Wheat Straw Pulp Papermaking Wastewater Treatment Process To Improve Program Design

The industrial wastewater of paper mills which make great threaten on environment is one of the most serious pollutant resources. There are too many smaller mill corporations in China which are short of woods and the straw-based pulp and paper mills become the main sources for these industries. The straw pulp and paper black liquor can be disposed by the method of reclaiming the Alkali. The white liquor may be reused by the conventional methods. However, the wastewater discharged from the mid-stage of this process not only has great quantities, but has similar components with that of black liquor which can not easily be treated using the biological methods because of the lower ratio of BOD5 to COD. Other conventional methods can also not be applied for this purpose efficiently in many field applications because of their higher operating cost and complicated process. A treatment process used for the wastewater discharged from the mid-stage which is technical reasonable, operate efficiently and easily is expected by the environmental engineers and owners.The objective of this thesis is to improve the existing treatment process for wastewater from mid-stage (30000m3/d) in Wei-fang Henglian Paper Pulp Co. The domestic and abroad literature reviews for mid-stage wastewater treatment processes were done and the experiences of successfully application of Carrousel system based on oxidation ditch in paper pulp wastewater treatment were applied in this thesis. Based on the use of existing preliminary treatment process, tertiary treatment process, aeration system, inverse-umbrella surface aeration system with anaerobic and aerobic functions, Carrousel oxidation ditch, biological aeration sedimentation tank were applied and the reasonability of this process was investigated. The research results show that the process is technical and economical reasonable. This process has many advantages such as simple, lower investment and operating cost, and the effluents can meet the regulations' requirements of recycling water used in Pulp-made workshop and more suitable for smaller or middle companies.