Study On Pre-oxidized Coagulation Precipitation Method In Papermaking Center-section Wastewater

This paper based on the papermaking center-section wastewater treatment technology at home and abroad,be directed against the characteristics of the papermaking center-section wastewater such as high concentrations of pollutants and poor biological and chemical ,proposed a pre-oxidation coagulation method to treatment the papermaking center-section wastewater。In this research,KMnO₄ oxidation is firstly used to treat the papermaking center-section wastewater. Then the wastewater is treated by coagulation. Firstly,conogonal experiments are used to determine the main factors of different processing units. Then,singlefactor rotates are used to research how every factor effect the results of the experiments and to get relationship curves of the factor and the results of the experiments(the removal efficiency of COD and chroma)to determine the best values of the factors.In the research,the effects of KMnO₄ dosage,pH,temperature on the result of pre- oxidation treatment are inspected;And the effects of PSAF dosage,pH ,mixing time, reaction time and temperature on the coagulation treatment are inspected.Through the experiments,the papermaking center-section wastewater treatment process is identified. And the optimum operating condition are also determined. The identified treatment process is a two-step process,including pre- KMnO₄ oxidation and coagulation sedimentation. The optimum operating condition for the pre- KMnO₄ oxidation is that the reacting temperature is 50℃,the dosage of KMnO₄ is 10～11ml/L and pH is 5～7. The optimum operating condition for coagulation sedimentation is that pH is 5～7,the dosage of PSAF is 230～250mg/L.The experiment prove that coagulation and KMnO₄ oxidation and flocculation process is an economic and efficient process of papermaking center-section wastewater treatment. In the optimum operating conditions,treating the wastewater with coagulation and KMnO₄ oxidation and flocculation process received a significant effect :the COD is debased from 1256mg/L to 78.2mg/L,the removal efficiency reaching 93.8%;the chroma is debased from 416 times to 4 times,the removal efficiency reaching 99.0%. The wastewater treated by the process is colourless,clear transparent. The wastewater treated can be reused or discharged,which offers a new solution to control paper making center-section wastewater pollution and to deal with water shortage of paper making industry.The economic and technical analyse prove that the medicament cost is the largest proportion of the running cost in the process,which is about 0.706. This is a good effect, and the pharmaceutical consumption is relatively low.