Iron and aluminum hydroxy (oxide) coated filter media for low-concentration phosphorus removal

The presence of phosphates in water and wastewater negatively affects the aquatic environment. Several processes have been used for the removal of phosphorus from water and wastewater; however, most failed in attaining removal levels that will alleviate the problems associated with its presence. In this study, laboratory experiments were conducted to determine the efficacy of iron aluminum hydroxy (oxide) coated filter media in removing low concentrations of phosphates. Two media (silica sand and olivine) were used in the experiments, and tests were conducted on distilled water, artificial groundwater, tap water, and treated wastewater. The effect of flowrates, ranging from 10 to 80 mL/min (3.4 to 27.2 m(3)/m(2).h), on phosphate removal efficiencies was evaluated for distilled water. Results indicate that the process was very effective in phosphate removal (more than 90%) present in low concentrations (approximately 0.5 mg/L) when applied to distilled water and artificial groundwater and with less success when applied to tap water (less than 80%) and treated wastewater effluent (less than 70%). This reduced removal may be attributed to the presence of competing species and, in this case, in the form of sulfates. The results also show that, for distilled water, the treated pore volumes before breakthrough (set at 0.1 mg/L ranged from 137 to 348 pore volumes (51 to 129 bed volumes) for sand and 245 to 370 pore volumes (100 to 152 bed volumes) for olivine, depending on the flowrates. The results for distilled water further indicated that the flowrates used in the experiments had negligible effect on the removal efficiency of the process, and operating rates of 27 m(3)/m(2).h could be applied to distilled water with negligible negative effects.