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)