POU for the Developing World

Jan. 16, 2015

Filtration system provides disinfection for Ghana communities

About the author: Michael D. Robeson, Ph.D., P.E., is general manager for ProCleanse LLC. Robeson can be reached at [email protected] or 970.682.2116.

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The technologies used for household water treatment in developing countries are vastly different from those used in the U.S. The reason is simple: the lack of a water treatment infrastructure or even indoor plumbing in developing rural communities. In this environment, where there are no faucets or water service pipe, and water fetched from local waterways may be contaminated with human and animal waste, many point-of-use (POU) solutions like carbon filters and reverse osmosis units cannot be utilized effectively.

Various organizations have developed household water treatment and safe storage solutions designed to address these challenges and reduce the 2.2 million deaths caused by waterborne diseases annually. POU options used in these settings range from chlorination and solar disinfection to a variety of free-standing filters that require users to pour raw water into a container for pathogen removal through porous stones and other natural materials.

WHO Specifications

In 2011, for the first time, the World Health Organization (WHO) published target microbiological performance levels for POU systems. These household water treatment specifications provide a benchmark for measuring the relative effectiveness of each technology option. 

The first solution to demonstrate compliance is a barrel-shaped filtration system with built-in storage recently introduced by ProCleanse LLC. Independent laboratory testing validated the filter’s ability to achieve greater than 99.999% reduction in E. coli, greater than 99.9999% reduction in protozoa and greater than 99.9% reduction in viruses, exceeding WHO specifications.

A field study currently being conducted in Ghana is examining the use, acceptance and performance of this filter in 265 households. The conditions in the community and the preliminary outcomes of the study illustrate the challenges of providing clean drinking water to the 900 million people around the globe who currently lack access to it.

These challenges go beyond the efficacy of the technologies used and the need to select the most appropriate treatment method for a community’s specific circumstances. Successful adoptions also require education, behavioral change, donor funding and/or subsidies, and partnerships with organizations such as non-governmental agencies to distribute POU devices in communities where no retail channels exist.

Multiple Choices

One POU solution used in developing countries is chlorination. In the most widely adopted model of this type, diluted sodium hypochlorite is manufactured locally, bottled and added to water by the capful for disinfection. Users agitate the water, then wait 30 minutes before drinking.

Another alternative is solar disinfection. Users fill plastic soda bottles with low-turbidity water, shake them for oxygenation, and place them on a roof or rack for six hours in sunny weather or two days in cloudy conditions. Ultraviolet light from the sun works in conjunction with increased temperature to improve water quality.

In the filter category, one option involves clay-based ceramic filters that remove bacteria through micro-pores in the clay, as well as other materials such as sawdust or wheat flour that are added to improve porosity. One of the best-known designs is a flowerpot-shaped device by the nonprofit organization Potters for Peace, which holds 8 to 10 liters of water and sits inside a 20- to 30-liter plastic or ceramic receptacle that stores the filtered water.

Slow-sand filters, on the other hand, remove pathogens and suspended solids through layers of sand and gravel. The household BioSand filter, sold commercially under the Hydraid brand, consists of a 170-lb concrete container that incorporates layers of large gravel, small gravel and clean medium-grade sand. Prior to use, the filter must be filled with water every day for two to three weeks, until a bioactive layer resembling dirt grows on the surface of the sand. Microorganisms in the bioactive layer consume disease-causing viruses, bacteria and parasites, while the sand traps organic matter and particles.

Ghana Field Study

The ProCleanse filter being tested in Ghana takes a different approach. Utilizing a hybrid ceramic/sand design, it blends porous ceramic particles with silver, zinc and copper, and deploys them in a layered configuration similar to slow-sand filtration. A strainer filters out large debris, and the ceramic/metal layer neutralizes harmful microorganisms through an ion exchange process that produces safe drinking water on the first day of use. The built-in storage chamber holds up to 18 liters of clean water that remain free of contamination, because active ions in the water continue the disinfection process on an ongoing basis.

While the device’s effectiveness in bacteria, protozoa and virus disinfection and compliance with WHO specifications have been validated in laboratory testing, the field study in Ghana is designed to lay the groundwork for large-scale implementation beyond small initial deployments in Latin America. The effort is being led by the IRC International Water and Sanitation Centre of the Hague, Netherlands, in partnership with World Vision, the University of Development Studies, the Global Environment & Technology Foundation, Water Health and other local government bodies. 

The study is taking place in 11 rural communities in northern Ghana with challenging sanitation and hygiene conditions, as well as high rates of illness among children under five, who are the most susceptible to the effects of unclean water. Of the children in the study, 40% suffered from diarrhea, 47% from stomach aches and 60% from fever.

The 265 households in the study live in clay or mud huts in family compounds of up to 30 people. Their drinking water comes from rivers, streams, and tube or pipe connected to nearby wells or other water sources. In most cases, it is consumed without chlorination or other treatment despite open defecation both by residents and their animals within the compounds and near the rivers where they grow their crops. The use of wide-mouth containers for both water transport and storage adds to the contamination risk.

In initial sampling of non-filtered water storage in participating households, 79% of the 265 samples tested positive for E. coli, even in communities where the water source itself contained no E. coli. Maximum levels were 21,000 cfu per 100 mL — 210 times higher than the acceptable WHO ceiling.

In samples taken from 140 households after the ProCleanse filter was put in place, only 10% tested positive for E. coli. Even those samples had dramatically reduced levels, with an average of 12 cfu per 100 mL — only slightly more than the less than 10 cfu per 100 mL considered safe by WHO standards. Researchers speculate that the contamination stems from incorrect placement or improper filter use, such as letting the hose drag in the dirt or be used by animals, suggesting that additional user education can virtually eradicate the problem. Two additional water sampling rounds are nearly complete, with final results expected early this year.

What is already clear from years of efforts by groups ranging from WHO to UNICEF, however, is the vital role that POU solutions can play in making clean drinking water available to populations in need. Multiple studies have proven the effectiveness of POU systems in consistently delivering potable water from heavily contaminated input water. Many already have been deployed through development-based health programs and government initiatives. The low price of emerging POU systems holds promise for higher adoption, along with reduced mortality from unsafe water.

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