TECHNOLOGY: Filter Used in South Touted amid Canada’s Water Woes

By Stephen Leahy Reprint | | Print |

Stephen Leahy

BROOKLIN, Canada, Mar 13 2002 (IPS) - A water filter used in more than 50 developing countries could have saved Canadian lives and might still hold the key to preventing outbreaks of water-borne disease, says the inventor of the device.

The safety of Canada’s drinking water was thrown into doubt two years ago, when bacteria in the water supply of the town of Walkerton killed seven people and sickened thousands more.

“There’s tremendous interest in the filter here,” says inventor David Manz, a former civil engineering professor at the University of Calgary. He operates Davnor Water Systems, a company that is commercialising his BioSand Water Filter in North America.

Tens of thousands of his portable filters are in use in the South. Most recently, 26 filters were installed in houses in Chegutu, Zimbabwe. Manz, who gives away his water filter technology for humanitarian purposes, taught students at Chegutu’s Mumpfure Self-Help College late last year how to make the concrete filters themselves from local materials.

“We teach basic water treatment methods and everything else needed to make, install and maintain the filters. It’s a complete transfer of technology,” he says.

He returned to Chegutu last month to check on training and solve any problems but everything was going well. The households with the filters no longer had anyone with diarrhoea, a chronic problem in many parts of Zimbabwe and a tremendous drain on its health clinics.

“They’re going to keep making the filters and take them through the whole country,” says Manz.

The World Health Organisation (WHO) estimates that dirty water is the cause of 30,000 deaths per day throughout the world.

According to the U.N. agency, slow-sand filtration brings about the greatest improvement in water quality of any single conventional water treatment process. “Bacterial removal will be 98-99.5 percent or more, E. coli will be reduced by a factor of 1,000, and virus removal will be even greater. A slow sand filter is also very efficient in removing parasites,” according to a WHO document, “Guidelines for drinking-water quality”.

All Manz has done is make simple improvements on an age-old use of sand as a filter.

The BioSand filter is a container of sand where water goes through and is collected in a perforated pipe on a gravel bed below. A standing layer of water sits on top of the sand in which a biological layer, or biofilm, develops at the surface of the sand. The biofilm contains micro-organisms such as algae, plankton, protozoa, and bacteria. Together, these organisms comprise an intensely active food chain, trapping and breaking down organic matter, including organisms that cause cholera, typhoid fever, amoebic dysentery and other diseases.

The filter also strains out particles causing cloudiness, iron, manganese, silt, sulphur, and other materials responsible for colour, taste and odour. Its effectiveness improves over time, as the biofilm matures and thickens. Periodically, the top inch of sand is removed and replaced. A household filter cleans between 20 and 60 litres per hour from rivers, streams, lakes, shallow and deep wells, springs, irrigation canals, dugouts, and rainwater. People lacking access to power or chemicals can use it.

Surface and groundwater supplies of Chileans in the Mapuche homelands were contaminated with not only faecal coliforms but also toxicants, many of which were pesticides. Solving the problem was difficult because each home had its own water supply, electricity was often unavailable and there were no local funds. The International Development Research Centre (IDRC) of Canada decided to test the BioSand filters and discovered that the filters removed most of the pesticide contaminants as well as 97 percent of the bacteria.

In Cambodia, the aid group Asian Outreach Cambodia shifted their efforts from digging new wells to making BioSand filters because they were cheaper to install and virtually indestructible. With the filters, unlike wells, there is no seepage contamination and low maintenance.

Manz says he saw the urgent need for low-cost water-filtration technology after working in southern Africa with the Canadian International Development Agency in the late 1980s. He developed the filter at the University of Calgary and convinced the agency to sponsor a pilot project in Nicaragua.

“It turned out to be the only region (in Nicaragua) that was cholera-free for the year,” Manz says. Local users easily managed the filter technology and performed the required laboratory testing, which led to the concept of a complete technology transfer.

In addition to the household units, filter systems that can process 50,000 litres per hour are available and high-capacity systems filtering 200,000 litres per hour and more will be available soon. Larger filters are used in a native reserve in Canada and will be used by the oil company Chevron for communities in Nigeria, says Manz.