7.0 MICROBIAL ASPECTS
EMERGING ISSUES
zoonatic pathogen pose the greatest challenge to ensure the safety of drinking water and ambient water
zoonatic pathogen make up 75% of the emerging pathogens.
global changes, human development, population growth and climate change influence water disease risk
PUBLIC HEALTH ASPECTS
effects and exposure to pathogens are not the same for all individuals . Not all infected individuals will develop symptomatic infections.
waterborne pathogen that contaminated through drinking water can lead to severe and life threatening. Eg: cholera, hepatitis, thyphoid.
developing and applying control on drinking water quality should be control such a outbreaks.
TABLE TO REFER
Table 7.2 (pg 121)
Microorganisms for which transmission through drinking
water has been proposed but evidence is lacking
Table 7.1 (pg 119)
Characteristics, behavior, resistance of pathogens
TREATMENT OF PATHOGEN
HOUSEHOLD TREATMENT
Combination (multiple-barrier) treatment approaches
Flocculation plus disinfection systems
e.g. commercial powder sachets or tablets
Coagulation, precipitation and / or sedimentation
Simple sedimentation
Thermal (heat) technologies
Boiling
UV light technologies using lamps
UV irradiation
Solar disinfection
Solar UV radiation + thermal effects
Granular media filter
Household-level intermittently operated slow sand fi ltration
Rapid granular, diatomaceous earth, biomass and fossil fuel - based filter
Membrane, porous ceramic or composite filters
Fiber and fabric filtration
Membrane filtration
Reverse osmosis
Ultrafiltration
Nanofiltration
Microfiltration
Porous ceramic and carbon block filtration
Chemical disinfection
Free chlorine disinfection
CENTRAL TREATMENT
There are positive and negative interactions occur between multiple steps and these can affect the overall of water quality.
The case that efficacy for microbial reduction differ among the microbial groups so different treatment process are needed.
For example : poor quality surface water require multiple treatments stages.
disinfection
filtration
sendimentation
flocculation
coagulation
Water treatment required to remove or destroy pathogenic microorganism
Validation is important in ensuring that treatment will achieve the desired goals
OCCURANCE
Discharge water is diluted in receiving surface water leading to reduce pathogen number with the dilution factor
Faecel indicator bacteria, such as E.Coli always present at high concentration in waste water
The concentration of pathogen in raw water can be estimated from concentration of pathogens in waste water
To provide treatment so that ensure health within water safety plan
To determine the pathogen concentration in source water
PERSISTANCE AND GROWTH IN WATER
high amount of biodegradable organic carbon together with warm water can permit growth of waterborne pathogen.
persistence is affected by several factors such as temperature.
pathogen with low persistence are more likely to be spread by person to person contact or poor personal hygiene.
IDENTIFYING LOCAL ACTIONS IN RESPONSE TO MICROBIAL WATER QUALITY PROBLEMS AND EMERGENCIES
Actions following an incident
Boil water advisories
METHODS OF DETECTION OF FAECAL INDICATOR ORGANISMS
The standardization of methods and of laboratory procedures is of great importance if criteria for the microbial quality of water are to be uniform in different laboratories and internationally.
Analysis for faecal indicator organisms provides a sensitive, although not the most rapid, indication of pollution of drinking-water supplies.
MICROBIAL MONITORING
Helminths
Microscopy
Protozoa parasites
Immunomagnetic separation in combination with immunofluorescence microscopy
Virus
Polymerase Chain Reaction (PCR)
Cell culture
Bacteria (E.coli)
Culture-based method
Solid media
Broth cultures
Included in
surveillance
operational
verification
To determine whether a treatment or other process is effective in removing target organisms.
QUANTITATIVE MICROBIAL RISK ASSESSMENT
Risk Assessment Paradigm For Pathogen Health Risks
Risk Characterization: Data collection on exposure, dose-response and incidence and severity of disease
Dose-Response Assessment: To derive the probability of an adverse effect following exposure to one or more pathogenic organisms
Exposure Assessment: Estimation of number of pathogen that is exposed to an individual through ingestion
Identify all possible hazards and their pathways from sources to recipients
Systemically combines information on exposure and dose-response models
REFERENCE PATHOGENS
PROTOZOA
Source of protozoa: Cryptospotidium and Balantidium
Least sensitive to inactivation by chemical disinfection
BACTERIA
Example: Vibrio, Campylobacter, E.coli O157, Salmonella and Shigella
Legionella and non-tuberculous mycobacteria can grow in water environment
Most sensitive to inactivation by disinfection
VIRUSES
Example: Rotaviruses, enteroviruses, and noroviruses
Can persist in a long period inn water
Smallest pathogen and difficult to remove by physical process (filtration)
Subtopic
ROUTE OF TRANSMISSION
Patients undergoing immunosuppressive
therapy or those with acquired
immunodeficiency syndrome (AIDS)
Ingestion of the eggs in food
contaminated with faeces or
faecally contaminated
Contact with water (dermal)
Inhalation of water droplets
