Post-treatment of secondary wastewater treatment plant effluent using a two-stage fluidized bed bioreactor system

The aim of this study was to investigate the performance of a two-stage fluidized bed reactor (fbr) system for thepost-treatment of secondary wastewater treatment plant effluents (shahrak gharb, tehran, iran). the proposedtreatment scheme was evaluated using pilot-scale reactors (106-l of capacity) filled with pvc as the fluidized bed(first stage) and gravel for the filtration purpose (second stage). aluminum sulfate (30 mg/l) and chlorine (1 mg/l)were used for the coagulation and disinfection of the effluent, respectively. to monitor the performance of the fbrsystem, variation of several parameters (biochemical oxygen demand (bod5), chemical oxygen demand (cod),turbidity, total phosphorous, total coliform and fecal coliform) were monitored in the effluent wastewater samples.the results showed that the proposed system could effectively reduce bod5 and cod below 1.95 and 4.06 mg/l,respectively. turbidity of the effluent could be achieved below 0.75 ntu, which was lower than those reported forthe disinfection purpose. the total phosphorus was reduced to 0.52 mg/l, which was near the presentphosphorous standard for the prevention of eutrophication process. depending on both microorganismconcentration and applied surface loading rates (5–10 m/h), about 35 to 75% and 67 to 97% of coliform wereremoved without and with the chlorine addition, respectively. findings of this study clearly confirmed the efficiencyof the fbr system for the post-treatment of the secondary wastewater treatment plant effluents without any solidproblem during the chlorination.