Interactions and effects of metal oxide nanoparticles on microorganisms involved in biological wastewater treatment

Abstract

To clarify the toxicological effects of metal oxide nanoparticles (NPs) on microorganisms with environmental relevance, it is necessary to understand their interactions. In this work, they were studied the effects and the morphological interactions of two metal oxide NPs (ZnO and TiO ) with microorganisms, during aerobic treatment of wastewater. The effects were evaluated according to nutrient removal from wastewater, while morphological interactions were determined by three different techniques such as TEM, HAADF-STEM, as well as an elemental mapping. According to results about effects of both NPs, they inhibited the removal of organic matter and ammonia nitrogen, and enhanced the orthophosphate removal. Related to morphological interactions, the electron-dense material of both NPs was mainly observed bounded to cell membrane. In tests with ZnO NPs, it was also observed electron-dense material internalized in microorganisms without physical damage in cell membrane. The elemental mapping was useful to determine that the electron-dense material corresponded to Zn and Ti. Both interactions, internalization and attachment of NPs on cell membrane of microorganisms may trigger the negative effect in the removal of organic matter and nitrogen.

Toxicity of Different Zinc Oxide Nanomaterials at 3 Trophic Levels: Implications for Development of Low‐Toxicity Antifouling Agents

“…Aggregated NPs can possess different uptake rates, toxic effects, and bioavailability (Misra et al 2012). Attachment of ZnONPs aggregates to the bacterial cells was responsible for significant membrane damage and higher toxicity (Jiang et al 2009;Leung et al 2016;Cervantes-Aviles et al 2017). Thus, the presence of NP aggregates in the test medium along with toxic action of Zn 2+ ions is one of the possible explanations for the higher toxicity of ZnONPs over ZnO nanorods in the present study.…”

Impact of seed priming with Selenium nanoparticles on germination and seedlings growth of tomato

“…Then, samples were washed in sodium cacodylate buffer, and postfixed in 1% osmium tetroxide at 4 °C for 24 h. The samples were washed with sodium cacodylate buffer and dehydrated in a graded series of ethanol (50–100%). Finally, samples were embedded in epoxy resin (EPON 812), sectioned with an ultramicrotome to 60–70 nm of thickness, and placed in Cu-based grids for TEM observation (TEM, JEOL JEM 1010) 36 , 37 .…”

The Inhibition of Engineered Nano-ZnO in the Biological Nitrogen Removal Process: A Review

“…It is also reported that the introduction of high concentration (450-2000 mg/L) ZnO NPs can result in a significant reduction in the removal efficiency of ammonia nitrogen in the activated sludge system [51]. However, as the concentration of ZnO NPs increases, the removal efficiency of ammonia nitrogen does not experience a further decline, and the decrease in ammonia nitrogen removal efficiency remains within the range of 13-14% [51]. Due to the limited research on the BNR exposed to a high concentration of nano-ZnO, the underlying mechanisms behind this phenomenon require further investigation.…”