Optimization of biological phosphorus removal from contaminated sediments with phosphate-solubilizing microorganisms

This study focused on the characteristics of phosphate-solubilizing microorganisms (PSMs) which can be applied for the removal of phosphorus from sediments to prevent eutrophication of lakes or ponds. A PSM isolated from rhizospheric soil and temporarily identified as Burkholderia glathei (MB 14) produced gluconate and acetate using glucose as a carbon source and its metabolic activity caused the pH of the liquid medium to decrease as low as 4.4. The molar ratio of solubilized PO43--P to total organic acids, gluconate and acetate, in the liquid medium was 1 : 2, which was lower than the theoretical molar ratio of 1 : 3 using Ca-3(PO4)(2) as a model phosphorus compound. In addition, biological PO43--P solubilization with MB 14 was more efficient than the direct addition of equivalent acid to the liquid medium. These results indirectly suggest that organic acids chelate Ca2+ during solubilization of PO43--P. The growth conditions for MB 14 that produced the maximum PO43--P solubilization were carbon sources of 8 g/l of glucose and 2 g/l of sucrose, and 0.1 g/l of arginine as a nitrogen source under an anoxic environment. The PSM species, MB 14, grown under these conditions was applied to treat contaminated dredged sediments in a bioslurry reactor. In 9 d, MB 14 solubilized 34.5% of total phosphorus in the contaminated dredged sediments.