Disinfecting water with sun rays

By Alfred Tumushabe. A woman standing by her rainwater harvesting tank watching her water being disinfected by solar with the WADI device

Stella Kyomuhangi is a mother of eight school age going children. She lives with her husband Bedius Aruho in Nyanja B village, in Nyanja parish Bukiro Sub- county Mbarara District, Western Uganda. The area, like many other places in the district, is scantly wooded. This poses a challenge of getting firewood, the only source of energy for cooking. Nyanja is highly populated. Some households are separated by a distance of 200 meters or even 100 meters. Majority have iron sheet roofed houses. The residents are mainly cultivators. In some homes, like Peter Bainomugisha’s, they rear a few goats, cows, chicken and pigs.

Realising that lack of safe water is a serious challenge in the community, Agency for Cooperation and Research in Development (ACORD) started a project to build tanks for harvesting rain water. The alternative sources of water were streams, swamps and communal wells. Whereas the tanks lessened the challenge of lack of water for household use, it did not end the unhealthy culture of drinking un-boiled water. People were still taking un-boiled water drawn from the tanks as they did with water from streams and wells. According to the residents, this was due to lack of firewood to boil the water. As a result, children would suffer diarrhea.

“It is not that we did not know the dangers of drinking un-boiled water but the challenge is lack of firewood, getting firewood in this area is a big hassle,” says Ms Komuhangi.

Blessings from the sun
ACORD had to find a way to sanitise the water without one going through the trouble of boiling it. That is how WADI (Water Disinfectant) devise came to be in the community in September 2015. A creation of Austrian company, Helioz, WADI is an Ultraviolet (UV) light measurement devise. The equipment is the size and shape of small pocket radio or tape voice recorder. The UV-radiation of the sun inactivates harmful pathogens in the water. Over time, the sun’s UV-radiation will make the contaminated water safe to drink. To disinfect water, it (water) is put in PET (Polyethylene Telephala) bottle-the common colourless plastics used to package processed water. The water in the transparent container is then placed on a rack or table and exposed to sunlight. WADI devise is then placed besides the bottles (they can be as many as 20 or more). Precisely, WADI devise helps to tell whether the target water has been disinfected of bacteria by sunlight.

The devise has a small screen showing the power bars that keep building (like a phone battery charging). Once four bars have built (one on top of another), it means that water in the bottles on the rack has been fully disinfected of bacteria by sunlight. The devise users also keep observing the small in-built cartoon on the screen. They have nicknamed it Kakyebezi (checker). Once it has a smilie, then it means the water has been disinfected and is ready for drinking. It takes between three to six hours for water to get disinfected.

“For the four months I have been using WADI devise, my children no longer suffer from cough and flue. I make sure I treat at least seven litres of water every day for the whole family. The children take some to drink at school,” says Komuhangi. She was trained by ACORD on how to use and keep it. Byamugisha says, “Children now have time to read. They had been spending a lot of time looking for firewood to boil water. Besides, this water tastes good unlike the one we boil which has a bad odor.” “I treat five litres of water daily for us to drink, and the children take some of the water to school. The neighbours who don’t have WADI bring their water here for disinfecting. Lack of firewood is a big problem here, it has been difficult for us to boil water, we have been taking it the way you get it from the tank,” says Adrine Nuwagaba, a resident.

Dunstan Ddamulira, programme manager, ACORD Uganda says they piloted the use of UV light to treat water in Kisoro District. They however used bottles to expose water to light for many hours but without a mechanism of ascertaining whether it has been disinfected or not.

How the device works
WADI devise costs Ugandan Shs 52,000. It is however not on the local market; it can only be imported from Austria. It uses solar and therefore does not need any other power source. The device is light weight and resistant to water. It has a guarantee of two years and is environmentally friendly. The water to be treated should be clear and without chemical contamination like lead and manganese. UV kills only biological contamination such as bacteria, virus and protozoa.

“We have been providing safe water through building rain water harvesting tanks; but even with that water, it has to be treated further. That means boiling. Some who cannot cook it drink it the way it is, yet it has pathogens which cause diseases,” says Mr Ddamulira. UV disinfects water from boreholes and springs (but only those in villages), gravity flow scheme and rainwater collected in a tank or container. This is because this water is largely free of chemical contamination. The disinfected water has be kept in clean containers and taken within two days.

Spreading the good news
“This is the same technology being used by those bottling water (for sale). They use UV light emitters, it is just bringing a simpler technology to (local) people,” says Ddamulira. About 500 homesteads are using UV-WADI device innovation. Three hundred are in Mbarara in the sub- counties of Biharwe, Bukiro, Mwizi, Kashare, Bubare, Rwanyamhembe and Rubaya. The other 200 are in Rwamwanja Refugee Settlement Camp in Kamwengye District. “Apart from saving people from disease, there other benefits you don’t see. WADI has created sort of peace in homes, and it saves time. Children are no longer harassed to go and look for firewood; wife and husband would at times be quarreling and fighting over boiling water,” says Ddamulira.

ACORD will be starting a two year phase of the innovation targeting to reach 74 schools and 500 households in the same areas starting this month. “In most schools it is difficult to boil water for the pupils, most can’t afford, they evade that cost,” he says. ACORD plans to popularise the innovation and involve businessmen in importing devices into the country so that they are easily accessed by individuals and institutions that want them. They also plan to buy transparent bottles for each beneficiary household to use in disinfecting water for drinking.

Story originally appeared in the The Daily Monitor, Uganda on Impact Journalism Day 25 June 2016



  • health
  • uganda
  • water