Department of Civil and Environmental Engineering, University of Missouri, E2509 Lafferre Hall, Columbia, MO 65211, USA.
Water Res. 2010 Oct;44(18):5432-8. doi: 10.1016/j.watres.2010.06.060. Epub 2010 Jul 17.
The growing release of nanosilver into sewage systems has increased the concerns on the potential adverse impacts of silver nanoparticles (AgNPs) in wastewater treatment plants. The inhibitory effects of nanosilver on wastewater treatment and the response of activated sludge bacteria to the shock loading of AgNPs were evaluated in a Modified Ludzack-Ettinger (MLE) activated sludge treatment system. Before shock-loading experiments, batch extant respirometric assays determined that at 1mg/L of total Ag, nitrification inhibitions by AgNPs (average size=1-29 nm) and Ag(+) ions were 41.4% and 13.5%, respectively, indicating that nanosilver was more toxic to nitrifying bacteria in activated sludge than silver ions. After a 12-h period of nanosilver shock loading to reach a final peak silver concentration of 0.75 mg/L in the MLE system, the total silver concentration in the mixed liquor decreased exponentially. A continuous flow-through model predicted that the silver in the activated sludge system would be washed out 25 days after the shock loading. Meanwhile, a prolonged period of nitrification inhibition (>1 month, the highest degree of inhibition=46.5%) and increase of ammonia/nitrite concentration in wastewater effluent were observed. However, nanosilver exposure did not affect the growth of heterotrophs responsible for organic matter removal. Microbial community structure analysis indicated that the ammonium-oxidizing bacteria and nitrite-oxidizing bacteria, Nitrospira, had experienced population decrease while Nitrobacter was washed out after the shock loading.
纳米银不断排入污水系统，增加了人们对废水处理厂中银纳米粒子（AgNPs）潜在不良影响的担忧。本研究采用改良的 Ludzack-Ettinger（MLE）活性污泥处理系统，评估了纳米银对污水处理的抑制作用以及活性污泥细菌对 AgNPs 冲击负荷的响应。在冲击负荷实验之前，通过批式现存呼吸测量法确定，在总银浓度为 1mg/L 的条件下，AgNPs（平均粒径为 1-29nm）和 Ag(+)离子对硝化的抑制率分别为 41.4%和 13.5%，这表明纳米银比银离子对活性污泥中的硝化细菌毒性更大。在将纳米银冲击负荷 12 小时以达到 MLE 系统中最终峰值银浓度 0.75mg/L 后，混合液中的总银浓度呈指数下降。连续流动模型预测，在冲击负荷后 25 天，活性污泥系统中的银将被冲洗出来。同时，观察到硝化抑制期延长（>1 个月，最大抑制程度=46.5%）以及废水出水中氨氮/亚硝酸盐浓度增加。然而，纳米银暴露并没有影响负责去除有机物的异养生物的生长。微生物群落结构分析表明，在冲击负荷后，氨氧化细菌和亚硝酸盐氧化细菌（Nitrospira）的种群数量减少，而 Nitrobacter 则被冲洗掉。
