Water Purification
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Transcript of Water Purification
Water Purification
Waterborne Enteric Pathogens
Bacterial Viral Protozoan
Campylobacter
Hep A Giardia
E.coli Enteric Viruses
Cryptosporidium
ShigellaS. TyphiY. Enterocolitica
Infectious DoseOrganism Minimal infectious
dose
Salmonella 105
V cholera 103
Shigella 10Cryptosporidium 30Giardia 10
Viability of Enteric Pathogens
in Cold WaterOrganism Survival
V cholera 4 – 5 weeksCampylobacter 3 – 5 weeksViruses 17 – 130 daysGiardia 2 – 3 monthsCryptosporidium 12 months
Infection
DiarrheaGas/flatulenceGreasy stoolStomach, abdominal crampsUpset stomachNauseaDehydration
Symptoms appear on average 7 days after becoming infected, last 2-4 weeks depending on immune system of host
Signs/Symptoms
Water Source
Water SourceLake or Stream?
?
Field Water Treatment Methods
Heat Clarification
SedimentationCoagulation/flocculationGranular activated charcoal
Filtration Chemical disinfection
ChlorineIodineChlorine dioxide
Ultraviolet
Water Disinfection by HeatAdvantages
ReliableSimpleWidely availableSterilizeNot dependent on water quality
DisadvantageLimited by fuel suppliesDoes not improve taste or
appearance of water
Thermal Death Points Giardia, E histolytica cysts
2-3 minutes at 60º C (140º F) Cryptosporidium oocysts
2 minutes at 64º C 1 minute at 72º C
Enteric virusesSeconds at 80º -100º C
Hepatitis A1 minute at 85º C
Enteric bacteria1 minute at 65º CSeconds at 100º C
Effect of AltitudeElevation Boiling Point
5,000 ft (1524 m) 95º C (203º F)
10,000 ft (3048 m) 90º C (194º F)
14,000 ft (4267 m) 86º C (187º F)
19,000 ft (5791 m) 81º C (178º F)
Water Disinfection by Filtration
AdvantagesSimple processNo taste impartedMany choicesMay improve appearance of water
DisadvantagesSpecial equipment adds weight to packMay not remove all virusesGradual clogging
Effective Filter Pore Size
Organism Maximum pore size (um)
Parasitic eggs and larvae 20
Giardia, E histolytica 5
Cryptosporidium 1
Enteric bacteria 0.2-0.4
Viruses 0.01
Halogen Disinfection Advantages
Inexpensive and widely availableFlexible dosing and equal ease with large and small quantities
DisadvantagesPotential toxicityLimited effect on CryptosporidiumImparts taste and odor
Sensitivity of microorganismsBacteria > Viruses > Protozoan cysts
Variables for Halogen Disinfection
PrimaryHalogen concentrationContact time
SecondaryTemperatureWater contaminantspH
Iodine Contraindications
Known iodine allergy
Thyroid disease
Pregnancy
Improving Taste of Halogens
Decrease dose, increase time Remove halogen
Granular activated charcoal Chemically remove taste
Ascorbic acidSodium thiosulfateHydrogen peroxide
Iodine Resins“Demand” disinfectant
Iodine molecules on resin transfer to organisms on contact
Minimal dissolved iodine
Various filter designs combine Microfilter for resistant cystsIodine resin for bacteria and virusesCharcoal to remove residual iodine
Chlorine DioxideAt least as effective as chlorine for bacteria
and more effective for viruses and Cryptosporidium
Controls/eliminates some odor, tastes, manganese and iron
Less affected by pH and ammonia nitrogenAvailable in liquid or tablets
Miox PurifierMixed Species Disinfectant
On-site production of mixed species disinfectants and oxidants
Uses battery current (electrolysis) to convert brine solution (table salt)
Generates mixed species includes free chlorine, chlorine dioxide, ozone, hydrogen peroxide, oxidants)
MIOX PEN
Ultra Violet Rays Advantages
Effective against all microorganismsLeaves no tasteExtra dosing is not harmful, it is safety factor Battery operated units available
DisadvantagesRequires power sourceOnly works in clear waterModerate costNo residual disinfectant action
EPA Testing for Microbiologic
Water Purifiers 6-log reduction of bacteria4-log reduction of viruses3-log reduction cysts
(Cryptosporidium)Testing at 20º C and 5º CWorse case scenario—high
pollution, turbidity
Susceptibility of Microorganisms to Field Disinfection
Heat Filtration HalogenIodine/chlorine
Chlorine Dioxide
Bacteria + + ++ +Viruses + +/-1 + +Protozoan cysts
++ ++ +2 +Parasitic eggs, larvae ++ ++ - +
1 General Ecology First Need and Sawyer Purifier claim virus removal 2 Cryptosporidium is highly resistant
Optimal TechniquesSingle step
HeatChlorine dioxideUltraviolet
Combinations1.) C-F followed by halogenation
or2.) Halogenation followed by
filtration (filtration last if charcoal matrix)