State Key Laboratory of Pollution Control and Resource Reuse, Key Laboratory of Yangtze River Water Environment, College of Environmental Science and Engineering, Tongji University, Shanghai 200092, China.
State Key Laboratory of Pollution Control and Resource Reuse, Key Laboratory of Yangtze River Water Environment, College of Environmental Science and Engineering, Tongji University, Shanghai 200092, China; Shanghai Institute of Pollution Control and Ecological Security, Shanghai 200092, China.
Water Res. 2023 May 15;235:119834. doi: 10.1016/j.watres.2023.119834. Epub 2023 Mar 4.
The microbial activities in sewer biofilms are recognized as a major reason for sewer pipe corrosion, malodor, and greenhouse gas emissions. However, conventional methods to control sewer biofilm activities were based on the inhibitory or biocidal effect of chemicals and often required long exposure time or high dosing rates due to the protection of sewer biofilm structure. Therefore, this study attempt to use ferrate (Fe(VI)), a green and high-valent iron, at low dosing rates to damage the sewer biofilm structure so as to enhance sewer biofilm control efficiency. The results showed the biofilm structure started to crush when the Fe(VI) dosage was 15 mg Fe(VI)/L and the damage enhanced with the increasing dosage. The determination of extracellular polymeric substances (EPS) showed that Fe(VI) treatment at 15-45 mgFe/L mainly decreased the content of humic substances (HS) in biofilm EPS. This is because the functional groups, such as C-O, -OH, and C=O, which held the large molecular structure of HS, were the primary target of Fe(VI) treatment as suggested by 2D-Fourier Transform Infrared spectra. As a result, the coiled chain of EPS maintained by HS was turned to extended and dispersed and consequently led to a loosed biofilm structure. The XDLVO analysis suggested that both the microbial interaction energy barrier and secondary energy minimum were increased after Fe(VI) treatment, suggesting that the treated biofilm was less likely to aggregate and easier to be removed by the shear stress caused by high wastewater flow. Moreover, combined Fe(VI) and free nitrous acid (FNA) dosing experiments showed for achieving 90% inactivation, the FNA dosing rate could be reduced by 90% with the exposure time decreasing by 75% at a low Fe(VI) dosing rate and the total cost was substantially decreased. These results suggested that applying low-rate Fe(VI) dosing for sewer biofilm structure destruction is expected to be an economical way to facilitate sewer biofilm control.
污水生物膜中的微生物活动被认为是污水管道腐蚀、恶臭和温室气体排放的主要原因。然而，传统的控制污水生物膜活性的方法是基于化学物质的抑制或杀菌作用，由于污水生物膜结构的保护，往往需要长时间的暴露或高剂量率。因此，本研究试图使用高铁酸盐（Fe(VI)），一种绿色的高价铁，以低剂量率来破坏污水生物膜结构，从而提高污水生物膜的控制效率。结果表明，当 Fe(VI)剂量为 15mg/L 时，生物膜结构开始破碎，随着剂量的增加，破坏作用增强。胞外聚合物物质（EPS）的测定表明，Fe(VI)处理在 15-45mgFe/L 时主要降低了生物膜 EPS 中腐殖质（HS）的含量。这是因为 2D 傅里叶变换红外光谱表明，HS 所具有的 C-O、-OH 和 C=O 等官能团是 Fe(VI)处理的主要靶标，从而破坏了 EPS 中保持 HS 大分子结构的螺旋链。因此，由 HS 保持的 EPS 链被展开和分散，导致生物膜结构变得松散。XDLVO 分析表明，Fe(VI)处理后微生物相互作用的能量势垒和二次能量最小值都增加了，这表明处理后的生物膜不太可能聚集，并且更容易被高废水流量引起的剪切力去除。此外，结合 Fe(VI)和游离亚硝酸（FNA）投加实验表明，在低 Fe(VI)投加率下，达到 90%灭活所需的 FNA 投加率可降低 90%，暴露时间减少 75%，总费用大幅降低。这些结果表明，应用低剂量率的 Fe(VI)破坏污水生物膜结构有望成为促进污水生物膜控制的一种经济方法。
