The Screening Of Lead-resistant Strain And Study On Its Application

In order to solve the problems of resistance and adsorptivity which were faced in treating heavy metal wastewater by biofilms.Our studies focus on the microorganisms in biofilm were cultured with active sludge of sewage disposal factory in Dalian development of economy and technique zone The microorganisms in biofilm were domesticated in different culture media which containing of Pb²⁺ and the dominant bacteria with high resistance and adsorptivity was screened out.The dominant bacteria were obtained by compareing with the uptake of Pb²⁺.The strain was identified as Klebsiella pneumoniae by the 16S rDNA analysis and comparing with NCBI and the physiology and biochemistry characteristics of strain are similar with Klebsiella pneumoniae.The adsorptive effects were discussed. The experimental results indicate that lead ion removal rate can reach up to 96.88% in the following conditions: pH=7.0, initial mass concentration of lead ion was 25mg/L and the mass concentration of bacteria was 1g/L, The uptake of lead ion can reach up to 150mg/g when initial mass concentration of lead ion was 300mg/L Meanwhile, the simulation results of Langmuir model and Freudlich equation show that the main adsorptive mechanism of Pb²⁺ was surface adsorption. In addition, IR spectrum also confirmed that the hydroxyl and carbonyl groups of polysaccharide and protein exhibited red shifts in various degrees, the peak width of C-O-C and hydroxyl groups widened a little bit and the absorption intensities of all peaks decreased. The AFM detections indicate that the elasticity of bacteria decreases, the adhesiveness increases and the mycelium shrinks after adsorption, which illustrates that lead was accumulated in the mycelium.The domesticated conditions were studied in this paper.The biofilms were respectively cultured by activated sludge, the dominant strain, the mixed dominant strain and activated sludge for dealing with wastewater containing lead concentration of 100 mg/L under optimal conditions. The results showed that the removal of lead and COD for the biofilms containing the dominant strains were more than 90% compareing with the 80% of the biofilms excepting the dominant strains . Biofilm before and after treating wastewater containing lead for 12 days,were anysised at the atomic force microscope and studied by IR - Infrared spectrometry. The results showed that the main adsorptive mechanism of Pb²⁺ was surface adsorption. The contents of organic components in extraction of extracellular polymers from biofilms were respectively determined.The contents of amylase,proteide,DNA were all bigger after adsorption lead ion, The contents of amylase was the biggest,which showed that the contents of amylase made a main role in adsorption lead ion. Doubtlessly, this research has paved the way for heavy metal wastewater treatment with biofilm.