week 2 - hwts treatment options
TRANSCRIPT
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A Framework for Water Safety
Introduction to Household Water Treatment and Safe Storage, Modu
Dr. Richard Johnston
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Safe drinking-water is
does not represent any risk to health over a lifeconsumption, includingsensitivities that may olife stages.
WHO Guidelines for Drinki4th Ed., 2011
Safe drinking water
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Health outcomes 10-6 DALYs/year 10-5 cancer cases per lifetim
Water quality guidelin
Performance Specified removal of hazar
Specified technologie E.g. requiring that surface w
Health-based targets
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Pre-
treatment
Post-
treatment
1 000 000 10 000 000 1 000 000 1 000 000 1 000 000 500 000 1 000 000 300 000 1 000 000 100 000
1 000 000 10 000 1 000 000 1 000 1 000 000 100 1 000 000 10 1 000 000 1
Performance measures
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Health-based targets
System Assessment Operational Monitori Management and Com
Verification
WHO Guidelines forDrinking Water Quality,2011 4th ed.
Water Safety Framework
Health-basedtargets
SystemAssessment
OperationalMonitoring
Managementand
Communication
Verification
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System Assessment Comprehensive understand Identify all hazards, catchm Put in place control measur
Operational Monitori Check that control measure
Management and Com What to do when things go Good record-keeping Two-way communication w
Water Safety Framework
Health-basedtargets
SystemAssessment
OperationalMonitoring
Managementand
Communication
Verification
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Health-based targets Acceptable level of risk
Water safety plan Risk identification and man
Verification Water quality measurement
Water Safety Framework
Health-basedtargets
SystemAssessment
OperationalMonitoring
Managementand
Communication
Verification
Water quality measurem
Water safety!
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Treatment Plant
Primarydisinfection
Chlorine Chlorine
dioxide Ozone Ultraviolet
Filtration
Rapid filtration Slow sand
filtration Membrane
filtration
Coagulation,flocculation,
sedimentation
Conventionalclarification
Dissolved airflotation
Lime softening
Pretreatment
Reservoirs Roughing
filters Bank
infiltration
Resourceprotection
Zoning laws Wellhead
protectionareas
Conventional treatment processes
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Household
Safe
Appcont
Hygloca
Disinfection
Chlorine Ultraviolet Heat
Filtration
Ceramicfiltration
Biosandfiltration
Membranefiltration
Sedimentation
Simple settling Coagulation
Sourceprotection
ImprovedSources
Household-level treatment processes
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Water Safety Framew Health-based targets Water Safety Plans (risk-ba Verification monitoring
Log Reduction Values
Processes in householtreatment are the samconventional treatmen
Summary
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Sedimentation
Introduction to Household Water Treatment and Safe Storage, Modu
Dr. Richard Johnston
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Turbidity
Settling Coagulation
Introduction
DisinfectiFiltrationSedimentation
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Suspended particles in wa Large particles Small particles (wont settle) Organic (algae), inorganic (silt,
Units Nephelometric Turbidity Units ( Formazin Turbidity Units (FTU)
Jackson Turbidity Units (JTU)
No health-based targets Impacts on subsequent treatmen < 5-10 NTU typically
Turbidity
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Depends on size of pa
Simplest HWTS meth Can remove some tur May improve visual a
Limited pathogen rem Opportunities for seco
contamination
Gravity Settling
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Three-pot sedimentation
Credit:
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Enhanced settling Make particles stick t Add more particles, a
Charge neutralization (mannegative charge)
Polymeric bridging
Coagulants
Also removes some dcompounds, improves
Coagulation
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Moringa oleifera 200 mg/L Africa, Asia
Prickly pear cactus (Oindica)
Latin America Nirmali seeds (Strychn
India Coagulant aid
Others
Plant-based coagulants
Credit: Crops for the Future Credit: Dick Culbert
Credit: Sengai Podhuvan
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Water-soluble protein Positive charge, polycation
Most effective at high(>30-50 NTU)
May have some antibproperties as well Adds dissolved organ
foster regrowth and evand odour problems
Plant-based coagulants
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Temperature pH and alkalinity
May need to add alkalinity,Ca(OH) 2 or sodium carbon
Mixing Coagulant dose
Optimal dose too much is Jar experiments
Factors affecting coagulation
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Concerns about links neurological problem Alzheimers disease
WHO has not set a heguideline for drinking
Drinking-water is a small p
Aesthetic recommend 0.1 mg/L for large treatmen 0.2 mg/L for small ones Dose optimization, filtratio
Residual aluminium in drinking water
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On the whole, the positive relationship between aluminium indrinking-water and AD [Alzheimer disease], which wasdemonstrated in several epidemiological studies, cannot betotally dismissed. However, strong reservations about inferringa causal relationship are warranted in view of the failure ofthese studies to account for demonstrated confounding factorsand for total aluminium intake from all sources.
Taken together, the relative risks for AD from exposure toaluminium in drinking-water above 0.1 mg/L, as determined inthese studies, are low (less than 2.0). But, because the riskestimates are imprecise for a variety of methodologicalreasons, a population-attributable risk cannot be calculated with precision.
WHO Guidelines for Drinking Water Quality, 2011
Concerns about links neurological problem Alzheimers Disease (
WHO has not set a heguideline for drinking
Drinking-water is a small p
Aesthetic recommend 0.1 mg/L for large treatmen 0.2 mg/L for small ones Dose optimization, filtratio
Residual aluminium in drinking water
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Sedimentation removsolids
Some pathogen remov Not complete treatment
Allows subsequent treto be more effective
Summary Safe StorageDisinfectionFiltrationSedimentation
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Filtration: Synthetic membranes
Introduction to Household Water Treatment and Safe Storage, Modu
Dr. Richard Johnston
M b fil i
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Rapidly growing fieldtreatment
Different kinds of me How they change wat Applications for hous
treatment
Membrane filtration
DisinfectiFiltrationSedimentation
P i b fil i
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Size exclusion Membrane pores Cake filtration
Electrostatic effects Charge exclusion Adsorption
Biological activity
Processes in membrane filtration
Diff f b fil i
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Algae
0.1
1
10
100
0.0001 0.001 0.01 0.1 1 10 100
Different types of membrane filtration
Ultrafiltration
Cloth1 nm
Size, microns
Barspsi
1
10
100
1000
ProtozoaBacteriaVirusesLarge ions
Small ions SiltClay
Nanofiltration
Reverse
Osmosis
Macromolecules
Microfiltration
C fi ti
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Flat sheet Spiral wound
Hollow fiber, tube
Dead-end Cross-flow
Configurations
M b f li g
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Result of particle retegrowth
Increase in operating Reversible Irreversible
Solution: Regular backwashing, cros Periodic cleaning
Membrane fouling
HWTS membrane systems (Ultra Filtration)
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Lifestraw 1.0 20 nm pore size
Protozoa, bacteria, viruses Hollow fibre, dead-end Manual backwash 9 Lph 18 000 L Halogen compartment
Since 2005 Emergencies Kenya: 880 000 distributed
HWTS membrane systems (Ultra Filtration)
HWTS membrane systems (Ultra Filtration)
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Lifestraw 2.0 Similar membrane,
80 micron prefilter Larger reservoirs
5 L dirty water, 5 L filtered 30 000 L lifetime
Del Agua Health Prog Lifestraw 2.0 + Improved c Rwanda: targeting 600 000
HWTS membrane systems (Ultra Filtration)
www.vestergaard.com
Other membrane systems
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Micro Filtration www.katadyn.com www.nerox.com www.sawyer.com
Ultra Filtration www.eawag.ch/membranef www.lifesaversystems.com
www.polymem.fr www.vestergaard.com
Other membrane systems
Considerations for membrane systems
http://www.nerox.com/http://www.nerox.com/http://www.sawyer.com/http://www.eawag.ch/membranefilterhttp://www.lifesaversystems.com/http://www.polymem.fr/http://www.vestergaard.com/http://www.vestergaard.com/http://www.polymem.fr/http://www.polymem.fr/http://www.lifesaversystems.com/http://www.eawag.ch/membranefilterhttp://www.sawyer.com/http://www.nerox.com/http://www.nerox.com/http://www.nerox.com/ -
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Advantages ChallengesAbsolute barrier to particles
protozoa, bacteria, (viruses)Looser membranes have little effchemicals
Simple operation Need for backwashing, cleaning
No change to taste of water No protection against recontamination
Reduces turbiditySome models require electricity, pressure
Supply chains for initial purchasreplacement parts, and service
Considerations for membrane systems
Summary Safe StorageDisinfectionFiltrationSedimentation
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Cloth filtration Large particles, including c
Synthetic membranes MF, UF, NF, RO Pore size and operating pre Exclude particles and disso
Advantages and chall
Summary
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Filtration: Ceramic filters
Introduction to Household Water Treatment and Safe Storage, Modu
Dr. Richard Johnston
Introduction
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Ceramic filtration
Ceramic pot filters Candle filters
Introduction
DisinfectiFiltrationSedimentation
Ceramic filtration
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Simple operation
Built-in safe storage
No electricity or con
Can be produced loc
Ceramic filtration
Types of ceramic filters
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Clay Burn-out material
Sawdust, ground rice hus Proportion and size
Additives Silver Iron oxides
Mixed, Pressed, Dri 700 980 C Around 6-20 hours firing
Flowerpot
Candle
Types of ceramic filters
Quality control
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Visual inspection, pin
Pressure testing
Flow rate testing 1.5 3 lph
Microbiological test
Failure rate 10%-20%
Quality control
Credit: RDI Cambodia
Physical removal
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y
Algae
0.1
1
10
100
0.0001 0.001 0.01 0.1 1 10 100
Ultrafiltration
Cloth1 nm
Size, microns
ProtozoaBacteriaVirusesLarge ions
Small ions SiltClay
Nanofiltration
Reverse
Osmosis
Macromolecules
Microfiltration
Bars
CeramicFilters
Electrostatic removal
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Viruses have negativ
Iron oxides (e.g. latepositive charge
Possibility of saturat
Silver
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Normally brushed on Quantity seems more imp
Sometimes baked in Low levels leach int
Arsenic! Contributes to bacter Prevents biofilm gro
Colloidal silver (nan Silver nitrate: 5 micr
Credit: D. Lantagne
Disinfection effectiveness
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Protozoa 2-5+ L Mainly physi
Bacteria 1-2+ L Complicated
recontaminat
Viruses 0-2 LR Mainly electr
Example Ceramic pots in Cambodia
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p p
Credit: PATH, 2011
Resource DevelopmCambodia (RDIC)www.rdic.org
International EnterprDevelopment (IDE)www.ide-cambodia.o
No subsidy Direct sales, vendors
Sale price ~US$8 - US$1 Production ~2,000 fi 100s of thousands so
Cambodia assessment
http://www.rdic.org/http://www.ide-cambodia.org/http://www.ide-cambodia.org/http://www.ide-cambodia.org/http://www.ide-cambodia.org/http://www.rdic.org/ -
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30% using at time of Time since impleme
2% breakage per month 50% of those who ha
Filling 1.8 times per Cleaning 2.3 times p
70% turbidity reduct E. coli LRV: 1.7 Older filtersnot less e
Source: WSP/UNICEF 2007www.unicef.org/eapro/WSP_UNICEF_FN_CWP_Final.pdf
Example candle filter application
http://www.unicef.org/eapro/WSP_UNICEF_FN_CWP_Final.pdfhttp://www.unicef.org/eapro/WSP_UNICEF_FN_CWP_Final.pdf -
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Tulip water filter
Hose adds hydrostat 70 cm 4-5 lph
Backwashing with b
10s of thousands sol India, Cambodia, Tanzani
Madagascar, Zambia, ZimSudan, Nicaragua, Ethiop
Credit: basicwaterneeds.com300in6.org
Considerations for Ceramic filtration
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Advantages Challenges
Social acceptability, high use Moderate effectiveness
Safe storage Low flow rate
One time capital cost Supply chains for replacement
Possibility of local production Variable quality
Visual improvement in water quality Lack of residual protection
Additional resources
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www.irc.nl/docsearch/title/175012 www.rdic.org/water-ceramic-fil
Summary
http://www.irc.nl/docsearch/title/175012http://www.rdic.org/water-ceramic-filtration.phphttp://www.rdic.org/water-ceramic-filtration.phphttp://www.rdic.org/water-ceramic-filtration.phphttp://www.rdic.org/water-ceramic-filtration.phphttp://www.irc.nl/docsearch/title/175012 -
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Fast-growing sector Can be locally produced Quality control is essentia
Removal mechanism Physical, Electrostatic, Ch
Modest removal effi High user satisfactio
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Biological filtration
Introduction to Household Water Treatment and Safe Storage, Modu
Dr. Richard Johnston
Biological filtration
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Slow sand filtration
Recent adaptation to hlevel
DisinfectiFiltrationSedimentation
Processes in biological filtration
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Size exclusion Large particles get trapped
Electrostatic effects Adsorption
Biological activity Predation Pathogen die-off
Biological filtration design
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Slow sand filtration Water column 60-120 c Sand bed 80-120 cm
D10 0.15-0.35 Continuous flow Filtration 10-30 cm
Flow control Initial ripening period
Schmutzdecke
Biological filtration design
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Biosand filtration Water layer 5 cm Sand bed 55 cm
< 0.7 mm Intermittent flow Design for 40 cm/h
600 cm2 area 400 mL/min, 24 lph
Slow sand filtration Water column 60-120 c Sand bed 80-120 cm
D10 0.15-0.35 Continuous flow Filtration 10-30 cm
Flow control Initial ripening period
Schmutzdecke
Source: CAWST - The Centre for Affordable Water and Sanitation Technology (www.cawst.org)
Concrete housing Plastic housing
Filter cleaning and ripening
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Biological layer takesdevelop
One month recommended
No backwashing! Clean when flow is low
SSF
Remove 1-3 cm Swirl anRipening 7-10 d RipeninFilter run 20-60 d Filter ru
Operation of Biosand filters
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Consistent water sour Turbidity < 50 NTU
Important to use the f Rest period of at least 1 hou
Keep biological layer Watch for leaks
Check flow rate, wate
Collect water safely
Removal efficiency
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Helminths > 2 LRV
Protozoa > 2 LRV
Bacteria 1-2 LRV
Viruses < 1 LRV
Removal efficiency
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Helminths > 2 LRV
Protozoa > 2 LRV
Bacteria 1-2 LRV
Viruses < 1 LRV
Turbidity 85% - 95%
Iron 90% - 95%
Arsenic Adapted version
Nitrate, nitrite May increase
Fe
As
N
Field application in Cambodia
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Samaritans Purse Ca Hagar Cambodia, CGA
Over 100 000 BSF sin 25 000 per year
Evaluation in 2010
World Bank/WSP 105 intervention household 102 matched controls
Field application in Cambodia
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High use 88% in use at time of visit
Most common reason for di Median 2 years, one case u
Two thirds reported tr Twice as likely to use filter
Treated water univers Half in open containers 80% with dipper or instrum
Field application in Cambodia
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E. coli reduction 73% raw water High risk ( 13% treated High risk (4 31% stored High risk
1-2 LRV (95%) Highly variable Stored water increase by ab
Considerations for biological filtration
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Advantages Challenges
Simple operation Need for cleaning, ripening period
No change to taste of water High risk of recontamination
Reduces turbidity Little effect on chemicals, may nitrif
Can be manufactured on site Heavy
Possible long-term use Limited removal of pathogens
Additional resources
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Manz Water Filters www.manzwaterinfo.ca
CAWST www.cawst.org/en/resources/biosand-filter
Samaritans Purse
www.samaritanspurse.ca/water-projects
www.biosandfilter.org
SSWM www.sswm.info/category/i
tools/water-purification/harwater-treatment/bio-sand-fi
AKVO akvopedia.org/wiki/Concre
Summary: Biological filtration
http://www.manzwaterinfo.ca/http://www.cawst.org/en/resources/biosand-filterhttp://www.samaritanspurse.ca/water-projectshttp://www.hydraid.org/http://www.sswm.info/category/implementation-tools/water-purification/hardware/point-use-water-treatment/bio-sand-filtrathttp://www.sswm.info/category/implementation-tools/water-purification/hardware/point-use-water-treatment/bio-sand-filtrathttp://www.sswm.info/category/implementation-tools/water-purification/hardware/point-use-water-treatment/bio-sand-filtrathttp://akvopedia.org/wiki/Concrete_Biosand_Filterhttp://akvopedia.org/wiki/Concrete_Biosand_Filterhttp://www.sswm.info/category/implementation-tools/water-purification/hardware/point-use-water-treatment/bio-sand-filtrathttp://www.sswm.info/category/implementation-tools/water-purification/hardware/point-use-water-treatment/bio-sand-filtrathttp://www.sswm.info/category/implementation-tools/water-purification/hardware/point-use-water-treatment/bio-sand-filtrathttp://www.sswm.info/category/implementation-tools/water-purification/hardware/point-use-water-treatment/bio-sand-filtrathttp://www.sswm.info/category/implementation-tools/water-purification/hardware/point-use-water-treatment/bio-sand-filtrathttp://www.sswm.info/category/implementation-tools/water-purification/hardware/point-use-water-treatment/bio-sand-filtrathttp://www.sswm.info/category/implementation-tools/water-purification/hardware/point-use-water-treatment/bio-sand-filtrathttp://www.sswm.info/category/implementation-tools/water-purification/hardware/point-use-water-treatment/bio-sand-filtrathttp://www.sswm.info/category/implementation-tools/water-purification/hardware/point-use-water-treatment/bio-sand-filtrathttp://www.sswm.info/category/implementation-tools/water-purification/hardware/point-use-water-treatment/bio-sand-filtrathttp://www.sswm.info/category/implementation-tools/water-purification/hardware/point-use-water-treatment/bio-sand-filtrathttp://www.hydraid.org/http://www.samaritanspurse.ca/water-projectshttp://www.samaritanspurse.ca/water-projectshttp://www.samaritanspurse.ca/water-projectshttp://www.cawst.org/en/resources/biosand-filterhttp://www.cawst.org/en/resources/biosand-filterhttp://www.cawst.org/en/resources/biosand-filterhttp://www.manzwaterinfo.ca/ -
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Adaptation of slow sa Similarities Differences
Operation and mainte Cleaning, ripening
Advantages and chall Moderate pathogen remova
Recommend to followdisinfection
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Key Messages, Week 2
Introduction to Household Water Treatment and Safe Storage, ModuDr. Richard Johnston
Introduction
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Water Safety Framew Sedimentation Membrane filtration Ceramic filtration
Biological filtration
Water Safety Framework
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= 10
Health-basedtargets
SystemAssessment
OperationalMonitoring
Managementand
Communication
Verification
DisiFiltrationSedimentation
Sedimentation
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Turbidity
Gravity settling Coagulation
Natural coagulants Metal salts
Membrane filtration
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Algae
0.1
1
10
100
0.0001 0.001 0.01 0.1 1 10 100
Ultrafiltration
Cloth1 nm
Size, microns
ProtozoaBacteriaVirusesLarge ions
Small ions SiltClay
Nanofiltration
ReverseOsmosis
Macromolecules
Microfiltration
Bars
Ceramic filtration
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Physical removal Electrostatic removal Chemical effects
Modest bacteria remo Variable to low virus
User-friendly
Biosand filtration
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Physical removal Electrostatic removal Biological removal
Modest bacteria remo Variable to low virus
User-friendly
Summary
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HWTS is analogous twater treatment
Multiple processes an
Sedimentation Reduce particles, turbidity
Filtration mechanism Physical and electrostatic Biological and chemical