Biodegradation kinetics of 2,4,6-Trichlorophenol by an acclimated mixed microbial culture under aerobic conditions

Abstract

The objective of this study was to achieve a better quantitative understanding of the kinetics of 2,4,6-trichlorophenol (TCP) biodegradation by an acclimated mixed microbial culture. An aerobic mixed microbial culture, obtained from the aeration basin of the wastewater treatment plant, was acclimated in shake flasks utilizing various combinations of 2,4,6-TCP (25-100 mg l(-1)), phenol (300 mg l(-1)) and glycerol (2.5 mg l(-1)) as substrates. Complete primary TCP degradation and a corresponding stoichiometric release of chloride ion were observed by HPLC and IEC analytical techniques, respectively. The acclimated cultures were then used as an inoculum for bench scale experiments in a 4 l stirred-tank reactor (STR) with 2,4,6-TCP as the sole carbon/energy (C/E) source. The phenol acclimated mixed microbial culture consisted of primarily Gram positive and negative rods and was capable of degrading 2,4,6-TCP completely. None of the predicted intermediate compounds were detected by gas chromatography in the cell cytoplasm or supernatant. Based on the disappearance of 2,4,6-TCP, degradation was well modelled by zero-order kinetics which was also consistent with the observed oxygen consumption. Biodegradation rates were compared for four operating conditions including two different initial 2,4,6-TCP concentrations and two different initial biomass concentrations. While the specific rate constant was not dependent on the initial 2,4,6-TCP concentration, it did depend on the initial biomass concentration (X (init)). A lower biomass concentration gave a much higher zero-order specific degradation rate. This behaviour was attributed to a lower average biomass age or cell retention time (theta(x)) for these cultures. The implications of this investigation are important for determining and predicting the potential risks associated with TCP, its degradation in the natural environment or the engineering implications for ex situ treatment of contaminated ground water or soil.

Biological treatment of 2,4,6-trichlorophenol (TCP) containing wastewater in a hybrid bioreactor system with effluent recycle

“…A number of studies were reported in literature on biodegradation of TCP (Armenante et al, 1999;Atuanya et al, 2000;Buitron et al, 1998;Correa et al, 2003;Vallecillo et al, 1999;Wang et al, 2000b;Garibay-Orijel et al, 2006;Snyder et al, 2006;Zilouei et al, 2006) which has an IC 50 value of 40 mg L À1 according to our determinations. Literature studies on aerobic biological treatment of TCP containing wastewaters were performed with low TCP concentrations (<150 mg L À1 ).…”

Degradation pathway, toxicity and kinetics of 2,4,6-trichlorophenol with different co-substrate by aerobic granules in SBR

“…A similar pathway has been reported by Louie et al (2002) with a single difference in the formation of 2,6-dichlor-p-hydroxyquinone instead of 3,5-dichlorcatechol. 3,5-Dichlorocatechol was also detected as an intermediate in the biodegradation of TCP by Snyder et al (2006).…”

“…These may be the products of dehalogenation after ring cleavage (chlorocatechols) and dehalogenation before ring cleavage (2,4 or 2,6-dichlorophenol, 2-chlorophenol, catechol etc.) (Snyder et al, 2006). Mostly chlorinated aromatics degraded via ortho-cleavage, however, in some cases, successful degradation of chloroaromatics via 3-chlorocatechol using the meta-cleavage has also been reported (Farrell and Quilty, 1999).…”

“…However, a very few studies are concerned with mixed culture (Eker and Kargi, 2009;Snyder et al, 2006;Farrell and Quilty, 1999). Therefore the present work focused on comparative study of TCP degradation in presence of glucose and acetate as cosubstrate by mixed culture and characterization of the biodegradation products including the kinetics and toxicity.…”

Degradation of 2,4,6-trichlorophenol by bacteria isolated from secondary sludge of a pulp and paper mill

“…Very few reports are available which dealt with sludge samples (Sanchez et al, 2004;Smith and Novak, 1987). Snyder et al (2006) reported complete removal of 2,4,6-TCP (100 mg L 1 (0.5 mM) by aerobic mixed microbial culture obtained from the aeration basin of a wastewater treatment plant. The consortia of the bacterial isolates used in this study were able to degrade 2,4,6-TCP completely from the sludge sample when the concentration of 2,4,6-TCP was more than 100 mg L 1 (0.5 mM).…”