| The paper industry is the basic raw material industry which is related to the national economy, and the pollution of paper mill effluents is an important factor to restrict its development. Paper mill effluents can remove more than 90% of the BOD and COD by biological treatment, but the effluents still contains nonbiodegradable lignin and its derivatives after biochemical treatment, which causes water hard to reach the national emission standard. In this paper, four typical lignin derivative models and the actual pulping effluent after biological treatment were studied. Studied on the removal effect of target pollutant and effect on biological degradation and discussed the degradation pathway of target pollutants in the ozone oxidation process.Firstly, the effects of initial pH, temperature, ozone concentration and initial concentration of the target pollutant on the removal efficiency of lignin derivatives and removal efficiency of CODCr were investigated. The results showed that in the experimental range, the removal efficiency of CODCr was enhanced with the increase of the initial pH value, temperature and the concentration of ozone, and degradation effect on initial concentration of eugenol, guaiacol, veratryl alcohol and DOP solution in 1.0 mmol / L, 0.5 mmol / L, 1.5 and 0.2 mmol / L were the best. The removal rate of eugenol, guaiacol, veratryl alcohol, DOP and paper mill effluents were respectively 67.77%,69.58%, 55.25%, 57.01% and 58% after 60 min of ozonation process. Based on removal efficiency of CODCr, lignin derivatives of CODCr removal kinetics are discussed. It is found that eugenol and guaiacol aqueous solution of CODCr removal followed two-stage pseudo-first-order kinetics(0-10 min and 10-60 min), veratryl alcohol aqueous solution of CODCr removal under different initial concentrations of target compounds range with two-stage pseudo-first-order kinetics(84~252 mg/L and 252 ~420mg/L), DOP aqueous solution of CODCr removal is consistent with a pseudo-first-order kinetic characteristic. The kinetics model of CODCr removal of four kinds of lignin derivatives was established respectively. The paper mill effluents in the initial =11 value of pH, the reaction temperature of 25 degrees, the ozone concentration of 24.83 mg/L, the initial concentration of wastewater for 386.61mg/L ozonation conditions, removal rate of 55% after 60 min oxidation process.Then, the changes of the biodegradability of the four lignin derivatives and paper mill effluents before and after ozone oxidation were studied. The results of the study have found that compared with the untreated waste water, the ozone oxidation process has a significant improvement on the biochemical effects of wastewater, and the biodegradability of the wastewater is greatly improved. The CODcr removal rate of eugenol, guaiacol, veratryl alcohol and DOP were 65%, 75.4%, 51.22% and 47% respectively after ozonation and biological treatment, biological wastewater treatment effect increases compared with without O3 pretreatment. And the CODCr total removal rate of 54.6% and 63.7% of paper mill effluents by ozonation for 30 min and 60 min and biological treatment process, results showed that the extension of the ozonation process can further improve the treatment effect after biochemical treatment.Finally, using gas chromatography-mass spectrometry analysis of changes in organic pollutants in wastewater of lignin derivatives before and after ozone oxidation process. It was found that, the lignin derivatives can be degraded into esters, aldehydes, alcohols and small molecular fatty acids(formic acid and acetic acid) and other substances after ozonation process, these substances is relatively easy to microbial degradation, so as to improve the wastewater biodegradability, which is the intrinsic reason that the ozone oxidation process can improve the biological degradation of lignin derivatives. |
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