为配合南水北调东线工程和山东省小清河流域水质改善，本课题针对城镇污水处理厂一级A提标改造的关键技术问题开展研究，包括A2/O工艺脱氮除磷优化运行参数、A2/O工艺化学强化除磷药剂种类、投加量及投加位点、一级A达标的深度处理工艺以及污水处理厂冬季运行时污泥膨胀的控制措施等。上述研究工作为城镇污水处理厂一级A提标改造工程的稳定达标运行提供了技术支撑。本研究取得的主要成果如下：依据进水的水质水量特点，通过中试研究提出了A2/O工艺的最佳运行条件为：水力停留时间（HRT）为10 h，混合液内回流比（r）为200%。其他条件为：污泥外回流比（R）为100%，污泥龄（SRT）为15 d，好氧区DO为2~4 mg/L。研究获得了辅助化学除磷与生物除磷的最佳协同效果，以好氧区末端为PAC化学药剂的投加点，投加浓度为29.3 mg/L ，出水TP可稳定控制在0.45 mg/L左右，优于《城镇污水处理厂污染物排放标准》（GB18918-2002）一级A标准。投加PAC不会对生物处理系统的污泥活性造成不良影响。纤维滤池以0.48 m的恒液位出水运行，在低浊度（5 NTU）进水条件下运行周期为24 h，高浊度（15 NTU）进水条件下运行周期为6 h，可以取得较好的出水水质。在实际运行条件下，砂滤池的滤速为10 m/h，反冲洗周期为20 h，反冲洗各阶段时间为：气洗3 min—气水联洗4 min—水洗3 min，该运行工况可以取得较好的运行效果。冬季气温低、进水污染物浓度高、有毒有害物质多，是污水处理厂运行最艰难的时期，污泥膨胀时有发生。投加PAFC对改善污泥沉降性能具有显著的效果，经过24天的投加，SV30由90%降至73%。
In order to corperate with the east route of south-to-north water diversion project and water quality improvement of Xiaoqing river, the key upgrading and reconstrcution technologies for municipal wastewater treatment plants to meet the discharge standard of level of A were studied, including the operation parameters of A2/O process for nitrogen and phosphorus removals, the selection of chemicals and the optimum dosing point for phosphorus removal, the advanced treatment technologies for meeting the level of A standard standard and the measures to control the activated sludge bulking in winter. These findings provided the related technical supports for the A2/O process of upgrading and reconstrcution of municipal wastewater treatment plant to meet the level of A standard. The major achievments are listed as follows.Based on the charaticristics of wastewater, the optimized operation conditions of the pilot scale A2/O reactor were presented as follows: hydraulic retention time (HRT) was 10 h; the internal return ratio of mixed liquer (r) was 200%. And other conditions were the sludge return ratio (R) of 100%, the sludge retention time (SRT) of 15 d and the dissolved oxygen (DO) concentration maintained in the aerobic zone of 2 ~ 4 mg/L.The optimized combined effect of assisted chemical phosphorus removal and biological phosphorus removal was found. The dosing concentration of PAC was 29.3mg/L with the dosing point at the end of the aerobic zone. The TP concentration in effluent was stably controlled under 0.45 mg/L, which met the national "urban sewage treatment plant pollutant discharge standard" (GB18918-2002), level of A standard. The PAC dosing caused the negligible impact on the activated sludge activities in the biological treatment system.The proper water level of fiber filter was 0.48 m with the running cycle of 24 h at the low turbidity (5 NTU) and 6 h at the high turbidity (15 NTU). The optimized operation conditions for the sand filter were obtained as follows: the filtration rate of 10 m/h, the backwash cycle of 20 h with the air backwash time of 3 min, the combined gas and water backwash time of 4 min and the water backwash time of 3 min for each cycle.Winter was the most difficult time for the operation of wastewater treatment plants as the lower temperatures, high concentration of pollutants, and more toxic and harmful substances. When the activated sludge bulking occurred, the dosing of PAFC had a significant effect on the improvement of sludge settling performance. After 24-day’s dosing, the SV30 value of activated sludge was reduced from 90% to 73%.
