Effect of Iron Shavings on Nitrogen and Phosphorus Removal in Anaerobic/Oxic/Anoxic Process

In order to achieve nitrogen and phosphorus removal from municipal domestic sewage at low energy consumption and normal temperature,the comparison test of adding iron shavings in the anaerobic/oxic/anoxic(A/O/A) process was performed.Steady nitrite nitrogen accumulation of 45.2% can be obtained at temperature of(25±1) ℃,pH of 8.0±1,DO of(1±0.5) mg/L,total iron concentration of(35±2) mg/L and HRT of 9 h.The average removal rates of COD,TN and TP are 86.6%,80.2% and 90.4% respectively.The effluent COD,TN and TP are 45.5 mg/L,8.4 mg/L and 0.29 mg/L respectively,meeting the first level A criteria specified in GB 18918-2002.TP removal is mainly due to precipitation and flocculation,with contribution rate of 80%.It is concluded that shortcut nitrification and denitrification can be accomplished by the combined biological and chemical processes,and high removal rates of COD,TN and TP can be achieved.