Intensified 4-chlorophenol biodegradation in an aerobic sequencing batch reactor: Microbial and kinetic properties evaluation

Abstract

In this paper, the microbial and biodegradation kinetics of acclimated-mixed sludge to 4-chlorophenol (4-CP) were investigated in an aerobic sequencing batch reactor (SBR). A molecular technique was applied to evaluate the bacterial variety and role in mixed biomass. Culture isolation and a 16S rDNA sequence authenticated the domination of Gram-positive high-G+C bacilli and coccobacilli with a 99% similarity belonging to the group of Actinobacteria. These isolates include Brevibacterium casei DSM20657, Corynebacterium callunae 10338, Microbacterium oxydan s XH0903, and Kocuria rhizophila Ag09. Those strains in the mixed condition aerobically removed 4-CP till a concentration of 800 mg L −1 . The biodegradation kinetics of 4-CP were adequately predicted by the Haldane formulae with a half-saturation constant ( K s ) and an inhibition constant ( K i ), of 9.12 and 609.7 mg L −1 , respectively. The maximum specific degradation rate ( q m ) was 20.33 mg 4-CP g −1 VSS h −1 . Amounts of the yield coefficient (Y) were among 0.25 and 0.48 mg VSS mg −1 COD. However, due to congregate of 5-chloro-2-hydroxymuconic semialdehyde (CHMS), an intermediate meta-cleavage product of 4-CP, the pure strains isolated from mixed sludge did not show a higher 4-CP-removal efficiency compared with the mixed sludge. Therefore, the use of mixed biomass in engineering systems has attracted increased attention for both environmental and biotechnological applications. • Representing firstly Gram positive high-G+C bacteria degrading 4-CP based on 16S rDNA. • Kinetic properties of acclimated-mixed sludge treating high concentration of 4-CP. • The Y value was observed to be from 0.25 to 0.48 mg VSS mg -1 COD. • The critical concentration of 4-CP and the K i /K s ratio were 74.5 mg L -1 and 66.85, respectively. • High concentration of 4-CP could be removed by SBR with acclimated-mixed sludge.