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Table 18 Maintenance of adsorption 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
Activated alumina As-37  
Aquabind – activated alumina with metal oxide Maintenance - Periodic media replacement at 6–8 months (Hossain et al., 2005).
Red haematite + quartz + sand + activated alumina Maintenance - Requires periodic sludge removal and/or backwash/cleaning (Hossain et al., 2005).
Activated alumina + AAFS-50, patented aluminium silicate + ferric hydroxide -
Aluminium silicate + ferric hydroxide Maintenance - Media recharging at four to six months (Hossain et al., 2005).
Adsorp-As (patented) Maintenance - Requires periodic backwashing (Hossain et al., 2005).
Slurry/granular ferric hydroxide Maintenance - Requires periodic backwashing two to three times a week (Hossain et al., 2005).
Samples 305 ARPs – based on typical ARP with granular ferric oxide Maintenance - Backwashing twice a week and disposal of backwashed sludge (Hossain et al., 2006).
BUET activated alumina filter Maintenance - Media to be replaced after 120,000L of filtered water. (Sutherland et al., 2002).
ALCAN Maintenance - Backwashing of media at least once a week for ~15 mins to remove silt, sands and iron flocs (Amiri et al., 2010).
Apyron Maintenance - Backwashing periodically to remove silt, sands and iron flocs (Amiri et al., 2010).
Wholly Water. Maintenance - Regular backwashing of the filter for at least 10 minutes at ~4L/min (Amiri et al., 2010).
Nelima -
Shapla -
Tank system with ferric oxide Maintenance - Ferric oxyhydroxde replaced ~ after 16 days. The total mass of arsenic produced by the tanks as a max of ~24g from 900g (dry) ferric oxyhydroxide used per tank per year. A regional centre to deal with the ferric oxyhydroxide renewal/recycling was set up at the University of Rajshahi (Anstiss et al., 2001).
Safi filter Maintenance - Washing schedule of fifteen days. Candle replacement required after two years (Jakariya, 2003).
Positive - Users preferred it because of formal shape. Allowed continued use of tubewells and was affordable for rural middle-class households (BRAC, 2000).
Negative - Almost half had technical problems: disintegration of candle to broken taps. Clogging of filter, with low flow rates. Capacity of filter to reduce arsenic reduced over time. BRAC Safi was the least favoured technology after 3 pitcher and Alcan (Jakariya, 2003, Jakariya et al., 2005).
As removal filter Maintenance - The need for waste disposal is mentioned – although the authors indicate the precipitate and sand is converted into concrete blocks. No leaching of arsenic was detected (Misra et al., 2005).
Well head treatment unit using activated alumina adsorption column Maintenance - The column is routinely backwashed for 10–15 min every day and the backwash water is passed through a coarse sand filter to retain the HFO particulates (Sarkar et al., 2005).
In situ regeneration – upon adsorption of the column (As conc approaching 50μg/L) the unit must be regenerated with 4%NaOH followed by 1%HCl, then water. Takes ~10 hr (Sarkar et al., 2005).
For every regeneration, the mass of sludge (dry weight) added to the top of the coarse filter is less than 400g. The authors estimate the on- site sand filter many collect and contain spent sludge for over 30 years (Sarkar et al., 2005).
Activated alumina Maintenance - Central facility for regeneration of adsorbent (Sarkar et al., 2005).
Iron oxide coated sand Maintenance - Monthly washing of upper sand bed.
Positive - User very happy due to not requiring any chemicals and periodic washing of the sand filter to maintain flow rate (Ashraf Ali et al., 2001).
Iron oxide coated sand Maintenance - Regeneration with 8.0L of 0.2N NaOH (Yuan et al., 2002).
UNESCO-IHE family filter Maintenance - Regular cleaning is necessary. The frequency of washing varied from once a week in the first months of operation, to once a day during rest of period (Petrusevski et al., 2008).
SIDKO Positive - After filtration water was ‘crystal-clear and arsenic free’. High-tech appearance means people keen to use it (BRAC, 2000).
Negative - Community SIDKO – people found these options demanded too much attention, they often did not provide the required maintenance (Hoque et al., 2004).
Very low flow rate (1 L/min) due to clogging in plant. Very expensive. Frequent changing of media with high arsenic and iron concentration in influent, which is costly. Media and system not locally available (from Germany), but could produce locally in long-run. Produces sludge which needs to be removed. Unlikely to be sustainable in long-run: maintenance, sludge & lots of users. People may not be prepared to travel to plants: observed initially plant used by 75 families, as other options became available this reduced to 20 families. People have preference for their own water source (BRAC, 2000).
Gravel bed with iron sludge -