Arsenic removal methods from water supplies that don't require the addition of iron
What methods exist to remove arsenic from water supplies which don't require the addition of iron but are also suitable for small-scale supplies in developing countries?
The Magc-Alcan and Nirmal filter are examples of household filters that use activated alumina as the adsorption medium.
Filters based on passive and solar oxidation make use of naturally occurring dissolved Fe(OH)2 in the groundwater to remove arsenic. The Swiss research institute Eawag has developed filters based on the SORAS (Solar Oxidation and Removal of Arsenic) method.
More information can be found at:
In mitigation of high arsenic levels UNICEF and WHO state the first option is to consider alternative water supplies such as uncontaminated boreholes or rainwater harvesting. However, where alternative sources are not available household treatment must be considered.
Significant research has been carried out considering a broad range of technical solutions (Wegelin 2000, Sutherland et al 2002, Souter et al 2003, Ngai et al 2007) and several reviews of household water treatment technologies have been written (Murcott 2000, Ahmed 2001, Pokhrel, Bhandari and Viraraghavan 2009) principally focused on experiences in Bangladesh and Nepal. Bangladesh Arsenic Mitigation Water Supply Project (BAMSWP) together with WaterAID and financed by UK Department for International Development (DFID) claims to have carried out the first ‘scientifically-based, independent, comparative assessment of the performance of a range of arsenic removal technologies at household level’ (Sutherland et al 2002). The study that Sutherland et al (2002) carried out compared a range of arsenic removal technologies on the basis of their technical strengths and recommended four: activated alumina (Alcan, BUET); metallic iron (Sono 3-Kolshi); anionic exchange resin (Tetrahedron) and iron coagulation (Stevens Institute Technology). Massachusetts Institute of Technology (MIT), Environment and Public Health Organisation, Nepal (ENPHO) and Centre for Affordable Water and Sanitation Technology (CAWST) carried out a literature and field study that commenced with a review of 50 technologies world wide from which eight were selected for assessment and evaluated against technical performance, social acceptability and economic affordability (Ngai et al 2007). This included 3 of the 4 technologies recommended by Sutherland et al (2002) and also the KanchanTM Arsenic Filter (KAF) that had been subsequently developed by MIT.
As you can see from this, the principal technologies recommended often include iron or alumina to aid removal of the arsenic. However, iron is only used in filters like the KAF filter in the form of iron nails (static in the filter) and no one has yet defined their life span, to my knowledge, so this may be an option for you even though you say you are trying to avoid the use of iron. The KAF filter has also been operated in Cambodia and shown to be a robust technology as well as being socially acceptable for household use.
Another option that does avoid the use of iron is the SAR technology developed by Dr Baskhar Sen Gupta and demonstrated in West Bengal. SAR uses in-situ oxidation of the groundwater so removing the need for disposal of any residues. It is a simple process mostly using equipment that can be bought in any local market, spraying water through shower heads into a tank to oxygenate it and then pumping the oxygenated water back into the aquifer, taking some off for use. However, it requires the community to develop the system together so isn’t suitable for individual household use. You can take a look at the technology on this link http://insituarsenic.org/publications.html.
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