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==
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.pdf&ei=gz72T6esPOmy2QXl8-ToBg&usg=AFQjCNHExV2LsQy4IgoZzMR2avHnREOnsg&sig2=ClJFwW7vj9UkNrgU-4udPA Household Water Treatment and Safe Storage Factsheet: Kanchan Arsenic Filter.]
'''Oxidation: Passive oxidation'''<br>
* Stir the water for 2 minutes
* Leave water overnight in an open container
'''Oxidation: Solar oxidation'''<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==
|Replace unit after 3-5 years
|}
'''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
|}
==Acknowledgements==