包头市北郊污水厂二期扩建工程的工艺优化研究

Process Optimization of Second-phase Extension Project of Baotou Beijiao Wastewater Treatment Plant

通过对包头市北郊污水处理厂工艺现状的分析,提出了二期扩建工程的工艺优化和设计方案。研究表明:2007年—2009年,在进水氨氮负荷持平或略有降低的情况下出水氨氮浓度略有上升,近2年的超标率为100%,说明工艺的处理效率有所下降。曝气池对氨氮的去除率低,只有9%～10%。通过分析各断面的氨氮浓度、沿程溶解氧和污泥活性,认为是过低的溶解氧浓度、较短的泥龄、硝化细菌所占比例低等因素的共同作用导致了出水氨氮超标。在二期扩建工程中,建议好氧区的溶解氧浓度呈递减分布,通过模型模拟得到好氧区的实际需氧量为40420kg/d,总需气量为40924m3/h。污水厂稳定达标(尤其是氨氮)和节能减排是最迫切需要解决的技术难题,而生物工艺优化控制系统可以实时调整工艺运行参数,满足达标排放要求,并可节省曝气费用为43.2～129.6万元/a,节电为(153.3～459.9)×104kW.h/a。

Through analyzing the process status of Baotou Beijiao WWTP, the process optimization and design plan of the second-phase extension project was proposed. The results show that though the am- monia nitrogen in the influent kept constant or decreased slightly, the ammonia nitrogen in the effluent slightly increased from 2007 to 2009, and the standard-exceeding rate of ammonia nitrogen in recent two years was 100%, which illustrated that the wastewater treatment efficiency was reduced. Only 9% to 10% of ammonia nitrogen was removed in the aeration tank. Based on the analysis of ammonia nitrogen in every process section, dissolved oxygen （DO） along the aeration tank and sludge activity, it came to the conclusion that many factors including excessively low DO concentration, short activated sludge age, low proportion of nitrobacteria and so on caused the ammonia nitrogen in the effluent to exceed the stand- ard. It is suggested that DO decreases gradually from the front to the back of the aeration zone. The actu- al oxygen demand and the total air amount predicted by the model are 40 420 kg/d and 40 924 m3/h re- spectively. Achieving the standard stably （especially for ammonia nitrogen）, saving energy and reducing emission are the most urgent technical problems needing solving in the second-phase extension project.The bioprocess optimization control system can adjust and control the operational parameters in real time so as to meet the emission limits. Simultaneously, it can save the aeration cost of 0. 432 to 1. 296 million yuan and the electricity of 1. 533 to 4. 599 million kW·h annually.