Removal Of PCP By Immobilization-cometabolism Method

Pentachlorophenol (PCP) is one of persistent organic pollutants. It is existed broadly in the waters. The research of toxicity and biodegradation of PCP is focused by international chemical field. The immobilization-cometabolism method is used to remove PCP which is existed in the wastewater. The toxicity of PCP and the mechanisms of immobilization- cometabolism have been investigated.The toxicity of pentachlorophenol (PCP) with protozoan community as target organism was studied. In the 12h-cute toxicity testing, the maximal tolerance and minimal all lethal were tigated, the half lethal concentration was 2.40 mg/L. Through mixed culture four strains that could live in the high concentration of PCP have been isolated by enriching, screening and culturing from activated sludge. They are called NERCDT-A, NERCDT-B, NERCDT-C, NERCDT-D. The four strains are identified by 16SrDNA as Klebsiella terrigena, Uncultured bacterium, Bacterium SV26II and Pseudomonas migulae, respectively. The fittest vegetal conditions and optimized biodegradation condition have been determined by orthogonal experiments and the bacteria growth curves. The PVA mixed algin has been chosen as embedding material and 10mL bacteria was embedded which absorbency is varied from 0.85nm to 0.90nm. The value of pH is 8.0.The experiments have been used in detail to compare the effect of PCP removal by bacteria in solution, the immobilized single bacteria and the immobilized mixed bacteria. Results show that the velocity of degradation used by immobile bacteria method is faster than that used by bacteria in solution. The removal rate of PCP is increased by 35%.Four cometabolism substrates have been used to compare the effect of different growth substrates, which include glucose, butyric acid, glycerol and phenol. Results show that the glucose and butyric acid can promote the degradation rate of PCP, and the glycerol will restrain it. The effect of phenol is related by the initial concentration of phenol. When the concentration of phenol is 10mg/L, the existing of phenol can promote the degradation rate of PCP by using immobilization-cometabolism. When the concentration of phenol is 5mg/L and 50mg/L, the restrain effect is obviously observed. Based on the experimental data and theoretical research of immobilization- cometabolism, single substrate and two substrates model are presented to quantificationally describe the process of PCP degradation. The result of simulation is in good agreement with the experiment data.