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Safe Storage and Treatment of Household Drinking Water: Scientific Review of the State-of-the-Art


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Title: Safe Storage and Treatment of Household Drinking Water: Scientific Review of the State-of-the-Art

Safe Storage and Treatment of Household Drinking
Water Scientific Review of the State-of-the-Art
  • Mark D. Sobsey
  • University of North Carolina
  • Chapel Hill, NC 27599 USA

Introduction and Background
  • Water
  • the fundamental nutrient
  • essential to life
  • a public, social and economic good
  • a human right

Water and Sanitation Interventions to Reduce
Waterborne, Water-washed and Water-related
  • Sanitation for feces and other household wastes
  • Hygiene handwashing and related personal and
    household hygiene
  • Food sanitation
  • Childcare sanitation and hygiene
  • Vector control
  • Water sanitation
  • Quantity
  • Quality

Water Sanitation to Reduce Household and
Community Enteric Disease
  • The role of microbiologically safe drinking water
    in reducing household and community enteric
    disease has been underestimated,
    under-appreciated and even ignored in both
    developed and developing countries
  • Health impact (enteric disease reduction) is
  • Developed countries 15-30 (Payment et al.
  • Developing countries 6-90

  • Much of the worlds population lacks access to
    adequate and safe water supplies
  • Waterborne disease and death are a worldwide
    burden in developed and developing countries
  • Microbial agents (pathogens) continue to be a
    major problem in drinking water supplies of
    developed and developing countries

Household Water TreatmentThe Case and Point
  • Large fraction of the worlds population is not
    served by a safe water supply
  • No access to community or household water
    supplies derived from suitable sources
  • No piped (treated) community supplies
  • No proper boreholes/wells or springs
  • Contaminated piped water supplies, urban and
  • Improved supplies often are not microbially
    safe misclassified

Prevailing Water Sources and Conditions of too
Many of the Worlds People
  • Inadequate water sources, conveyances and
    household storage practices
  • Water collection in any available vessel from an
    informal source for household storage/use
  • Water collection in any available vessel from a
    borehole, spring or other ground water source
  • Informal/illegal collections from or taps onto
    piped water supplies or diversions from
    contaminated surface water sources
  • Inadequate storage of initially safe/unsafe water
    that becomes further contaminated ? unsafe

Previous Guidelines on Drinking Water Quality
  • Did not directly address or have relevance to
    conditions of many people in the World
  • Did not directly address or provide relevant
    guidance on improving water sources, treatment
    options, delivery, handling and storage practices
  • Presumed norm or goal was access to or
    development of community water supply
  • derived from a suitable source
  • properly treated
  • properly conveyed by pipes, drawn from a proper
    well or collected in a proper storage system
  • meets WHO or country guidelines for quality

Collected, Stored Household Water Supplies
Correcting Past Misinformation and Interpretations
  • Until now, articulated principles for community
    water supply were not adequately accepted,
    endorsed, applied and promoted for collected,
    stored household water
  • Prevailing notion that improving the microbial
    quality of drinking water will have little/no
    positive impact on health in the absence of
    adequate sanitation and hygiene is a myth
  • This notion is now disproved and rendered
    incorrect by numerous recent studies of drinking
    water microbiology and epidemiology (health

Developments in On-site Storage and Treatment of
Household Drinking Water
  • Appropriate, affordable, effective and socially
    acceptable treatment technologies and storage
    systems of proven effectiveness are now available
  • They can dramatically improve and protect
    microbial quality
  • They can reduce diarrheal and other waterborne
  • Epidemiologically proven by intervention and
    other types of studies
  • Effective even without other hygiene measures,
    such as improved sanitation
  • Such findings are summarized here

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

Increased Microbial Contamination (Decreased
Microbial Quality) and Infectious Disease Risks
from Inadequately Stored Household Water
Increased Microbial Contamination (Decreased
Microbial Quality) and Infectious Disease Risks
from Inadequately Stored Household Water
Characteristics of Preferred Water Storage Vessels
  • Appropriate material, size, shape, dimensions,
  • Depends on collection, Rx method, use conditions
  • 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
  • Inlet fitted with a lid
  • Durable spigot or spout for pouring

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

Household Water Containers for Safe Storage
Household Treatment Barrier(s) against Microbial
Contamination and Waterborne Disease
  • Barriers
  • Collect from a safe source
  • Store in a container with contamination
  • Treat to reduce microbial contamination
  • Physical treatments
  • Chemical treatments
  • Combined physical-chemical treatments

Criteria for Preferred Household Water Treatment
  • Appreciably improves microbial quality
  • Reduces pathogens
  • Reduces waterborne disease risks
  • Simple to learn, teach and use (low technical
  • Accessible or available
  • materials and other requirements
  • Robust and reproducible
  • Affordable
  • Socially and culturally acceptable
  • Sustainable and spreadable

Physical Methods for Household Water Treatment
A in US dollars/yr lt10 for low, gt10-100 for
moderate and gt100 for high. B lt1 log10 (lt90)
low, 1 to 2 log10 (90-99) moderate and gt2
log10 (gt99 high). cDepends on heating method
and availability and fuel costs (range from
low-high). dAvailability of type of lamps,
housings, availability cost of electricity, OM
needs eDifferent ones practicality,
availability, cost and microbial efficacy vary
among them g Possible synergism with other Rx
(solar disinfection with sunlight)
Boiling (Heating) with Fuel
  • Disadvantages
  • Fuel requirement
  • Expensive
  • Ecological impacts
  • Small treatable volumes
  • No residual for protection from recontamination
  • Transfer for storage in another vessel poses
    recontamination risks
  • Advantages
  • Widely practiced
  • Effectively inactivates microbes
  • Easy to use
  • Cultural and social acceptance is widespread

Boiling is not a highly recommended or preferred
treatment, despite its widespread use, except
where renewable fuel is readily available at low
Disinfection by UV Irradiation with Lamps
  • Advantages
  • Simple installation
  • Esp. units with lamps above shallow water layer
  • Microbial efficacy
  • Flexible operation
  • Disadvantages
  • No residual disinfectant
  • Recontamination vulnerability of treated, stored
  • Requires electricity
  • Requires trained MO
  • Process verification issues
  • Relatively costly
  • initial unit cost
  • replacement lamp cost and availability

UV lamp technology is recommended but not highly
for use in household water treatment
Recommended Technologies for Physical Treatment
  • Solar disinfection with UV heat
  • SODIS and SOLAIR (clear bottle black side)
  • Microbial and epidemiological data
  • Solar disinfection with heat
  • black or opaque bottle or pot
  • solar cooker
  • solar reflector
  • Wax temperature indicator
  • Microbial data

Black surface on bottle or on resting surface
clear plastic bottle
  • Advantages
  • Inactivates pathogens
  • Disinfects small quantities of water for
  • Relies on solar energy only
  • Does not directly change chemical quality of
  • Apparent synergistic effects of thermal and UV
    inactivation mechanisms
  • Treatment option for use mainly at household level
  • Limitations
  • Not useful to treat large volumes of water
  • Requires relatively clear water (turbidity lt30
  • Needs solar radiation
  • Exposure times
  • 6 hours under bright sky or up to 50 cloudy sky
  • 2 consecutive days under 100 cloudy sky
  • No disinfectant residual

Epidemiological Evidence for Diarrheal Disease
Reduction by SODIS Solar Disinfection of
Household Water
aTotal diarrheal disease bSevere diarrheal disease
Household or POU Water Treatment by Solar Cooking
or Solar Thermal Effects
  • Heat to gt60oC in black or opaque vessels (e.g.,
    cooking pots)
  • Solar cooker or reflector increases temperature
  • Water and other liquids are pasteurized most
    enteric viruses, bacteria and parasites are
    rapidly inactivated
  • Where now used, it is practical, accessible and
  • Low cost solar reflectors or cookers can be made
    from simple economical materials cardboard and
    aluminum foil.
  • Only small volumes (?10 L) can be exposed
    conveniently at one time per water container and
    solar reflector
  • In many regions of the world, sunlight conditions
    are suitable approximately 200-300 days per

Physical Removal Processes for Household Water
Treatment Applications and Issues
  • Treatment Method
  • Plain Sedimentation
  • Filtration Methods
  • Rapid granular media
  • Slow sand filter
  • Ceramic filter
  • Fabric, paper fiber
  • Membrane filters
  • Microbial reductions
  • low (lt90)
  • 90-99
  • High (gt99)
  • Potentially high
  • Potentially high
  • Depends on microbe pore size
  • High
  • Depends on microbe and pore size

Filtration Technologies for Household Water
Treatment Issues and Special Concerns
  • Some simple, accessible, low cost technologies
  • not efficient for microbial removal rapid
    granular filters
  • efficient only for some microbes
  • paper, membrane or fabric filters for guinea worm
  • a key intervention but not applicable to all
  • Some simple, low-cost technologies may not be
    accessible or are of uncertain efficacy (ceramic
  • Some effective technologies (capable of efficient
    microbial removal) are inaccessible to many
  • Complex, expensive and only externally available
    (microporous membranes)
  • Some simple and effective technologies are
    unsuited to household use due to their scale and
    OM needs (SSF)

Physical Treatment Technologies for Turbidity
Reduction in Household Waters a Special Need
  • Waters collected for household use may be highly
  • Interferes with disinfection
  • physical shielding/protection of microbes
  • disinfectant demand or consumption
  • Contains pathogens and other microbes
  • Microbial regrowth
  • Aesthetics
  • Turbidity reduction by physical or chemical
    methods ofen needed to prior to household
  • Sedimentation and several filtration methods
  • rapid granular media, fiber, cloth, membranes
  • possibly SSF, but less amenable to household use

Chemical Methods for Household Water Treatment
Chemical Methods for Household Water Treatment
Coagulation, Adsorption Ion Exchange
  • Coagulation-Flocculation (Sedimentation)
  • Inorganic coagulants (alum, iron, etc.)
  • Seed extract coagulants
  • Not recommended due to required technical skill,
    lack of process control tools, lack of material
    availability and variable efficacy
  • Adsorption clay, activated carbon, charcoal and
    crushed organic matter
  • Not recommended due to poor and variable
    performance and lack of process control
    monitoring tools
  • Ion Exchange
  • Not recommended due to lack of availability,
    cost, lack of process control monitoring tools

Candidate Chemical Disinfectants for Household
Water Treatment
  • Disinfectant Recommended?
  • Free chlorine, Na or Ca OCl- Yes
  • Electrochemical oxidant fr. NaCl Yes
  • Chloramines No
  • Ozone No
  • Chlorine dioxide No
  • Acids (lime juice and strong acids) No
  • Chemical coagulation free chlorine Yes
  • (commercial products)
  • except lime juice on emergency basis for cholera

Household Chlorination InterventionsCDC
Safewater Intervention and Similar Systems
  • Bottles of free chlorine solution (0.25-1)
  • Commercial source (Na or Ca OCl-)
  • Electrolysis of NaCl (on-site)
  • Generator located in community
  • Operated by a trained, local worker
  • Replenish solution regularly (e.g., weekly)
  • Cap used as a measuring device
  • Add chlorine solution to household water
    container (improved storage vessel)
  • Free Chlorine Doses
  • between 1-5 mg/l

Behavioral and Educational Components of the
Household Chlorine Interventions
  • Behavior change techniques
  • social marketing
  • community mobilization
  • motivational interviewing
  • communication
  • education
  • Increase awareness of the link between
    contaminated water and disease and the benefits
    of safe water
  • influence hygiene behaviors including the
    purchase and proper use of the water storage
    vessel and disinfectant.

Chlorination and Safe Storage of Household
WaterDisease Reduction and Microbial Quality
Chlorination and Safe Storage of Household
WaterDisease Reduction and Microbial Quality
Effectiveness of combined coagulation-flocculation
-sedimentation-filtration systems
  • Effective (gt99.9) reductions of viruses,
    bacteria and parasites in lab studies with
    different waters
  • Effective (gt99) reductions in indicator bacteria
  • Intervention studies document (22-26 and 38-50)
    reductions in household diarrheal disease in
    intervention groups compared to control groups
  • PUR system
  • Procter Gamble and CDC studies

Cost Estimates per Household for Alternative
Household Water Treatment and Storage Systems
Summary and Conclusions
  • Results clearly document that simple systems of
    manually treating collected household water and
    storing it in a safe vessel significantly
    improves microbiological quality and reduces
    waterborne diarrheal disease risks
  • Solar disinfection with UV and heat
  • chlorination and storage in an improved vessel
  • Combined coagulation-flocculation-sedimentation
    and filtration systems (commercial products)
  • System fulfill (exceed) the requirements of an
    appropriate global intervention to reduce disease
    burden because diarrheal disease is reduced by

Summary and Conclusions
  • Systems are being accepted, used, and considered
    affordable by participants based on
  • Compliance
  • Acceptability
  • Willingness to pay studies
  • Sustainability and dissemination still uncertain
    at present
  • Need follow-up studies to document sustainability
    and to identify reasons for lack of it
  • Need approaches and systems to achieve

Research and Demonstration Needs
  • Several effective technologies in principle have
    not been adequately evaluated for microbial
    efficacy and waterborne disease reduction in the
  • Solar cookers and reflectors
  • UV with lamps
  • Ceramic filters
  • Granular medium filters
  • Alone
  • With chemical (e.g., chlorine) disinfection
  • Combined chemical coagulants and chlorine
  • Limited data now becoming available very
    favorable results

Next Steps
  • Recognize and promote the message that household
    and other local water interventions are effective
    and deserve equal consideration with other
  • Consensus-building on most effective systems
  • Technical training and how to educational
  • Economic and policy analyses
  • Development of infrastructures and policies to
    disseminate accepted and proven technologies
  • Creation and implementation of an international
  • Financial and other resources needed for a large
    scale and sustained initiatives
  • Linkage to and integration with related elements
    of the water and sanitation movement

WHO Guidelines for Drinking-water Quality, 3rd
Ed. Microbiological Issues for Non-piped Supplies
  • Encourage implementation of guidelines for
    systems to improve microbiological quality of
    non-piped household water and reduce waterborne
    infectious disease
  • Provide guidance on and describe systems for safe
    collection, treatment and storage of non-piped
    household water
  • Communicate the documented evidence that these
    systems reduce diarrheal and other waterborne
    infectious disease

Household treatment works and is included in the
next WHO Guidelines for Drinking Water Quality
Further Information
  • Household chlorination and improved storage
    vessel system
  • Critical review on household storage and
  • Managing Water in the Home Accelerated Health
    Gains from Improved Water Supply,
    WHO/SDE/WSH/02.07, World Health Organization,
    Geneva, 2002
  • http//