Study On The Character And Mechanism Of Degradation Of Lignin In Paper Industry Black Liquor With Efficient Bacteria

Paper industry is one of the industries that cause serious environmental pollution. The key of paper industry sewage treatment is the efficient treatment of lignin. By a host of experiments, On the basis of exploration of new assistant reagent and its effect for paper industry black liquor, a detailed study had been done on separation of efficient lignin-degrading bacteria, their growth, reproduction, enzyme activity and lignin-degrading capacity, and synthetic experiments of bioaugmentation factors and practical simulated experiments, which offer theoretical basis to improve removal effect of lignin in paper industry black liquor.By a host of experiments, the study lias got new assistant reagents for modified acid precipitation process. Compared with the conventional, process using of the reagents has such advantages as higher removal ratio of CODcr and chroma, and lower water content of the deposited lignin particles. When the pH value is 3.0, the highest CODcr removal ratio can reach 68%, the chroma removal ratio over 92%, and lowest water content of scum is 81 %. The similar removal effect of lignin occurs when the pH is controlled between 4 and 4.5, which is helpful to conquer the disadvantages of large amount of acid consumption, hard to dehydrating, necessity of heating equipments, and difficult treatment of sludge. The result showed that the NO. 1 assistant reagent has the best effect.Six bacteria and five mildews have been separated from 119 strains, wliich grew well on the culture media contained lignin. The result of taxonomic identification is that XI, X2 and X3 belong to Pseudomonas, X4 and X5 belong to Xanihomonas, X6 belongs to Mycoplana. A preliminary study has been carried out on the capacity of lignin degradation of the 6strains of bacteria, and strains X2 and X4 were chose to carry out the experiments. The most favorable temperature for the 2 strains is 30癈, and the pH is 7; After being treated by ultraviolet rays, activity of all the three kinds of lignin-degrading enzyme produced by the strains can be increased greatly, the bacteria increasing rate is remarkably improved.Detailed study has been carried out on specific property of the separated efficient bacteria, the chief results are that shaking culture at 110r/min is favorable for the growth and reproduction of the bacteria; After comparing the effects among kinds of primary carbon and nitrogen sources, sucrose is determined as the suitable primary source for co metabolizing, and ammonium nitrate as the nitrogen source; the removal ratio of lignin can be greatly unproved after adding 10mg/l manganese ion, 0.lmg/1 copper ion, 0.25mg/l ferrous ion and 10mg/1 calcium ion into the culture media; Synthetically cultivating results show that the best effect occurs when the concentration of sucrose is 1 mg/1, ammonium nitrate is 1.5mg/l with corresponding inorganic ion, and the proportion of bacteria isX2:X4 equals 1:1.According to the determination of enzyme activity and chromatogram- mass spectrum analysis of intermediate, the mechanism of lignin-degrading by efficient bacteria is that the synthetically bioaugmentation factors improve the activity of lignin-degrading enzymes, which augment die lignin-degrading reaction in outer cell and inner cell.A ideal effect has been got as well when continuous simulated experiments were done to treat paper industry sewage in a bioaugmentation system added with bioaugmentation factors, which included effect lignin-degrading bacteria, primary carbon for co metabolizing, nitrogen sources and kinds of inorganic ions; under the function of synthetic bioaugmentation factors, the highest COD removal ratio is 75.3%, the average is over 74%, the COD value descend from l000mg/L in influent to about 260mg/L in effluent, and the removal ratio of scum is over 90%.