| The pulp and paper industry produces a strongly colored effluent with high levels of biochemical oxygen demand （BOD） and chemical oxygen demand （COD）. These effluents contain large amount of organic matter, including fine fibers, lignin and associated bleaching by-products such as chlorophenols and benzodioxins etc, in particular, chlorinated organics, most of them being difficult to eliminate by conventional waste water treatment processes and accumulated in the environment. Therefore, pollution problem caused by the pulp and paper mill effluent has been one of the important environmental problems. Although physical and chemical methods are available for treatment of pulp and paper mill effluent, they are less desirable than biological treatment because of cost-ineffectiveness and residual effects. Biological treatment is known to be effective in reducing the organic load and toxic effects of pulp and paper mill effluent. There are a number of biological methods such as using fungus, anaerobic or aerobic sludge reactor to treat this type of wastewater, have been presented. However, as people increasing awareness of the environment protection, these traditional methods could not meet the people’s needs any more. Meanwhile, pulp and paper mills also produced a lot of waste paper sludge and waste fibers, which contain a large amount of carbohydrate components. It will be a great waste of resources if these materials can’t be utilized reasonably. Based on the above situation, a mixed-culture community was constructed by statistical experimental design in this study for the degradation of pulping effluents, and intensified aerobic granular sludge with this mixed-culture community in order to improve the capability of sludge for degrading pulping effluents. Aim at the problem of organic chlorides in pulping effluents, a protoplast fusion experiment was carried out and a recombinant strain was constructed with an ability of degrading chlorophenols efficiently. In addition, biogas was produced by using the mixture of pulping effluent, waste paper sludge and manure from pig farm. The waste from pulp and paper mills was used as resources. The result of study is significant to enhance the biotreatment of pulping effluents and promote resource utilization of waste from pulp and paper mills.According to our research purpose, in order to analyze character parameters of pulping effluents rapidly, a new method is proposed for determination of chroma in pulping effluent by using ratio spectrum–derivative spectrophotometry. A linear regression equation was obtained. The ratio derivative value at 366 nm was used to calculate chroma, which is not affected by pH value and suspended solid in pulping effluent, so the procedure does not require adjusting pH value and removing suspended solid before detection of chroma. The test procedures were simplified and the error caused by human factors was avoided. The method has high precision and accuracy with a relative difference within±5% when the chroma of samples is in the range of 50-390 color unit （C.U.）. The new method was satisfactorily applied for determination of chroma in pulping effluent. To the same purpose, a method for the determination of COD in pulping effluent was described based on chemometrics-assisted spectrophotometry method. Two calibration models were established by inducing UV-visible spectroscopy （Model 1） and derivative spectroscopy （Model 2） combined with chemometrics software Smica-P. Correlation coefficients of two models are 0.9954 （Model 1） and 0.9963 （Model 2） respectively when COD of samples is in the range of 0 to 405 mg/L. Confirmatory experiment showed that average relative error of Model 2 （4.25%） was lower than that of Model 1 （5.00%）, which indicated predictability of Model 2 was better than that of Model 1. Chemometrics-assisted spectrophotometry method did not need chemical reagents, testing time was shortened evidently.Statistically based experimental designs were used to construct a mixed-culture community for maximizing COD degradation of pulping effluents by the use of six different strains, i.e., Agrobacterium sp., Bacillus sp., Enterobacter cloacae, Gordonia, Pseudomonas stutzeri, and Pseudomonas putida. Significant effects of single and mixed strains on COD degradation were quantified first by applying a fractional factorial design （FFD） of experiments, and four strains were selected as the main driving factors in the process of biodegradation of effluents. Then the Steepest Ascent method was employed to approach the experimental design space, followed by an application of response surface methodology to further optimize the proportion of cell concentration for different strains in pulping effluent. A quadratic model was found to fit COD removal efficiency. Response surface analysis revealed that the optimum levels of the tested variables for the degradation of COD, and optimized cells concentrations (OD600) of four strains in mixed-culture community were 0.35 Agrobacterium sp., 0.38 Bacillus sp., 0.43 Gordonia sp., and 0.38 P. putid., respectively. In a confirmatory experiment, three tests were performed by using the optimized conditions, and a COD removal efficiency of （65.3±0.5） % was observed, which was in agreement with the prediction. The aerobic granular sludge was intensified with the mixed-culture community constructed in this study. The pulping effluent was treated firstly with anaerobic sludge, and followed by further treatment of aerobic granular sludge and intensified aerobic granular sludge, respectively. COD of pulping effluent was decreased from 629mg/L to 203mg/L and chroma declined to 91C.U. from 118C.U. after treatment by original aerobic granular sludge. By contrast, the efforts of intensified aerobic sludge was better, COD was dropped to 146mg/L from 629mg/L, and chroma declined to 72C.U. from 118C.U.A new strain with an ability of degrading chlorophenols efficiently was constructed by protoplast fusion between Pseudomonas putida and Psathyrella candolleana. 20 recombinant strains were screened and used to degrade pentachlorophenol （PCP） synthetic wastewater in order to determine their capabilities of chlorophenol degradation. Also, a new method quantifying PCP was proposed based on derivative spectroscopy, which can detect PCP content in synthetic wastewater within a short time, so chlorophenol biodegradability of recombinant strains could be measured rapidly. The results indicated that the removal efficiency of PCP in synthetic wastewater by 4 recombinant strains viz., Xz 6-1, Xz 6-3, Xz 6-5 and Xz 8-2 were 75.98%, 66.12%, 28.40% and 43.26%, respectively which showed that the removal rate was improved by 27.71% by Xz6-1 as compared with Pseudomonas putida （removal rate of PCP is 54.27%）. The aerobic sludge was intensified by Xz6-1 and Pseudomonas putida respectively, so as to improve it’s capabilities of chlorophenol degradation. The results showed that PCP removal rate of original sludge was only 10.69%, but this value was enhanced after intensification. The removal rates of PCP were 30.03% and 21.20% after treatment with the sludge intensified by Xz6-1 and Pseudomonas putida respectively.The mixture of pulping effluents, waste paper sludge and pig manure was used to produce biogas by anaerobic fermentation. A moderate feeding concentration of 2% was selected. Significant effects of three factors including carbon-nitrogen ratio （C/N）, temperature （T） and initial pH value were quantified by applying FFD experiment. The results showed that three impact factors were significant for biogas production. The temperature was fixed （35℃） based on the research of the predecessor, and further optimized C/N, initial pH value by using the orthogonal experimental design. Finally, the optimal C/N （25） and pH （7.5） were fixed. Biogas production is 368mL under the condition of feeding concentration of 2%, temperature of 35℃, C/N of 25 and pH value of 7.5, COD and BOD of pulping effluent were reduced by 28.97% and 72.40% after anaerobic fermentation. |
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