Week 2 - HWTS Treatment Options

8/11/2019 Week 2 - HWTS Treatment Options

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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


Health-basedtargets

SystemAssessment


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


Health-basedtargets

SystemAssessment


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




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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



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


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




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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


www.vestergaard.com

Other membrane systems
http://www.vestergaard.com/http://www.vestergaard.com/


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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


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Ceramic filtration

Ceramic pot filters Candle filters

Introduction


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


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





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Slow sand filtration

Recent adaptation to hlevel


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



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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



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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




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= 10

Health-basedtargets

SystemAssessment


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


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

Week 2 - HWTS Treatment Options

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