Effect of sludge-fly ash ceramic particles (SFCP) on synthetic wastewater treatment in an A/O combined biological aerated filter

Novel media–sludge-fly ash ceramic particles (SFCP) employed in an upflow lab-scale A/O BAF were investigated for synthetic wastewater treatment. The influences of hydraulic retention time (HRT), air–liquid ratio (A/L) and recirculation on the removals of chemical oxygen demand (CODcr), ammonia ( NH 4 + – N ) and total nitrogen (TN) were discussed. The optimum operation conditions were obtained as HRT of 2.0 h, A/L of 15:1 and 200% recirculation. Under the optimal conditions, 90% CODcr, more than 98% NH3–N and approximately 70% TN were removed. The average consumed volumetric loading rates for CODcr, NH 4 + – N and TN with 200% recirculation were 4.06, 0.36 and 0.29 kg (m3 d)−1, respectively. The CODcr and TN removal mainly occurred in the anoxic zone, while nitrification was completed at the height of 70 cm from the inlet of the bottom due to a suitable column layout of biological aerated filter (BAF). The characteristics of wastewater and backwashing affected TN removal to a large degree. In addition, the features of media (SFCP) and synthetic wastewater contributed to a strong buffer capacity in the BAF system so that the effluent pH at different media height fluctuated slightly and was insensitive to recirculation.