Study On Microbial Remediation Mechanism Of Phenanthrene Pollution

Phenanthrene, containing three benzene rings, is one of the typical PAHs with low-molecular-weight, persistent organic pollutants (POPs) and high detection rate. Phenanthrene can easily migrate into the the organism, sediment and organic matte, or accumulate in the human body through the food chain, which can endanger human health. So the research on the phenanthrene migration and transformation in the environment can provide reference for the bioremediation of pollution with phenanthrene and other PAHs. This study on selection, isolation and preliminary identification of six phenanthrene degradation strains were conducted. The characteristics of the volatilization, adsorption, biodegradation of phenanthrene by domesticated sludge and the strains were studied. The biodegradation model by strain Bacillus sp. and the enzymatic reaction and inhibition kinetics by strain Sphingobacterium sp. 1, Bacillus sp. and Arthrobacter sp. were discussed. The results of the study are as follows:1. The volatilization of phenanthrene in domesticated and each of the strains could be fit with the first-order kinetics model. The increase of water flow velocity and temperature promoted the volatilization rate. The volatilization rate constant ka and the total mass transfer coefficient k obtained from the experiment data and the calculated total mass transfer coefficient using the empirical formula was 2.240×10-6 m/s.2. The strains isolated from the domesticated sludge conclude: Sphingobacterium sp. (P-1, P-4), Bacillus sp. (P-2), Arthrobacter sp. (P-3), Variovorax sp. (P-5), Kocuria sp. (P-6). All of the six strains are gram-positive bacteria except for the strain P-1.3. The adsorption of phenanthrene on domesticated and each of the strains fitted well with Langmuir adsorption isotherm equation and Freundlich adsorption isotherm equation. The adsorption equilibrium time was 1 h. The adsorption kinetics could be expressed by second-order kinetic equation. The activation energy of the sludge, strain Sphingobacterium sp. 1, strain Bacillus sp. on the phenanthrene adsorption were 6.63 kJ/mol, 25.66 kJ/mol, 13.38 kJ/mol, respectively. The values of gibbs free energy (ΔG < 0) and enthalpy (ΔH > 0) showed that the adsorption reactions of phenanthrene were spontaneous reactions and endothermic reactions. The adsorptions of naphthalene were higher than phenanthrene on the strain Sphingobacterium sp. 1 and strain Bacillus sp.. The competitive adsorption isotherm of naphthalene and phenanthrene on strain Sphingobacterium sp. 1 fitted well with Langmuir and Freundlich competitive isotherm models.4. The experimental outcomes of the degradation of phenanthrene by domesticated sludge and each of the strains could be fit well with the first-order biodegradation kinetics model. The removal efficiency of the phenanthrene degradation by strains Sphingobacterium sp. 1、Bacillus sp.、Arthrobacter sp.、Sphingobacterium sp. 2、Variovorax sp.、Kocuria sp. for 100 mg/L of phenanthrene in 15 d were 100%, 94.0%, 68.1%, 64.4%, 81.3%, 14.3%, respectively. The addition of glucose and yeast powder increased the phenanthrene degradation rates. Temperature and pH value had great impacts on the degradation. Co-metabolism occurred on phenanthrene degradation by strain Sphingobacterium sp. 1 when added in phenol or Naphthalene. Naphthalene promoted the phenanthrene mineralization by strain Kocuria sp. but leaded to competitive inhibition on the phenanthrene degradation by strain Bacillus sp. replenish oxygen accelerated the phenanthrene degradation rates.5. competitive inhibition existed between naphthalene and phenanthrene on the degradation of phenanthrene by strain Bacillus sp. and the value of the competitive inhibition constant KI was 0.4240 mg/L. The high-phenanthrene concentration inhibited the enzymatic reaction of strain Kocuria sp. Substrate inhibition constant kS and the optimum substrate concentration [S]opt were 3.173 mg/L and 0.683 mg/L, respectively.