By Kelly A. Reynolds, MSPH, PhD
Safe drinking water is a basic human need and yet, a substantial portion of the world’s population still lacks access to clean drinking water. The POU industry has made it possible to provide safe water to both crowded and remote communities using cost-effective, sustainable approaches.
Populations most at risk
Since 1990, 2.6 billion people gained access to improved drinking water sources, for a total 6.6 billion of the world’s population. This equates to 91 percent of the globe—an increase from 76 percent over the last 25 years.(1) According to the World Health Organization (WHO), child mortality rates for the under-five age group dropped in half from 2,000 deaths per day 15 years ago to 1,000 deaths per day in 2015. This improvement in childhood mortality is attributed to reduction of waterborne diarrheal diseases via improved water, sanitation and hygiene—the known causes of 88 percent of all diarrhea cases.(2) (Frequent episodes of diarrhea can lead to other health complications, such as malnutrition, enteric dysfunction and stunting.(3)
While considered a major public health achievement, this gain in access to improved water sources does not eliminate the risk of exposure to waterborne contaminants. WHO defines ‘improved water sources’ as those protected from contamination (especially fecal contamination) but the sources may vary dramatically, including piped systems or community delivery points, cisterns for rainwater collection, protected natural springs or underground wells. Each of these sources are vulnerable to contamination during delivery, storage or at other points prior to consumption.
Marginalized communities
An estimated 663 million people are still without access to improved drinking water sources.(1) Countries with the least amount of improved drinking-water source access are Angola, Equatorial Guinea and Papua New Guinea, where more than 50 percent of the population lacks access. Sub-Saharan Africa and Southeast Asia host the largest under-served population. Disparities are most evident in rural populations, where eight out of 10 people with substandard water sources live.
Improving water sources in rural areas is challenging, given lack of centralized collection, treatment and distribution networks, and implausible costs associated with infrastructure development. Even in areas that reported improvement in water service, sustainability of water supply systems is often questionable. Increased demand from population growth and decreased supply from poor maintenance of some physical infrastructure systems contributes to failed service.(4) Regions where capital investment costs were initially invested may suffer from a lack of funds for operations, maintenance and routine improvements.
Consistency of water supply is also a widespread and evolving problem. Two-thirds of the global population (four billion people) experience severe water scarcity at least one month of the year.(5) Up to 2.9 billion people live in conditions of severe water scarcity at least four to six months per year. Water supply shortages dramatically affect water quality and public health and development. The UN predicts that by 2050, global population growth will increase to 9.1 billion people, along with a 55-percent increase in water demand.
POU devices save lives
POU water treatment devices have been shown to dramatically reduce adverse health effects in developed and less developed countries. Research has shown a 45-percent reduction in diarrhea morbidity with the use of filters and safe storage practices in communities with unimproved water sources.(6) Even when improved water sources were available, POU filter interventions reduced diarrhea morbidity by 35 percent, indicating that even improved water sources are frequently contaminated with waterborne pathogens. Thus, use of POU devices provides greater health benefits than what can be achieved at the source with improved water and sanitation practices. POU devices are especially essential for persons with reduced immunity, such as HIV/AIDS patients, where infectious diarrhea can result in fatal outcomes. Globally, there are more than 35 million people living with HIV. For this population, POU interventions have been found to reduce diarrhea illness by 43 percent.(7)
Sustainable POU technologies
Low cost, low energy use POU device design is preferred in the developing world. Studies have found that chlorination and solar treatment of drinking water are minimally effective compared to filtration options. Gravity filtration offers a method for on-site treatment of drinking water supplies and is widely accepted in low-resource regions. Ceramic and slow sand filters are popular choices in such regions.
Researchers from the University of North Carolina evaluated a range of POU interventions for purification efficacy and sustainability.(8) Technologies that exhibit sustained performance capabilities and have been documented to effectively remove microbes and reduce diarrheal disease were critically reviewed, including: chlorination with safe storage; combined coagulant with chlorine disinfection (i.e., dry coagulant-flocculant agents with chlorine tablets or sachets); SODIS (solar disinfection using natural UV light and heat-penetrating transparent polyethylene terephthalate bottles); ceramic filters and biosand filters.
In order for a POU technology to be sustainable in the developing world, it must produce appropriate levels of water at high quality, be easy to use, have a low cost and be readily available for purchase and use. In the UNC study, biosand filtration was found to have the highest sustainability rating, followed by ceramic filtration, chlorine disinfection, SODIS and coagulation/chlorination, in decreasing order. In a meta-analysis of current literature, ceramic and biosand filtration had the highest estimated diarrheal-disease reduction in users, with averages of 63 percent and 47 percent, respectively.(8) Both methods had high user compliance values at over 85 percent.
POU devices must also be effective over a wide range of source-water quality. Conditions of periodic or routine levels of high turbidity or organic matter challenge many POU technologies. Use of biosand or ceramic filtration again perform well against these criteria, as they can be effective across a broad range of source-water quality conditions. Biosand filtration has the added benefit of low cost for the initial investment and low maintenance needs over time.(9)
Innovative designs
POU treatment in the developing world commonly utilizes simple, low-cost technologies. There is still room, however, for innovation and improvement for POU development and application. Global Citizen highlights new innovations for POU water treatment, including the ceramic water purifier that reduced diarrhea in Cambodia by 50 percent since it was introduced in 2001.(10) Also featured is the Eliodomestico, which uses the disinfecting power of the sun to steam and purify five liters (1.32 gallons) of drinking water during the day. Then there is the Solarball, designed by a graduate student from Monash University, that also harnesses the sun’s heat to condense three liters (0.79 gallons) of purified water per day. Similarly, the Life Sack is first used to ship grains and re-purposed as a solar water treatment device. It can even be used as a backpack.
Building on the success of the UN’s Millennium Development Goals, evaluating 25 years of improved drinking-water resources in 2015, the UN recently released the 2016 Sustainable Development Goals. The POU industry will play a major role in reaching the 2030 goals of access to safe and affordable drinking water for all, especially in light of predicted climate, population and supply challenges.
References
(1) WHO/UNICEF. Progress on Sanitation and Drinking Water: 2015 Update and MDG Assessment. Water Sanitation Hygiene (2015). at www.who.int/about/licensing/copyright_form/en/index.html
(2) Centers for Disease Control and Prevention. CDC–Global Sanitation and Hygiene Related Diseases and Contaminants–Global Water, Sanitation and Hygiene–Healthy Water.
(3) Prüss-Ustün, A., Wolf, J., Corvalán, C., Bos, R. and Neira, M. Preventing disease through healthy environments. A Global Assessment of the Burden of Disease from Environmental Risks 176 (2016). at http://apps.who.int/iris/bitstream/10665/204585/1/9789241565196_eng.pdf?ua=1
(4) Lockwood, H. and Smits, S. Supporting Rural Water Supply (2011). doi:10.1017/CBO9781107415324.004
(5) Mekonnen, M. M. and Hoekstra, A. Y. Four billion people facing severe water scarcity. Sci. Adv. 2 (2016).
(6) Wolf, J. et al. Systematic review: Assessing the impact of drinking water and sanitation on diarrhoeal disease in low- and middle-income settings: systematic review and meta-regression. Trop. Med. Int. Heal. 19, 928–942 (2014).
(7) Peletz, R. et al. Water, sanitation, and hygiene interventions to improve health among people living with HIV/AIDS: a systematic review. AIDS 27, 2593–601 (2013).
(8) Sobsey, M. D., Stauber, C. E., Casanova, L. M., Brown, J. M. and Elliott, M. A. Point of Use Household Drinking Water Filtration: A Practical, Effective Solution for Providing Sustained Access to Safe Drinking Water in the Developing World. Environ. Sci. Technol. 42, 4261–4267 (2008).
(9) Adeyemo, F. E., Kamika, I. and Momba, M. N. B. Comparing the effectiveness of five low-cost home water treatment devices for Cryptosporidium, Giardia and somatic coliphages removal from water sources. Desalin. Water Treat. 56, 2351–2367 (2015).
10. Bencik, F. 5 innovative ways people in the developing world purify their water! Global Citizen (2015). at https://www.globalcitizen.org/en/content/5-innovative-ways-people-in-the-developing-world-p/
About the author
Dr. Kelly A. Reynolds is an Associate Professor at the University of Arizona College of Public Health. She holds a Master of Science Degree in public health (MSPH) from the University of South Florida and a doctorate in microbiology from the University of Arizona. Reynolds is WC&P’s Public Health Editor and a former member of the Technical Review Committee. She can be reached via email at reynolds@u.arizona.edu