbidity.
    Excessive turbidity, or cloudiness, in drinking water is aesthetically unappealing, and may also represent a health concern. Turbidity can provide food and shelter for pathogens. If not removed, turbidity can promote regrowth of pathogens in the distribution system, leading to waterborne disease outbreaks, which have caused significant cases of gastroenteritis throughout the United States and the world. Although turbidity is not a direct indicator of health risk, numerous studies show a strong relationship between removal of turbidity and removal of protozoa. The particles of turbidity provide “shelter” for microbes by reducing their exposure to attack by disinfectants. Microbial attachment to particulate material has been considered to aid in microbe survival. Fortunately, traditional water treatment processes have the ability to effectively remove turbidity when operated properly.

4. Chemical treatment. Advantages: Very effective vs pathogens. Disadvantages: expensive, materials not locally available, requires extensive training to use effectively, does not remove particulates, Chemicals may harm people if improperly used or handled improperly.
Chemical treatment is also known as disinfection. Chemical treatment is often applied to water after it has past through a filter in order to prevent the stored potable water from becoming recontaminated. Pathogens killed by chemical treatment include: viruses, bacteria, including Salmonella, Cholera, Campylobacter and Shigella, and protozoa, including Giardia lamblia and other cryptosporidia. Following the introduction of any chemical disinfecting agent, the water is usually held in temporary storage – often called a contact tank or clear well to allow the disinfecting action to complete.
The most common chemical disinfecting agent is chloramine. Chemical disinfection is not often used in developing nation because of the cost, required training, and lack of locally available sources of chemicals.


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It is very difficult to communicate with those in charge of the project since they are currently on site in Rwanda. We have exchanged a couple emails but find it challenging to move forward with ideas when we have so many questions. We are waiting to learn about the following:
– ability to use PVC pipe EDIT: we can use PVC pipe.
– budget EDIT: $1,000
– main sources of funding EDIT: Sponsors/GoFundMe
– volume of people who will be drinking the water on site at the library EDIT: 200
– volume of people from the community who will be taking the water home with them EDIT: 100
– the water quality issues that this location experiences and that we need to account for EDIT: Diarrhea, malnourishment, constipation
– stakeholders involved that could negatively impact project EDIT: The community. This might be invasive or foreign.
– capacity of community to participate in construction of filters and fog catchment system EDIT: As many as we want!


We have spoken more with Carly about our questions (see ‘EDITS‘ above) and have a better idea about what the Community Center’s needs are. We have decided to recommend that they use ceramic filtration, as they have seen these types of filters in other communities and can confirm their effectiveness and acceptance into the community. This technology is inexpensive and easy to assemble and maintain. Carly and her team loved the idea of fog catchment and informed us that the equipment would be placed on the hill above the library, facing Lake Burera (see map with added fog catchment location at beginning of website). She informed us that we need account for gale force winds, so we are recommending that the equipment be built on a pulley system, similar to a sail, to allow for easy breakdown and set up according to wind presence in order to prevent damage from storms.

Carly and her team are aiming for this filtration and fog catchment system to be assembled in Spring 2018 as other projects are currently prioritized, such as the Composting Waste project. Therefore, we suggest that the Spring 2018 Appropriate Technology class pick up this project and continue the development and implementation of this technology. Carly is excited about and open to the idea of students coming and implementing our designs at that time in the spring.


Music Credits:
<a href=”http://www.hooksounds.com“>Music by HookSounds</a>


https://www.youtube.com/watch?v=AQis6QlWDaQ – fog video
https://www.youtube.com/watch?v=O01JMhZzE3k – ceramic filter video


Gabriel Seelig – gseelig@calpoly.edu
Catie Michel – cbmichel@calpoly.edu
Saul Flores – sflore07@calpoly.edu