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 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 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

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%

Background Much of the world’s 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 Treatment: The Case and Point Large fraction of the world’s 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

Prevailing Water Sources and Conditions of too Many of the World’s 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 impact)

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

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

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

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 safeguards Treat to reduce microbial contamination –Physical treatments –Chemical treatments –Combined physical-chemical treatments

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

Physical Methods for Household Water Treatment A in US dollars/yr: $ for moderate and >$100 for high. B 2 log 10 (>99% = high). c Depends on heating method and availability and fuel costs (range from low-high). d Availability of & type of lamps, housings, availability & cost of electricity, O&M needs e Different ones; practicality, availability, cost and microbial efficacy vary among them g Possible synergism with other Rx (solar disinfection with sunlight)

Boiling (Heating) with Fuel Advantages: Widely practiced Effectively inactivates microbes Easy to use Cultural and social acceptance is widespread Disadvantages: Fuel requirement: – Expensive – Ecological impacts – Small treatable volumes No residual for protection from recontamination Transfer for storage in another vessel poses recontamination risks Boiling is not a highly recommended or preferred treatment, despite its widespread use, except where renewable fuel is readily available at low cost

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 M&O – 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

SODIS clear plastic bottle Black surface: on bottle or on resting surface

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 <30 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

Epidemiological Evidence for Diarrheal Disease Reduction by SODIS Solar Disinfection of Household Water a Total diarrheal disease b Severe diarrheal disease

Household or POU Water Treatment by Solar Cooking or Solar Thermal Effects Heat to >60 o C in black or opaque vessels (e.g., cooking pots) Solar cooker or reflector increases temperature to  65 o C 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 days per year.

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 (<90%) 90-99% High (>99%) 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 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 O&M needs (SSF)

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

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 DisinfectantRecommended? Free chlorine, Na or Ca OCl - Yes Electrochemical oxidant fr. NaClYes ChloraminesNo OzoneNo Chlorine dioxideNo Acids (lime juice and strong acids) No * Chemical coagulation + free chlorineYes (commercial products) * except lime juice on emergency basis for cholera

Household Chlorination Interventions: CDC 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 Water: Disease Reduction and Microbial Quality Improvement

Effectiveness of combined coagulation- flocculation-sedimentation-filtration systems Effective (>99.9%) reductions of viruses, bacteria and parasites in lab studies with different waters Effective (>99%) reductions in indicator bacteria reductions Intervention studies document (22-26% and %) 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 (US$)

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 >5%

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

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

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

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: SODIS: 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,