Continuous phosphorus removal from water by physicochemical method using zero valent iron packed column

Excessive phosphorus in aquatic systems causes algal bloom resulting in eutrophication. To treat wastewater including effluent of wastewater treatment plant containing various amounts of phosphorus, a series of continuous experiments on removal of phosphorus from water were performed by using an electrochemical method. The spherical type of zero valent iron (ZVI) and silica sand were packed at appropriate volume ratio of 1:2 in a cylindrical column. An electric potential was applied externally, which can be changed as per the operational requirement. The results indicate that optimum hydraulic retention time of 36 min was required to meet the effluent standards with our laboratory-scale experimental setup. Lower amounts of phosphorus were removed by precipitation due to contact with iron, and additional electric potential was not required. In order to remove high amounts of phosphorus (around 150 mg/L as phosphate), external electric potential of 600 V was applied to the reactor. As the precipitation of phosphate mainly occurs at neutral pH, it is likely that FeHPO₄ will be the main phosphorus-containing compound. Through the results of the large-scale experiments, the ZVI packed reactor can be used as a filter for removal of phosphorus of less than 10 mg/L as phosphate concentration.