|Alternative Title||Effects of water source quality on stability of iron corrosion in distribution systems|
|Place of Conferral||北京|
|Keyword||铁腐蚀 地下水 地表水 氯 氯胺 微生物腐蚀 Iron Corrosion Groundwater Surface Water Chlorine Chloramine Microbially Influenced Corrosion|
（1）以北方某城市发生和未发生“黄水”区历史给水铸铁管段为研究对象，探讨了水源切换条件下“黄水”释放机制。结果表明，未发生“红水”区地表水管段消毒剂消耗少，水质稳定，垢层主要由α-FeOOH，Fe3O4和γ-FeOOH组成，垢内微生物以铁还原菌（IRB）Geothrix sp.为主，并伴随少量的铁氧化菌（IOB）Gallionella sp.。“黄水”发生区地下水管段消毒剂消耗较多，出水浊度高，管垢以-FeOOH为主，垢层内微生物以IOB Gallionella sp.和Sediminibacterium sp.为主。添加消毒剂运行后，地下水管段出水渐趋稳定，铁离子释放少，垢层中 IRB出现并成为优势菌。腐蚀层中IOB和IRB的协同作用可以降低铁离子的释放从而减缓“黄水”的发生。
（2）使用市售新铸铁管进行模拟实验，研究了不同水源中铁管的腐蚀机制。地下水管网中腐蚀产物主要以疏松的α-FeOOH为主，BET比表面积为85.5 m2g-1；地表水管网中腐蚀产物较致密，以晶形良好的 α-FeOOH、Fe3O4和CaCO3为主，相应的 BET比表面积为18.8 m2 g-1。在硝酸盐浓度为 5~7.9 mg N L-1的地下水管网中，腐蚀稳定性主要受依赖于硝酸盐还原菌（NRB）和 IOB驱动的二价铁氧化影响；在含较低浓度硝酸盐（0.9~2.2 mg N L-1）的地表水管网中，腐蚀主要受 NRB厌氧呼吸诱导的铁氧化还原循环影响。上述结果在生物膜反应器中也进一步得到证实。NRB驱动的铁氮循环影响腐蚀层的稳定。
（3）为了进一步考察非稳定态的地下水管网腐蚀特性，研究了氯胺消毒的铸铁管网腐蚀产物与管垢微生物特性。氯胺的降解导致水体中氨的增加，腐蚀初期硝化作用明显，硝酸盐还原受抑制；随着反硝化菌比例的增加，反硝化占主导地位。α-FeOOH为其主要腐蚀产物，与氯消毒管网相比，氯胺管网中腐蚀产物较致密。分子生物学表征结果说明氯胺增加了水体中 NRB和IOB相对含量，说明 NRB驱动的硝酸盐还原的二价铁氧化促进致密腐蚀层形成。
|Other Abstract|| Water shortage has been a serious problem in many cities over the world while|
water source switches applied to alleviate the pressure of the water supply. Unstable
corrosion scales might trigger “red water” issues when water quality entering
distribution systems changed significantly. The groundwater and surface water from a northern city drinking water treatment plants were used in this study. The experimental pipe distribution systems and biofilm annular reactors (BARs) were used to simulate the DWDSs combined with the methods of XRD, SEM,
PCR-DGGE and pyrosequencing. The purpose of this research was to investigate the corrosion processes and effects of water quality on corrosion stability in distribution systems with different water sources. The main conclusions were as follows.
(1) Aged cast iron pipes from both affected and unaffected areas were used to establish experimental drinking water distribution systems under different disinfection conditions. In pipe samples from the unaffected area, the dense and thick corrosion layer included predominantly -FeOOH, Fe3O4, and γ-FeOOH, and iron-reducing bacteria (IRB) were predominant with fewer iron-oxidizing bacteria (IOB) such as Gallionella sp. being observed. The composition of corrosion products did not exhibit large variation over time although their crystallinity did exhibit a slight decrease throughout the duration of the experiment. In contrast, in the pipe samples from the affected area, the corrosion layer was thinner and loosely attached with -FeOOH being the main compound present. Compared to pipe samples from the unaffected area, less γ-FeOOH and Fe3O4 were present and IOB such as Gallionella sp. and Sediminibacterium sp. were the dominant bacteria observed. With increasing time, the corrosion layers became significantly thicker and IRB appeared in pipe samples from the affected area which had been treated with chlorine and chloramine as disinfectants. These results indicated that the synergistic interaction of IRB/IOB with the dense corrosion layer inhibited the iron release from a cast iron pipe following changes in water quality.
(2) The composition of biofilm bacterial communities and iron corrosion scales were studied in two drinking water distribution systems transporting groundwater (DWDS-GW) and surface water (DWDS-SW)，as well as biofilm annular reactors (BARs). The results showed that a loose corrosion layer was formed containing reddish filaments of α-FeOOH with a BET surface area of 85.5 m2g-1 in DWDS-GW,while in DWDS-SW, a dense corrosion layer was formed, including crystallized particles of α-FeOOH, γ-FeOOH, Fe3O4 and CaCO3 with a BET surface area of 18.8 m2g-1. Based on the MPN enumerations and qPCR of denitrifying functional bacteria,the formation of corrosion products was mainly affected by nitrate-dependent Fe(II)oxidation of NRB-Fe and Fe(II) oxidation of IOB Sediminibacterium in the DWDSs transporting GW with nitrate concentration from 5 to 7.9 mg N L-1, but reduction of Fe(III) and oxidation of Fe(II) occurred from the anaerobic respiration of NRB-Fe in the DWDSs transporting SW with lower nitrate concentration (0.9~2.2 mg N L-1).These results were consistent with the research in BARs. It was found that nitrate-reducing bacteria in biofilms that are associated with iron cycling played a large role in the stability corrosion layers.
(3) The effect of chloramine disinfection on bacterial communities and the corrosion of cast iron pipes was also studied in drinking water distribution systems (DWDSs) transporting groundwater. α-FeOOH was the main corrosion product for both systems. Most of the NO3- -N in the raw water was biologically denitrified through chlorine DWDSs in the experimental period, whereas the same phenomena occurred only when denitrifying bacteria were increased in the effluent due to the role of autotrophic microbial nitriﬁcation in chloramine DWDSs. Furthermore，nitrate-dependent Fe(II) oxidation occurred to a greater extent, leading to denser corrosion scales in DWDSs with chloramine compared with those disinfected with chlorine.
(4) The effects of groundwater and surface water under different Larson indices on cast iron corrosion were studied. The results show that the Larson index is not enough to fully express corrosion difference between groundwater and surface water while nitrate concentration and microbial components under different water sources may play a large role on the corrosion stability and network features.
|李肖肖. 水源水质对铸铁管网腐蚀稳定性的影响[D]. 北京. 中国科学院研究生院,2015.|
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