The study compared the performance of a biosand filter (BSF) with two BSFs modified by introducing a layer of zero-valent iron (ZVI) during a long-duration test (4 months) mimicking the household use pattern in developing countries. Results of the study showed that for bacterial removal, ZVI-amended BSFs outperformed the BSF by at least 1 log10 unit throughout the filter operation. Effluent turbidity in the BSF and modified BSFs was not significantly influenced by influent values for the turbidity range tested in the study (17.0–45.4 NTU). Removal efficiency of nitrates was higher in the modified BSFs, with up to ∼89% removal in the modified BSFs compared with ∼29% in the BSF. Sharp decline in dissolved oxygen (DO) was observed during the passage of water through the filters. The DO decline was more in the modified filters compared with the conventional BSF. Effluent iron remained within the drinking-water quality standards. The study thus indicates the potential of ZVI to improve the performance of BSFs.

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