reasons to assess HWTS

  1. understand if the HWTS tech is actually achieving the objective of improving health
    • by removing the pathogens that cause the diarrheal disease
    • if treating a particular outbreak, then direct checks towards that
    • else make sure all common pathogens are targets
  2. communicate effectiveness of HWTS devices to governments, implementers and investors
    • those groups of people do not have any methods to evaluate performance
  3. enforce correct and consistent use of HWTS tech
    • to maximize health benefits

WHO recommendations on evaluating HWTS

goal:

  • protect health of users, increase access to safe water

target pathogens:

  • viruses
  • bacteria
  • protozoa

derivation of targets

  • based on WHO guidelines for drinking water risk-based approach
    • (QMRA models)

tiered approach:

  • highly protective
  • moderately protective
  • limited protection

laboratory protocols:

  • provides best practice principle

assessing performance

log-removal

  • highly protective (10^-6 DALYs/P/yr)
    • bacteria: ≥ 4
    • viruses: ≥ 5
    • protozoa: ≥ 4
    • examples
      • boiling
      • ultrafilters
      • combined approaches
  • moderately protective (10^-4 DALYs/P/yr)
    • bacteria: ≥ 2
    • viruses: ≥ 3
    • protozoa: ≥ 2
    • examples
      • membrane filters
      • flocculant disinfectant
  • limited protection
    • protective for two classes of pathogens
    • examples
      • chlorine
      • ceramic filters
      • biosand filters

benefits

  • even low economic regions can benefit from limited protection

test water

  • two types of test water:
    • model actual field condition
      • pH
      • temperature
      • TOC
      • turbidity
      • TDS
      • alkalinity
  • GTW (general testing water)
    • representing high quality groundwater or rainwater
    • non-stresses phase of testing
    • not technology specific
  • CTW (challenge testing water)
    • representing turbid surface-water
    • stresses challenge phase of testing
    • based on the product’s technology

WHO scheme to evaluate HWT

  • promote independent testing of HWTS based on WHO criteria
  • support governments in building technical capability of research institutions
    • especially in applying WHO guidelines on drinking-water quality

diffusion of innovation

  • five stages
    • knowledge
    • persuasion
    • decision
    • implementation
    • confirmation
  • five attributes of innovation
    • relative advantage
    • compatibility
    • complexity
    • trialability
    • observability

RANAS theory of behavior change

  • Risks
    • perceived vulnerability
    • perceived severity
    • factual knowledge
  • Abilities
    • action knowledge
    • self-efficacy
  • Norms
    • descriptive
    • injunctive
    • personal
  • Attitudes
    • instrumental beliefs
    • affective beliefs
  • Self-regulation
    • action control/planning
    • coping planning
    • remembering
    • commitment

Integrated Behavioral Model - WAHS

  • three classes of factors
    • contextual
    • psychosocial
    • technology
  • five levels
    • societal.structural
    • community
    • interpersonal.household
    • individual
    • habitual

EAWAG monitoring and Evaluation Toolkit Indicators

  • reported and observed use
  • correct, consistent use and storage
  • knowledge and behavior
  • other environmental health interventions
  • water quality

Cost Effectiveness

  • cost-benefit analysis
    • money for money
  • cost effectiveness analysis
    • money for DALYs
  • willingness to pay
    • money for HWTS

formal HWTS selection

  • the selection steps are as follows
    1. establish decision context
    2. identify options
    3. identify objectives, criteria
    4. scoring
    5. weighting
    6. calculate tools
    7. examine results
    8. sensitivity analysis
  • decision trees are used to obtain the implementation rationale for a given scenario

field tests for e.coli

  • challenges of testing in labs
    • distance
    • testing should be done within 6-24h
  • new options for testing in field
    • most probable number methods
    • portable membrane filtration
    • enzyme growth media
    • low-cost incubators
  • application is mics surveys
    • millipore microfil filtration
    • nissui compact dry EC plates
    • body belt incubation

summary of process

  • a glass of water people would drink

  • a sample from the source

  • filtered through special paper
  • allow bacteria to grow
    • e.coli preferred indicator of fecal contamination

  • count the colonies

  • 100mL test
    • for low contamination
  • 1 mL test
    • for high contamination

equipment

  • plastic funnels
  • plastic syringe (100 mL)
  • plastic syringe (1 mL)
  • pen
  • filter instrument
  • alcohol wipe
  • filter paper
  • forceps
  • growth media (compact dry)

analysis

  • consistency checks
    • 100mL vs 1 mL results
  • quality control
    • blanks
    • expert visits
  • risk classes
    • < 1: low
    • 1 - 10: intermediate
    • 11 - 100: high
    • 100+: very high
  • standard tables, scripts
  • summary reports, detailed reports