再生水管网生物膜中微生物代谢产物对水泥内衬管的腐蚀机理

As the reclaimed water was gradually realized to large-scale centralized treatment and utilization, problems due to microbially induced corrosion (MIC) of pipes in reclaimed water distribution system had aroused people's high concern. Because of relatively low chemical and biological stability of reclaimed water, cement lined ductile iron pipe could be damaged by microbially induced corrosion, which had a detrimental effect on safe transportation and reclaimed water usage. Though much work on the localized corrosion of metal material induced by sulfate - reducing bacteria (SRB) has been done, it is lack of the research focus on microbial metabolites corrosion behavior on cement material, some questions about the corrosion mechanism of the biofilm/cement interface have not been solved. Based on the cement liner degradation and water quality deterioration caused by microbial metabolism, this study will use simulation system test and in situ test as main technique. The study will reveal the relationship between reclaimed water qualities, microbial metabolism, microbial community structure and cement liner degradation, investigate cement liner degradation law and water quality deterioration process under MIC and finally discuss cement liner degradation mechanism induced by metabolites. This research will provide theoretic and scientific basis for microbially induced corrosion protection and water quality deterioration control.

随着我国再生水逐步实现大规模集中处理和有效利用，再生水管网管材的腐蚀所引发的管网安全运行问题已引起人们的高度重视。再生水水质的化学和生物稳定性都较差，具水泥内衬球墨铸铁管易受到再生水腐蚀而发生劣化，这将影响管网安全输配和再生水的后续使用。硫酸盐还原菌对金属材料的局部腐蚀，已有众多学者做过较深入研究。但生物膜代谢产物对水泥材料的腐蚀行为研究较少，生物膜/水泥界面腐蚀机制还不明确。本项目基于微生物生长代谢可能引发的水泥内衬劣化失效和管网水质恶化问题，以模拟实验和实际调查相结合为主要研究手段，揭示再生水水质特征，微生物生长代谢、群落结构和水泥内衬劣化三者之间的相互关系；明确微生物腐蚀作用下水泥内衬劣化规律及由此导致的管网水质恶化机制；探讨微生物代谢产物腐蚀水泥内衬的机理。本项目的研究可为提出控制微生物腐蚀、避免管网水质恶化的技术方案提供理论基础和科学依据。

再生水水质的化学和生物稳定性都较差，再生水管网水质安全及其管材腐蚀引发的管网安全运行问题已引起人们的高度重视。本研究主要针对再生水管网中广泛使用的具水泥内衬球磨铸铁管，搭建再生水模拟管网装置，长期监测实际再生水对模拟管网中水泥砂浆内衬的腐蚀作用。采用失重率, XRD, XRF, SEM/EDX等表征和揭示不同材质水泥砂浆劣化状况。模拟管网出水pH、总氮和TOC等指标受影响超出某些限制标准，水泥砂浆成分(钙、镁等)泄露速率是先快后慢并逐渐稳定，这与其表面形成的碳酸钙钝化膜有关。由于制作工艺和组成成分差异，自制水泥砂浆试片被侵蚀的速率始终较高，管网出水pH、钙和镁等含量呈增高趋势，总氮浓度也超限制标准。采用Miseq高通量测序技术监测模拟管网中微生物群落结构特征，HPC和DAPI染色法监测微生物总量的变化。管网水中微生物和水泥砂浆试片表面微生物丰度和群落多样性在2年多实验期内仍然呈增加趋势，优势菌群为多产小分子有机酸代谢产物的变形菌门(Proteobacteria)，放线菌门(Actinobacteria)和拟杆菌门(Bacteroidetes)。优势菌属中有少量硫还原菌和硫氧化菌检出。硝化菌在水泥砂浆表面的硝化作用促进了水泥的劣化。利用PCA, NMDS和RDA等多种统计方法分析不同时期微生物群落结构的差异及其与水质参数的关系。RDA分析表明影响管网水中微生物群落结构或者生长的水质因素主要是pH、DO、电导率、总氮、总磷和氨氮；影响管壁生物膜中微生物群落结构或者生长的水质因素主要是pH、DO、电导率和氧化还原电位。评价甲醇-超声、阳离子交换树脂两种方法对微生物代谢产物的提取效果，选取后者为最优方法，应用响应面曲线法确定最佳提取条件(树脂投加量、搅拌速率、搅拌时间)。采用GC-MS测得微生物代谢产物以脂肪酸、氨基酸和糖类为主。再生水中高含盐量、高营养元素含量和微生物代谢活动是水泥砂浆受侵蚀的主要因素。.基于本研究可以提出：(1)如何控制关键水质参数抑制水泥基材料的腐蚀劣化，保障再生水的后续有效利用；(2)提出相应措施改进水泥基材料的抗腐蚀性能，延长管材的使用寿命。