LAUSR

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 oxydans 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.