Engineered nanoparticles in wastewater and wastewater sludge--evidence and impacts

Spinel ferrite nanoparticles and nanocomposites for biomedical applications and their toxicity

This review focuses on the biomedical applications and toxicity of spinel ferrite nanoparticles (SFNPs) with more emphasis on the recently published work. A critical review is provided on recent advances of SFNPs applications in biomedical areas. The novelty of SFNPs in addressing the bottleneck problems encountered in the areas of health; in particular, for diagnosis and treatment of tumour cells are well reviewed. Furthermore, research gaps, toxicity of SFNPs and areas which still need more attention are highlighted. Based on the result of this review, the SFNPs have unlimited capacity in cancer treatment, disease diagnosis, magnetic resonance imaging, drug delivery and release. Overall, stepping out of the conventional way of treatment is difficult but also essential in bringing long lasting solution for cancer and other diseases treatment. In fact, the toxicity study and commercialisation of the SFNPs based cancer treatment options are the main challenges and need further study, in order to reduce unforeseen consequences.

Core-composite mediated separation of diverse nanoparticles to purity

A generalized method for sorting nanoparticles based on their cores does not exist; it is an immediate necessity, and an approach incorporating cost-effectiveness and biocompatibility is in demand. Therefore, an efficient method for the separation of various mixed core-compositions or dissimilar metallic nanoparticles to their pure forms at the nano-bio interface was developed. Various simple core-combinations of monodispersed nanoparticles with dual cores, including silver plus gold, iron oxide plus gold and platinum plus gold, to the complex three-set core-combinations of platinum plus gold plus silver and platinum plus iron plus gold were sorted using step-gradient centrifugation in a sucrose suspension. Viscosity mediated differential terminal velocities of the nanoparticles permitted diversified dragging at different gradients allowing separation. Stability, purity and properties of the nanoparticles during separation were evaluated based on visual confirmation and by employing advanced instrumentations. Moreover, theoretical studies validated our experimental observations, revealing the roles of various parameters, such as the viscosity of sucrose, the density of the particles and the velocity and duration of centrifugation, involved during the separation process. This remarkably rapid, cost-efficient and sustainable strategy can be adapted to separate other cores of nanoparticles for various biomedical research purposes, primarily to understand nanoparticle induced toxicity and particle fate and transformations in natural biotic environments.

Morphological Transformation of Silver Nanoparticles from Commercial Products: Modeling from Product Incorporation, Weathering through Use Scenarios, and Leaching into Wastewater

There is increasing interest in the environmental fate and effects of engineered nanomaterials due to their ubiquitous use in consumer products. In particular, given the mounting evidence that dramatic transformations can occur to a nanomaterial throughout its product lifecycle, the appropriateness of using pristine nanomaterials in environmental testing is being questioned. Using a combination of transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), and inductively coupled plasma-mass spectrometry (ICP-MS), this work examines the morphological and compositional effects of conditions mimicking a typical lifecycle of a nano-enabled product, from the production of the silver nanoparticle (AgNP)-laden textiles, through its use, laundering, and then finally, its leaching and incubation in the wastewater collection system. These simulated weathering conditions showed evidence for the transformation of AgNPs into AgCl and Ag₂S. Incubation in raw wastewater had the most dramatic effect on the AgNPs in terms of transformation, no matter what initial weathering was applied to the NPs prior to incubation. However, despite extensive transformation noted, AgNPs were still present within all the samples after the use scenarios.

Soybean Interaction with Engineered Nanomaterials: A Literature Review of Recent Data

With a continuous increase in the production and use in everyday life applications of engineered nanomaterials, concerns have appeared in the past decades related to their possible environmental toxicity and impact on edible plants (and therefore, upon human health). Soybean is one of the most commercially-important crop plants, and a perfect model for nanomaterials accumulation studies, due to its high biomass production and ease of cultivation. In this review, we aim to summarize the most recent research data concerning the impact of engineered nanomaterials on the soya bean, covering both inorganic (metal and metal-oxide nanoparticles) and organic (carbon-based) nanomaterials. The interactions between soybean plants and engineered nanomaterials are discussed in terms of positive and negative impacts on growth and production, metabolism and influences on the root-associated microbiota. Current data clearly suggests that under specific conditions, nanomaterials can negatively influence the development and metabolism of soybean plants. Moreover, in some cases, a possible risk of trophic transfer and transgenerational impact of engineered nanomaterials are suggested. Therefore, comprehensive risk-assessment studies should be carried out prior to any mass productions of potentially hazardous materials.

Anatase TiO2 Nanoparticles Induce Autophagy and Chloroplast Degradation in Thale Cress (Arabidopsis thaliana)

The extensive use of TiO₂ nanoparticles and their subsequent release into the environment have posed an important question about the effects of this nanomaterial on ecosystems. Here, we analyzed the link between the damaging effects of reactive oxygen species generated by TiO₂ nanoparticles and autophagy, a housekeeping mechanism that removes damaged cellular constituents. We show that TiO₂ nanoparticles induce autophagy in the plant model system Arabidopsis thaliana and that autophagy is an important mechanism for managing TiO₂ nanoparticle-induced oxidative stress. Additionally, we find that TiO₂ nanoparticles induce oxidative stress predominantly in chloroplasts and that this chloroplastic stress is mitigated by autophagy. Collectively, our results suggest that photosynthetic organisms are particularly susceptible to TiO₂ nanoparticle toxicity.

Long-term impacts of carboxyl functionalized multi-walled carbon nanotubes on the performance, microbial enzymatic activity and microbial community of sequencing batch reactor

The performance, microbial community and enzymatic activity of sequencing batch reactors (SBRs) were evaluated under long-term exposure of 0, 10 and 30 mg/L carboxyl functionalized multi-walled carbon nanotubes (MWCNTs-COOH). The presence of 10 mg/L MWCNTs-COOH displayed no adverse impacts on the COD and NH₄⁺-N removal of SBR, whereas 30 mg/L MWCNTs-COOH declined the COD and NH₄⁺-N removal. MWCNTs-COOH inhibited the denitrifying process and led to the accumulation of effluent NO₂^--N concentration. The inhibition of MWCNTs-COOH on the oxygen utilization rate, nitrogen removal rate and enzymatic activity of activated sludge gradually enhanced with the increase of operating time and influent MWCNTs-COOH concentration. MWCNTs-COOH stimulated more reactive oxygen species production and lactate dehydrogenase release, which might affect the microbial physiological functions and morphology. The microbial diversity and richness was declined evidently after long-term exposure of MWCNTs-COOH. The relative abundance of nitrifying and denitrifying bacteria showed some changes under MWCNTs-COOH stress.

Irrigation Water Quality—A Contemporary Perspective

In the race to enhance agricultural productivity, irrigation will become more dependent on poorly characterized and virtually unmonitored sources of water. Increased use of irrigation water has led to impaired water and soil quality in many areas. Historically, soil salinization and reduced crop productivity have been the primary focus of irrigation water quality. Recently, there is increasing evidence for the occurrence of geogenic contaminants in water. The appearance of trace elements and an increase in the use of wastewater has highlighted the vulnerability and complexities of the composition of irrigation water and its role in ensuring proper crop growth, and long-term food quality. Analytical capabilities of measuring vanishingly small concentrations of biologically-active organic contaminants, including steroid hormones, plasticizers, pharmaceuticals, and personal care products, in a variety of irrigation water sources provide the means to evaluate uptake and occurrence in crops but do not resolve questions related to food safety or human health effects. Natural and synthetic nanoparticles are now known to occur in many water sources, potentially altering plant growth and food standard. The rapidly changing quality of irrigation water urgently needs closer attention to understand and predict long-term effects on soils and food crops in an increasingly fresh-water stressed world.

The effect of silver nanoparticles on the mutagenic and the genotoxic properties of the urban wastewater liquid sludges

Nanoparticles are very effective compounds to transform and detoxicate common environmental contaminants. For this reason, crude urban liquid wastewater sludges were treated by silver nanoparticles (Ag-NPs, 100 nm) for 24 h. Both Ag-NPs' treated and untreated sludges were examined for the evaluation if there are possible mutagenic/anti-mutagenic, cytotoxic, and genotoxic/anti-genotoxic effects by Ames and Allium cepa tests. The results were then subjected to statistical analyses by using SPSS software and p < 0.05 was accepted as a significant value. The data obtained from the Ames test showed that while untreated crude liquid sludge had a significant mutagenic effect, Ag-NP-treated one decreased its mutagenicity. Similar effects were also observed in the chromosome aberration-Allium cepa tests. Significant chromosome aberrations observed were C-metaphase, sticky metaphase, sticky anaphase, anaphase bridge, vagrant chromosome, and multipolar anaphases. Both tests demonstrated that silver nanoparticle treatment decreased the major mutagenicity and genotoxicity detected in the liquid wastewater sludges.

Non-antibacterial as well as non-anticancer activity of flower extract and its biogenous silver nanoparticles

Silver nanoparticles were synthesized by using the white flower extract of Albizia lebbeck as a source of reducing and capping agents. A. lebbeck white flower extract and silver nanoparticles were checked for their antibacterial activity against Staphylococcus aureus, Escherichia coli, Pseudomonas aeroginosa and Ba cillus subtilis by using Mueller Hinton agar, nutrient agar and Luria Bertani agar using the well diffusion method. The synthesized silver nanoparticles did not show antibacterial activity at lower (0.1-0.4 mg ml^-1) or higher (0.5-2.5 mg ml^-1) concentrations against any of the four organisms on either of the media, even though silver nanoparticles have been well known to show antibacterial activity even at lower concentrations. The non-antibacterial properties of the synthesized silver nanoparticles against all four bacteria were confirmed using viability counting. With this unique non-antibacterial property of biogenous silver nanoparticles observed in this study, it can be stated that case by case evaluation of every synthesized silver nanoparticle needs to be done as there are multiple factors influencing their properties. Anticancer activity of these nanoparticles at different concentrations against A549 cancer cells did not show any significant decrease in cell viability highlighting its biocompatible nature. Thus, these silver nanoparticles can be a best suited candidate for drug delivery.

A review on the interactions between engineered nanoparticles with extracellular and intracellular polymeric substances from wastewater treatment aggregates

Engineered nanoparticles (ENPs) will inevitably enter wastewater treatment plants (WWTPs) due to their widespread application; thus, it is necessary to study the migration and transformation of nanoparticles in sewage treatment systems. Extracellular polymeric substances (EPSs) such as polysaccharides, proteins, nucleic acids, humic acids and other polymers are polymers released by microorganisms under certain conditions. Intracellular polymeric substances (IPSs) are microbial substances contained in the body with compositions similar to those of extracellular polymers. In this review, we summarize the characteristics of EPSs and IPSs from sewage-collecting microbial aggregates containing pure bacteria, activated sludge, granular sludge and biofilms. We also further investigate the dissolution, adsorption, aggregation, deposition, oxidation and other chemical transformation processes of nanoparticles, such as metals, metal oxides, and nonmetallic oxides. In particular, the review deeply analyzes the migration and transformation mechanisms of nanoparticles in EPS and IPS matrices, including physical, chemical, biological interactions mechanisms. Moreover, various factors, such as ionic strength, ionic valence, pH, light, oxidation-reduction potential and dissolved oxygen, influencing the interaction mechanisms are discussed. In recent years, studies on the interactions between EPSs/IPSs and nanoparticles have gradually increased, but the mechanisms of these interactions are seldom explored. Therefore, developing a systematic understanding of the migration and transformation mechanisms of ENPs is significant.

An integrated approach to highlight biological responses of Pisum sativum root to nano-TiO2 exposure in a biosolid-amended agricultural soil

This study focused on crop plant response to a simultaneous exposure to biosolid and TiO₂ at micro- and nano-scale, being biosolid one of the major sink of TiO₂ nanoparticles released into the soil environment. We settled an experimental design as much as possible realistic, at microcosm scale, using the crop Pisum sativum. This experimental design supported the hypotheses that the presence of biosolid in the farming soil might influence plant growth and metabolism and that, after TiO₂ spiking, the different dimension and crystal forms of TiO₂ might be otherwise bioavailable and differently interacting with the plant system. To test these hypotheses, we have considered different aspects of the response elicited by TiO₂ and biosolid at cellular and organism level, focusing on the root system, with an integrative approach. In our experimental conditions, the presence of biosolid disturbed plant growth of P. sativum, causing cellular damages at root level, probably through mechanisms not only oxidative stress-dependent but also involving altered signalling processes. These disturbances could depend on non-humified compounds and/or on the presence of toxic elements and of nanoparticles in the biosolid-amended soil. The addition of TiO₂ particles in the sludge-amended soil, further altered plant growth and induced oxidative and ultrastructural damages. Although non typical dose-effect response was detected, the most responsiveness treatments were found for the anatase crystal form, alone or mixed with rutile. Based on ultrastructural observations, we could hypothesise that the toxicity level of TiO₂ nanoparticles may depend on the cell ability to isolate nanoparticles in subcellular compartments, avoiding their interaction with organelles and/or metabolic processes. The results of the present work suggest reflections on the promising practice of soil amendments and on the use of nanomaterials and their safety for food plants and living organisms.

The revolution of performance, sludge characteristics and microbial community of anammox biogranules under long-term NiO NPs exposure

Given the increasing applications of NiO nanoparticles (NPs) in battery products, the potential effects of NiO NPs on anaerobic ammonium oxidation (anammox) systems were studied for the first time. The results showed that the anammox system performance obviously differed under the stresses of different NiO NPs concentrations. After the withdrawal of NiO NPs, the nitrogen removal performance of the anammox reactor returned to nearly that of the initial phase within 35 days. Compared with 0 mg L^-1 NiO NPs, the specific anammox activity first increased and then decreased to the minimum value of 116.8 ± 13.8 mg TN g^-1 VSS d^-1 at 60 mg L^-1 NiO NPs. The variations in the heme c contents and extracellular polymeric substance amounts were similar to the variations in the specific anammox activity throughout the whole experiment. Additionally, the relative abundance of the dominant bacteria (Candidatus kuenenia) increased from 20.44% at 60 mg L^-1 NiO NPs to 23.14% at the end of the last phase. Thus, the potential effects of NiO NPs on anammox systems should be a cause for great concern.

An investigation of the fate and behaviour of a mixture of WO3 and TiO2 nanoparticles in a wastewater treatment plant

The fate and behaviour of WO₃ and TiO₂ mixture were investigated following the Organisation for Economic Co-operation and Development 303A guidelines. The nanoparticles were found not to influence the chemical oxygen demand removal efficiency which was maintained >80% hence the activated sludge process was on affected. The nanoparticles were eliminated from the wastewater with a greater percentage of 99.8% for TiO₂ and 95.5% for WO₃ found in the sludge. The activated sludge process also had no effect of the polymorphs of the nanoparticles as X-ray diffraction revealed presence of monoclinic WO₃ and anatase TiO₂ which were spiked into the influent. The nanoparticles were mainly removed by bio-adsorption on the activated sludge surface. The total plate count revealed that the bacterial colonies present in the control and the test units were comparable during the gradual introduction of nanoparticles in the chambers. The biomass was >0.75 MLVSS/MLSS (mixed liquor volatile suspended solids/mixed liquor suspended solids) in both the aeration vessels thus a greater proportion of the sludge were the microorganisms. A greater percentage of the Ti and W found in the effluent was mainly due to the nanoparticles adsorbed on the suspended solids with only 3.6% Ti and 28.6% W due to dissolution of nanoparticles.

How do zinc oxide and zero valent iron nanoparticles impact the occurrence of antibiotic resistance genes in landfill leachate?

ZnO NP exposure accelerated the dissemination of ARGs by dominantly driving changes in bacterial community, and Fe⁰ NP exposure promoted the attenuation of ARGs by mainly decreasing the abundances of MGEs.

A Review on Nanoparticles as Boon for Biogas Producers—Nano Fuels and Biosensing Monitoring

Nanotechnology has an increasingly large impact on a broad scope of biotechnological, pharmacological and pure technological applications. Its current use in bioenergy production from biomass is very restricted. The present study is based on the utilization of nanoparticles as an additive to feed bacteria that break down natural substances. The novel notion of dosing ions using modified nanoparticles can be used to progress up biogas production in oxygen free digestion processes. While minute nanoparticles are unstable, they can be designed to provide ions in a controlled approach, so that the maximum enhancement of biogas production that has been reported can be obtained. Nanoparticles are dissolved in a programmed way in an anaerobic atmosphere and are supplied in a sustainable manner to microbiotic organisms responsible for the degradation of organic material, which is a role that fits them well. Therefore, biogas fabrication can be increased up to 200%, thereby increasing the degradation of organic waste.

Simultaneously enhanced biopolymers production and sludge dewaterability of waste activated sludge by synergetic integration process of short-time aerobic digestion with cocoamidopropyl betaine and calcium oxide

Waste activated sludge (WAS) has seriously threatened the environment safety and the public health due to its rapid growth and complex components. Simultaneously enhanced the biopolymers production and the sludge dewaterability of WAS were investigated by synergetic integration process of the short-time aerobic digestion (STAD) with cocoamidopropyl betaine (CAPB) and calcium oxide (CaO). STAD could improve the biopolymers production by biosynthesis. CAPB could further significantly enhance the biopolymers production and optimized the constituents. CaO (0.1-0.2 g/g TSS) could dramatically enhance the sludge dewaterability by forming a multi-grid skeleton in WAS, while the biopolymers production could almost remain stable. Especially, the synergetic integration process of STAD with 0.1 g CAPB/g TSS for 8 h and 0.1 g CaO/g TSS could cost-effectively enhance both the biopolymers production and the sludge dewaterability. The produced biopolymers showed strong adsorbability for heavy metals (eg, 375 mg Cu²⁺/g biopolymers). Accordingly, the developed novel process is of big significance for resource utilization and volume reduction of WAS.

What kind of effects do Fe2O3 and Al2O3 nanoparticles have on anaerobic digestion, inhibition or enhancement?

Fe₂O₃ and Al₂O₃ nanoparticles are widely used in products and find their way to wastewater treatment plants through the contact of water with these products. In this study, impacts of Fe₂O₃ and Al₂O₃ nanoparticles on methane potential of waste activated sludge (WAS) were investigated by comparing long and short term toxicity test results, modelling and FISH analysis. Methane production from the samples treated with the maximum concentration of Fe₂O₃ nanoparticles decreased 28.9% at the end of the long term BMP test. EC₅₀ value for BMP test of the Fe₂O₃ nanoparticles was calculated as 901.94 mg/gTS with high coefficient of determination. Methane production from the samples treated with Al₂O₃ nanoparticles increased up to 14.8% (p > 0.05) at the end of the BMP test. However, short term toxicity tests for Fe₂O₃ and Al₂O₃ nanoparticles showed no impact on anaerobic digestion of WAS. Kinetic parameters obtained from models and captured FISH images were consistent with these results. Different impacts of nanoparticles on methane production suggested that anaerobic microorganisms can be affected from nanoparticles in various mechanisms. Hydrolysis (k_H) and overall reaction rates (k_R) values were determined as 0.0277 and 0.1441 d^-1, respectively for each concentration of Al₂O₃ nanoparticles and raw WAS. Similarly, methane production from WAS containing 5, 50, 150 and 250 mgFe₂O₃/gTS were modeled with same kinetic values. However, k_H constant was calculated as 0.0149 d^-1 for 500 mgFe₂O₃/gTS. This means that Fe₂O₃ nanoparticles starting from this concentration inhibited the methanogenic consortium and caused decreased biogas production and spesific methane production rate.

Deposition of engineered nanoparticles (ENPs) on surfaces in aquatic systems: a review of interaction forces, experimental approaches, and influencing factors

The growing development of nanotechnology has promoted the wide application of engineered nanomaterials, raising immense concern over the toxicological impacts of nanoparticles on the ecological environment during their transport processes. Nanoparticles in aquatic systems may undergo deposition onto environmental surfaces, which affects the corresponding interactions of engineered nanoparticles (ENPs) with other contaminants and their environmental fate to a certain extent. In this review, the most common ENPs, i.e., carbonaceous, metallic, and nonmetallic nanoparticles, and their potential ecotoxicological impacts on the environment are summarized. Colloidal interactions, including Derjaguin-Landau-Verwey-Overbeek (DLVO) and non-DLVO forces, involved in governing the depositional behavior of these nanoparticles in aquatic systems are outlined in this work. Moreover, laboratory approaches for examining the deposition of ENPs on collector surfaces, such as the packed-bed column and quartz crystal microbalance (QCM) method, and the limitations of their applications are outlined. In addition, the deposition kinetics of nanoparticles on different types of surfaces are critically discussed as well, with emphasis on other influencing factors, including particle-specific properties, particle aggregation, ionic strength, pH, and natural organic matter. Finally, the future outlook and challenges of estimating the environmental transport of ENPs are presented. This review will be helpful for better understanding the effects and transport fate of ENPs in aquatic systems. Graphical abstract ᅟ.

Factors impacting the interactions of engineered nanoparticles with bacterial cells and biofilms: Mechanistic insights and state of knowledge

Since their advent a few decades ago, engineered nanoparticles (ENPs) have been extensively used in consumer products and industrial applications and their use is expected to continue at the rate of thousands of tons per year in the next decade. The widespread use of ENPs poses a potential risk of large scale environmental proliferation of ENPs which can impact and endanger environmental health and safety. Recent studies have shown that microbial biofilms can serve as an important biotic component for partitioning and perhaps storage of ENPs released into aqueous systems. Considering that biofilms can be one of the major sinks for ENPs in the environment, and that the field of biofilms itself is only three to four decades old, there is a recent and growing body of literature investigating the ENP-biofilm interactions. While looking at biofilms, it is imperative to consider the interactions of ENPs with the planktonic microbial cells inhabiting the bulk systems in the vicinity of surface-attached biofilms. In this review article, we attempt to establish the state of current knowledge regarding the interactions of ENPs with bacterial cells and biofilms, identifying key governing factors and interaction mechanisms, as well as prominent knowledge gaps. Since the context of ENP-biofilm interactions can be multifarious-ranging from ecological systems to water and wastewater treatment to dental/medically relevant biofilms- and includes devising novel strategies for biofilm control, we believe this review will serve an interdisciplinary audience. Finally, the article also touches upon the future directions that the research in the ENP-microbial cells/biofilm interactions could take. Continued research in this area is important to not only enhance our scientific knowledge and arsenal for biofilm control, but to also support environmental health while reaping the benefits of the 'nanomaterial revolution'.

Discrepant effects of metal and metal oxide nanoparticles on anammox sludge properties: A comparison between Cu and CuO nanoparticles

Metal and metal oxide nanoparticles (NPs) show differences in antimicrobial activity due to different chemical and physical properties. Using copper as a representative example, this study compared the NP effects on anaerobic ammonium oxidation (anammox) bacteria in wastewater treatment. Long-term exposure to 5 mgCu L^-1 CuNPs reduced the physiological activity and abundance of anammox bacteria, thereby causing deterioration of reactor performance. However, anammox granules exhibited stronger resistance and resilience to perturbation by 1-160 mgCu L^-1 CuONPs, and no adverse effects on performance were observed. Moreover, the level of Cu(II) released from NPs in the influent exhibited good correlations with variations of the community structure and sludge properties. Therefore, the effects of Cu-based NPs on anammox sludge properties are dependent on their forms and levels, and their discrepant effects are partially attributed to their ability to release ionic copper.

Strategies and relative mechanisms to attenuate the bioaccumulation and biotoxicity of ceria nanoparticles in wastewater biofilms

Inhibitory effects of ceria nanoparticles (CeO₂ NPs) on biofilm were investigated individually and in combination with phosphate (P), ethylene diamine tetraacetic acid (EDTA), humic acid (HA) and citrate (CA) to further explore the toxicity alleviating solutions. Exposure to 20 mg/L CeO₂ NPs significantly decreased the performance of biofilm in nutrients removal. Distribution experiments suggested >98% of the CeO₂ NPs retained in microbial aggregates, leading to 51.26 μg/L Ce ions dissolution. The dissolved Ce^IV and its further being reduced to Ce^III stimulated the formation of O₂^- and OH, which increased lipid peroxidation level to 130.93% in biofilms. However, P/EDTA/CA captured or precipitated Ce ions, whereas EDTA/HA/CA shielded NPs-bacteria direct contacts, both disturbing the NPs adsorption, intercepting the redox transition between Ce^IV and Ce^III, reducing the generation of O₂^- and OH, thus mitigating the toxicity of CeO₂ NPs. These results illustrate the main drivers of CeO₂ NPs biotoxicity and provide safer-by-design strategies.

One Step Hydrothermal Synthesis of Magnesium Silicate Impregnated Palm Shell Waste Activated Carbon for Copper Ion Removal

Magnesium silicate impregnated onto palm-shell waste activated carbon (PPAC) underwent mild hydrothermal treatment under one-pot synthesis, designated as PPAC-MC. Various impregnation ratios from 25 to 300% of MgSiO3 onto PPAC were tested. High levels of MgSiO3 led to high Cu(II) adsorption capacity. A ratio of 1:1 (PPAC-MS 100) was considered optimum because of its chemical stability in solution. The maximum adsorption capacity of PPAC-MS 100 for Cu(II) obtained by isotherm experiments was 369 mg g−1. The kinetic adsorption data fitted to pseudo-second-order model revealed as chemisorption. Increasing ionic strength reduced Cu(II) adsorption capacity due to the competition effect between Na+ and Cu2+. In addition, PPAC-MS 100 showed sufficient adsorption capacity for the removal of Zn(II), Al(III), Fe(II), Mn(II), and As(V), with adsorption capacities of 373 mg g−1, 244 mg g−1, 234 mg g−1, 562 mg g−1, 191 mg g−1, respectively. Three regeneration studies were also conducted. PPAC-MS was characterized using Fourier Transformed Infrared (FTIR), X-Ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and Field Emission Scanning Electron Microscope (FESEM). Overall, PPAC-MS 100 is a competitive adsorbent due to its high sorption capacity and sufficient regeneration rate, while remaining economical through the reuse of palm-shell waste materials.

Influence of the Composition on the Environmental Impact of Soft Ferrites

The aim of this paper is to analyze the influence of the composition on the environmental impact of the two main types of soft ferrites, allowing scientists and engineers to compare them based not only on cost and properties, but also on an environmental point of view. Iron oxides are the basis of soft ferrites, but these ferrites have a wide range of compositions, using materials such as manganese or nickel, which affect their magnetic properties, but also modify the environmental impact. A Life Cycle Assessment has been carried out for manganese‒zinc (MnZn) and nickel‒zinc (NiZn) soft ferrites, with a Monte Carlo approach to assess multiple compositions. The LCA model was developed with SimaPro 8.4, using the EcoInvent v3.4 life cycle inventory database. Environmental impact values were calculated under the ReCiPe and Carbon Footprint methodologies, obtaining a broad variety of results depending on the composition. The results were also significantly different from the standard EcoInvent ferrite. For the analyzed soft ferrites, the presence of manganese or nickel is a key factor from an environmental perspective, as these materials involve high environmental impacts, and their supply risk has increased during recent years, making them a concern for European manufacturers.

Effect of magnesium oxide nanoparticles on microbial diversity and removal performance of sequencing batch reactor

The performance, microbial enzymatic activity and microbial community of a sequencing batch reactor (SBR) have been explored under magnesium oxide nanoparticles (MgO NPs) stress. The NH₄⁺-N removal efficiency kept relatively stable during the whole operational process. The MgO NPs at 30-60 mg/L slightly restrained the removal of chemical oxygen demand (COD), and the presence of MgO NPs also affected the denitrification and phosphorus removal. The specific oxygen uptake rate, nitrifying and denitrifying rates, phosphorus removal rate, and microbial enzymatic activities distinctly varied with the increase of MgO NPs concentration. The appearance of MgO NPs promoted more reactive oxygen species generation and lactate dehydrogenase leakage from activated sludge, suggesting that MgO NPs had obvious toxicity to activated sludge in the SBR. The protein and polysaccharide contents of extracellular polymeric substances from activated sludge increased with the increase of MgO NPs concentration. The microbial richness and diversity at different MgO NPs concentrations obviously varied at the phylum, class and genus levels due to the biological toxicity of MgO NPs.

Detarium microcarpum: A novel source of nutrition and medicine: A review

Detarium microcarpum is a plant indigenous to Africa, which occurs naturally in many African countries, particularly in savannah regions. Its leaves and fruits are used mainly as food and as folk medicine. It has anti-diabetic, antioxidant, and hepatitis C inhibitor properties and has been traditionally utilised in cancer treatment. This review examines published work on the nutritional, pharmacological, and traditional uses of Detarium microcarpum. This plant may become valuable if the fruit, stems, roots, and leaves are extracted for nutraceutical purposes.

Tough and Self-Healable Nanocomposite Hydrogels for Repeatable Water Treatment

Nanomaterials with ultrahigh specific surface areas are promising adsorbents for water-pollutants such as dyes and heavy metal ions. However, an ongoing challenge is that the dispersed nanomaterials can easily flow into the water stream and induce secondary pollution. To address this challenge, we employed nanomaterials to bridge hydrogel networks to form a nanocomposite hydrogel as an alternative water-pollutant adsorbent. While most of the existing hydrogels that are used to treat wastewater are weak and non-healable, we present a tough TiO₂ nanocomposite hydrogel that can be activated by ultraviolet (UV) light to demonstrate highly efficient self-healing, heavy metal adsorption, and repeatable dye degradation. The high toughness of the nanocomposite hydrogel is induced by the sequential detachment of polymer chains from the nanoparticle crosslinkers to dissipate the stored strain energy within the polymer network. The self-healing behavior is enabled by the UV-assisted rebinding of the reversible bonds between the polymer chains and nanoparticle surfaces. Also, the UV-induced free radicals on the TiO₂ nanoparticle can facilitate the binding of heavy metal ions and repeated degradation of dye molecules. We expect this self-healable, photo-responsive, tough hydrogel to open various avenues for resilient and reusable wastewater treatment materials.

Silica micro- and nanoparticles reduce the toxicity of surfactant solutions

In this work, the toxicity of hydrophilic fumed silica micro- and nanoparticles of various sizes (7 nm, 12 nm, and 50 μm) was evaluated using the luminescent bacteria Vibrio fischeri. In addition, the toxicity of an anionic surfactant solution (ether carboxylic acid), a nonionic surfactant solution (alkyl polyglucoside), and a binary (1:1) mixture of these solutions all containing these silica particles was evaluated. Furthermore, this work discusses the adsorption of surfactants onto particle surfaces and evaluates the effects of silica particles on the surface tension and critical micellar concentration (CMC) of these anionic and nonionic surfactants. It was determined that silica particles can be considered as non-toxic and that silica particles reduce the toxicity of surfactant solutions. Nevertheless, the toxicity reduction depends on the ionic character of the surfactants. Differences can be explained by the different adsorption behavior of surfactants onto the particle surface, which is weaker for nonionic surfactants than for anionic surfactants. Regarding the effects on surface tension, it was found that silica particles increased the surface activity of anionic surfactants and considerably reduced their CMC, whereas in the case of nonionic surfactants, the effects were reversed.

The removal of silver nanoparticle by titanium tetrachloride and modified sodium alginate composite coagulants: floc properties, membrane fouling, and floc recycle

In this study, a modified sodium alginate (MSA) composited with TiCl₄ was used to treat the synthetic Ag nanoparticles (AgNPs) water in coagulation-ultrafiltration process. The floc properties and membrane fouling of TiCl₄ and MSA composite coagulants (TiCl₄ + MSA) were investigated by a laser diffraction instrument and ultrafiltration fouling model. The recycle of the AgNP-containing flocs was evaluated by XRD and photocatalytic experiments. The results showed that TiCl₄ + MSA could achieve better coagulation performance than TiCl₄ alone with AgNP and DOC removal up to 97 and 59% at the optimum condition (pH = 5 and dosage = 12 mg TiCl₄/L). TiCl₄ + MSA produced larger and looser flocs than TiCl₄ and TiCl₄ + SA composite coagulant (TiCl₄ + SA), which was benefit for the inhibition of subsequence membrane fouling. The strongly attached external fouling resistance (R_ef-s) and the reversible internal fouling resistance (R_if-r) of TiCl₄ + MSA were only 43 and 39.2% of those achieved by TiCl₄ at the optimal coagulation condition. Besides, the adopted AgCl-TiO₂ could be recycled from AgNP-containing flocs. And MSA could promote the form of TiO₂ anatase. It gives us a possible way for silver nanoparticle recycle.

Effects of metal oxide nanoparticles on nitrification in wastewater treatment systems: A systematic review

While the variety of engineered nanoparticles used in consumer products continues to grow, the use of metal oxide nanoparticles in electronics, textiles, cosmetics and food packaging industry has grown exponentially in recent years, which will inevitably result in their release into wastewater streams in turn impacting the important biological processes in wastewater treatment plants. Among these processes, nitrification play a critical role in nitrogen removal during wastewater treatment, however, it is sensitive to a wide range of inhibitory substances including metal oxide nanoparticles. Therefore, it is essential to systematically asses the effects of metal oxide nanoparticles on nitrification in biological wastewater treatment systems. In this review we discuss the present scenario of metal oxide nanoparticles and their impact on biological wastewater treatment processes, specifically nitrogen removal through nitrification. We also summarize the various methods used to measure nitrification inhibition by metal oxide nanoparticles and highlight corresponding results obtained using those methods. Finally, the key research gaps that need to be addressed in future are discussed.

Influence of septic system wastewater treatment on titanium dioxide nanoparticle subsurface transport mechanisms

Engineered nanomaterials (ENMs) are commonly incorporated into food and consumer applications to enhance a specific product aspect (i.e., optical properties). Life cycle analyses revealed ENMs can be released from products during usage and reach wastewater treatment plants (WWTPs), with titanium dioxide (TiO₂) accounting for a large fraction. As such, food grade (FG) TiO₂, a more common form of TiO₂ in wastewater, was used in this study. Nanomaterials in WWTPs have been well characterized, although the problematic septic system has been neglected. Elution and bioaccumulation of TiO₂ ENMs from WTTPs in downriver sediments and microorganisms has been observed; however, little is known about mechanisms governing the elution of FG TiO₂ from the septic drainage system. This study characterized the transport behavior and mechanisms of FG TiO₂ particles in porous media conditions after septic waste treatment. FG and industrial grade (IG) TiO₂ (more commonly studied) were introduced to septic tank effluent and low-ionic strength electrolyte solutions prior to column transport experiments. Results indicate that FG TiO₂ aggregate size (200-400 nm) remained consistent across solutions. Additionally, elution of FG and IG TiO₂ was greatest in septic effluent at the higher nanoparticle concentration (100 ppm). FG TiO₂ was well retained at the low (2 ppm) concentration in septic effluent, suggesting that particles that escape the septic system may still be retained in drainage field before reaching the groundwater system, although eluted particles are highly stabilized. Findings provide valuable insight into the significance of the solution environment at mediating differences observed between uniquely engineered nanomaterials. Graphical abstract.

Effects of multi-walled carbon nanotube materials on Ruditapes philippinarum under climate change: The case of salinity shifts

The toxicity of carbon nanotubes (CNTs) is closely related to their physico-chemical characteristics as well as the physico-chemical parameters of the media where CNTs are dispersed. In a climate change scenario, changes in seawater salinity are becoming a topic of concern particularly in estuarine and coastal areas. Nevertheless, to our knowledge no information is available on how salinity shifts may alter the sensitivity (in terms of biochemical responses) of bivalves when exposed to different CNTs. For this reason, a laboratory experiment was performed exposing the Manila clam Ruditapes philippinarum, one of the most dominant bivalves of the estuarine and coastal lagoon environments, for 28 days to unfunctionalized multi-walled carbon nanotube MWCNTs (Nf-MWCNTs) and carboxylated MWCNTs (f-MWCNTs), maintained at control salinity (28) and low salinity 21. Concentration-dependent toxicity was demonstrated in individuals exposed to both MWCNT materials and under both salinities, generating alterations of energy reserves and metabolism, oxidative status and neurotoxicity compared to non-contaminated clams. Moreover, our results showed greater toxic impacts induced in clams exposed to f-MWCNTs compared to Nf-MWCNTs. In the present study it was also demonstrated how salinity shifts altered the toxicity of both MWCNT materials as well as the sensitivity of R. philippinarum exposed to these contaminates in terms of clam metabolism, oxidative status and neurotoxicity.

Zinc, zinc nanoparticles and plants

Zinc belongs to the mineral elements, the so-called micronutrients, which are essential for all types of plants. Embedding itself into the enzymes associated with proteosynthesis and energy processes, zinc is necessary for maintaining the integrity of biomembranes and also plays an important role in the development of seeds and generative organs. This review focuses on summarising the findings on the interaction of zinc and plants and translates into the knowledge of the effect of zinc nanoparticles on plants. The findings include an overview of both positive and negative effects on plants. In conclusion there is a great interest in nano-zinc as improving the knowledge about individual forms of zinc and their uptake and assimilation within higher plants may be the first step towards a wider involvement of zinc nanoparticles into agriculture.

Transient disturbance of engineered ZnO nanoparticles enhances the resistance and resilience of anammox process in wastewater treatment

The increasing use of engineered nanoparticles (NPs) in consumer and industrial products raises concerns about their environmental impacts, but their potential influence on anaerobic ammonium oxidation (anammox) process in wastewater treatment remains unknown. In this study, the response of granule-based anammox reactor to different loads of ZnONPs was investigated. The introduction of 1-5mgL^-1 ZnONPs did not affect reactor performance, but 90% of the nitrogen removal capacity was deprived by a shock of 10mgL^-1 ZnONPs within 3days. Anammox activity was significantly inhibited, but no significant stimulation of intracellular reactive oxygen species (ROS) production or extracellular lactate dehydrogenase (LDH) activity was observed. The inhibition was thus mainly due to the accumulation of toxic Zn(II) ions in anammox biomass. However, the resistance and resilience of this anammox reactor to ZnONPs were enhanced by intermittent perturbations in the mode of "shock-recovery". The up-regulated abundance of Zn(II)-exporter ZntA might contribute to the enhanced resistance. In addition, these repeated transient disturbances improved the functional specificity of the anammox community despite the reduction of its diversity. Overall, these results may provide useful references for evaluating and controlling the risk of NPs to anammox process.

Silver engineered nanoparticles in freshwater systems - Likely fate and behaviour through natural attenuation processes

Growth in the nanotechnology sector is likely introducing unnatural formations of materials on the nanoscale (10^-9m) to the environment. Disposal and degradation of products incorporating engineered nanomaterials (ENMs) are likely being released into natural aquatic systems un-intentionally primarily via waste water effluents. The fate and behaviour of metallic based nanoparticles (NPs) such as silver (Ag) in aquatic waters is complex with high levels of variability and uncertainty. In-situ physical, biological and chemical (natural attenuation) processes are likely to influence ENM fate and behaviour in freshwater systems. Surfaced functionalized particles may inhibit or limit environmental transformations which influence particle aggregation, mobility, dissolution and eco-toxic potential. This paper focuses on ENM characteristics and the influence of physical, chemical and biological processes occurring in aquatic systems that are likely to impact metallic ENMs fate. A focus on silver NPs (while for comparison, reporting about other metallic ENMs as appropriate) released to aquatic systems is discussed relating to their likely fate and behaviour in this dynamic and complex environment. This paper further highlights the need for specific risk assessment approaches for metallic ENMs and puts this into context with regard to informing environmental policy and potential NP influence on environmental/human health.

Toxicity of mixtures of zinc oxide and graphene oxide nanoparticles to aquatic organisms of different trophic level: particles outperform dissolved ions

Concomitant releases of various engineered nanoparticles (NPs) into the environment have resulted in concerns regarding their combined toxicity to aquatic organisms. It is however, still elusive to distinguish the contribution to toxicity of components in NP mixtures. In the present study, we quantitatively evaluated the relative contribution of NPs in their particulate form (NP_(particle)) and of dissolved ions released from NPs (NP_(ion)) to the combined toxicity of binary mixtures of ZnO NPs and graphene oxide nanoplatelets (GO NPs) to three aquatic organisms of different trophic levels, including an alga species (Scenedesmus obliquus), a cladoceran species (Daphnia magna), and a freshwater fish larva (Danio rerio). Our results revealed that the effects of ZnO NPs and GO NPs were additive to S. obliquus and D. magna but antagonistic to D. rerio. The relative contribution to toxicity (RCT) of the mixture components to S. obliquus decreased in the order of RCT_{GO NP(particle)} > RCT_{ZnO NP(particle)} > RCT_{ZnO NP(ion)}, while the RCT of the mixture components to D. magna and D. rerio decreased in the order of RCT_{ZnO NP(particle)} > RCT_{GO NP(particle)} > RCT_{ZnO NP(ion)}. This finding also implies that the suspended particles rather than the dissolved Zn-ions dictated the combined toxicity of binary mixtures of ZnO NPs and GO NPs to the aquatic organisms of different trophic level. The alleviation of the contribution to toxicity of the ionic form of ZnO NPs was caused by the adsorption of the dissolved ions on GO NPs. Furthermore, the ZnO NP_(particle) and GO NP_(particle) displayed a different contribution to the observed mixture toxicity, dependent on the trophic level of the aquatic organisms tested. The difference of the contributions between the two particulate forms was mainly associated with differences in the intracellular accumulation of reactive oxygen species. Our findings highlight the important role of particles in the ecological impact of multi-nanomaterial systems.

Current opinion: What is a nanoplastic?

With the large amount of attention being given to microplastics in the environment, several researchers have begun to consider the fragmentation of plastics down to lower scales (i.e., the sub-micrometer scale). The term "nanoplastics" is still under debate, and different studies have set the upper size limit at either 1000 nm or 100 nm. The aim of the present work is to propose a definition of nanoplastics, based on our recently published and unpublished research definition of nanoplastics. We define nanoplastics as particles unintentionally produced (i.e. from the degradation and the manufacturing of the plastic objects) and presenting a colloidal behavior, within the size range from 1 to 1000 nm.

Ecotoxicological effects of carbon based nanomaterials in aquatic organisms

An increasing amount of carbon-based nanomaterials (CNM) (mostly fullerenes, carbon nanotubes and graphene) has been observed in aquatic systems over the last years. However, the potential toxicity of these CNM on aquatic ecosystems remains unclear. This paper reviews the existing literature on the toxic effects of CNM in aquatic organisms as well as the toxic effects of CNM through influencing the toxicity of other micro-pollutants, and outlines a series of research needs to reduce the uncertainty associated with CNMs toxic effects. The results show that environmental concentrations of CNM do not pose a threat on aquatic organisms on their own. The observed concentrations of CNM in aquatic environments are in the order of ngL^-1 or even lower, much below than the lowest observed effect concentrations (LOEC) on different aquatic organisms (in the order of mgL^-1). Toxic effects have been mainly observed in short-term experiments at high concentrations, and toxicity principally depends on the type of organisms, exposition time and CNM preparation methods. Moreover, we observed that CNM interact (establishing synergistic and/or antagonistic effects) with other micro-pollutants. Apparently, the resulting interaction is highly dependent on the chemical properties of each micro-pollutant, CNM acting either as carriers or as sorbents, thereby modifying the original toxicity of the contaminants. Results stress the need of studying the interactive effects of CNM with other micro-pollutants at environmental relevant concentrations, as well as their effects on biological communities in the long-term.

Fate of nanoparticles during alum and ferric coagulation monitored using single particle ICP-MS

In this study, aluminum sulfate, ferric sulfate, ferric chloride, and poly(diallyldimethylammonium chloride) (pDADMAC) coagulation removal of citrate-stabilized silver and gold nanoparticles (NPs) and uncoated titanium dioxide, cerium dioxide, and zinc oxide NPs was investigated using a single particle (SP) ICP-MS direct monitoring technique. Zone 2 (charge neutralization) coagulation was performed in river water and more commonly used Zone 4 (sweep floc) coagulation was performed in both river and lake water with environmentally relevant concentrations of selected NPs added. SP-ICP-MS was used to detect NP and dissolved species, characterize the size distribution, and quantify particle concentration as well as dissolved species before and after treatments. Other parameters including pH, dissolved organic carbon, turbidity, and UV₂₅₄ absorbance were monitored to characterize treatment efficiency. Charge neutralization (Zone 2) coagulation resulted in 48-85% removal of citrate-stabilized NPs and 90-99% removal of uncoated NPs from river water. Sweep floc (Zone 4) coagulation in river water resulted in 36-94% removal of citrate-stabilized NPs and 91-99% removal of uncoated NPs both with and without polymer addition. Zone 4 coagulation conditions in lake water resulted in 77-98% removal of citrate-stabilized NPs and 59-96% removal of uncoated NPs without polymer. These results indicate that NP removal depends on NP surface and stability, the nature of the source water, and the coagulant type and approach.

Silver nanoparticles in sewage treatment plant effluents: chronic effects and accumulation of silver in the freshwater amphipod Hyalella azteca

BACKGROUND

Increasing amounts of engineered nanoparticles (NPs) in wastewater can reach the aquatic environment by passing through the sewage treatment plant (STP). NPs can induce ecotoxicological effects due to their specific chemical properties. However, their bioavailability and toxicity are potentially influenced by transformation processes caused by substances present in the STP, e.g., humic acids or sulfides. Due to the lack of a test system allowing to test NPs under realistic environmental conditions, we coupled two existing test systems, the activated sludge simulation test (OECD TG 303A 2001) and the chronic exposure test with the freshwater amphipod Hyalella azteca (Environment Canada 2013), to gain a test scenario that allows to consider the altered behavior and fate of NPs induced by the STP process. This should improve the environmental realism of the chronic exposure test with Hyalella. In the first study, we tested the STP effluent containing AgNPs. In the second and third study, tap water and control STP effluent were spiked with AgNPs and used as test media.

RESULTS

The chronic exposure studies with the freshwater amphipod H. azteca showed that the investigated AgNPs lose most of their toxicity while passing through the STP. Over all studies with total Ag concentrations ranging from 0.85 to 68.70 µg/L, significant effects of the AgNPs were only observed in the survival of test animals exposed to tap water containing the highest Ag concentration (62.59 µg/L). Accumulation of silver in the body of test animals was clearly dependent on the pretreatment of the AgNPs. Silver ions (Ag+) released from AgNPs are supposed to be the major pathway leading to body burden following exposure to test media containing AgNPs.

CONCLUSION

The coupled test system is suitable for testing substances that can reach the environment via the STP effluent. The investigated AgNPs lose most of their toxicity while passing through the STP. Accumulation of silver in the animals exposed to the different treatments was apparent, whereby silver ions (Ag+) released from AgNPs were supposed to be the major pathway leading to body burden.

Investigating long-term effect of nanoparticles on growth of Raphanus sativus plants: a trans-generational study

In the past decade, there has been an unprecedented growth in the application of nanoparticles (NPs) worldwide. Even though the acute toxicity of CuO and ZnO NPs to plants has been investigated in past, the trans-generational effects of these NPs in the environment are still unknown. In this study, we investigated whether the treatment of radish plants with CuO and ZnO NPs as single compound and as a binary mixture (10, 100 and 1000 mg/Kg soil) through their lifecycle would affect the seed quality and the development of second-generation seedlings or not. Results showed reduced root length, shoot length and biomass in F1 seedlings of NPs treated plants. The treated F1 seeds had smaller seed weight with accumulated Cu and Zn. The effect of toxic interaction between CuO and ZnO on plant growth was antagonistic in nature. Evaluation of the trans-generational impact is important to understand the long-term effect of NPs on the environment.

Environmental transformations and ecological effects of iron-based nanoparticles

The increasing application of iron-based nanoparticles (NPs), especially high concentrations of zero-valent iron nanoparticles (nZVI), has raised concerns regarding their environmental behavior and potential ecological effects. In the environment, iron-based NPs undergo physical, chemical, and/or biological transformations as influenced by environmental factors such as pH, ions, dissolved oxygen, natural organic matter (NOM), and biotas. This review presents recent research advances on environmental transformations of iron-based NPs, and articulates their relationships with the observed toxicities. The type and extent of physical, chemical, and biological transformations, including aggregation, oxidation, and bio-reduction, depend on the properties of NPs and the receiving environment. Toxicities of iron-based NPs to bacteria, algae, fish, and plants are increasingly observed, which are evaluated with a particular focus on the underlying mechanisms. The toxicity of iron-based NPs is a function of their properties, tolerance of test organisms, and environmental conditions. Oxidative stress induced by reactive oxygen species is considered as the primary toxic mechanism of iron-based NPs. Factors influencing the toxicity of iron-based NPs are addressed and environmental transformations play a significant role, for example, surface oxidation or coating by NOM generally lowers the toxicity of nZVI. Research gaps and future directions are suggested with an aim to boost concerted research efforts on environmental transformations and toxicity of iron-based NPs, e.g., toxicity studies of transformed NPs in field, expansion of toxicity endpoints, and roles of laden contaminants and surface coating. This review will enhance our understanding of potential risks of iron-based NPs and proper uses of environmentally benign NPs.

Aged-engineered nanoparticles effect on sludge anaerobic digestion performance and associated microbial communities

To investigate the potential effect of aged engineered nanoparticles (a-ENPs) on sludge digestion performance, 150L pilot anaerobic digesters (AD) were fed with a blend of primary and waste activated sludge spiked either with a mixture of silver oxide, titanium dioxide and zinc oxide or a mixture of their equivalent bulk metal salts to achieve a target concentration of 250, 2000, and 2800mgkg^-1 dry weight, respectively. Volatile fatty acids (VFA) were 1.2 times higher in the spiked digesters and significantly different (p=0.05) from the control conditions. Specifically, isovaleric acid concentration was 2 times lower in the control digester compared to the spiked digesters, whereas hydrogen sulfide was 2 times lower in the ENPs spiked digester indicating inhibitory effect on sulfate reducing microorganisms. Based on the ether-linked isoprenoids concentration, the total abundance of methanogens was 1.4 times lower in the ENPs spiked digester than in the control and metal salt spiked digesters. Pyrosequencing indicated 80% decrease in abundance and diversity of methanogens in ENPs spiked digester compared to the control digester. Methanosarcina acetivorans and Methanosarcina barkeri were identified as nano-tolerant as their relative abundance increased by a factor of 6 and 11, respectively, compared to the other digesters. The results further provide compelling evidence on the resilience of Fusobacteria, Actinobacteria and the Trojan horse-like effect of ENPs which offered a competitive advantage to some organisms while reducing microbial abundance and diversity.

Microbial stress mediated intercellular nanotubes in an anaerobic microbial consortium digesting cellulose

The anaerobic digestion process is a multi - step reaction dependent on concerted activities such as exchange of metabolites among physiologically different microbial communities. This study investigated the impact of iron oxide nanoparticles on the anaerobic sludge microbiota. It was shown there were three distinct microbial phases following addition of the nanoparticles: microbial stress and cell death of approximately one log order of magnitude, followed by microbial rewiring, and recovery. Furthermore, it was noted that cellular stress led to the establishment of intercellular nanotubes within the microbial biomass. Intercellular nanotube - mediated communication among genetically engineered microorganisms and ad hoc assembled co - cultures have been previously reported. This study presents evidence of intercellular nanotube formation within an environmental sample - i.e., anaerobic sludge microbiota subjected to stress. Our observations suggested a mode of microbial communication in the anaerobic digestion process not previously explored and which may have implications on bioreactor design and microbial functions.

Nanopyroxene Grafting with β-Cyclodextrin Monomer for Wastewater Applications

Emerging nanoparticle technology provides opportunities for environmentally friendly wastewater treatment applications, including those in the large liquid tailings containments in the Alberta oil sands. In this study, we synthesize β-cyclodextrin grafted nanopyroxenes to offer an ecofriendly platform for the selective removal of organic compounds typically present in these types of applications. We carry out computational modeling at the micro level through molecular mechanics and molecular dynamics simulations and laboratory experiments at the macro level to understand the interactions between the synthesized nanomaterials and two-model naphthenic acid molecules (cyclopentanecarboxylic and trans-4-pentylcyclohexanecarboxylic acids) typically existing in tailing ponds. The proof-of-concept computational modeling and experiments demonstrate that monomer grafted nanopyroxene  or nano-AE of the sodium iron-silicate aegirine are found to be promising candidates for the removal of polar organic compounds from wastewater, among other applications. These nano-AE offer new possibilities for treating tailing ponds generated by the oil sands industry.