EFFECT OF INFLUENT C/N RATIO ON PHOSPHORUS AND NITROGEN REMOVAL BY PARTIAL NITRIFICATION-DENITRIFICATION IN A2/O PROCESS WITH LOW DISSOLVED OXYGEN CONCENTRATION
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摘要: 研究重点考察了低氧条件下(0.5 mg/L),A2/O处理不同C/N污水(2.5~7.0)的短程硝化反硝化除磷脱氮性能。实验结果表明,进水中80%的COD在厌氧区被去除,主要用于合成PHA。当进水C/N<4.5,出水COD会随进水出现较大波动。水体中TN去除主要通过短程硝化、内源反硝化、反硝化除磷等过程来实现。当进水C/N为2.5、3.5,TN去除率均维持在80%左右;当进水C/N为4.5、5.0时,亚硝酸盐有明显积累,平均积累率分别为24.4%、31.9%,出水TN可以稳定达到10 mg/L以下,去除率最高可达到85.3%。因此,适当提高进水C/N能有效提高TN去除效果。水体中磷主要通过反硝化除磷过程被去除。当进水C/N为2.5时,系统磷平均去除率为65%左右,除磷效果较差。当C/N提高至3.5,系统除磷效果达到最佳,出水PO3-4-P平均浓度为0.3 mg/L,去除率达到92.1%,缺氧吸磷占比为74.6%。另外,当进水C/N为5.0~7.0时,系统内反硝化除磷、内源反硝化、短程硝化、好氧吸磷过程能够有效耦合运行,实现有机物、磷、氮的同步高效去除,COD、TN、PO3-4-P 去除率可分别最高达84%、85%和85%以上。经16S rDNA高通量测序分析,系统中起脱氮除磷作用的微生物主要为聚糖菌——Candidatus Competibacter,反硝化细菌——Azospira,硝化细菌——Nitrospira、Nitrosomonas及反硝化聚磷菌——Hyphomicrobium、Candidatus Accumulibacter等。Abstract: The phosphorus and nitrogen removal by partial nitrification-denitrification of A2/O with different C/N ratios (2.5~7.0), were investigated under a low dissolved oxygen condition (0.5mg/L). Results showed that 80% of the influent COD was used for synthesizing PHA in the anaerobic zone. When the C/N ratio was below 4.5, the effluent COD fluctuated with the influent. TN was mainly removed by partial nitrification, endogenous denitrification, and denitrifying phosphorus removal process. When the C/N ratio was 2.5 and 3.5, the TN removal both remained at a level of 80%. The average accumulation rate of nitrite reached 24.4% and 31.9% respectively, under a C/N ratio of 4.5 and 5.0. The effluent TN stably reached 10 mg/L below with a maximum removal rate of 85.3%. Therefore, Increasing the influent C/N appropriately could effectively improve TN removal. Phosphorus was mainly removed through the denitrifying phosphorus removal process. When the C/N ratio was 2.5, the phosphorus removal rate was reduced to 65%. When the C/N ratio was 3.5, the effluent phosphorus concentration was 0.3 mg/L, achieving the best phosphorus removal rate of 92.1%. The anoxic phosphorus uptake took up 74.6% of the total removal. It was found that when the influent C/N of the system was within 5.0 to 7.0, the coupled operation of denitrifying phosphorus removal, endogenous denitrification, partial nitrification, and aerobic phosphorus absorption in the system effectively achieved synchronous and efficient removal of organic matter, phosphorus, and nitrogen, with a removal rate of 84%, 85%, and 90%, respectively. Through the 16S rDNA high-throughput sequencing analysis, the microorganisms that play a role in nitrogen and phosphorus removal in the A2/O system were mainly polysaccharide bacterium, Candidatus Competitor, denitrifying bacteria, Azospira, Nitrobacteria, Nitrospira, Nitrosomonas, and denitrifying phosphorus accumulating bacteria, Hypomicrobium and Candidatus Accumulibacter.
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