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Drinking Water Sources and Storage. ENVR 890-2 Mark D. Sobsey Spring, 2009. WHO Risk-based Framework. Water Sources and Water Treatment. Drinking water should be essentially free of disease-causing microbes, but often this is not the case.

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Drinking Water Sources and Storage

ENVR 890-2

Mark D. Sobsey

Spring, 2009



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Water Sources and Water Treatment

  • Drinking water should be essentially free of disease-causing microbes, but often this is not the case.

    • A large proportion of the world’s population drinks microbially contaminated water, especially in developing countries

  • Using the best possible source of water for potable water supply and protecting it from microbial and chemical contamination is the goal

    • In many places an adequate supply of pristine water or water that can be protected from contamination is not available

  • The burden of providing microbially safe drinking water supplies from contaminated natural waters rests upon water treatment processes

    • The efficiency of removal or inactivation of enteric microbes and other pathogenic microbes in specific water treatment processes has been determined for some microbes but not others.

    • The ability of water treatment processes and systems to reduce waterborne disease has been determined in epidemiological studies


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Source Water Protection: Water Resources Management

  • Integral to the preventive management of drinking-water quality.

  • Preventing microbial and chemical contamination of source water is the first barrier against drinking-water contamination of public health concern.

  • Water resource management and potentially polluting human activity in catchments and aquifers influence water quality.

  • This impacts treatment steps required to ensure safe water

  • Preventive action may be preferable to upgrading treatment.


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Influence of Land Use on Water Quality

  • Assess land use influence on water quality

  • Not normally undertaken by health authorities or drinking-water supply agencies alone

  • Establish close collaboration between public health authority, water supplier and resource management agency

    • may include other sectors, .e.g., agriculture, traffic, tourism or urban development.

  • National authorities must interact with other sectors to formulate national policy for integrated water resource management

  • Set up regional and local structures to implement policy

    • National authorities need to guide regional and local authorities by providing tools


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Land Uses to Consider that Influence Water Quality

  • land cover modification

  • extraction activities

  • construction/modification of waterways

  • application of fertilizers, herbicides, pesticides and other chemicals

  • livestock density and application of manure

  • road construction, maintenance and use

  • various forms of recreation

  • urban or rural residential development

    • Pay particular attention to excreta disposal, sanitation, landfill and waste disposal

  • other potentially polluting human activities, such as industry, military sites,


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Drinking Water Sources

  • Ground Water

  • Surface water

  • Rainwater

  • Condensed water from the atmosphere

  • Reclaimed wastewater

  • Other?


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Groundwater

  • Water table or surficial aquifer

    • First water encountered through the soil or subsurface

    • Often subject to contamination from the land surface

  • Confined aquifer

    • Water found below a confining subsurface later of clay, rock or other impervious material

    • Often protected from contamination lan surface

  • Both may contain geological chemical contaminants

    • Arsenic and fluoride are probably of most health risk

  • Confined aquifer water is often better protected from surface contamination


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Surface Waters

  • Lakes, ponds and other and “confined” bodies of water

  • Rivers, streams, creeks and other flowing bodies of water

  • All are subject to direct contamination from wastewater and excreta discharges

  • All are subject to contamination from land runoff

  • Surface water should be assumed to be contaminated unless proven otherwise by direct and indirect evidence from observations and analysis


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Rainwater

  • Rainwater as it falls from the sky is essentially free of pathogens and toxic chemicals

  • Airborne contaminants can cause low level contamination with microbes and chemicals

  • Rainwater is collected primarily on roofs or other impervious collectors

    • Contamination from roof/impervious surface chemicals and microbes is possible

  • Rainwater is often stored in barrels, cisterns and other surface and sub-surface collectors or impoundments

    • Contamination is very likely unless special precautions are taken to protect the collected water from fecal and other sources of contamination


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Condensed water from the atmosphere

  • Atmospheric water as clouds, fod and airborne mist can be harvested at it impacts impervious surfaces.

  • Solar Stills

    • Water evaporated from standing water also can be condensed and harvested

    • Solar condensers collect evaporated water

    • Solar energy can supply heat


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Reclaimed Water

  • Water can be purified from sewage and other wastewater

  • Reuse for non-potable purposes in encouraged

  • Reuse for potable purposes is discouraged

    • Indirect reuse is considered feasible and of less risk by recharging aquifers or reservoirs and allowing addition die-off and further treatment

  • WHO and countries have regulations for non-potable and potable reuse


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Water Treatment Processes: Storage

Reservoirs, aquifers & other systems:

  • store water

  • protect it from contamination

  • Factors influencing microbe reductions (site-specific)

    • detention time

    • temperature

    • microbial activity

    • water quality: particulates, dissolved solids, salinity

    • sunlight

    • sedimentation

    • land use

    • precipitation

    • runoff or infiltration


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    Larger Scale Water Storage

    • Reservoir impoundments and other water storage diversions

    • Tanks and other fabricated vessels

      • Above and below ground cisterns, reservoirs and tanks


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    Household Water Containers for Safe Storage:

    • Material: Depends on Rx; easy to clean; lightweight, durable, impact- and oxidation- resistant, heat-resistant (if thermal Rx)

      • High-density polyethylene (HDPE)

        for chemical Rx

      • Transparent beverage bottles

        for solar-UV + heat (PET)

      • Black or opaque for solar-heat only

    • Can adapt traditional vessels to safer storage

      • Add cover

      • Add spout or spigot


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    Characteristics of Preferred HH Water Storage Vessels

    • Appropriate material, size, shape, dimensions,

      • Depends on collection, Rx method, use conditions & user

    • Volume: usually 10 and 30 liters (not too heavy)

      • smaller volumes (1-1.5 L) for solar Rx; multiples

    • Handles to facilitate lifting and carrying

    • Stable base to prevent overturning

    • Uniform size for standard chemical dosing

    • Opening: large enough to fill and clean; small enough to discourage hands, cups or other dip utensils.

      • Inlet: fitted with a lid

    • Durable spigot or spout for pouring


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    Household Water Containers for Safe Storage

    Plastic vessels are commonly used – many have safe features

    Traditional vessels, such as pots, urns and bowls can be made safe by covering and providing a dispenser (spigot or spout)


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    Household Water Storage: Disease Risks and Containers for Improved Protection

    • Inadequate storage results in microbial contamination and waterborne disease

    • Improved storage vessels reduce microbial contamination and disease risks

    • Improved storage can be coupled with household treatment to further improve microbial quality and reduce disease risks

    • Best implemented and sustained if supported with behavior modification, education, motivation and social marketing


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    Increased Microbial Contamination (Decreased Microbial Quality) and Infectious Disease Risks from Inadequately Stored Household Water


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    Increased Microbial Contamination (Decreased Microbial Quality) and Infectious Disease Risks from Inadequately Stored Household Water


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    Reservoir Water Storage and Microbial Reductions Quality) and Infectious Disease Risks from Inadequately Stored Household Water

    • Microbe levels reduced over time by natural antimicrobial processes and microbial death/die-off

    • Human enteric viruses in surface water reduced 400-1,000-fold when stored 6‑7 months (The Netherlands)

      • Indicator bacteria reductions were less extensive, probably due to recontamination by waterfowl.

    • Protozoan cyst reductions (log10) by storage were 1.6 for Cryptosporidium and 1.9 for Giardia after about 5 months (The Netherlands; G.J Medema, Ph.D. diss.)

      • Recent US EPA ICR data indicates lower protozoan levels in reservoir or lake sources than in river sources; suggests declines in Giardia & Cryptosporidium by storage


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