Influence of dissolved oxygen on removal efficiency of ammonia, iron and manganese in biofilter

In order to study the influence of dissolved oxygen (DO) on the removal efficiency in biofilter, as well as the variation rule of ammonia, iron and manganese, the DO was gradually reduced from about 10.5mg/L to 7mg/L. The results showed that when DO was about 10.5mg/L, the concentration of ammonia, total iron and manganese in effluent were 0.050mg/L, 0.065mg/L and 0.022mg/L, respectively, and ammonia, iron and manganese were mainly removed at 0-1.2m, 0-0.4m and 0-1.2m of the filter layer, respectively. When DO was reduced to about 9mg/L, 8mg/L and 7mg/L, total iron in effluent was lower than 0.1mg/L; manganese in effluent increased significantly at first, then decreased to below 0.05mg/L; and ammonia in effluent increased to 0.17mg/L, 0.41mg/L and 0.61mg/L, respectively. When DO was insufficient, iron was mainly removed in the upper filter layer where DO was sufficient; DO was preferentially used by manganese oxidizing bacteria to oxidize manganese dioxide, and the oxidation rate of manganese was not significantly reduced; the oxidation rate of ammonia was significantly reduced. Thus, biofilter could be operated under lower DO conditions to reduce the operation cost. © 2020, Chemical Industry Press. All right reserved.