Treatment efficiency was investigated for advanced treatment of coal chemical industry wastewater by expansive ^ow biological aerated filter. Removal efficiencies of COD and total phenols rose with the prolonging of hydraulic retention time (HRT). The removal efficiencies of COD and total phenols increased from 56.3 to 66.7 and from 63.8 to 74.2 respectively when HRT expanded from 6 h to 12 h. NH4+-N removal efficiency decreased with the augment of HRT. Shorter HRT induced higher hydraulic loading rate, which could promote mass transfer between biofilm and wastewater, accelerating the reaction rate. Turbidity and chroma in effluent were 3.66 NTU and 26.22 at the HRT of 9 h, with the removal efficiency of 98.03 and 91.67 respectively. The optimal backwashing time was 6 minutes in pulse manner with air and water intensity of 8.0 L/(sm2) and 2.5 L/(sm2), according to the amount of suspended solid and recovery time.
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