Study On Biodegradation Of Dichlorophenol And Trichlorophenol By Photosynthetic Bacteria

In this paper, the multiplication of mixed cultures photosynthetic bacteria PSB-DR and the degradation characteristics of 2,6-dichlorophenol (2,6-DCP) and 2,4,6-trichlorophenol (2,4,6-TCP) by PSB-DR were investigated. It consists of the following three aspects:In the first place, the dominant bacteria of PSB-DR are identified according to their cells morphological properties and physiological biochemical characteristics. Then the culture medium for PSB-DR were optimized to be incubation with 2.4³.2 g/L sodium acetate as carbon source, 1.2 g/L ammonium chloride as nitrogen source and 2 mL/L growth factor solution under light (30℃, 4800 Lx).In the next place, the degradation of 2,6-DCP by PSB-DR at different carbon source concentrations, illumination, oxygen supply conditions, initial pH, inoculum density and nitrogen source concentrations were investigated. The results showed that the degradation conditions were optimized to be incubation with an initial pH 6.0, inoculum density of 30%, sodium acetate and ammonium chloride concentrations of 0 g/L under light in unsealed flasks. Under such optimum conditions, about more than 80% of 2,6-DCP with initial concentration of 50 mg/L was removed after 7 d incubation. Moreover, the degradation pathway of 2,6-DCP was preliminarily studed. The result indicated that the degradation of 2,6-DCP might proceed via the hydroquinone pathway.In the end, the degradation of 2,4,6-TCP by PSB-DR at different carbon source concentrations, illumination, inoculum density, initial pH, nitrogen source concentrations and reaction times were investigated. The results showed that the degradation conditions were optimized to be incubation with an inoculum density of 30%, initial pH 7.0, sodium acetate and ammonium chloride concentrations of 0 g/L under light. Under such optimum conditions, about 82.3% of 2,4,6-TCP with initial concentration of 50 mg/L was removed after 5 d incubation. In addition, the biodegradation of 2,4,6-TCP can be well described by the enzymatic reaction of high concentration inhibition, with the maximum substrate utilization rate 1.746 h^-1, Michaelis-Menten constant 38.333 mg/L and inhibitory constant 260.87 mg/L, respectively.