Abstract

In this study a novel media, polystyrene coated by sand (PCS) was made and then applied in a -pilot-scale down-flow biological aerated filter (BAF), named PCS BAF. The efficiency of PCS BAF reactor was compared with efficiencies of puzzolana BAF, gravel BAF, and polystyrene BAF in advanced domestic wastewater treatment through three stages. The inner structure of BAFs consisted of a media with a height of 150 cm for biological attached growth that was modified by a 20 cm layer of silica particles at the bottom of columns to increase the reactors' performance. The physical and chemical parameters of turbidity, BOD5, TCOD, and SCOD, as well as parameters related to backwashing were investigated for BAFs' efficiency. Results of this research indicated that PCS BAF can decrease the turbidity, BOD5, TCOD, and SCOD in the influent, from 20 NTU, 22, 53, and 36 mg/L, to a rate of 1.3 NTU, 9, 26, and 21 mg/L in the effluent, respectively. Moreover, the backwashing time required for PCS BAF was less than half of the other three BAF reactors and the backwashing interval was about once every 19 d.