Study On Immobilization Of Citric Bacteria And Treatment Of Organic Wasewater Containing Naphthalene And Phenanthrene

The concentration of naphthalene and phenanthrene in industrial waste water which produced by printing,dyeing,coking and petrochemical industries is relatively high.It can cause potential hazards to the environment and the health of the human body.Immobilized microorganism technology has the advantages of high treatment efficiency and no two pollution on the treatment of refractory organic pollutants,so it has good application and research prospects.In this paper,we first studied the growth activity of citric acid bacteria,and select the logarithmic growth phase of the strains for subsequent experiments.Then polyvinyl alcohol,sodium alginate and gelatin were selected as embedded materials.Through the analysis of the difference and variance of orthogonal experiment,it was found that the effect of polyvinyl alcohol on the removal rate of naphthalene or phenanthrene was the most significant.It is concluded that the best embedding material mass ratio is polyvinyl alcohol3.5%,sodium alginate 1.7%,gelatin 0.5%.Scanning electron microscopy was used to observe the microstructures of immobilized citrate and PVA-SA-gelatin carriers.Fourier transform infrared spectrometer was used to characterize the effective functional groups on the surface of immobilized beads.Secondly,the factors affecting the removal of simulated wastewater containing naphthalene or phenanthrene by immobilized citric acid bacteria were studied.The effects of immobilized citric acid bacteria on the removal of naphthalene and phenanthrene were investigated from 3 aspects:time,substrate concentration and concentration of bacteria.The results were as follows:（1）The best removal time for naphthalene and phenanthrene by immobilized citrate was 2h and 4h,and the removal rate can reach 92.58%and 87.84%.（2）When the initial concentration of naphthalene was 400mg/L,the removal rate reached92.69%.When the initial concentration of phenanthrene was 200mg/L,the removal rate reached the highest value of 87.85%.（3）the optimum concentration of citric acid bacteria was 35g/L,and the removal rates of naphthalene and phenanthrene by immobilized citric acid bacteria were 91.38%and 87.9 8%.Under the best reaction conditions,the adsorption capacity of naphthalene or phenanthrene by immobilized citrate,immobilized gel carrier and citric acid bacteria was compared.The results show that:Immobilized citrate bacilli>immobilized gel carrier>citric acid bacteria.The adsorption-analysis test of 6000mg/L’s Tween80 solution as eluent shows that,When immobilized citric acid bacteria adsorbed naphthalene or phenanthrene in5 cycles,the adsorption rate of naphthalene was more than 85%,and the adsorption rate of phenanthrene reached more than 82%.Desorption of naphthalene and phenanthrene by Tween80 eluent 5 times,the desorption rate of naphthalene was more than 60%and the desorption rate of phenanthrene was more than 65%.Then,the kinetics of degradation of naphthalene or phenanthrene by immobilized citric acid bacteria was studied.It was found that the removal of naphthalene or phenanthrene by immobilized citric acid pellets was in accordance with the first-order reaction kinetic model.It was found that there wer a large number of intact citric acid bacteria attached to the internal of immobilized citric acid bacilli which removal of naphthalene and phenanthrene.It indicates that citric acid bacteria can absorb and absorb nutrients in the surrounding environment and maintain their life activity in immobilized materials.It is concluded that the PVA-SA-gelatin carrier has strong mass transfer performance,and it also explains why the immobilized citric acid bacillus has good regeneration.By comparing the characteristic peaks in the infrared spectra of immobilized citric acid before and after removal of naphthalene and phenanthrene,the results showed that,there are OH,COOH,ring C-H or B-O groups involved in the removal of naphthalene,there are COO,ring C-H or B-O,carbonyl and CH₂-groups involved in the removal of phenanthrene.