低流速下合流制排水管道CH4和N2O产排模拟研究

Simulation Study on CH4 and N2O Emissions from Combined Sewage Drainage Pipes at Low Flow Rate

摘要:

针对低流速下排水管道碳产排不清楚的问题，以南京24 处合流制排水管道为研究对象，考察了甲烷（CH₄）和氧化亚氮（N₂O）在管道低流速下的产排变化特征，分析了低流速下管网碳氮污染物沉积/悬浮特性，搞清了碳氮污染物与CH₄和N₂O产排关系，并探讨了微生物菌群及其代谢对CH₄和N₂O产排的作用。结果表明，管道低流速（0.01~0.09 m·s^-1）运行时溶存态CH₄和N₂O最大产率分别为168.58 μg·g^-1·d^-1及1.23 μg·g^-1·d^-1；在0.05 m·s^-1流速下运行40 min后累积沉积物总碳排放产率最大（5 047.92 μg·g^-1·d^-1），与水流冲刷导致水相和固相中碳氮污染物的显著变化有关。气态CH₄与Proteobacteria、Acinetobacter、JGI-0000079-D21及脱氢酶呈正相关，而气态N₂O与Firmicutes、Actinobacteriota、norank_f_JG30-KF-CM45、Bacteroidetes_vadinHA17及蛋白酶呈正相关，上述生物诱因在排水管道碳减排过程中应予以重点关注。

Abstract:

To address the issue of unclear carbon emission in drainage pipeline at the low flow rate, taking 24 combined sewage drainage pipelines in Nanjing as a study object, the variation characteristics of CH₄ and N₂O emissions at the low flow rate of the pipeline are inspected. The deposition / suspension characteristics of carbon and nitrogen pollutants in the pipeline network at the low flow rate are analyzed. The relationship between the carbon and nitrogen pollutants and the CH₄ and N₂O emissions is clarified. And the effects of microbial flora and their metabolism on the production and excretion of CH4 and N₂O are explored. The results show that when the pipelines are operated at the low flow rate (0.01~0.09 m·s^-1), the maximum yields of dissolved CH₄ and N₂O are 168.58 μg·g^-1·d^-1 and 1.23 μg·g^-1·d^-1, respectively. After operated at a flow rate of 0.05 m·s^-1 for 40 min, the total carbon emission yield of the accumulated sediment is the maximum (5 047.92 μg·g^-1·d^-1), which is related to the significant changes of carbon and nitrogen pollutants in the aqueous and solid phases caused by water flow erosion. Gaseous CH₄ shows the positive correlations with Proteobacteria, Acinetobacter, JGI-0000079-D21 and dehydrogenases. And Gaseous N₂O exhibits the positive correlations with Firmicutes, Actinobacteriota, norank_f_JG30-KF-CM45, Bacteroidetes_vadinHA17 and proteases. The above-mentioned biological triggers should be given special attention in the process of carbon emission reduction of drainage pipelines.