Table 9 Summary of interventions with details on mechanisms, where available

Amin (2010)

MGH filter

Two bucket filter – the iron content Fe(II) of the source water is converted to a hydrous ferric oxide from (Fe(III) as HFeO or FeOH) by aeration, which reacts with the As(V) species. As(V) is removed by adsorption, co-precipitation and sand filtration.

Berg (2006), Tobias (2011)

Sand filter

Pumped water trickles through the sand filter – oxic conditions, assume co-ppt with co-existing Fe-OH.

Al-Muyeed (2006), Hoque (2000), Brennan (2011a) and (2011b)

A/IRP

Aeration/sedimentation chamber followed by filtration.

BAMWSP (2001), Sutherland (2001), Hoque (2000), Sutherland (2002), Rahman (2005), Hoque (2004)

GARNET

Passive coagulation with iron (from alkaline brick chips) and adsorption to sand.

BAMWSP (2001), Sutherland (2001)

Ardasha filter

Passive sedimentation and adsorption to clay/carbonised organic matter candle.

BAMWSP (2001), Sutherland (2001), Hoque (2000)

Passive sedimentation

Bhattacharyya (2004)

Domestic clay candle filter

Passive sedimentation and adsorption to clay candle.

Hassan (2009)

Iron oxidising bacteria

Water flows through biological fixed bed reactor comprising of gravel bed media and coconut husk (iron oxidising bacteria have been shown to oxidise arsenite). In second reactor the water passes through a sand filter, iron matrix wooden charcoal and another sand filter.

Sharma (2005), Hassan (2008)

A/IRU

Aeration, sedimentation and filtration of groundwater.

Shafiquzzaman (2011)

Iron removal ceramic filter

Biological oxidation of Fe and filtration. Also uses an iron net as additional source of Fe and iron bacterial sludge, however, aeration and biological oxidation seen as primary process.

Delowar (2006)

Asian Arsenic Network (AAN) Filter

Delowar (2006)

NIFSF

Coagulation, co-precipitation and filtration

Extends the processes operating at Fe-MN removal plants by adding metal salts onto which As is adsorbed.

Tend to be complex, comprising a chemical feed system, mixing equipment, basins for mixing, flocculation and settlement, a filter medium and filter medium.

BAMWSP (2001), Sutherland (2001), Sutherland (2002)

DPHE/Danida two bucket system

Based on the addition of aluminium sulphate and permanganate.

Hoque (2000)

Alum treatment of contaminated water

BAMWSP (2001), Sutherland (2001), Sutherland (2002), Cheng (2004), Meng (2001)

Stevens Institute technology

Based on the addition of iron sulphate (coagulant) and hypochlorite (oxidant).

Amiri (2010), BCSIR (2008)

CIWPL, STAR

Ferric sulphate – coagulation, then filter to remove flocs.

Norton (2009)

Procter & Gamble powder

Flocculant-disinfectant.

Ali (2001)

Alum and iron coagulation

Hossain (2005)

Chlorinating agent (BP) + ferric alum

Adsorption processes

Activated alumina, synthetic iron oxyhydroxide adsorbents, granular ferric hydroxide and granular ferric oxide, iron oxide coated sands

Hossain (2005)

Variations on activated alumina and ferric hydroxide (x7)

Hossain (2006)

Samples 305 arsenic removal plants (ARPs) – based on typical ARP with granular ferric oxide

Amiri (2010), BCSIR (2008)

Apyron

Alumina and modified alumina.

Amiri (2010), BCSIR (2008)

Nelima

Granular ferric oxide.

Amiri (2010), BCSIR (2008)

Shapla

Fe₂O₃ impregnated brick chip.

Amiri (2010), BCSIR (2008)

Wholly water

Arsenic removal filter filled with MnO₂, brass powder, ferric sulphate modified alumina and granular activated carbon. Second filter of activated alumina.

Anstiss (2001)

Tank system with ferric oxide

Synthetic ferric oxyhydroxide (suspension) – adsorbs and settles – sand/gravel filter.

Jakariya (2003, 2005, 2007), Rahman (2005), BRAC (2000)

Safi filter

The Safi candle is prepared from laterite soil, ferric oxide, manganese dioxide, aluminium hydroxide and meso-porous silica.

Misra (2005)

As removal filter

Reactant material is a processed waste from the steel industry, followed by fine cloth filter, sand and another fine cloth filter.

Sarkar (2008), BRAC (2000), Sarkar (2005), Amiri (2010), Sutherland (2002), BCSIR (2003, 2008), BAMWSP (2001), Sutherland (2001), Sutherland (2002), Jakariya (2003, 2007), Ahmad (2005)

Activated alumina filter

Yuan (2002), Ali (2001), Petrusevski (2008)

Iron oxide coated sand (IOCS)

IOCS

BRAC (2000), BCSIR (2003), Jakariya (2003)

SIDKO

Granular iron hydroxide

Ali (2001)

Gravel bed with iron sludge

BCSIR (2003)

READ-F

A proprietary filter media. Arsenic is adsorbed on the media.

Zero-valent iron

Use of low cost iron filings/nails – process appears to work by co-precipitation and adsorption

BAMWSP (2001), Sutherland (2001), Hussam (2007), Jakariya (2003, 2005, 2007), Neku (2003), Shafiquzzaman (2009), Sutherland (2002), Milton (2007), BRAC (2000), BCSIR (2003), Delowar (2006), Ngai (2007), Ngai (2006), Uy (2009), Hoque (2004), Ahmad (2006)

SONO – 3 kolshi arsenic filter-three gagri-three pitcher

Passive coagulation with Fe and/or adsorption to sand matrix.

Iron filings or CIM matrix which is a mixture of metal iron and iron hydroxides.

Ion exchange

Hossain (2005)

Ferric hydroxide

Hossain (2005)

Bucket of resins

Hossain (2005)

Catalytic precipitation/electron exchange

BAMWSP (2001), Sutherland (2001), Sutherland (2002), BCSIR (2003)

Tetrahedron/Tetratreat

Ion exchange resin filter with a gentle oxidative hypochlorite pre-wash.

Sarkar (2007)

ArsenX

Anion exchange resin beads containing dispersed nanoparticles of hydrated ferric oxide.

Membrane technology

Reverse osmosis, nanofiltration, microfiltration and ultrafiltration

Oh (2000)

Low pressure nanofiltration

Feed water pre-filtrated by microfiltration or directly applied to NF membrane (tight RO membrane).

Arsenic removal in situ

Via oxygenation

Van Halem (2010), Gupta (2010), Rott (2008)

Subterranean arsenic removal

Aerated water injected into tubewell to create oxidation zone.

Electrolytic methods

Wan (2011)

Electrocoagulation

Electrocoagulation with iron electrodes, followed by candle filter.