哈尔滨工业大学工程硕士学位论文 Abstract Urban wastewater is one of the major polluting sources for natural water. To remove hazards pollutants by treating urban wastewater by suitable technical processes before discharge is one of the necessary means to protect the natural wate. Currently all the urban wastewater was directly discharged to natural water without any treatment in the petrochemical area of Daqing. Therefore, it is emergent to construct new wastewater treatment plant in order to solve the pollution issue of natural water around the petrochemical area and the corresponding adverse impact on residential areas. However, the choice of cost-effective, proven and reliable wastewater treatment technology is the key to the success in this project. Based on technical and economic analysis, it is extremely urgent to take into account of the environmental characteristics of Daqing petrochemical area, water quality requirements of the receiving water, and the wastewater quality characteristics of the urban wastewater in Daqing petrochemical area.

The combined processes of pre-conditioning+pre-denitrification (DN) + biological aerated filter (C/N) were employed in this project. The raw wastewater was firstly entered into the flocculation reaction-grit tank, at the same time an appropriate amount of phosphorus removal chemical was also added in the grit tank. The effluent of grit tank was mixed with the recycling water, which was entered into the de-nitrification filter, by using the original organic matter in the wastewater as de-nitrification carbon source. The denitrified effluent then went into the nitrification filter, where the NH4+-N was converted to NO3—N, meanwhile a part of the nitrified water was recycled to the denitrifying filter, and the rest part was discharged as final effluent. The recycling rate in this project was set at 200%, resulting in a strong adapting capacity to shock loading of the pre-denitrification process, and an excellent quality of the final effluent, as well as reasonable stability of the process for the TN and COD removal. Pre-denitrification BAF technology is the first case in the similar processes in China.

After practically operation, the performance of the wastewater treatment plant was investigated in both summer and winter. In summer, the average influent COD,