| Banknote printing wastewater is one type of organic industrial wastewater generating in operation process of banknote printing industries which is relatively difficult to treat. Directly discharging the wastewater after casual treatment which has a great chroma, a high concentration of pollutants a nd a complex composition can cause serious environment pollution, in addition, the banknote printing wastewater has not yet been studied on its advanced treatment and the effluent quality could reach standard for surface water. The research adopted corresponding advanced treatment processes according to the wastewater quality characteristics in stages on studying the removal effect in banknote printing wastewater and establishing pilot model, providing technology support for practical engineering.In the experiment, the advanced treatment process included two stages which were small-scale test and pilot test. In the small- scale test, raw water from the total outlet of the new sewage treatment station of Chengdu Banknote Printing Company Limited was treated by the Fenton oxidation process and O3 oxidation process. To determine the optimum advanced oxidation process of the pilot test, the removal efficiency of CODCr was taken as the evaluation index. In the pilot test, raw water was the effluent of the inclined tube sedimentation tank and ink tank of the previous treatment station. Though the process of A1-A2-O + sedimentation tank + O3 contact tank + BAF, the removal effect of CODCr and NH4+-N of the wastewater were taken as the evaluation index to determine the optimum operating conditions of each reactors.The results of the small- scale test showed that when the p H of raw water was 3, the dosages of 30% H2O2, FeSO4·7H2O, Ca(OH)2, and 0.1% PAM were 0.50 mL/L, 1.362 g/L, 0.48 g/L, and 2 ml/L, respectively, and hydraulic retention time was 40 minutes, the best removal effect was achieved by the Fenton advanced oxidation process and the CODCr removal rate was 75% approximately. And when the p H of raw water remained unchanged, the dosage of O3 was 6.5 g/h and hydraulic retention time of 30 minutes, and the dosage of activated carbon was 2.00 g/L and hydraulic retention time of 60 minutes, the best removal effect was achieved by the O3 advanced oxidation process and the CODCr removal rate was about 79%. From the view of economic and technology, when dealing with the banknote printing wastewater in the light of its characteristics via the depth treatment, the treatment effect of using the O3 advanced oxidation process was relatively good and has a stable effluent quality.The results of the pilot test showed that when DO concentration of the anaerobic tank, anoxic tank and aerobic tank of the A1-A2-O reactor respectively were less than 0.5mg/L, 0.85mg/L and 2.95mg/L approximately, the reflux ratio of the mixed liquor and the sludge were 200% and 150%, respectively, and the dosage of O3 was about 28g/h, both of CODCr and NH4+-N in the wastewater were pretty removed and the removal rates were 85% and 76%, respectively. After the linkage operation for some time, the depth treatment appeared the stronger ability to resist the impact load, the better quality of effluent and the stable operation. The concentration of CODCr and NH4+-N in the effluent were about 25mg/L and 0.6 mg/L, respectively and completely reached the Forth Le vel of 《Environmental quality standards for surface water》(GB 3838-2002). Besides, the operation cost of the process is 9.25 yuan/m3 by technical and economic analysis. |
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