Treatment Of Wastewater From Paperboard Mill

Clean production technology of papermaking is the basic method to solve the pollution of papermaking wastewater thoroughly among many technologies. But, as far as most paperboard mills are concerned, the improving of process equipment and machine is the proper mean to reduce or alleviate pollution to environment for lacking of the technological and feasible clean production. Most paperboard mill located in small town or countryside where the realize of environmental protection is poor and level of management is weak, much wastewater from paperboard mill without any treatment or treated not completely is discharged into local river and lake directly, which results in higher turbidity, deeper color even foul odor, polluting the water and harming to people's health. So, it is urgent to treat this type of water. Thinking of the characteristics of paperboard mill wastewater and economic principle, biological method is adopted to deal with it. In this paper, the optimum operational conditions are established, and efficient flocculant Polysilicia-Aluminum Chloride (PASC) are prepared to decolour the effluent from bioreactor as last step for the wastewater treatment.In the first part of the paper, anaerobic and aerobic biological treatment is studied. The optimum Hyhrolic Retention Time (HRT) of wastewater in anaerobic and aerobic reactor are determined by experiments, and the shock resistance of the biological reactor is discussed. During the stable operation, chemical oxygen demand (COD), biological oxygen demand (BOD₅), turbidity, colourity and pH value of inffluent and effluent are also studied. The results show that turbididy can be removed more effectively than CODcr, and ti is difficult to remove color efficiently, which results in the color of effluent faint yellow.In the second part, efficient PASC flocculant is prepared from sodium silicate and aluminium chloride under giving circumstance by orthogonal experiment, which can be used to decolour the output effectively.. The conditions of preparation of PASC are as follows: the mole ratio of aluminium to silicon is 1.5, mass percent silicon dioxide 2%, the pH value of active silicic acid 5.5,and curing time is two days. The PASC flocculant has many characteristics: liquid without color of smell, soluble, with density: 1.076 kilogram per liter, pH: 1.76 and basicity:79%.The result shows: the CODcr, BOD₅. TSS, pH, turbidity and color of the wastewater taken from paperboard mill through anaerobic, aerobic anddecolourization processes meeting requirement of the standards of National wastewater Discharge in papermaking industry (GWPB 2-1999).