Effects of iron concentrations, filter hydraulic loading rates, and porosities on iron removal by rapid sand filtration

Oxidation of iron particles occurring as a result of oxidation of ferrous iron Fe(II) result in undesirable effects in water quality. These iron particles can be removed from water through physical treatment processes of filtration, adsorption, and membrane systems. Iron removal with a rapid sand filtration method was investigated. Effects of iron concentrations, filter hydraulic loading rates, and porosities were studied for the effluent iron concentration, turbidity, and head loss parameters. Plexiglas filter column system with an inner diameter of 30 mm and an equivalent diameter of silica sand with 0.59 mm was used. Four iron concentrations and four hydraulic loading rates were applied. Effects of filter hydraulic loading rates depend on the influent iron concentrations. Low iron concentrations could be removed by rapid sand filtration without high head loss occurrences. Moreover, effluent iron concentrations obtained for this situation were found to be lower than 0.2 mg/L, which is the legislative limit of Turkish Drinking Water Regulation (TDWR). Filter operation time increased with increasing the porosity. Filter operation time was about 2.4 times higher at the porosity of 0.40 than that at the porosity value of 0.36. Low effluent iron concentrations were obtained at the porosity value of 0.36.