Arsenic in drinking water
Arsenic in drinking-water is a hazard to human health. It has attracted much attention since recognition in the 1990s of its wide occurrence in well-water in Bangladesh. It occurs less extensively in many other countries also.
The main source of arsenic in drinking-water is arsenic-rich rocks through which the water has filtered. It may also occur because of mining or industrial activity in some areas.
Inorganic arsenic can occur in the environment in several forms but in natural waters, and thus in drinking-water, it is mostly found as trivalent arsenite (As(III)) or pentavalent arsenate (As (V)).
Decentralised, no energy needed arsenic removal using SONO Filtration
Based on initial experiences with various types of household filters, the following criteria for any household arsenic filter should be established. The filter
- must require no external addition of any chemicals for normal operation.
- must not produce any sludge requiring disposal as part of its normal operation.
- must be manufactured from materials that are generally available within the country (in this case Bangladesh).
- must not require the regular replacement of filter media for normal operation.
- must provide consistent arsenic removal to less than 10 ppb regardless of the level of influent arsenic contamination.
Simple and effective Arsenic Filter based on Composite Iron Matrix (CIM)
Arsenic and most other heavy metals remain strongly bound to the active media (hydrous ferric oxide) with a mechanism very similar to that of mineralization process in soil. The active media works for at least five years without replacement and by that time 1 million liter of water can be filtered. It is believed the filter will last much longer, but test results guarantees the filter to work for five years.
The filter media can be disposed on top soil because the media turns into soil after this period or their properties are very close to normal soil. Leaching tests show no environmental contamination from the waste.
Specific test results Original feed water vs. Sono filtered water
Summary of 3 yrs filter data with more then 100,000 L filtered
- As(III) was always bdl, <2 ug/L
- As(V) was below 10 ppb, 95% cases
- As(total) was below 20 ppb 100% cases
- pH was increased by 1 pH unit
- Al, Ba, Ca, Fe, Mn, Sr, Zn were decreased
- Sb, Cd, Be, Cr, Cu, Co, Pb, Mo, Ni, Se, Ag
- Tl, and V were mostly below BDL.
- Eh increased with dissolved Fe(II)
- Dissolved oxygen increased by 1 mg/L
Key advantages of using SONO Filters
- 20-30 Liters per hour
- As(Total) < 10 ppb (CL 95%)
- As(III) < 2 ppb (CL 99.9%)
- No pretreatment of water is necessary ?acompletely non chemical filtration system.
- No backwashing or regeneration is necessary.
- Removes iron, manganese, heavy metals, nitrate, nitrite and many anions quantitatively.
- Life: 5 Years Minimum
- Maintenance: Very low
- Cost: ? 50 - ? 55 (or lower)
- Waste: Completely nontoxic ?passed TCLP, TALP
- Bangladesh Government approved and ETVAM program verified
Field Experience with SONO Filters by SIM Bangladesh
SIM Bangladesh (SIM) is an international NGO registered by the Government of Bangladesh. SIM has been conducting arsenic related activities in Bangladesh since June of 1999.
In July of 2002 they began the process of investigating alternatives to provide safe drinking water at the household level. They initially evaluated and tested several different arsenic filter alternatives. Some of the alternatives required chemical addition and produced a chemical sludge that required disposal.
A paper is being written and published to detail SIM's field-based experience with the SONO Filter.