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Table 19 Maintenance for zero valent iron technologies

From: Are interventions to reduce the impact of arsenic contamination of groundwater on human health in developing countries effective? A systematic review

Intervention Comments
SONO – three kolshi arsenic filter-three gagri-three pitcher Maintenance - Three pitcher filters required cleaning after ~ every four months.
Hussam and Munir (2007) state no special maintenance required other than the replacement of the upper sand layers when the flow rate decreases. The presence of soluble iron and formation of HFO precipitate is also a common problem with other filtration technology. Used sand is considered nontoxic with less than 16 ug/l As.
Positive - Inexpensive. Simple to construct. Made from locally available materials. Uses material familiar to rural people. Still using tubewell water. Portable, so can be relocated. BRAC. Forty five percent of the users were satisfied, 21% were very satisfied and 4.5% were not satisfied with the quality of the water based on taste (Shafiquzzaman et al., 2009).
Negative - People did not appreciate maintenance needs (Hoque et al., 2000). The stated reasons for not using Sono filters were: i) they had been injured while cleaning the iron pieces in the filter media, and/or ii) they could not replace/maintain the iron media when it clumped and solidified while used. The pitchers broke frequently during maintenance (Hoque et al., 2004).
Difficult to move and slow flow rates (Sutherland et al., 2002) . The three kolshi tended to clog (to <1L/hr) after a few months of usage (Ngai et al., 2007).
Produces sludge containing arsenic and potential for contamination with micro-organisms in atmosphere as pitchers not covered (BRAC, 2000).
Bad taste and smells, inadequate amount of water produced by the filter unit, unavailability of filter materials, hazardous maintenance, broken pitchers and water that was too cold to drink were some reasons reported by the participants for not using the three-pitcher filter. People seemed reluctant to collect materials from local market on their own (Milton et al., 2007).
Some problems in terms of leaching of arsenic and clogging in iron filings. In some cases the iron filings were clogged by forming a hard structure (hydrous ferric oxide) which could not be removed from the pitcher (Delowar et al., 2006).
Thirty one filters abandoned after one year, seven broken after six months and 18 abandoned within six months of installation. The connection between the two buckets had been broken in most damaged filters (Shafiquzzaman et al., 2009).
Forty-one percent reported that the filters were frequently clogged and that the flow was too slow to get enough water for their daily needs. About 51% indicated the cleaning technique was burdensome (Shafiquzzaman et al., 2009).
Households were asked about maintenance. A workshop was conducted before providing the filter. Over 80% of households had the filter manual, containing guidance for cleaning the filter. However, 80% of the households performed cleaning based only on the workshop training. One of the reasons may be that it was full of textual rather than pictorial instructions. However, most (about 80%) of the households were knowledgeable about the maintenance of the filter and they maintained it or cleaned it once or twice a week (Shafiquzzaman et al., 2009).
According to the manual, the sludge should be kept in a pot for environmental safety. Most users disposed of the sludge either in drains (58%) or directly in ponds (35%) (Shafiquzzaman et al., 2009).
Kanchan filter Maintenance - Replacement of nails every three years. Filter cleaning ~ every one to three months (Ngai et al., 2007).
Positive - In terms of social acceptability, the Kanchan filter ranked better than the three or two Kolshi, for example, the slow flow of the three kolshi caused some users to skip filtration when they had no time. Ngai (2007) 83% sustained use after one year. 86% found it simple to use. Eight-five percent would recommend (Ngai et al., 2007).
Tubewell sand filter -