Tham khảo tài liệu 'environmental management in practice part 9', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Pollution Prevention in the Pulp and Paper Industries 231 Rajvaid and Markandey 1998 reported 70-80 of removal in the sedimentation. Dissolved air flotation and filtration are the other option as primary treatment for pulp and paper mills. Fig. 3. Flow scheme of general wastewater treatment plant of pulp and paper industry Secondary Treatment Aerobic lagoons activated sludge systems anaerobic treatment and sequential biological treatment aerobic-anaerobic or anaerobic-aerobic are the most common biological treatment application for pulp and paper mills. In this section the details of these processes are given and they are discussed. Performances of various biological treatment processes are summarized in Tables 4. Activated Sludge Systems This conventional treatment system is used in treatment of several industrial wastewater types in order to remove COD BOD SS and AOX. There are a lot of studies in the literature to show the treatability of pulp and paper mills by activated sludge system. Some of them focused on the BOD COD AOX and other specific compound removal under different operation conditions. Schnell et al. 1997 showed that 74 of filtered COD nearly 100 BOD5 resin and fatty acid removal were achieved in the full-scale plant. Saunamaki 1997 reported that 82 and 60 COD removal efficiency at paper mills and pulp mills respectively in full-scale activated sludge systems of Finland. Knudsen et al. 1994 claimed high COD and BOD removal efficiency by two stage activated sludge process. Also Hansen et al. 1999 and Chandra 2001 showed similar results. The other part of these studies focused on the removal of AOX and other specific compounds such as chlorinated phenols guaiacols catechols vanillins 1 1-dichlorodimethyl sulfone DSS and chlorinated acetic acid Mohamed et al. 1989 Demirbas et al. 1999 Bajpai 2001 Chandra 2001 . The main operational problems of the pulp and paper mills are macro nutrient N and P limitation in the systems and growth of the filamentous .
