Global Issues in Water, Sanitation, and Health Workshop Summary (2009) / Chapter Skim
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4 Addressing Risk for Waterborne Disease
4 Addressing Risk for Waterborne Disease
Pages 200-276
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From page 200... ...
In the developing world, the profound disease burden attributed to diarrhea makes it the most important target for waterborne disease prevention, according to workshop speaker Thomas Clasen of the London School of Hygiene and T ropical Medicine. Following a systematic review of interventions to improve water quality for preventing diarrheal disease (Clasen et al., 2007a)
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From page 201... ...
However, despite these achievements, the mission of the Network to "achieve a significant reduction of waterborne disease, especially among children and the poor" is far from realization. Presently, only a tiny fraction of the millions of people who could benefit from household water treatment and safe storage (HWTS)
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From page 202... ...
These include • the widely held belief that diarrhea������������������ is not a disease; • skepticism about the effectiveness of water quality interventions; • technology shortcomings with the available interventions; • need for correct, consistent, sustained use (as compared with one-time interventions, such as vaccines) ; • the existence of several transmission pathways for waterborne disease; • suspicion on the part of the public health sector regarding the commercial �������������������������������� agenda and lack of standards governing HWTS products; • the orphan status of HWTS within governmental ministries; and • the lack of focused international commitment and funding for diarrheal diseases.
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From page 203... ...
"If safe water and appropriate sanitation are to become accessible to those who are not currently served, new approaches and modern technologies must be employed. This will require a significant change in the way water and wastewater treatment systems are conceived and how they interact with other infrastructures systems (i.e., energy)
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From page 204... ...
Improvements in water and sanitation services are significant only if they lead to change at the household level, they contend; therefore, household access to these services must be monitored and evaluated. Ultimately, the threat of waterborne disease must be addressed through investment in safe water and sanitation interventions.
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From page 205... ...
. Drinking Water Disinfectants Several different types of disinfectants are used to treat drinking water: • free chlorine (HOCl/OCl–)
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. Hypochlorous acid is a more potent disinfec CT = product of free chlorine residual (C)
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From page 207... ...
In a municipal water treatment facility, chlorine is usually applied to the raw water at the head of the treatment plant or after sedimentation or filtration, and the residual is measured at the point of entry to the distribution system. The difference between the dose and the residual is the chlorine demand and is due to consumption of chlorine by reduced organic and inorganic substances in the water.
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From page 208... ...
Iron, manganese, and sulfide typically derive from natural sources, whereas ammonia is often associated with municipal and agricultural discharges. Drinking water sources contaminated by sewage contain not only fecal bacteria and potentially pathogenic microorganisms but also organic material and ammonia, both of which exert substantial chlorine demands.
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From page 209... ...
Raw drinking waters generally contain a combination of chlorine-demanding impurities. A poor-quality surface water, for example, might contain 0.5 mg/L of ammonia and 6 mg/L of dissolved organic carbon, giving a total chlorine demand of 11-14 mg/L (5 mg/L to oxidize the ammonia in accordance with the breakpoint curve in Figure 4-2 and 6 to 9 mg/L for the 6 mg/L of dissolved organic carbon)
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From page 210... ...
210 FIGURE 4-2 Breakpoint chlorination curve when chlorine is added to an ammonia-containing water. SOURCE: Reprinted from Water Chlorination/Chloramination Practices and Principles (M20)
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From page 211... ...
Thus, measurements of free chlorine residual are subject to some uncertainty and must be interpreted carefully depending on water quality conditions. Turbidity and Particle Content The effectiveness of disinfection is impacted by the presence of particulate material in the water.
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From page 212... ...
Resistivity-based methods, which measure the volume displacement of water by particles of different sizes in a salt solution, provide information on the size distribution of particles according to their volume-equivalent particle diameter. Image analyzers are recent additions to particle characterization techniques in water quality analysis.
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, engineered filtration (e.g., granular media filtration in a water treatment plant) , or household filtration (e.g., filtration in a biosand or ceramic pot filter, both of which are being widely promoted for use in rural villages in developing countries)
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Of the world's 6.5 billion-plus inhabitants, an estimated 1.2 billion people lack access to safe drinking water and 2.6 billion, or 42 percent of the world's population, lack access to basic sanitation (World Water Assessment Programme, 2006)
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From page 215... ...
Correspondingly, it is necessary to understand the flow, storage, and treatment of water through engineered systems used for the collection, treatment, and distribution of potable water and wastewater. For the purposes of clarity and consistency, the process of water movement and storage on Earth without human intervention is referred to as the "natural hydrologic cycle." Water movement through infrastructure systems for the delivery of clean drinking water to the public is referred to as the "engineered hydrologic cycle."
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From page 216... ...
and as a liquid. The inflow, or precipitation that falls on land, is the predominant source of water required for human consumption, agriculture and food production, industrial waste disposal processes, heat dissipation in energy production, and for support of natural and seminatural ecosystems (World Water Assessment Programme, 2003)
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From page 217... ...
. In conjunction with creating water supplies, the development of resource protection programs ensures water quality.
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From page 218... ...
. Water and Wastewater Treatment To ensure clean water supplies in the developed world, engineers have created treatment systems to provide safe drinking water from both surface water and groundwater sources, and to return the resulting wastewater to surface waters (on rare occasions water is returned to aquifers)
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From page 219... ...
Practices implemented in one part of a watershed have the capacity to impact its potential use as a water source. Consequently, the conventional engineered solution for drinking water and wastewater treatment, as seen in the developed world, imparts its own engineered hydrologic cycle in concert with the natural water cycle, providing integrated resource protection to reduce vulnerability and maintain the quality of water sources.
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with permission, www.abb.com/water. FIGURE 4-6 Detailed diagram of conventional water and wastewater treatment systems.
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Wastewater Treatment Level† Preliminary Removal of wastewater constituents such as rags, sticks, floatables, grit, and grease that may cause maintenance or operational problems with the treatment operations, processes, and ancillary systems. Primary Removal of a portion of the suspended solids and organic matter from the wastewater.
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From page 222... ...
Water quality regulations in the United States and other developed countries require that water be properly managed to improve human health and minimize environmental degradation. In the United States, the number of water quality parameters evaluated on a routine basis at water treatment and wastewater treatment plants is considerable.
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From page 223... ...
, urea; Color: metals, NOM, algae; Turbidity: solids and algae; Staining: Metals Algae Wastewater plant discharges, septic Taste and odor; filter clogging; some systems, landfill leachate, urban and algae species toxic to aquatic life. agricultural runoff, precipitation Dissolved Organic matter, wastewater Water treatment problems; release of oxygen discharges, runoff, consumption by iron and manganese; taste and odor aerobic aquatic life and chemical problems; ammonia.
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• Chemical Use. Water and wastewater treatment require large quantities of chemicals to treat water efficiently and to remove elements that may inhibit water quality.
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Specific examples of barriers that effectively prohibit the reliable and effective use of conventional water and wastewater infrastructure systems are illustrated below. Water supply stress Worldwide water supplies and the quality of freshwater are being impacted by climate change, demographic shifts, and population growth, creating regions experiencing water stress.
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From page 226... ...
Poor sanitation The effect of poor or nonexistent sanitation on water resources can overwhelm the ability of conventional water treatment systems to provide safe water. Without regulations, surface and groundwater systems are subject to contamination with fecal matter, rendering them unfit for use as a drinking water source without advanced treatment systems.
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From page 227... ...
The adoption of a traditional water infrastructure system by many institutions has reached a plateau as environmental and social concerns have increased. Population growth and changing demographics have limited unbridled expansion opportunities that existed in the nineteenth and twentieth centuries.
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From page 228... ...
These systems focus on point-ofuse or point-of-entry drinking water treatment and storage. Chlorination and fl occulation/chlorination methods are scalable at the village and national level; scalability issues exist for biosand, ceramic, solar disinfection, and filtration/ chlorination options.
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From page 229... ...
By comparison, TABLE 4-5 Paradigm Shifts Addressing Water and Sanitation Infrastructure Old Paradigm New Paradigm Slow implementation Rapid implementation Prescriptive technologies Adaptive solutions Low social acceptance criteria High social acceptance criteria One water quality type fits all Provision of water quality based on use Low priority on energy efficiency High priority for energy efficiency "Siloed" health, economic, engineering Integrated systems approach Financing via taxes, subsidies, tariffs Innovative financing and business models Centralized energy provider Distributed energy systems Less priority on resource conservation High priority on resource conservation
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From page 230... ...
On the other hand, energy production uses and impacts domestic water supplies. As stated previously, cooling water represents nearly half of the volumetric water use in the United States annually.
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From page 231... ...
As markets increase, the cost of onsite power generation will decrease due to economies of scale and it should be possible to infuse developing countries with power generation without the 10 to 20 years of construction of conventional stationary power systems. With the advent of distributed energy comes the potential for distributed water and wastewater treatment, using technologies or approaches that differ significantly from conventional water and wastewater systems.
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From page 232... ...
Bringing these opportunities to fruition requires strong collaboration between the engineering, financial, and health sectors to ensure community acceptance and economic sustainability. New Water and Sanitation Technologies As was discussed previously, most research in the United States and elsewhere has focused on improving conventional infrastructure.
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From page 233... ...
The development of low power lamps that produce UV in a spectrum similar to a mercury vapor lamp would be ideal for use in the developing world to disinfect water, again coupled with a distributed energy source. Microbial Fuel Cells One promising technology for the treatment of human and animal wastes is microbial fuel cells (MFCs)
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. Multidisciplinary innovations such as these provide a foundation for better decision making on global issues of water quality, water resources, and sanitation.
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London School of Hygiene and Tropical Medicine Pete Kolsky, Ph.D. The World Bank Caroline Hunt, Ph.D.
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The water cycle within the urban area, as illustrated in Figure 4-7, occurs at each spatial scale of the city; for a given neighbourhood, the rest of the city is seen as the broader environment. These different subdivisions, or boundaries, often create institutional issues which in turn have an impact upon service quality and health; these are explored in the fourth section of the chapter.
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From page 237... ...
Water quality only affects faecal-oral diseases, whereas quantity affects both faecal-oral and water washed diseases. The relative importance of water quantity and its quality will be discussed later in this chapter.
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Approximately 90 per cent of diarrhoeal disease cases are estimated to be attributable to environmental factors (Murray and Lopez, 1996)
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From page 239... ...
The F-diagram also shows that while water quality only affects one route, the quantity of water available for personal and domestic hygiene affects almost all routes. Following the discovery in the 19th century of the undeniable role that water quality played in the epidemics of cholera and typhoid, there was a natural focus on the improvement of drinking water quality.
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From page 240... ...
. There is also increasing evidence that improving water quality at the point of use has a positive health impact (Conroy et al, 2001; Iijima et al, 2001; Fewtrell et al, 2005; Clasen, 2006)
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From page 241... ...
Only when drinking water is the main source of infection will water quality be more important than quantity. This is rarely the case where diarrhoea is endemic.
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From page 242... ...
. Targets For the Future The UN Millennium Summit adopted the target of halving the proportion of people who are unable to reach, or to afford safe drinking water by the year 2015.
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org/files/NER_wat.pdf. improved access, which is probably a reflection of the interest of the water utility in keeping track of its customers and the ease of defining this way of delivering water to households.
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In 1977, the UN Water Conference at Mar del Plata set up an ‘International Drinking Water Supply and Sanitation Decade' for 1981–1990. Its aim was to make access to clean drinking water available across the world.
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Even attempts under the supervision of eminent specialists to measure the health impacts of water supplies and sanitation have produced almost useless or meaningless results (Cairncross, 1999)
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From page 246... ...
However, increasing access to water and sanitation is clearly recognized as leading to health benefits, and new international targets have been set for that reason. Although improved access might improve health, it is methodologically extremely difficult to attribute improvements in health exclusively to specific interventions, on a project-by-project basis.
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From page 247... ...
Improving the quality of river water by controlling the quality of the wastewater discharge may be of ecological benefit, but it makes no difference to a household's health unless that improvement is translated into improved drinking water quality at the household scale. The public health priority for environmental improvement thus becomes the household, followed by its immediate neighbourhood.
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Source: Kolsky (2006) unpublished lecture notes, London School of Hygiene and Tropical Medicine.
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unpublished lecture notes, London School of Hygiene and Tropical Medicine.
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From page 250... ...
unpublished lecture notes, London School of Hygiene and Tropical Medicine. Unfortunately, the poor live in the outermost ‘marginal' rings.
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From page 251... ...
This situation is known to economists as an ‘externality', and in this case, explains why wastewater treatment always lags behind drinking water as a community priority. Drinking water affects the members of a community directly, so it is in their interest to take appropriate action to ensure its quality.
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From page 252... ...
For example, at the start of the International Drinking Water Supply and Sanitation Decade, a need was recognized to integrate the services of water supply and ‘sanitation', used here as a euphemism for excreta disposal. This made sense both in conceptual public health terms (as both are involved in the spread of faecal-oral disease)
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From page 253... ...
Many studies have investigated the links between public water supplies and household contamination of stored water (Kirchhoff et al, 1985; Deb et al, 1986; Jonnalagadda and Bhat, 1995; Mintz et al, 1995; Jagals et al, 1997; Quick et al, 1999)
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From page 254... ...
seems to indicate that there are health benefits from improving drinking water quality at the household level. Further research will be required to determine if this is true for households with limited access to water.
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From page 255... ...
Apart from a variety of other possible explanations, it is crucial to bear in mind that domestic drinking water supply and sanitation make up a very small fraction of any nation's demand for water resources. Solutions to Boundary Problems?
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From page 256... ...
Conclusion The problems of the poor, are suffered by the poor, and dealt with by the poor, The problems of the rich, are suffered by the public, and dealt with by the Government. Marianne Kjellen Scale of the Problem At present, an estimated 2.6 billion people lack access to improved sanitation and 1.1 billion people lack access to improved water supply.
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From page 257... ...
Reasonable access to services such as ‘improved' water is a complex idea with many facets, encompassing not just water quality, but also its quantity, cost, operational reliability, seasonal availability and collection time and effort. Measuring access to improved services, although essential, is not straightforward.
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From page 258... ...
Recent epidemiology of disease transmission and hygiene has stressed the need to create conditions in which households can manage the domestic domain more effectively, through increased water use, household sanitation and improved personal hygiene. Regional water stress is sometimes portrayed as the major determinant of households' access to adequate water and sanitation.
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From page 259... ...
Examples are not delineated in depth but were chosen to offer illustrative examples. Clean water and sanitation was selected as the topic area in part because of the enormous toll in death, disability, and human suffering exacted due to poor water quality and sanitation: nearly 10 percent of the global burden of disease could be prevented by improving water, sanitation, and hygiene, and in the 32 worst-affected countries, this figure would be 15 percent (Prüss-Üstün, 2008)
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From page 260... ...
Efforts to provide sustainable energy and clean water in remote villages, to conserve rainforests, to ensure quality education for all, to dismantle landmines, and to teach children living in poverty how to become self-sufficient are just some of the challenges being supported by social entrepreneur organizations. Efforts in the not-for-profit sector are complemented by those in the private sector, which has also taken up the mantle of social entrepreneurship.
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From page 261... ...
Clean Water and Sanitation -- Consideration of Two Social Entrepreneurial Approaches Boxes 4-2 and 4-3 provide snapshots of two Ashoka Fellows in Indonesia, each of whom approached the clean water challenge differently. Both cases represent operational strategies related to collection and use of water data or to provision and marketing of sanitation services. In one case, river water was collected and analyzed from multiple locations across the span of several years to show the burden of pollution to nearby inhabitants.
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From page 262... ...
. The citizen base, including children and adults, conduct water quality monitoring and testing.
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From page 263... ...
Such outreach paved the way for policy maker involvement, leading directly to new laws requiring the monitoring of the river's water quality. Finally, both cases point to the benefits of systems thinking.
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From page 264... ...
Dr. Joseph Graziano and his colleagues provided critical insights into the health impacts of arsenic, including the molecular mechanisms underlying disease.
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From page 265... ...
Dr. Colwell and her team devised and tested a simple intervention to filter out particles larger than 20 microns, including copepods, from drinking water.
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From page 266... ...
With accomplishments in lead toxicology already, Dr. Graziano turned attention to the issue of arsenic and manganese in drinking water.
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From page 267... ...
First, how community members were included in the work had an impact on the overall outcomes. The social entrepreneurship model embraces community perspectives as true experts, thereby ensuring that voices heard from the earliest of stages are those from ultimate beneficiaries, and that the work witnesses and subsequently accounts for the incentives faced by those whose social behavior it seeks to change.
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From page 268... ...
Looking at the two models, it could be speculated that some medical researchers would benefit from a granting system that provided longer term support, perhaps on a 10-year cycle, which included a mid-term review timed to moving basic science knowledge into practice. Such an approach could capture the best elements of both systems.
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From page 269... ...
2007b. Cost-effectiveness of water quality interventions for preventing diarrhoeal disease in developing countries.
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From page 270... ...
1999. Water quality and treatment: a handbook of community public water supplies, 5th ed.
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From page 271... ...
2006. Household water treatment andsafe storage options in developing countries: a review of current implementation practices.
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From page 272... ...
(2006) ‘Household water treatment for the prevention of diarrhoeal disease.
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(2001) ‘A randomized, blinded, controlled trial investigating the gastrointestinal health effects of drinking water quality', Envi ronmental Health Perspectives, vol 109, no 8, pp773–778 Hinrichsen, D., Robey, B
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From page 274... ...
who.int/water_sanitation_health/waterforlife.pdf WHO/UNICEF (2006) Meeting the MDG Drinking Water and Sanitation Target: The Urban and Rural Challenge of the Decade, www.childinfo.org/areas/water/pdfs/ jmp06final.pdf World Bank (1976)
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From page 275... ...
2004. How to change the world: social entrepreneurship and the power of new ideas.
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