POU Arsenic RemovalPOU Arsenic Removal

Team DHMOTeam DHMOJustin FerrentinoJustin FerrentinoBarry Schnorr Barry Schnorr Haixian HuangHaixian HuangDavid HarrisonDavid Harrison

Arsenic in BangladeshArsenic in Bangladesh

BackgroundBackground

• Historically, drinking water was Historically, drinking water was primarily taken from surface waterprimarily taken from surface water– Open dug wellsOpen dug wells– PondsPonds– RiversRivers

• High population density High population density disease disease– diarrhea, dysentery, typhoid, cholera diarrhea, dysentery, typhoid, cholera

and hepatitis and hepatitis

Arsenic Concentrations in Arsenic Concentrations in Water Districts of Water Districts of Bangladesh/IndiaBangladesh/India

WellsWells

• In the past 30 years, programs have In the past 30 years, programs have provided safer drinking water with wellsprovided safer drinking water with wells

• 8-12 million shallow tube-wells 8-12 million shallow tube-wells • Reduction in waterborne diseaseReduction in waterborne disease• Well water was the preferred water sourceWell water was the preferred water source• Approximately 90% of Bangladesh’s 130 Approximately 90% of Bangladesh’s 130

Million served by wellsMillion served by wells

ArsenicArsenic

• 1993, Arsenic discovered in 1993, Arsenic discovered in Bangladesh groundwaterBangladesh groundwater

• Arsenic is naturally occurring in Arsenic is naturally occurring in geological formations under geological formations under BangladeshBangladesh

• British Geological Survey in 1998British Geological Survey in 1998– >70% of shallow tube wells (in 61 of >70% of shallow tube wells (in 61 of

64 districts) had [As] > 10 ppb64 districts) had [As] > 10 ppb– 27% had [As] > 50 ppb27% had [As] > 50 ppb– estimated that 28-35 million exposed estimated that 28-35 million exposed

to [As] above 50 ppb and 46-57 to [As] above 50 ppb and 46-57 million exposed to [As] above 10 ppbmillion exposed to [As] above 10 ppb Well marked with red X due

to Arsenic contamination

EffectsEffects

• Most common disease result is skin lesionsMost common disease result is skin lesions

• Skin and internal cancer rates are expected Skin and internal cancer rates are expected to rise over the next decadeto rise over the next decade

OptionsOptions

• Providing low arsenic groundwaterProviding low arsenic groundwater– Safe shallow groundwaterSafe shallow groundwater– Deep (>200 m) aquifersDeep (>200 m) aquifers

• Rain water harvestingRain water harvesting

• Pond sand-filtrationPond sand-filtration

• Household chemical treatmentHousehold chemical treatment

• Piped water from safe/treated sourcesPiped water from safe/treated sources

Chemical Treatment TechnologiesChemical Treatment Technologies

• Common methodsCommon methods– Oxidation & co-precipitationOxidation & co-precipitation

•Alum additionAlum addition

– Adsorption to mediaAdsorption to media•Activated carbon, iron & manganese coated Activated carbon, iron & manganese coated

sandsand

– Ion exchange and membrane techniquesIon exchange and membrane techniques•Membrane filters (Reverse Osmosis)Membrane filters (Reverse Osmosis)

Bucket Treatment UnitBucket Treatment Unit• Oxidize in one bucket, Oxidize in one bucket,

filter in anotherfilter in another

• Red / Green buckets Red / Green buckets (Bangladesh well code)(Bangladesh well code)

• Collect As(V) on alum, Collect As(V) on alum, FeClFeCl33, , Fe2(SO4)3 , other Fe other Fe compoundscompounds

Red Bucket: OxidationRed Bucket: Oxidation• Oxidizing agent: 2 mg/L KMnOOxidizing agent: 2 mg/L KMnO44

– Color and safety issuesColor and safety issues– Color removed in filter?Color removed in filter?

– Alternative oxidants: CaClAlternative oxidants: CaCl22OO22, aeration, aeration

• Adsorption of As(V)Adsorption of As(V)– Naturally occurring Fe removalNaturally occurring Fe removal

• Can also disinfectCan also disinfect

Red Bucket: Co-precipitationRed Bucket: Co-precipitation• Add packet, mix with stickAdd packet, mix with stick

• DHPE-Danida unit: 30-60 s mixing and DHPE-Danida unit: 30-60 s mixing and 90 s gentle stirring recommended90 s gentle stirring recommended

• Settling for 1-2 hoursSettling for 1-2 hours

• Stevens Institute Unit: Settling in filter Stevens Institute Unit: Settling in filter bucketbucket

Green Bucket: FiltrationGreen Bucket: Filtration• Sand filter bedSand filter bed

– Sometimes inside cloth filterSometimes inside cloth filter

• Needs washing 1-8 times/month Needs washing 1-8 times/month – Where does As go?Where does As go?

• Bacterial growth in filter bedBacterial growth in filter bed

OxidationOxidation

• Oxidation of arsenite [As (III)] to Oxidation of arsenite [As (III)] to arsenate [As (V)] with potassium arsenate [As (V)] with potassium permanganate (KMnOpermanganate (KMnO44) )

• As (V) is 60 times less toxic than As As (V) is 60 times less toxic than As (III)(III)

• As (III) occurs in non-ionized form As (III) occurs in non-ionized form

• Use 2 mg/L of KMnOUse 2 mg/L of KMnO4 4 for aluminum for aluminum coagulation and 1.4 mg/L for ironcoagulation and 1.4 mg/L for iron

Coagulation and Co-Coagulation and Co-precipitationprecipitation

• Aluminum coagulationAluminum coagulation

-use 200 mg/L of aluminum sulfate -use 200 mg/L of aluminum sulfate

[Al[Al22(SO(SO44))33]] to form Al-As complexto form Al-As complex

• Iron coagulationIron coagulation

-use 100 mg/L of ferric chloride -use 100 mg/L of ferric chloride

(FeCl(FeCl33) or ferric sulfate ) or ferric sulfate

[Fe[Fe22(SO(SO44))337H7H22O] to form Fe-As complexO] to form Fe-As complex

Aluminum vs. IronAluminum vs. Iron

• For arsenic concentration < 1000 ppb both For arsenic concentration < 1000 ppb both resulted in > 90% removal resulted in > 90% removal • For arsenic concentration > 1000 ppb, For arsenic concentration > 1000 ppb,

ferric salts were found to be better than ferric salts were found to be better than aluminum sulfate aluminum sulfate

• Ferric salts are effective over a wider pH Ferric salts are effective over a wider pH rangerange

Iron: pH of 6.0- 8.5Iron: pH of 6.0- 8.5 Aluminum: pH of 7.2-7.5Aluminum: pH of 7.2-7.5

A Temporary SolutionA Temporary Solution

• Bucket treatment must be a Bucket treatment must be a temporary solution, not a permanent temporary solution, not a permanent one.one.

• It creates toxic sludge that needs to It creates toxic sludge that needs to be disposed ofbe disposed of

• The ultimate goal should be to The ultimate goal should be to connect people to a safe and connect people to a safe and sustainable water sourcesustainable water source

Alternative SolutionsAlternative Solutions• Stop relying on groundwater. Use surface water.Stop relying on groundwater. Use surface water.

– Problem: Surface water is contaminated with fecal Problem: Surface water is contaminated with fecal matter.matter.

– It is easier to treat water for fecal matter than for It is easier to treat water for fecal matter than for arsenic. Invest in treatment plants.arsenic. Invest in treatment plants.

• Use rainwater. Set up rainwater catchments. Use rainwater. Set up rainwater catchments. This is only a partial solution, because there is a This is only a partial solution, because there is a 3-month dry season.3-month dry season.

• Dig surface wells, or drill deep aquifer wells - Dig surface wells, or drill deep aquifer wells - both are less likely than tubewells to become both are less likely than tubewells to become contaminated with Arsenic.contaminated with Arsenic.

Current Developments in Current Developments in BTUBTU• BTU’s are in demand and available all over BTU’s are in demand and available all over

Bangladesh and West Bengal. They cost $US Bangladesh and West Bengal. They cost $US 6.00. There are NGO programs that subsidize 6.00. There are NGO programs that subsidize the cost for the very poor.the cost for the very poor.

• The WHO wants NGO’s, not foreign The WHO wants NGO’s, not foreign companies, to manufacture and install the companies, to manufacture and install the BTU’s.BTU’s.

• There are over 13000 BTU’s in Bangladesh There are over 13000 BTU’s in Bangladesh and West Bengal, as of Dec 2000 [can’t find a and West Bengal, as of Dec 2000 [can’t find a more recent number]more recent number]

References:References:• Alliance for Global Sustainability:

http://www.eawag.ch/research_e/w+t/ags/web-UT/oben.html• WHO:

http://www.who.int/mediacentre/factsheets/fs210/en/http://www.who.int/water_sanitation_health/dwq/arsenic2/en/index3.htmlhttp://www.who.int/water_sanitation_health/dwq/arsenic2/en/index3.html

• “Rapid Assessment of Technologies for Arsenic Removal at the Household Level”, Sutherland et al. 2001, “An Overview of Arsenic Removal Technologies in Bangladesh and India”, M. Ahmed 2001“Development of Low-cost Technologies for Removal of Arsenic from Groundwater”, Ali et al. 2001All from:BUET-UNU International Workshop on Technologies for Arsenic Removal from Drinking Water

• Groundwater Arsenic Contamination in Bangladesh and West Bengal, India:http://ehp.niehs.nih.gov/members/2000/108p393-397chowdhury/chowdhury-full.html

• BBC Coverage: BBC Coverage: http://news.bbc.co.uk/1/hi/world/south_asia/252308.stmhttp://news.bbc.co.uk/1/hi/world/south_asia/252308.stm

• Supply Chain Initiative:Supply Chain Initiative:http://http://www.wsp.org/publications/sa_arsenic.pdfwww.wsp.org/publications/sa_arsenic.pdf