ZIMBABWE: Filtering Fact From Fiction About D.I.Y. Water Treatment

By Ignatius Banda Reprint | | Print |

Ignatius Banda

BULAWAYO, Feb 2 2011 (IPS) - The southern Zimbabwean city of Bulawayo has not been spared the heavy rains that have fallen across Southern Africa; the water is welcome in this semi-arid part of the country, but the coming of the rainy season has provoked fresh memories of the 2008 cholera epidemic.

The city’s water and sewage infrastructure is still in poor condition. Though Bulawayo mayor Thaba Moyo insists the frequently brown water from the city’s taps is safe to drink, many Bulawayo residents are falling back on their own resources to protect themselves against waterborne diseases.

Sikhulekile Banda, who lives in Tshabalala, a crowded low-income township, uses makeshift sand filters for both the rainwater she harvests and the brown water she gets sporadically from her kitchen tap.

“This is what we used when we were growing up in the rural areas, way before independence [in 1980],” she says as she filled a bucket with a perforated bottom with sand.

She then pours water into the bucket, where it will slowly drip through the night into another container set below. The previously muddy water emerges sparkling clean, but Banda is not sure whether this is enough to protect her family’s health.

“What I want is clean water, if it looks clean I assume it is not contaminated,” she says.

Where Banda relies on earth, the 49-year-old Zvenyika looks to the sun. She places harvested rainwater and tap water alike in a large metal dish that she leaves out in the scorching sun from sunrise to sunset.

“When the water heats up, I know it is better to use than directly from the roof or tap,” she said.

Necessity is the mother of invention, but do either of these methods offer protection?

Properly constructed sand filters can reduce the risk of waterborne disease, says Eric Fewster, of the NGO BioSand Filter. Fewster’s organisation promotes the use of such filters in developing countries.

“[Bio-sand filters] are great and provide a great intermediary step between people drinking directly from ponds and some better services such as piped supply,” Fewster said.

Sand filters are commonly used as part of the treatment process in bulk-water plants. Bio-sand filters for use at the domestic level filter water far more slowly, reducing the level of potentially harmful pathogens by a combination of the action of various single-celled organisms in the top 40 cm of filter and the physical barrier of the very fine sand.

“There are health impact studies showing reduction of diarrhoea with the use bio-sand filters,” Fewster told IPS.

Research in the Dominican Republic and Kenya found the incidence of diarrhoea due to water-borne disease was reduced by roughly half when properly-constructed bio-sand filters were used.

Comparing Banda’s system to the specifications from Fewster, a very significant difference could be that slow sand filtration is most effectively if there is always water passing through it; this is to allow the formation and maintenance of what’s called a schmutzdecke – German for “dirty layer” – where most of the biological action that cleans the water occurs.

Mavis Chizulu, a senior municipality nurse who works on an anti-diarrhoea drive among children under five says even if mothers have other water-treatment methods like sand filters, they must not neglect to boil the water.

“They must have the water boiling vigorously for between three and five minutes to ensure it is safe to drink,” Chizulu said. But boiling all drinking water can be difficult in a city faced by frequent power outages: it takes a lot of firewood to boil drinking water for a large family.

Up to a billion people across the world are without access to clean water, and home-based treatment methods offer an important, cost-effective way to help fight waterborne ailments. Bulawayo City Council Water engineer Garfield Nyoni believes water purification technologies must be made available at domestic level.

“There is no doubt a need to introduce water purification at household level as residents continue to complain about unclean water, and the rains have only made it worse,” Nyoni said.

“Sand filters could help if people were taught how to build them.”