The recent development of advanced wastewater treatment by ozone and biological aerated filter.

The combination of ozone and biological aerated filter (O/BAF) has been widely studied and applied in polishing different biological secondary effluents. O/BAF has the advantages of high pollutants removal rate, low operating cost, and flexible combination types. The principle and combination, effect of ozone dosage and influent suspended solids (SS) on O/BAF, applications, current research focuses, and development are discussed. The ozone can break refractory macromolecules into small and biodegradable fragments, increasing the biodegradation. It benefits the operation of BAF. The coupling of ozonation and BAF is efficient in the removal of refractory organic pollutants from different wastewaters. Ozonation can also be used as the post-treatment option after BAF to guarantee the effluent qualities. Normally, the ozone dosage varied from 5 to 125 mg/L with the contact time of 4 to 60 min, while the hydraulic retention time (HRT) of BAF is usually between 2 to 5 h when treating different biological effluents. The effluent COD is normally lower than 50 mg/L. Most of the organic micropollutants (OMPs) in the biological effluent, such as antibiotics, pharmaceuticals, personal care products, steroid hormones, and industrial chemicals, can be efficiently removed by O/BAF. More importantly, the O/BAF can obviously reduce the toxicity of the wastewater. The residual ozone of about 0.2 mg/L in the ozonation effluent benefits the performance of BAF. The future trends of O/BAF are also discussed in the paper.