Tam H L S, Tang D T W, Leung W Y, Ho K M, Greenfield P F
Drainage Service Department, Revenue Tower, Wanchai, Hong Kong.
Water Sci Technol. 2004;50(10):59-65.
Bench-scale systems, using conventional and compact hybrid activated sludge configurations, were set up to evaluate the systems' nitrification-denitrification performance, operating sludge age/MLSS concentration and sludge settleability at a Hong Kong municipal STW. Configurations tested were the continuous clarifier modified Ludzack Ettinger (MLE) and the sequencing batch reactor (SBR) with and without hybrid suspended biofilm carriers. Results demonstrated that the hybrid SBR and MLE systems consistently achieved close to complete nitrification (effluent NH4-N = 2.4 and 6.9 mg/L) and 75% and 67% removal of nitrogen (N) (effluent NO3-N < 10 mg/L) with an overall hydraulic retention time of only 7.5 hours, operating sludge age as short as 5.2 days, and mixed liquor suspended solids concentration of approximately 1,300 mg/L with a sludge volume index of 109 and 229 mL/g, respectively. The most sensitive and slowest growing nitrifiers attached to the hybrid biofilm carriers. This allowed the hybrid processes to be operated at a sludge age shorter than the critical nitrifying sludge age while still retaining near complete nitrification. In contrast, to achieve complete nitrification, the conventional MLE system needed to be operated at 1.5 to 2.5 times the critical sludge age. These results indicate that the hybrid MLE configuration is a suitable process for use in upgrading existing conventional works for N removal and for increasing hydraulic capacity of existing N removal works, without major civil works modifications, in Hong Kong. For new works, consideration might be given to the use of the hybrid SBR, which shows a more stable N removal performance than the MLE process due to its inherent in-basin equalization capacity and better reaction conditions for nitrification in terms of higher initial NH4-N level. It was also observed that the conventional SBR produced better nitrification performance than the hybrid MLE process tested. Design parameters and operating conditions of the hybrid systems should be subjected to further full-scale trial for higher hydraulic capacity and N removal performance.
搭建了采用传统紧凑型混合活性污泥配置的实验室规模系统，以评估香港某市政污水处理厂各系统的硝化反硝化性能、运行污泥龄/混合液悬浮固体浓度及污泥沉降性能。测试的配置包括连续澄清池改良型Ludzack Ettinger工艺（MLE）以及带有和不带有混合悬浮生物膜载体的序批式反应器（SBR）。结果表明，混合SBR和MLE系统始终能实现接近完全的硝化（出水NH4-N分别为2.4和6.9mg/L）以及75%和67%的氮（N）去除率（出水NO3-N<10mg/L），总水力停留时间仅为7.5小时，运行污泥龄短至5.2天，混合液悬浮固体浓度约为1300mg/L，污泥体积指数分别为109和229mL/g。最敏感且生长最慢的硝化菌附着在混合生物膜载体上。这使得混合工艺能够在短于关键硝化污泥龄的污泥龄下运行，同时仍能保持接近完全的硝化。相比之下，为实现完全硝化，传统MLE系统需在关键污泥龄的1.5至2.5倍下运行。这些结果表明，混合MLE配置是香港现有传统污水处理厂升级脱氮及增加现有脱氮污水处理厂水力处理能力的合适工艺，无需进行重大土建工程改造。对于新建污水处理厂，可考虑采用混合SBR，因其具有内在的池内均衡能力以及在较高初始NH4-N水平下更有利于硝化的反应条件，所以其脱氮性能比MLE工艺更稳定。还观察到，传统SBR的硝化性能优于所测试的混合MLE工艺。混合系统的设计参数和运行条件应进行进一步的全尺寸试验，以提高水力处理能力和脱氮性能。
