MBBR+磁混凝用于CAST工艺升级改造的效果分析

Upgrading and Reconstruction of CAST Process by MBBR and Magnetic Coagulation Process

浙江省某市政污水处理厂设计规模为10×10^4m^3/d,出水水质执行《城镇污水处理厂污染物排放标准》(GB 18918-2002)的一级B标准,采用MBBR+磁混凝工艺对其进行一级A升级改造,改造完成至今已运行1年多,在冬季低温条件下仍具有较好的运行效果。改造后,出水COD、BOD5、氨氮、TN、TP和SS平均浓度分别为13.87、2.10、0.75、10.83、0.10和5.3 mg/L,稳定达到了GB 18918-2002的一级A标准。不改变原有CAST工艺的运行方式和池容,在主反应区镶嵌MBBR,安装搅拌器,增加反硝化时序,有效提高了系统的脱氮效果;深度处理采用磁混凝+纤维转盘滤池工艺,以微小磁粉作为晶核,强化混凝效果,确保出水SS和TP稳定达标。生化系统内主要的硝化菌群为Nitrosomonas和Nitrospira,硝化菌群在悬浮载体上的相对丰度达到8.71%,高于活性污泥中的4.85%;主要的反硝化菌群为Azoarcus和Zoogloea,反硝化菌群在悬浮载体上的相对丰度达到11.58%,在活性污泥中为9.78%。

The design scale of a municipal sewage treatment plant in Zhejiang Province was 10 ×104^ m^3/d,and the effluent quality was required to meet the first level B criteria in Discharge Standard of Pollutants for Municipal Wastewater Treatment Plant (GB 18918-2002). MBBR and magnetic coagulation process was adopted to improve the effluent quality to meet the first level A criteria in GB18918-2002 standard. The project has been reconstructed for more than one year,which still has good performance under low temperature in winter. After reconstruction,the average effluent COD,BOD5,NH4+ -N,TN,TP and SS were 13. 87 mg/L,2. 10 mg/L,0. 75 mg/L,10. 83 mg/L,0. 10 mg/L and 5. 3 mg/L,respectively,which reached the first level A criteria in GB 18918-2002 standard stably.Without changing the operation mode and tank capacity of the original CAST process,the MBBR process was embedded in the main reaction area,and a stirrer was installed to increase the sequence of denitrification,which effectively improved the nitrogen removal effect of the system. The process of magnetic coagulation and fiber disc filter were adopted in the advanced treatment,and tiny magnetic powder was used as the crystal nucleus to enhance the coagulation and flocculation effect,so as to ensure that the effluent SS and TP could reach the standard stably. Nitrosomonas and Nitrospira were the main nitrifying bacteria in the system,and the relative abundance of nitrifying bacteria on the suspended carrier reached 8. 71%,which was higher than that of the activated sludge (4. 85%). The main denitrifying bacteria were Azoarcus and Zoogloea,and the relative abundance of denitrifying bacteria on suspended carrier and activated sludge reached 11. 58% and 9. 78% respectively.