[[Image:Ceramic_filter_icon.png|right|80px]][[Image:arsenic removal.jpg|thumb|right|250px200px| Arsenic removal system: oxidation method. <br>Photo: Ngai.]][[Image:arsenic removal two.jpg|thumb|right|250px200px|Magc-Alcan Filter (left) and Nirmal Filter (right): adsorption method. Photo: Ngai.]]__NOTOC__ <small-title />
There are at least five ways to remove arsenic from drinking water. The adsorption method, the coagulation-flocculation method, the surface complexation method, a Kanchan arsenic filter, or removal by oxidation.
The Sono Filter is a three bucket system with a composite iron matrix (CIM) as the active arsenic removal component. It creates surface complexation of arsenic on the CIM followed by a filtration. The filter is manufactured from indigenous materials and it works without chemical treatment, without regeneration, and without producing toxic waste. It is efficient to remove arsenic and 22 other heavy metals as well as bacteria.
'''Kanchan Arsenic arsenic filter'''<br>
The Kanchan Arsenic Filter (KAF) is an adaptation of the biosand filter. The KAF has been designed to remove arsenic from drinking water, in addition to providing microbiological water treatment. Arsenic removal is achieved by incorporating a layer of rusty nails in the diffuser basin of the filter.
'''Passive Oxidationand solar oxidation'''<br>
Passive oxidation is based on oxidation mechanisms of iron compounds that naturally reduce the arsenic content of groundwater. Naturally occurring dissolved Fe(OH)2 in the groundwater undergoes a natural chemical process called oxidation (when an element loses electrons) to produce a solid form or precipitate of Fe(OH)3 which attracts arsenic to stick to it, a process called adsorption (Ahmed, 2002). This adsorption produces a co-precipitate of Fe(OH)3 and arsenic that settles to the bottom of the container thereby removing the arsenic from the water. This technology does not require chemicals, but rather is based on the passive oxidation process and subsequent sedimentation.
Passive oxidation is seen as an easy technology, because of the natural habits of rural people to store their water in pitchers, before they drink it. Nevertheless, its performance at removing arsenic at safe levels has not been proven.
The SORAS (Solar Oxidation and Removal of Arsenic) method is similar to the SODIS one but with use of lemon juice. Sunlight as a source of UV causes the oxidation (loss of electrons) of As(III) to As(V). The resulting As(V) is strongly attracted to iron hydroxides particles present in the water and sticks to these particles. The As(V)/Fe(OH)3 co-precipitate then settles to the bottom of the container. SORAS removes arsenic in a two-step procedure:<br>* First step: As(III), which only weakly adsorbs to iron hydroxides, is oxidized to the strongly adsorbing As(V).* Second step: Fe(III) hydroxide precipitates formed from naturally present iron are allowed to settle to the bottom of the container with the adsorbed As(V) and the clear water is decanted. Instead of adding chemical oxidants such as chlorine or permanganate, reactive oxidants are produced photo chemically with sunlight. ===Construction, operations and maintenance===[[Image:shapla filter.jpg|thumb|right|200|Shapla arsenic filter. Photo: Ngai.]][[Image:2-Kolshi filter.jpg|thumb|right|200|2-Kolshi arsenic filter. Photo: Ngai.]][[Image:Sono filter.jpg|thumb|right|200|Sono arsenic filter. Diagram: [http://www.robrasa.com robrasa.com]]][[Image:Kanchan filter.jpg|thumb|right|200|Kanchan arsenic filter. Diagram: CAWST.]][[Image:Asia arsenic filter.jpg|thumb|right|200|Asia arsenic filter. Drawing: Asia Arsenic Network, (2001).]]
'''Adsorption: Magc-Alcan filter'''<br>
* Place two buckets (with taps) filled with activated alumina media in series using a stand.
Contaminated water is poured into the top of the filter on an intermittent basis. The water slowly passes through the diffuser, and percolates down through the biolayer, sand and gravel. Treated water naturally flows from the outlet. The biolayer is the key pathogen removing component of the filter. Without it, the filter is significantly less effective. It may take up to 30 days to establish the biolayer depending on inlet water quality and frequency of use. The water from the filter can be used during the first few weeks while the biolayer is being established, but disinfection is recommended during this time, as during regular on-going use.
Much more information and details on the Kanchan arsenic filter: [http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=2&ved=0CFYQFjAB&url=http%3A%2F%2Fwww.cawst.org%2Fassets%2FFile%2FHWTS_Fact_Sheet_KAF/assets/File/HWTS_Fact_Sheet_KAF.pdf&ei=gz72T6esPOmy2QXl8-ToBg&usg=AFQjCNHExV2LsQy4IgoZzMR2avHnREOnsg&sig2=ClJFwW7vj9UkNrgU-4udPA Household Water Treatment and Safe Storage Factsheet: Kanchan Arsenic Filter.] '''Oxidation: Passive'''<br>* Stir the water for 2 minutes* Leave water overnight in an open container
'''Passive Oxidation: Solar'''<br>* Fill PET (or other UV–A) transparent bottles with water* Add lemon juice to bottles* Place the bottled in the sunlight for 1-2 days* During the night, place the bottles in vertical position* The water can then be filtered through textile cloth or clay filters
===Costs===
'''Adsorption: Magc-Alcan filter'''<br>
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'''Oxidation: Passive'''<br>{|border="1" cellspacing="0" |-! scope="col" |Treatment Efficiency! scope="col" |Production! scope="col" |Cost|-|Typically 30 to 50% arsenic removal|No limit|Minimal cost|} '''Oxidation: Solar'''<br>{|border="1" cellspacing="0" |-! scope="col" |Treatment Efficiency! scope="col" |Production! scope="col" |Cost|-|If iron > 8 ppm, 75-90% arsenic removal. If iron < 5 ppm, <50 % arsenic removal. Excellent microbial removal (99+%)|No limit|Minimal cost|} ===Field experiences===The following projects make use of arsenic filtration: {|style="border: 2px solid #e0e0e0; width: 60%; text-align: justify; background-color: #e9f5fd;" cellpadding="2"<!--rsr logo here-->|- style="vertical-align: top"|[[Image:akvorsr logo_lite.png|center|60px|link=http://akvo.org/products/rsr/]]| <!--place holder-->|[[Image:akvorsr logo_lite.png|center|60px|link=http://akvo.org/products/rsr/]]<!--project blocks here-->|- style=Acknowledgements"vertical-align: bottom"|[[Image: rsr 476.jpg|thumb|center|140px|<font size="2"><center>[http://rsr.akvo.org/project/476/ RSR Project 476]<br>Ensure access to safe water and sanitation</center></font>|link=http://rsr.akvo.org/project/476/]] * |[[Image: rsr 769.jpg|thumb|center|140px|<font size="2"><center>[http://wwwrsr.akvo.org/project/769/ RSR Project 769]<br>Life-WASH</center></font>|link=http://rsr.googleakvo.comorg/project/769/url?sa]] |[[Image:rsr 770.jpg |thumb|center|140px|<font size=t&rct"2"><center>[http://rsr.akvo.org/project/770/ RSR Project 770]<br>Intervention Efforts in WASH</center></font>|link=j&qhttp://rsr.akvo.org/project/770/ ]] |} =&esrc=s&source=web&cdAcknowledgements=3&ved=0CHMQFjAC&url=* [http%3A%2F%2Fwww://www.cawstsswm.org%2Ffr%2Fresources%2Fpubs%2Fcategory%2F25info/category/implementation-facttools/water-sheetspurification/hardware/point-academic%3Fdownload%3D40%253Ahwtsuse-factwater-sheetarsenictreatment/arsenic-removalpdfoct09&ei=oi32T5bROeWW2AWlremoval-fDCBg&usg=AFQjCNHtsMduzuzEZMNKHgbl2BN1dHjr2g&sig2=VgGZabK2qsBHhJQkLL2TKQ Household Water Treatment for Arsenic Removal Fact Sheet: Adsorption.] CAWSTRaju Shrestha, Environment and Public Health Organisation, ENPHO.* [http://wwwresources.googlecawst.comorg/asset/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&ved=0CG4QFjAA&url=http%3A%2F%2Fafghanlivelihoods.com%2Fvirtualarsenic-removal-library%2FShelter%2Fbiosandfact-filtration%2Fresources%2Fcasesheets-studies%2Fcaseadsorption_fr French Factsheet]. CAWST.* [http://resources.cawst.org/asset/arsenic-studyremoval-koshishfact-pakistan.doc&ei=STv2T4uhOvO_2QXxwJjaBg&usg=AFQjCNGUyPcn5C4VZdt_mjYo0sheets-0MktUnkw&sig2=yBKPzMiE6wkNRWtSR3kTPg coagulation_fr Household Water Treatment for Arsenic Removal Fact Sheet: Coagulation-Flocculation.] CAWST. (French version).* [http://www.googlesswm.cominfo/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&ved=0CGkQFjAA&url=ftp%3A%2F%2Fftp.wpro.who.intsites/default/files/reference_attachments/CAWST%2Fscratch202009%2FENH20Household%2FHWTS20Water%2FWHO20Treatment%2520Final20and%2FParticipant20Safe%2520Manual20Storage%2FAppendices20Fact%2FParticipant20Sheets%2520Manual_Appendix20Academic%25202_HWTS20Arsenic%2520Fact20Removal%2520Sheets_2011-09-05%2F6_Arsenic%2520Removal%2FHWTS%2520Fact%2520Sheet_Arsenic%2520Removal_Complexation_2011-0620Complexation.doc&ei=JT32T7b3F4Ow2QW97pn8Bg&usg=AFQjCNHvayfxy_1Ml3uEd_7Y9fhbmyQJcA&sig2=ViTGkFqtns4j4WaOjEVQPQ pdf Household Water Treatment for Arsenic Removal Fact Sheet: Surface Complexation.] CAWST.* [http://www.cawst.org/assets/File/HWTS_Fact_Sheet_KAF.pdf Household Water Treatment and Safe Storage Factsheet: Kanchan Arsenic Filter.] CAWST.
* [http://www.cawst.org/en/resources/pubs/category/24-fact-sheets-simplified Household Water Treatment Fact Sheets.] CAWST.