Recovery of phosphorus from natural water bodies using iron-oxidizing bacteria and woody biomass

There is a global concern that phosphorus (P) resources will be depleted in the near future, but the P flux from water to land is extremely limited, whereas the reverse flux is substantial. A new method for the recovery of P from natural water bodies was proposed using iron-oxidizing bacteria and woody biomass (heartwood of conifer) as a carrier and a practical demonstration was presented. The woody carrier was immersed in water abundant in iron-oxidizing bacteria and removed 1-10 weeks later. Our results showed that the immersed carrier collected biogenic iron (Fe) oxides produced by iron-oxidizing bacteria, and contained about 0.2 mg g^-1 of P after 3 weeks; this amount was higher than that contained in some P fertile soils used for cultivating plants. The biogenic Fe oxides on the carrier acted as a source of P for plant cultivation, and they could adsorb P from P-rich solutions (10 mg L^-1 of PO₄-P). Although our study involved only a small-scale trial, the proposed method can potentially aid in the effective use of P in water and in water quality improvement if conducted on a large scale.