Immobilization method for the household-level removal of iron through (chemical) coagulation and/or an oxidation or biological immobilization stage. The process often features an aeration-sedimentation-(sand/gravel)-filtration sequence. Key proponent: IRF. Slow or rapid sand filtration with post-sedimentation can already achieve moderate removal.
Reportedly, a semi-centralized (shared/small-community) aeration-sand filtration unit costs ~USD200. A concrete-made container is the only significant cost at household-level; filter media (charcoal; sand or gravel) are inexpensive. Chemical additives may present a significant recurring O&M cost for the filtration units.
Can be applied at level of household or small group of households. Method might be advocated from central level. Supply of the chemicals might also be centrally organized. Simple filtration requires little training; chemical methods necessitate education on proper dosing/post-management.
Iron may originate from groundwater, but also from rusting well/pump parts. If so, parts to be replaced with non-ferric components. Presence of manganese or arsenic requires more extensive treatment. Low concentration iron can be treated with aeration-filtration; high concentration necessitates chlorination-filtration.
Coagulation-flocculation involving methods are likely to be more labor-intensive. Simple aeration-filtration methods are easier to manage, requiring only infrequent washing of filter media. O&M costs are limited, only regular chlorine/lime addition may present regular purchase items.
Coloring/turbidity effect may motivate users to prefer (contaminated) surface water, where treatment is insufficient. The integrated IRF design has proved a best practice method in the Philippines. Very limited maintenance requirements allow for comfortable daily use.
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