Survey on efficiency of BF/AS integrated biological system in phenol removal of wastewater

Abstract

Due to the efficiency and flexibility of integrated biological systems, they have been widely developed for the treatment of various waste-waters in recent decades. Present study aims at revealing the efficiency of bio-filter and activated sludge (BF/AS) integrated biological system in phenol removal from wastewater. The cylindrical bioreactors (continuous flow, 12 L) are made from Plexiglas. Interlaced plastic discs were fixed inside the reactor to hold the biofilm. The effects of pH (6.5-8), phenol concentration (100-500 mg/L), nitrogen (30-80 mg/L), phosphorous (6-16 mg/L), glucose concentration (50-500 mg/L), MLSS concentration (1450-3500 mg/L) and hydraulic retention time (2-4.4 h) were evaluated. Results of the study showed that this system could remove 500 mg/L of phenol concentration and 4-4.5 kg COD/m(3)d organic load in 4 h under favorable conditions. Pearson correlation coefficient between removal efficiency and phenol concentration was -0.446 (P < 0.001). By increasing phenol concentration, removal efficiency decreased. Appropriate COD/N/P for maximum efficiency was equal to 100/10/2. Dominant identified bacteria in the system include: Pseudomonas aeruginosa, Pseudomonas alcaligenes, acetinobacter, morexella and Brevundiomonas vesicalaris. Phenol decomposition was done according to the second-order kinetic reaction. Concentration difference (Delta A) to retention time difference (Delta T) ratio were 53.9, 69.5 and 100 for retention times of 2.2, 6 and 7 h, respectively. The BF/AS integrated biological system is highly efficient in removing phenol from aqueous and as an environment-friendly procedure could treat waste-waters containing average phenol concentrations in a relatively short period.