Anaerobic Nitrate Reduction With Oxidation Of Natural Siderite By Citrobacter Freundii Strain PXL1-a Potential Candidate For Simultaneous Removal Of Nitrate And Phosphate

Anaerobic Fe（II） Oxidizing Denitrifiers （AFODN） has been researched for about twenty years, it offering the ability of reducing the nitrate and oxidizing the ferrous iron an aerobically. This culture can use ferrous iron as the only electron donor and nitrate as the electron acceptor, nitrate will be reduced to N₂ or N₂O. This culture plays an important role in iron and nitrogen cycling. In the present study, an AFODN strain-PXL1 was used to study the possibility of removing nitrate and phosphate coexist with siderite. A batch of experiments was conducted to study the effect of TOC、 HRT on the removal rate, to find out if the AFODN’s existing can affect the natural siderite. The conclusions are as follows:（1） PXL1 can coexist with denitrifying bacteria and removal the nitrate together, at the same time, PXL1 can oxidize siderite slowly and iron oxides was reduced to adsorb the phosphate.（2） Nitrate mainly reduced by denitrifying bacteria, so the change of TOC will affect the removal of nitrate.（3） The change of TOC will not affect the removal of phosphate because PXL1 are mixotrophy.（4） The coexisting of siderite n PXL1 and denitrifying bacteria can meet he need of simultaneous removal of nitrate and phosphorus, the removal rate of phosphate and nitrate are 67.4% and 82.7% with the HRT=10h, removal rate will decreased to 60.8% and 82.7% with the HRT=5h, the initial concentration of phosphate and nitrate are 1 mg/L and 149.1 mg/L.（5） PXL1 can’t accumulate phosphorous but oxidize the ferrous to iron oxide to absorb phosphorous.