BAF using large-size lightweight ceramic filter media for pretreatment of micro-polluted raw water

On account of the features of micro-polluted raw water, biological aerated filter (BAF) using large-size lightweight ceramic filter media as pretreatment simplifies the BAF process and increases filtration rate greatly. NH₃-N in effluent of BAF was lower than 0.5mg/L, which meets the Sanitary standard for drinking water (GB5749-2006) directly. This BAF is equipped with both up-flow and down-flow backwash systems, there is no need to set a extra grit chamber. Turbidity removal was 1/3 as high as ordinary BAF. The head loss of BAF was below 0.6m after 24 h running, varying less than 0.1 m after backwash. Thus, it is possible for multiple filters sharing a centralized aeration system to achieve uniform aeration. Since lack of time for biochemical action, the COD_Mn removal rate of BAF for pretreatment of micro-polluted raw water is low. COD_Mn in raw water was 0.89-5.6mg/L, 0.61-4.3mg/L in BAF effluent, and the average removal rate was 18.9%. Meanwhile, the effluent of BAF, carrying rich microbes and DO, enhanced the biological effect of removing COD_Mn in the conventional process.