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

1
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
• Mark_Sobsey_at_unc.edu

2
Introduction and Background

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

3
Water and Sanitation Interventions to Reduce
Waterborne, Water-washed and Water-related
Diseases

• 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

4
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
  great
• Developed countries 15-30 (Payment et al.
  studies)
• Developing countries 6-90

5
Background

• 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

6
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
  rural
• Improved supplies often are not microbially
  safe misclassified

7
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

8
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

9
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
  impact)

10
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
  diseases
• Epidemiologically proven by intervention and
  other types of studies
• Effective even without other hygiene measures,
  such as improved sanitation
• Such findings are summarized here

11
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

12
Increased Microbial Contamination (Decreased
Microbial Quality) and Infectious Disease Risks
from Inadequately Stored Household Water
13
Increased Microbial Contamination (Decreased
Microbial Quality) and Infectious Disease Risks
from Inadequately Stored Household Water
14
Characteristics of Preferred 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

15
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

16
Household Water Containers for Safe Storage
17
Household Treatment Barrier(s) against Microbial
Contamination and Waterborne Disease

• Barriers
• Collect from a safe source
• Store in a container with contamination
  safeguards
• Treat to reduce microbial contamination
• Physical treatments
• Chemical treatments
• Combined physical-chemical treatments

18
Criteria for Preferred Household Water Treatment
Technologies

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

19
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)
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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
cost
21
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
  water
• 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
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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

23
SODIS
Black surface on bottle or on resting surface
clear plastic bottle
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SODIS and SOLAIR

• Advantages
• Inactivates pathogens
• Disinfects small quantities of water for
  consumption
• Relies on solar energy only
• Does not directly change chemical quality of
  water
• 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
  NTU)
• 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

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Epidemiological Evidence for Diarrheal Disease
Reduction by SODIS Solar Disinfection of
Household Water
aTotal diarrheal disease bSevere diarrheal disease
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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
  to?65oC
• Water and other liquids are pasteurized most
  enteric viruses, bacteria and parasites are
  rapidly inactivated
• Where now used, it is practical, accessible and
  affordable
• 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
  year.

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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

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Filtration Technologies for Household Water
Treatment Issues and Special Concerns

• Some simple, accessible, low cost technologies
  are
• 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
  microbes
• Some simple, low-cost technologies may not be
  accessible or are of uncertain efficacy (ceramic
  filters)
• Some effective technologies (capable of efficient
  microbial removal) are inaccessible to many
  households
• 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)

29
Physical Treatment Technologies for Turbidity
Reduction in Household Waters a Special Need

• Waters collected for household use may be highly
  turbid
• 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
  disinfection
• Sedimentation and several filtration methods
  recommended
• rapid granular media, fiber, cloth, membranes
• possibly SSF, but less amenable to household use

30
Chemical Methods for Household Water Treatment
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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

32
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

33
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

34
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.

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Chlorination and Safe Storage of Household
WaterDisease Reduction and Microbial Quality
Improvement
36
Chlorination and Safe Storage of Household
WaterDisease Reduction and Microbial Quality
Improvement
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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
  reductions
• 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

38
Cost Estimates per Household for Alternative
Household Water Treatment and Storage Systems
(US)
39
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
  gt5

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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
  sustainability

41
Research and Demonstration Needs

• Several effective technologies in principle have
  not been adequately evaluated for microbial
  efficacy and waterborne disease reduction in the
  field
• 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

42
Next Steps

• Recognize and promote the message that household
  and other local water interventions are effective
  and deserve equal consideration with other
  interventions
• Consensus-building on most effective systems
• Technical training and how to educational
  materials
• Economic and policy analyses
• Development of infrastructures and policies to
  disseminate accepted and proven technologies
• Creation and implementation of an international
  movement
• 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

43
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

44
Household treatment works and is included in the
next WHO Guidelines for Drinking Water Quality
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Further Information

• Household chlorination and improved storage
  vessel system www.cdc.gov/safewater
• SODIS www.sodis.ch
• Critical review on household storage and
  treatment
• Managing Water in the Home Accelerated Health
  Gains from Improved Water Supply,
  WHO/SDE/WSH/02.07, World Health Organization,
  Geneva, 2002
• http//www.who.int/water_sanitation_health/Documen
  ts/WSH0207/WSH02.07.pdf