Article

Occurrence, characterisation and fate of (nano)particulate Ti and Ag in two Norwegian wastewater treatment plants

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Abstract

Due to their widespread application in consumer products, elemental titanium (e.g., titanium dioxide, TiO2) and silver (Ag), also in nanoparticulate form, are increasingly released from households and industrial facilities to urban wastewater treatment plants (WWTPs). A seven-day sampling campaign was conducted in two full-scale WWTPs in Trondheim (Norway) employing only primary treatment. We assessed the occurrence and elimination of Ti and Ag, and conducted size-based fractionation using sequential filtration of influent samples to separate particulate, colloidal and dissolved fractions. Eight-hour composite influent samples were collected to assess diurnal variations in total Ti and Ag influx. Measured influent Ti concentrations (up to 290 µg L-1) were significantly higher than Ag (<0.15–2.1 µg L-1), being mostly associated with suspended solids (>0.7 µm). Removal efficiencies ≥70% were observed for both elements, requiring for one WWTP to account for the high Ti content (~2 g L-1) in the flocculant. Nano- and micron-sized Ti particles were observed with scanning transmission electron microscopy (STEM) in influent, effluent and biosolids, while Ag nanoparticles were detected in biosolids only. Diurnal profiles of influent Ti were correlated to flow and pollutant concentration patterns (especially total suspended solids), with peaks during the morning and/or evening and minima at night, indicating household discharges as predominant source. Irregular profiles were exhibited by influent Ag, with periodic concentration spikes suggesting short-term discharges from one or few point sources (e.g., industry). Influent Ti and Ag dynamics were reproduced using a disturbance scenario generator model, and we estimated per capita loads of Ti (42–45 mg cap-1 d-1) and Ag (0.11 mg cap-1 d-1) from households as well as additional Ag load (14–22 g d-1) from point discharge. This is the first study to experimentally and mathematically describe short-term release dynamics and dry-weather sources of emissions of Ti and Ag in municipal WWTPs and receiving environments.

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... In several small-and medium-sized communities in Northern regions (e.g., Norway, Iceland, Canada) and South-East Europe, WWTPs with only preliminary and primary treatment are in use (Government of Canada, 2017;European Environmental Agency, 2017;Berge and Saether, 2018). Such limited treatment can result in a reduced removal of conventional pollutants (suspended solids, organics, nutrients) and emerging pollutants compared to WWTPs with biological and advanced treatment steps (Vogelsang et al., 2006;Polesel et al., 2018). Within the past decades, several studies and monitoring programs have investigated the fate of inorganic elements (including metals and toxic elements) in WWTPs, largely focusing on full-scale facilities with secondary and tertiary treatment steps (Buzier et al., 2006;Cantinho et al., 2016;Goldstone et al., 1990aGoldstone et al., , 1990bGoldstone et al., , 1990c (Shafer et al., 1998;Yoshida et al., 2015). ...
... Atmospheric deposition and stormwater runoff, which contains trafficrelated emissions from tire wear, asphalt wear and exhaust particles, contribute to discharges mostly under wet weather conditions (Becouze-Lareure et al., 2016;Sabin et al., 2005;Shafer et al., 1998;Sorme and Lagerkvist, 2002). Chemically-enhanced treatment (e.g., flocculants) may also lead to a considerable additional input to WWTPs (Buzier et al., 2006;Polesel et al., 2018). Recent advances in nanotechnology have led to an increase in the use of metal and metalloid engineered nanomaterials (ENMs) in consumer products such as paints, fabrics and washing machines (Benn and Westerhoff, 2008;Farkas et al., 2011;Kaegi et al., 2010Kaegi et al., , 2008. ...
... Release of ENMs from products can lead to increased metal loads in household discharges during dry weather periods. For example, Ti and Ag ENMs originating from clothing, washing machines, personal care products and food are frequently detected in WWTP influents (Kiser et al., 2009;Li et al., 2013;Polesel et al., 2018;Westerhoff et al., 2011). ...
Article
Full-text available
Many small- or medium-sized communities in Northern Europe employ only primary wastewater treatment plants (WWTPs) and effluent discharges can be a relevant source of pollution. The current study combines monitoring and modelling approaches to investigate concentrations, influent patterns, size distribution and removal of 20 elements for the two primary WWTPs (Ladehammeren, LARA; Høvringen, HØRA) serving Trondheim, the third largest city in Norway. Element concentrations were determined in raw influent wastewater, effluents and biosolids, and diurnal inflow patterns were assessed. The elemental distribution in particulate, colloidal and dissolved fractions of untreated wastewater was characterized using filtration separation and electron microscopy. An influent generator model and multivariate statistical analyses were used to determine release patterns and to predict the (co-)occurrence of selected elements. Raw influent wastewater concentrations for most elements were similar in the two WWTPs, with only Ca, Mn, Fe, Co and Ba being significantly higher (p < 0.05) in HØRA (which receives more household and hospital discharges). Removal efficiencies varied between elements, but in most cases reflected their association with particulates. Nanosized particles of several elements were detected, with Cu/Zn being most common. Measured concentrations of most elements followed typical diurnal wastewater discharge patterns and enrichment factors calculated for biosolids confirmed the importance of anthropogenic sources for P, Cu, Zn, Cd, As, Cr, Ni, Pb, V, Co and Fe. Elemental concentrations generally correlated well with total suspended solid (TSS) concentrations at HØRA, while this was less pronounced in LARA (possibly due to higher industrial contributions). In one of its first applications for WWTP influent pattern examination, principal component analysis was found to be instrumental for source identification of target elements, showing significant differences between LARA and HØRA influents. The combined experimental, statistical and modelling approaches used herein allowed for improved understanding of element sources, patterns of discharge and fate in primary WWTPs.
... J o u r n a l P r e -p r o o f 3 Most Ag-NPs and dissolved ionic Ag + in consumer products are released into sewer systems and thus reach wastewater treatment plants (WWTPs) (Kaegi et al., 2011). Silver concentrations in WWTP influent have been reported in the range of 1.8 to >100 µg/L (Polesel et al., 2018;Shafer et al., 1998), while in the WWTP effluent, concentrations were lower than 1 µg/L (Gottschalk et al., 2013). A general conclusion from previous investigations of Ag-NPs behaviour at laboratory scale is that about 90% of the Ag-NPs are efficiently removed by biological treatment and accumulated in activated sludge or biosolids as Ag 2 S (Benn and Westerhoff, 2008;Cervantes-Avilés et al., 2019;Kaegi et al., 2011;Kim et al., 2010;Nowack, 2010;Tiede et al., 2010). ...
... In previous studies these ranged from small (population equivalent < 2000) to large sized WWTPs (population equivalent < 25000), processing household and occasionally industrial sewage, while in this study the septic tanks received only domestic wastewater. Another factor that might impact sludge composition is sludge maturity and the content of humic substances(Tao et al., 2012).Sludge Ag concentrations range from 0.15 to 0.84 mg/kg DW for ST1 and from 0.17 to 0.52 mg/kg DW for ST2, which are in the lower part of the range (0.22 -856 mg/kg DW) reported in previous studies for WWTPs(Kaegi et al., 2011;Kim et al., 2010;Östman et al., 2017;Polesel et al., 2018;Tou et al., 2017) and exhibited one of the lowest abundances compared with the trace elements(Figure 3). Differences in Ag distribution among the various fractions (acidexchangeable, reducible, oxidizable and residual fractions) were observed between chambers CH1 and CH2 of both septic tanks(Figure 4). ...
... The Ag concentration in the supernatant corresponds to approximately 2% of the total Ag added, which implies that approximately 98% of Ag-NPs added were retained in the solid phase. Our finding is in line with earlier studies concluding that Ag-NPs strongly partition into the sludge(Kaegi et al., 2011;Lombi et al., 2013;Polesel et al., 2018; Tuoriniemi et al., 2017) where Ag-NPs sulfidation occurs. Given the pH (pH ~ 7 in CH1 and CH2), Eh (-178.6 mV for CH1 and -64.8 mV for CH2) and the relatively high sulphur content (~1 wt %) in the sludge, sulfidation of Ag-NP is thermodynamically favoured(Thalmann et al., 2014). ...
Article
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Untreated sludge from small-scale on-site domestic wastewater treatment systems (septic tanks) was spiked with 20, 60 and 100 nm silver nanoparticles (Ag-NPs) to investigate Ag-NP behaviour in these systems that are widely distributed in rural areas. In addition, the release of Ag-NPs from a previously spiked clay-rich loam reference soil (LUFA 2.4) was evaluated, in the presence and absence of untreated sludge, to simulate the common practice of sludge disposal by spreading on agricultural land. Single particle ICP-MS was used to determine Ag-NP size distribution and the results were compared with total Ag (Ag-NP and ionic) measured in acid digested samples. As documented previously for large municipal scale wastewater treatment plants, Ag-NPs are found to be overwhelmingly (~98%) retained in the sludge in these small-scale systems. The Ag-NP retention efficiency on the LUFA reference soil amended with sludge is approximately 10 times greater than that of LUFA soil alone (in the absence of sludge). For soil spiked with 60 nm Ag-NPs, the calculated average diameter of Ag-NPs in the supernatant, after 24 h was 45 ± 3 nm (dissolution rate 7.2E−06 mol/m²·h for 60 nm Ag-NP), smaller than that of supernatant from the combined sludge/soil system (52 ± 2 nm), indicating lower Ag-NP dissolution rates in the sludge-amended soil. This study provides new information about the leachability of Ag-NPs from septic tank sludge and suggests that the effluent and sludge from septic tanks are potential sources of both nano- and dissolved ionic-Ag to environmental waters.
... The concentration of Ti-based NPs was the highest (10,700 ng/L) in the influent wastewater. However, this concentration is lower than that measured in the influent of a couple of WWTPs in Norway, 154 ± 34 μg/L in LARA and 188 ± 44 μg/L in HØRA, respectively ( Polesel et al., 2018 ), and in other studies performed in WWTP influents in Arizona, which measured mean Ti concentrations of 185-377 μg/L ( Westerhoff et al., 2011 ). These values included the engineered and naturally occurring Ti-based nanoparticles such as Ti-silicate minerals. ...
... NPs extracted from the waste activated sludge and anaerobic sludge using centrifugation (3800 g, 10 min and 20 °C) represent around the 65% of NP present in these matrices based on previous studies ( Huang et al., 2020 ). Moreover, the concentrations in the sludges may not reflect internalized or tightly-adsorbed NPs in the flocs ( Polesel et al., 2018 ;Tuoriniemi et al., 2017 ), which must be considered in our results. Despite this and as expected, the content of metal-based NPs in the sludges was much higher than in the ef- fluent due to their high removal in the biological processes ( Fig. 8 ). ...
Article
Metal-based nanoparticles (NPs) can be found in wastewater streams, which are significant pathways for the release of NPs to the environment. Determination of the NPs concentration in wastewater streams is important for performing appropriate ecotoxicological evaluations. The aim of this work was to determine the incidence of NPs from 13 different elements throughout the wastewater treatment process by using single particle inductively coupled plasma mass spectrometry (spICP-MS). The incidence was determined in samples of the influent, post-primary treatment and effluent of the activated sludge process, as well as in the reclaimed water of a full-scale wastewater treatment plant (WWTP). In addition, concentration of NPs was determined in the waste activated sludge and in the anaerobic digester. The concentration of metal-based NPs in the influent wastewater were between 1,600 and 10,700 ng/L for elements such as Ti, Fe, Ce, Mg, Zn and Cu, while that for Ni, Al, Ag, Au, Co and Cd was below 100 ng/L. Concentrations in reclaimed water ranged between 0.6 and 721 ng/L, ranked as Mg > Ti > Fe > Cu > Ni > Ce > Zn > Mn > Al > Co > Ag > Cd > Au. Results indicated that the activated sludge process and reclaimed water system removed 84–99% of natural and engineered metal-based NPs from influent to reclaimed water, except for Mg, Ni and Cd where the removal ranged from 70 to 78%. The highest concentrations of NPs were found in the waste activated sludge and anaerobic sludge, ranging from 0.5 to 39,900 ng/L. The size distribution of NPs differed in different wastewater streams within the WWTP, resulting in smaller particles in the effluent (20–180 nm) than in the influent (23–233 nm) for most elements. Conversely, NPs were notably larger in the waste activated sludge samples than in the anaerobic sludge or wastewater, since conditions in the secondary treatment lead to precipitation of several metal-based NPs. The incidence of metal-based NPs from 13 elements in wastewater decreased significatively after the conventional wastewater treatment train. However, anaerobic digesters store high NPs concentrations. Hence, the disposal of sludge needs to take this into account to evaluate the risk of the release of NPs to the environment.
... The increased production of nAg has raised some concerns about their release in the environment and resulting toxicity to wildlife (McGillicuddy et al., 2017). The total Ag loadings of municipal effluents are thought to originate from the inappropriate handling and disposal of nAg from consumer products finding their way in municipal effluents (Polesel et al., 2018). In addition, uncoated nAg could degrade in municipal wastewaters and form secondary nanoparticles in situ from dissolved Ag + (Azodi et al., 2016). ...
... These concentrations were chosen based on previous studies with zebra mussels exposed to nanosilver (Zimmermann et al., 2017). Moreover, the exposure concentrations of total Ag as nanoparticles represents an upper limit scenario of Ag emanating from municipal effluents (Polesel et al., 2018;Azodi et al., 2016). Mussels were not fed 12 h prior and during the exposure period. ...
Article
The question about the influence of the geometry of silver nanoparticle (nAg) towards toxicity in aquatic organisms is largely unanswered. The purpose of this study was to examine if different geometries of nAg could initiate biophysical stress in the soft tissues of mussels. Freshwater Dreissenna bugensis mussels were exposed for 48 h at 15 °C to 10 and 50 μg/L of ionic Ag and to 3 forms of polyvinylpyrrolidone (PVP)-coated nAg of similar size: sphere, cube and prism. At the end of the exposure period, mussels were allowed to depurate overnight and the post-mitochondrial fraction of the soft tissues were analyzed for the levels of liquid crystals (LCs), changes in the activity and fractal dimensions of the pyruvate kinase-lactate dehydrogenase (PK-LDH), F-actin and protein-ubiquitin (UB) levels. The data revealed that exposure to nAg forms lead to increased formation of LCs in increasing order of intensity: prismatic > cubic > spherical nAg. The activity in PK-LDH was decreased by all forms of nAg but not by ionic Ag⁺ (as with the following). Fractal kinetics of the PK-LDH system revealed that the nAg forms increased the spectral dimension (sD) in increasing order: spherical > cubic > prismatic nAg. A decrease in the fractal diffusion rate (fDR) with small changes in the fractal dimension (fD) was also obtained. The levels of F-actin and protein-UB were significantly affected for most forms of nAg and followed a pattern similar to LCs levels. In conclusion, the geometry of nAg could influence the formation of LCs, alter the fractal kinetics of the PK-LDH system, F-actin levels and protein damage in the soft tissues of freshwater mussels.
... Numerous approaches have been proposed for the detection and characterization of NMs in water samples (see also tables 2 to 5) including microscope-based techniques (TEM, SEM, autoSEM), light scattering methods and several based on chromatography (Tiede et al. 2009, Bäuerlein et al. 2017, Gondikas et al. 2018 (Tiede, Boxall et al. 2009) combined with element specific detectors. Polesel et al. (2018) suggest a general scheme for sample pre-treatment involving sequential filtration in order to separate particulate, colloidal and dissolved fractions followed by acid digestion and ICP-MS analysis in order to enable Ti and Ag nanoparticles detection in waste water ( figure 4). In this study, real waste water samples from two Norwegian waste water treatment plants were sampled and analysed concerning the occurrence, characterisation and fate of (nano)-particulate Ti and Ag. ...
... Fractionation procedure used to separate and characterize Ti and Ag as particulate, colloidal and dissolved (ionic) fractions. From Polesel et al. (2018) The separation technique CPE followed by atom emission spectrometry analysis was proposed by Hartmann et al. (2013) for the analysis of Ag NMs in environmental aqueous samples. Samples of different complexity such as river water, treated and untreated municipal wastewater and synthetic solutions containing dissolved and particulate organic matter with a total organic carbon (TOC) content up to 10 mg L−1 were spiked with different concentrations of Ag-NMs. ...
Technical Report
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etection of manufactured nanomaterials (NM) still features enormous challenges for environmental exposure assessment and management of NM. The expert opinion presents a comprehensive survey on existing experimental approaches to detect NM in the environment and analyses to what extent these approaches could be utilized and advanced to be used routinely for data collection to assess and manage environmental exposure. Recommendations for actions on a short and long term basis are deduced for the establishment of standardized protocols for sampling, sample preparation and analysis which can now be used to prioritize further action in improving measurement techniques of NM in the environment.
... The development of public datasets containing information about nanomaterials and their presence in products could be promoted for practical and regulatory decision-making and the advancement of scientific research. Dong et al., 2017;Polesel et al., 2018). The lack of field research was highlighted in the expert consultation. ...
... Cervantes- Aviles et al., 2019; Cervantes-Aviles et al., 2021;Choi et al., 2017;Li et al., 2016;Polesel et al., 2018). The incidence of Ag(Cervantes-Aviles et al., 2019; Cervantes-Aviles et al., 2021; Li et al., 2016; Polesel et al., 2018), Ti (Cervantes-Aviles et al., 2021; Choi et al., 2017; Polesel et al., 2018); Zi (Cervantes-Aviles et al., 2021; Choi et al., 2017), Fe, Ce, Mg, Cu, Ni, Al, Au, Co, and Cd (Cervantes-Aviles et al., 2021) have been reported in wastewater treatment plants in Norway and the US. ...
Article
This study updates and expands on the document “Nanomaterials in Waste Streams – Current Knowledge on Risks and Impacts" published by OECD in 2016. It covers ten topics: • Waste streams containing nanomaterials. • Behaviour and fate of nanomaterials in waste processes. • Exposure of waste management workers to nanomaterials. • Benefits and challenges of nanomaterials posed to the circular economy. • Impact of nanomaterials on recycling. • Main streams of nanomaterial recyclates. • Recycling abatement systems residues. • Potential for substitution of hazardous substances by nanomaterials in the recyclate streams. • Emission of nanomaterials. • Emission control and best available techniques.
... In sewage sludge samples collected from 26 WWTPs in Shanghai, China, Tou et al. [29] found anatase and rutile aggregates with sizes ranging from 50 to 400 nm. Polesel et al. [30] studied two WWTPs in the city of Trondheim (Norway), and observed agglomerates and aggregates of TiO 2 particles from 500 nm to >1 µm in size. Choi et al. [31] conducted a full year study in a WWTP in Maryland (U.S.A.). ...
... Choi et al. [31] Maryland, US 1200 to 4670 Johnson et al. [68] Southern region, England 370 to 670 Khosravi et al. [69] Peterborough, Canada 320 Kim et al. [26] Midwest and West regions of the USA 960 to 4510 Kiser et al. [18] Central Arizona, USA 1100 Polesel et al. [30] Trondheim, Norway 700 Shi et al. [28] Shijiazhuang, Hebei Province, China 1360 Tong et al. [27] Skokie, IL, USA 1700 Tou et al. [29] Shanghai, China 33 to 2700 Wielinski et al. [32] Wallisellen, Switzerland 1000 to 1800 This study Chihuahua State, Mexico 1900 to 2600 ...
Article
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TiO2 nanoparticles (TiO2-NPs) have a wide range of industrial applications (paintings, sunscreens, food and cosmetics) and is one of the most intensively used nanomaterials worldwide. Leaching from commercial products TiO2-NPs are predicted to significantly accumulate in wastewater sludges, which are then often used as soil amendment. In this work, sludge samples from four wastewater treatment plants of the Chihuahua State in Mexico were obtained during spring and summer (2017). A comprehensive characterization study was performed by X-ray based (laboratory and synchrotron) techniques and electron microscopy. Ti was detected in all sludge samples (1810–2760 mg/kg) mainly as TiO2 particles ranging from 40 nm up to hundreds of nm. Micro-XANES data was analyzed by principal component analysis and linear combination fitting enabling the identification of three predominant Ti species: anatase, rutile and ilmenite. Micro-XANES from the smaller Ti particles was predominantly anatase (68% + 32% rutile), suggesting these TiO2-NPs originate from paintings and cosmetics. TEM imaging confirmed the presence of nanoscale Ti with smooth surface morphologies resembling engineered TiO2-NPs. The size and crystalline phase of TiO2-NPs in the sludge from this region suggest increased reactivity and potential toxicity to agro-systems. Further studies should be dedicated to evaluating this.
... Environments 2020, 7, 109 2 of 18 and they are embedded in many consumer products such as clothes, shoes, masks and sport wares, thereby limiting fouling and odors [5], and are commonly found in municipal effluents [6] (Polesel et al., 2018). Cerium oxide nanoparticles (nCeO2) are widely used in biomedical sector as antioxidants in biological systems, fuel additives and ceramic applications [7][8][9]. ...
Article
Full-text available
The toxicological effects of nanoparticles mixtures in aquatic organisms are poorly understood. The purpose of this study was to examine the tissue metal loadings and sublethal effects of silver (nAg), cerium oxide (nCeO), copper oxide (nCuO) and zinc oxide (nZnO) nanoparticles individually at 50 µg/L and in two mixtures to freshwater mussels Dreissena bugensis. The mixtures consisted of 12.5 µg/L of each nanoparticle (Mix50) and 50 µg/L of each nanoparticles (Mix200). After a 96-h exposure period, mussels were analyzed for morphological changes, air time survival, bioaccumulation, inflammation (cyclooxygenase or COX activity), lipid peroxidation (LPO), DNA strand breaks, labile Zn, acetylcholinesterase (AChE) and protein–ubiquitin levels. The data revealed that mussels accumulated the nanoparticles with nCeO and nAg were the least and most bioavailable, respectively. Increased tissue metal loadings were observed for nCeO and nCuO in mixtures, while no mixture effects were observed for nAg and nZnO. The weight loss during air emersion was lower in mussels exposed to nCuO alone but not by the mixture. On the one hand, labile Zn levels was increased with nZnO but returned to control values with the Mix50 and Mix200, suggesting antagonism. On the other hand, DNA strand breaks were reduced for both mixtures compared to controls or to the nanoparticles individually, suggesting potentiation of effects. The same was found for protein–ubiquitin levels, which were decreased by nCeO and nCuO alone but not when in mixtures, which increased their levels. In conclusion, the data revealed that the behavior and effects of nanoparticles were influenced by other nanoparticles where antagonist and potentiation interactions were identified.
... Effluent TiO 2 concentrations in all the studied WWTPs, except Rifle Range, are similar to the predicted environmental concentrations for nano-TiO 2 in water (0.7-16 μg L −1 ) reported by Mueller and Nowack (2008), although higher effluent TiO 2 concentrations (calculated from Ti concentrations) have been reported in Norway (47.1 ± 7.2 to 155 ± 17 μgTiO 2 L −1 ) and China (43.4 to 71.8 μgTiO 2 L −1 ) (Shi et al., 2016). The higher TiO 2 concentrations reported in Norway have been attributed to the use of inorganic ClFeO 4 S flocculant, which contains approximately 1.9 g Ti L −1 (1.25 g kg −1 ) (Polesel et al., 2018). The TiO 2 engineered particle concentrations reported above were all calculated using the average reference water Ti/Nb ratio of 267 ± 9. Using instead the average crustal Ti/Nb ratio of 320 as the natural background ratio would slightly decrease (<3%) the proportion of influent TiO 2 engineered particles in all samples, except for the Columbia WWTP (9 to 13% decrease in the estimated TiO 2 engineered particle concentrations). ...
Article
The growing use of engineered particles (e.g., nanosized and pigment sized particles, 1 to 100 nm and 100 to 300 nm, respectively) in a variety of consumer products increases the likelihood of their release into the environment. Wastewater treatment plants (WWTPs) are an important pathways of introduction of engineered particles to the aquatic systems. This study reports the concentrations, removal efficiencies, and particle size distributions of Ag and TiO2 engineered particles in five WWTPs in three states in the United States. The concentration of Ag engineered particles was quantified as the total Ag concentration, whereas the concentration of TiO2 engineered particles was quantified using mass-balance calculations and shifts in the elemental ratio of Ti/Nb above their natural background elemental ratio. Ratios of Ti/Nb in all WWTP influents, activated sludges, and effluents were 2–12 times higher (e.g., 519 to 3243) than the natural background Ti/Nb ratio (e.g., 267 ± 9), indicating that 49–92% of Ti originates from anthropogenic sources. The concentration of TiO2 engineered particles (in μg TiO2 L⁻¹) in the influent, activated sludge, and effluent varied within the ranges of 70–670, 3570–6700, and 7–30, respectively. The concentration of Ag engineered particles (in μg Ag L⁻¹) in the influent, activated sludge, and effluent varied within the ranges of 0.11–0.33, 1.45–1.65, and 0.01–0.04, respectively. The overall removal efficiency (e.g., effluent/influent concentrations) of TiO2 engineered particles (e.g., 90 to 96%) was higher than that for Ag engineered particles (e.g., 82 to 95%). Particles entering WWTPs are in the nanosized range for Ag (e.g., >99%) and a mixture of nanosized (e.g., 15 to 90%) and pigment sized particles (e.g., 10 to 85%) for TiO2. Nearly all Ag (>99%) and 55 to 100% of TiO2 particles discharged to surface water with WWTP effluent are within the nanosize range. This study provides evidence that TiO2 and Ag engineered nanomaterials enter aquatic systems with WWTP effluents, and that their concentrations are expected to increase with the increased applications of TiO2 and Ag engineered nanomaterials in consumer products.
... Therefore, this study aimed to elucidate the acute and sublethal effects of Ag + in fish behavior and neurotoxicity. Silver concentrations in the influent of wastewater treatment plants (WWTPs) have been reported to lie in the range of 1.8-100 ppb (Polesel et al., 2018;Kaegi et al., 2011); by contrast, in WWTP effluent, concentrations were < 1 ppb (Gottschalk et al., 2013). Studies have demonstrated that ionic silver is more toxic to fish, at an LC 50 of approximately 58 μg/L, than to mammalian cells or bacteria (LC 50 = 2 and 3.3 ppm, respectively; Bondarenko et al., 2013). ...
Article
Silver and silver nanoparticles are used in several consumer products, particularly sterilizing agents. Ag+ released from the particles causes physiological damages of aquatic organisms. However, the effects of silver on neural and behavioral functions of fish remain unclear. Here, we used zebrafish as a model to investigate the impacts of silver on learning and memory behaviors in teleost. Adult zebrafish showed mortality rates of 12.875% and 100% on 72-h exposure to 30 and ≥50 ppb of silver nitrate, respectively. Silver accumulation in the brain increased on exposure to 10 and 30 ppb of AgNO3. The physical fitness of the zebrafish, measured by novel tank diving test and swimming performance, decreased after 72-h incubation in 30 ppb of AgNO3. Exposure to 10 ppb of AgNO3 impaired social preference, social recognition, learning, and memory, but did not affect anxiety level, aggressiveness, and shoaling behavior. In situ hybridization of c-fos mRNA showed that AgNO3 treatment decreased neural activity in the brain areas crucial for learning, memory, and social behaviors, including the medial and dorsal zones of the dorsal telencephalic area. In conclusion, 72-h exposure to AgNO3 in a sublethal level impaired learning and social behaviors, indicating neurotoxicity in adult zebrafish.
... According to several studies, wastewater treatment plants (WWTPs) receive TiO 2 NPs through wastewater streams, and then NPs are released to the aquatic and terrestial ecosystems via treated effluent and biosolids, respectively (Adam et al., 2018;. Some studies have confirmed the presence of TiO 2 NPs in the wastewater of different WWTPs around the world, and the concentration have ranged from μg/L to ng/L levels (Cervantes-Avilés et al., 2018;Polesel et al., 2018;Westerhoff et al., 2011). This means that TiO 2 NPs are eventually present in the outlet flows of the WWTPs such as, treated effluent and biosolids. ...
Article
Titanium dioxide nanoparticles (TiO2 NPs) are widely used in consumer products and one of their major fate is the wastewater treatment plants. However, NPs eventually arrive to aquatic and terrestrial ecosystems via treated water and biosolids, respectively. Since low concentration of NPs is accumulating in the upflow anaerobic sludge blanket (UASB) reactors that treat wastewater and reclaim water quality, the accumulation of TiO2 NPs in these reactors may impact in their performance. In this work, the long-term effects of TiO2 NPs on the main benefits of treating wastewater by UASB reactors such as, biogas production, methane fraction in biogas and organic matter removal were evaluated. Evaluation consisted of monitoring such parameters in two identical UASB reactors, one UASB-Control (without NPs) and the experimental one (UASB-TiO2 NPs) that received wastewater with TiO2 NPs. The fate of NPs in the UASB reactor was also determined. Results indicated that biogas production increased by 8.8% due to the chronic exposure of UASB reactor to TiO2 NPs during the first 44 days of experiment. However, the methane content in the biogas had no significant differences between both UASB, ranging between 78% and 90% of methane during the experiment. The removal of organic matter in both UASB was similar and ranged 92-98% along the experimental time. This means that accumulation of TiO2 NPs did not altered the biogas production and organic matter removal. However, the content of total volatile solids (TVS) in UASB-TiO2 NPs dropped off from 137.8 g to 64.2 g in 84 days, while for control reactor that decreased from 141.6 g to 92.4 g in the same period. Hence, the increased biogas production in the UASB exposed to TiO2 was attributed to hydrolysis of the TVS in this reactor. The main fate of TiO2 NPs was the granular sludge, which accumulated up to 8.56 mg Ti/g, which represent around 99% of the Ti spiked to the reactor and the possible cause of the biomass hydrolyzation in the UASB. Disposal of UASB sludge containing NPs from may raise ecotoxicological concerns due to the use of biosolids in agricultural activities.
... The increasing use and disposal of nAg-contaminated products have led to the release of nAg into the environment, which could lead to harmful effects in wildlife [3]. Ag is mainly released by municipal wastewaters into the aquatic environment [4]. A previous study revealed that most Ag particles at the nanoscale (1-100 nm) were effectively removed (95%) but significant amounts were still released in effluents, albeit at the low ng/L range [5]. ...
Article
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The contribution of the form of silver nanomaterials (nAg) towards toxicity in aquatic organisms is not well understood. The purpose of this study was to examine the toxicity of various structures (sphere, cube and prism) of nAg in Dreissena bugensis mussels. Mussels were exposed to increasing concentrations of polyvinyl-coated nAg of the same size for 96 h at 15 °C. They were then analyzed for biophysical changes in the cytoplasm (viscosity, protein aggregation and lipids), neuro-activity (fractal kinetics of acetylcholinesterase (AChE)), oxidative stress (labile zinc (Zn) and lipid peroxidation) and inflammation (arachidonate cyclooxygenase). Although some decreasing effects in protein aggregation were observed, viscosity was more strongly decreased in mussels exposed to spheric and prismatic nAg. The activity of AChE was significantly decreased in the following form-dependent manner: prismatic > cubic > spheric nAg. The fractal dimension of AChE reactions was reduced by all geometries of nAg, while dissolved Ag had no effects. For nanoparticles with the same coating and relative size, spheric nAg produced more significant changes towards the fractal dimension of AChE, while prismatic nAg increased both protein aggregation and viscosity, whereas cubic nAg decreased protein aggregation in the cytoplasm. It is concluded that the geometries of nanoparticles could influence toxicity in aquatic organisms.
... Few applications of spICPMS in environmental matrix have been assessed, especially in aquatic media. Most studies are about silver ENPs detected (Mitrano et al., 2012;Tuoriniemi et al., 2012;Wang et al., 2020) or spiked (Telgmann et al., 2014) in wastewater samples (Polesel et al., 2018) and in natural waters (Mitrano et al., 2014;Yang et al., 2016). One study deals with the detection of ZnONPs in water by using both a binding resin and spICPMS (Hadioui et al., 2015). ...
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The need to quantify engineered nanoparticles (ENPs) in the environment is due to the increasing incorporation of these particles in the daily products, which threatens human health and can possibly impact natural systems. Ceria NPs (CeO 2 NPs) and titanium dioxide NPs (TiO 2 NPs) are two of the most used ENPs in the world. In this study their occurrence was determined in river waters with accurate and relevant techniques such as single particle ICP-MS (spICPMS). In the Loire River (France), the variation of both CeO 2 NPs and TiO 2 NPs could be assessed locally, with an increase of the concentrations near a wastewater treatment plant (WWTP) outlet as well as in a lake connected to the river and dedicated to outdoor activities. In the upstream river water, supposedly less impacted by NPs, 6.4 ± 1.2 × 10 4 part mL −1 Ce-bearing and 13.4 ± 1.8 × 10 4 part mL −1 Ti-bearing particles were measured. These values increased to 33.9 ± 3.4 × 10 4 part mL −1 Ce-bearing and 80.3 ± 3.4 × 10 4 part mL −1 Ti-bearing particles near the WWTP outlet. Equivalent size for sphere distributions ranged from 24 nm to 70 nm for CeO 2 and from 80 nm to 500 nm for TiO 2 in the river water. In the lake, a raise of the concentrations has been observed with 38.3 ± 2.0 × 10 4 part mL −1 and 71.6 ± 2.1 × 10 4 part mL −1 containing Ce and Ti, respectively, with similar size distributions. FEG-SEM imaging confirms the occurrence of Ce-and Ti-bearing particles in the water samples. On the contrary, NPs seem to undergo strong heteroaggregation in the Loire river water. The Ce/La elemental ratios does not evolve from upstream to downstream the WWTP outlet, suggesting that a natural origin cannot be excluded to explain the increase observed in NPs number concentration. On the contrary, the Ce/La ratio increases in the outdoor activities center, which suggests the contribution of NPs potentially related to the cars parked nearby. Besides, elemental ratios Ti/V and Ti/Y have been assessed to highlight an anthropogenic source of Ti in both sampling sites, possibly to the sunscreens used during the summer.
... At these concentrations of TiO 2 NPs, (spiked or cumulative concentrations in the reactors), have been observed effects over the nitrifying bacteria (Zheng et al. 2011) and in the dissolved organic carbon elimination (Gartiser et al. 2014). Moreover, high concentrations of Ti (lg/L to mg/L), presumable as TiO 2 , have been measured in influent wastewater and activated sludge of WWTPs (Polesel et al. 2018;Huang et al. 2020). Before addition of NPs to the reactors, the suspensions were dispersed in an ultrasonic bath during 1 h. ...
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The rapid growth of the use of nanomaterials in different modern industrial branches makes the study of the impact of nanoparticles on the human health and environment an urgent matter. For instance, it has been reported that titanium dioxide nanoparticles (TiO2 NPs) can be found in wastewater treatment plants. Previous studies have found contrasting effects of these nanoparticles over the activated sludge process, including negative effects on the oxygen uptake. The non-utilization of oxygen reflects that aerobic bacteria were inhibited or decayed. The aim of this work was to study how TiO2 NPs affect the bacterial diversity and metabolic processes on an activated sludge. First, respirometry assays of 8 h were carried out at different concentrations of TiO2 NPs (0.5–2.0 mg/mL) to measure the oxygen uptake by the activated sludge. The bacterial diversity of these assays was determined by sequencing the amplified V3–V4 region of the 16S rRNA gene using Illumina MiSeq. According to the respirometry assays, the aerobic processes were inhibited in a range from 18.5 ± 4.8% to 37.5 ± 2.0% for concentrations of 0.5–2.0 mg/mL TiO2 NPs. The oxygen uptake rate was affected mainly after 4.5 h for concentrations higher than 1.0 mg/mL of these nanoparticles. Results indicated that, in the presence of TiO2 NPs, the bacterial community of activated sludge was altered mainly in the genera related to nitrogen removal (nitrogen assimilation, nitrification and denitrification). The metabolic pathways prediction suggested that genes related to biofilm formation were more sensitive than genes directly related to nitrification–denitrification and N-assimilation processes. These results indicated that TiO2 NPs might modify the bacteria diversity in the activated sludge according to their concentration and time of exposition, which in turn impact in the performance of the wastewater treatment processes.
... A further aspect of emission estimation is the impact of wastewater treatment plants to environmental emission. Various publications reported the removal efficiency of inorganic nanomaterials in model and real wastewater treatment plants, indicating that >90% and ≥70% of the amount of introduced nanomaterials were removed from the water phase, respectively, and most end up in the sewage sludge (e.g., Kaegi et al. 2013;Polesel et al. 2018;Simelane and Dlamini 2019). However, it needs to be clarified whether this is generally valid for all types of nanomaterials or whether there are differences based on chemistry or complexity (e.g., functional groups) of the nanomaterials. ...
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Within the REACH regulation (EC) No. 1907/2006) specific provisions for nanomaterials were included, which have become effective at the 01 January 2020. Although knowledge on the peculiarities of testing and assessing fate and effects of nanomaterials in the environment strongly increased in the last years, uncertainties how to perform a reliable and robust environmental risk assessment for nanomaterials still remain. These uncertainties are of special relevance in a regulatory context, challenging both industry and regulators. This paper presents current challenges in regulatory hazard and exposure assessment under REACH as well as classification of nanomaterials and makes proposals to address them. Still, the nano‐specific considerations made here are expected to be also be valid for environmental risk assessment approaches in other regulations of chemical safety. Inter alia, these proposals include a way forward to account for exposure concentrations in aquatic toxicity test systems, a discussion how to account availability of dissolving nanomaterials in aquatic test systems and a pragmatic proposal to deduce effect data for soil organisms. Furthermore, it specifies how to potentially deal with nanoforms under CLP and outlines the needs for proper exposure assessments of nanomaterials from a regulatory perspective. This article is protected by copyright. All rights reserved.
... The model incorporates new rate equations and phenomena, which take into account the behavior of nanoparticles colloidal suspensions and provide model parameters permitting the transport and effects of TiO 2 , SiO 2 , CuO, and ZnO particles through the soils of landfills protective layers to be predicted. These nanoparticles have been selected due to their importance and abundance in the simultaneous disposal of waste materials in the landfill [4,[23][24][25]. Therefore, it is an attempt to develop an efficient tool to quantitate the impact of the disposal of harmful nanomaterials in landfills, providing a way to select suitable conditions for waste disposal and treatment. ...
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The technological applications of the newly developed nanoparticles are continuously increasing. Nevertheless, their reduced size forming colloidal suspensions may facilitate the transport and bioaccumulation in the environment. The particular properties of each nanoparticle and its interaction with the dissolved organic matter (DOM) and the living organisms are important issues in this scenario. The landfill waste disposal method is still worldwide dominant. In the landfill, the nanoparticles can undergo phenomena such as leaching, agglomeration, flocculation, complexation, adsorption, dissolution, and neoformations. Among the concerns, it is recognized that the nanoparticles behave as carriers for the contaminants in the environment strongly impacting the water resources. This research is focused on the development of a mathematical model having an ability to predict the transports of TiO2, SiO2, ZnO, and CuO nanoparticles and their mutual interactions within soils commonly used as protective layers of controlled landfill for municipal waste disposal. A combined methodology based on numerical procedures using inverse method principles, and controlled experimental column experiments are carried out. First, the model parameters are determined, and second, the model is validated against numerical and experimental data. The model formulated newly address the interactions phenomena of colloidal suspensions of nanoparticles percolating through protective layers of landfill soils. It has been found that SiO2 nanoparticles presented the strongest deleterious effect on the efficiency of the soil protective layers, while ZnO plays a positive role promoting flocculation and complexation with soil particles and enhance their effectiveness.
... These concentrations were measured in the water column only, and represent the colloidal and ionic silver fractions in the various steps of the wastewater treatment processes, but may not account for silver in larger particles which were removed by the 0.45 mm nitrocellulose filter. Given the high removal from influent to secondary and tertiary effluents observed here, the majority of Ag NPs are in the sludge (Polesel et al., 2018;Tuoriniemi et al., 2017). ...
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While the predicted or observed concentrations of Ag NPs in wastewater treatment plants (WWTPs) have ranged from μg/L to ng/L, there is still uncertainty with regards to the realistic concentration range of Ag NPs in WWTPs. In addition, the persistence, removal, and size of Ag NPs throughout WWTP process is also not well investigated, particularly in real operating conditions. In this study, the incidence and persistence of Ag NPs in the wastewater process were studied by using single particle inductively coupled plasma mass spectrometry (sp-ICP-MS). The incidence of Ag NPs was determined in samples collected at the influent and effluent of the conventional process, as well as reclaimed and backwash waters of the ultrafiltration (UF) system in a WWTP (Santa Barbara, CA), showing a concentration of 13.5, 3.2, 0.5 and 9.8 ng/L, respectively, with relative standard deviations (RSDs) < 5%. Total Ag concentration (Ag NP and Ag ⁺ ) ranged from 40 to 70 ng/L, in line with lower predicted values. Most of the Ag NPs detected were below 100 nm, with a few above 100 nm in the conventional effluent. Biological and physical processes in the secondary treatment removed 76.3% of the colloidal Ag fraction, while with the tertiary treatment (UF) the WWTP achieved a removal of 96.3% of the colloidal fraction. Persistence of Ag NPs in various water matrixes, including a synthetic wastewater (SWW), was determined by spiking 300 ng/L of Ag NPs (40 nm) and monitoring the concentrations and size change for 15 days. The persistence of Ag NPs in suspension was Influent > Effluent > Reclaimed > SWW. Partial dissolution of NPs in all waters was observed from time 0 h. Although the current concentrations in the outlet flows from WWTP (effluent and reclaimed waters) were low, the presence of small and stable Ag NPs may raise ecotoxicological concerns via bioaccumulation.
... A typical exposure of dietary TiO 2 for a US adult is estimated 0.2-0.7 mg TiO 2 kg -1 of body weight day -1 with most entering into wastewater treatment plants (WWTPs) (Weir et al., 2012). Nanoparticle removal efficiency can be up to 96% (Kiser et al., 2009;Polesel et al., 2018;Westerhoff et al., 2011) but the presence of en-TiO 2 in effluents after treatment is still identified at the level of µg L -1 (Westerhoff et al., 2011). These studies demonstrate that en-TiO 2 has entered our aquatic systems and therefore evaluating the potential risk to ecosystems, as well as to humans, through bioaccumulation is of great importance. ...
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Surface waters from three catchments having contrasting land-uses (forested, agricultural, and urban) were sampled monthly and analysed for nanoparticulate titanium dioxide (NPs-TiO2) by single particle ICPMS and electron microscopy. We report one-year of data for NPs-TiO2 having average number and mass concentrations of 9.1 ×10⁸ NPs-TiO2 particles L⁻¹ and 11 µg NPs-TiO2 L⁻¹ respectively. An increase in concentration during warmer months is observed in the forested and agricultural catchments. Both concentrations of NPs-TiO2 are within the range of recently reported values using similar analytical approaches. The positive correlations for NPs-TiO2 mass concentration or particle number with the concentration of some trace elements and DOC in the forested and agricultural catchments suggest the detected NPs-TiO2 in these two systems are mostly from geogenic origin. Additionally, microscopy imaging confirmed the presence of NPs in the three catchments. Furthermore, the land-area normalized annual flux of NPs-TiO2 (1.65 kg TiO2 year⁻¹ km⁻²) was highest for the agricultural catchment, suggesting that agricultural practices have a different impact on the NPs-TiO2 dynamics and exports than other land-uses (urban or forestry). A similar trend is also found by the reanalysis of recent literature data.
Chapter
Recent advances in the field of nanoscience and nanotechnology enabled the development of precise processes that are used across the most diverse science fields to control individual atoms and molecules. Inorganic nanomaterials, specially zinc and silver nanoparticles (Zn-NPs, Ag-NPs), have been attracting attention in the last decades due to their versatility, with applications as active componentes in eletronics, pharmaceuticals, cosmetic and agricultural products. However, safe nanotechnology unfortunatelly did not progress at the same speed, and hazardous nanomaterials are still disposed indiscriminately, crompromising the environment. Herein, the most recent and relevant contributions related to Zn-NPs and Ag-NPs, with regard to their chemical properties, utilization, disposal, interaction with biological systems and environmental impacts, are presented and discussed.
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Increased use of silver nanoparticles (AgNPs) in commercial products inevitably leads to their release into the environment through sludge discharge from wastewater treatment facilities. The silver morphology and speciation in sludge plays an important role in the biotoxicity and subsequent risk assessment of AgNPs. In this study, we investigated the morphology and speciation of AgNPs after coagulation and subsequent sludge thermal treatment, treated simulated water samples that were prepared with bare and macromolecule polymers (PVP) coated AgNPs. Results from X-ray photoelectron spectroscopy and X-ray diffraction analysis demonstrated that bare AgNPs, which aggregated to large sizes before coagulation, existed as crystalline metallic silver (68.8%) and argentic chloride (31.2%) in flocs. As bare AgNPs flocs were calcinated at 600 °C, part of the metallic silver transferred to silver oxide (Ag2O). Analysis of Ag fractions showed that the percentages of dissolved silver and nano silver in bare AgNPs flocs increased drastically over 30% in acidic conditions or in the presence of calcium ions and humic acid, and further increased after calcination. In comparison, most of the PVP coated AgNPs were immobilized in flocs as Ag2O and argentic chloride. The sludge calcination did not produce any further modification in silver speciation. Comparison of the results between bare and PVP coated AgNPs demonstrated that nanoparticle aggregation before treatment is not conducive to immobilization of AgNPs in flocs, and results in health hazards and ecological risks due to the release of silver.
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The engineered silver nanoparticles (AgNPs) used in consumer products are ultimately released to the environment either as Ag(0), silver sulfide (Ag2S(s)), silver chloride (AgCl(s)) and/or dissolved Ag(I) complexes. Of these, AgCl(s) and Ag2S(s) exhibit semiconducting properties and hence may have significant implications to oxidant generation and subsequent redox transformations in natural waters. In this work, we investigate the transformation and photo-reactivity of AgCl(s) under simulated natural water conditions with the photo-reactivity probed by measuring the oxidation of formate (HCOO−), a simple compound with well-defined oxidation pathway. Our results show that AgCl(s) undergoes rapid dissolution in the presence of chloride concentrations representative of seawater (ca. 0.5 M NaCl) forming dissolved Ag(I) complexes but is stable in fresh waters and slightly brackish waters (≤ 200 mM NaCl). We further show that under these lower salinity conditions in which AgCl(s) is stable, pH has a significant impact on the reactivity of semiconducting AgCl(s). The photoreactivity (measured as initial HCOO− oxidation rate) of AgCl(s) is relatively constant at pH 4.0 for periods of 24 h or more however decreases rapidly under alkaline conditions. The rapid transformation (or “aging”) of AgCl(s) under alkaline conditions suggests that AgCl(s), potentially transported through wastewater effluent to fresh or brackish water environments, may not have a significant impact in such environments. In comparison, in-situ formed AgCl(s), potentially formed as a result of the oxidation of high concentrations (≥60 µg Ag.L-1) of Ag(0) and/or Ag2S(s) , may have significant implications to oxidant generation in natural waters.. Our results further show that rapid cycling of Ag between the 0 and +I redox states in sunlit surface waters as a result of the presence of AgNP oxidants (such as H2O2 and organic radicals) will further enhance the rate and extent of oxidant generation by AgCl(s).
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The risk of heavy metal cadmium (Cd) on aquatic organisms has drawn widespread attentions, but the effects of nanomaterials (e.g. graphene (G)) on Cd toxicity are rarely clarified. It was known that mixture of contaminants may exhibit more severe impact than the individual metal. Here, we conducted a study systematically on the effects of nanomaterials on the toxicity of Cd to Scenedesmus Obliquus (S. obliquus) with or without the presence of graphene family materials (GFMs) derived from G, such as graphene oxide (GO) and amine-modified graphene (GNH). Our results showed that the influence of GFMs on the acute toxicity of Cd to S. obliquus is in the order of GO > G > GNH based on their EC50 of Cd-GFMs. The effects of GFMs on the cytotoxicity and oxidative damage of Cd to S. obliquus are varied with the concentrations of GFMs. The differences between the effects of GFMs on Cd toxicity may attribute to their different surface oxygen-containing functional groups contained in the nanomaterials. The adsorption capacity of nanomaterials on metal ions, their dispersibility in water and their interaction mode with organisms, may dominate main contributions to their effects on Cd toxicity. Our study aids to clarify the interference of nanoparticles on the ecotoxicity of metals, to avoid the misunderstanding of the potential risk of metals in the complicate water environments.
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Treated wastewater is reclaimed to irrigate crops in a growing number of arid and semi-arid areas. In order to study the impacts of metallic nanoparticles (NPs) present in treated wastewater on soil ecosystems, a soil micro-ecosystem containing Arabidopsis thaliana plants, soil microorganisms, and Eisenia fetida earthworms was developed. The soil was irrigated with deionized water containing environmentally relevant concentrations of 70 µg/L of TiO 2 NPs; or 20 µg/L of an Ag mixture, which included 90% (w/w) Ag 2 S NPs, 7.5% (w/w) Ag ⁰ NPs, and 2.5% (w/w) Ag ⁺ to represent speciation of aged Ag NPs in treated wastewater; or a combination of the TiO 2 NPs and the Ag mixture to reflect the frequent presence of both types of materials in treated wastewater. It was found that TiO 2 NPs alone were not toxic to the soil micro-ecosystem. Irrigation water containing 20 µg/L of the Ag mixture significantly reduced the soil microbial biomass, and inhibited the growth of plants and earthworms; however, a combination of 70 µg/L of TiO 2 and 20 µg/L of Ag did not show toxic impact on organism growth compared to the Control of deionized water irrigation. Taken together, these results indicate the importance of investigating the effects of different nanomaterials in combination as they are introduced to the environment—with environmentally relevant concentrations and speciation—instead of only selecting a single NP type or residual ion. Moreover, the results of this study support the safe application of reclaimed water from wastewater treatment plants for use in agricultural lands in regard to limited concentrations of aged NPs (i.e., TiO 2 and Ag) if present in combination.
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Natural organic matter (NOM) can influence the properties and behavior of metal nanoparticles (MNPs) in aquatic environments. Thus, understanding the effect of NOM on MNPs’ physiochemical properties is critical for identifying an effective water treatment processes, and controlling the potential risk they pose to ecological and human health. In this study, adsorption and leaching experiments were performed with powder activated carbon (PAC), to investigate the effect of humic acid (HA) and bovine serum albumin (BSA) on the removal of ZnO nanoparticles (ZnONPs) from an aqueous environment and their stability on the adsorbed PAC. The different ZnONPs forms— particulate, colloidal, and dissolved Zn fractions, were respectively considered. The adsorption experiments demonstrated that both colloidal and dissolved Zn fractions can adsorb on the PAC’s surface. As the HA concentration increased from 0 to 20 mg/L, the colloidal Zn fraction’s adsorption efficiency decreased from 74.49% to 61.24%. However, BSA did not significantly influence the colloidal Zn fraction’s adsorption. The leaching experiments showed that the colloidal Zn fraction would release from the PAC’s surface, and most of them transferred to the dissolved Zn fraction. As the HA concentration increased from 0 to 20 mg/L, the Zn concentration leached from the PAC adsorbed ZnONPs reduced from 0.956 to 0.694 mg/g. Comparatively, the leached Zn concentration varied only slightly with an equal increase in BSA concentration.
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s The behavior and toxicity of nanoparticles could be affected significantly by the ubiquitous natural organic matter (NOM) in aquatic environments. However, the influence of NOM on nanoparticles along the food chain remains largely unknown. This study constructed bacteria Escherichia coli (E. coli) – protozoa Tetrahymena thermophila (T. thermophila) to evaluate the influence of NOM on the bioaccumulation, trophic transfer and toxicity of silver nanoparticles (Ag NPs). Results demonstrated that NOM could reduce the toxicity of Ag NPs to E. coli and T. thermophila by different influence mechanisms (e.g., reduce Ag NPs accumulation or complex with dissolved silver ion (Ag⁺)) which related to the type of NOM and organisms. Moreover, Ag NPs can be transferred and biomagnified to T. thermophila via trophic transfer. Three typical NOM could significantly increase the trophic transfer factors of Ag NPs ranging from 1.16 to 2.49, which may be ascribed to NOM reducing the capacity for T. thermophila to excrete total silver (Ag) as NOM could significantly change the form of Ag. These findings provide a novel insight into the impact of NOM on the ecological risk posed by Ag NPs through the food chain and emphasize the need to understand further the interactions between nanoparticles and NOM in various ecosystems.
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In this study, the effects of aged Ag and TiO2 NPs, individually and as a mixture, in wastewater relative to their pristine counterparts on the development of the copepod nauplii (Tisbe battagliai) were investigated. NP behavior in synthetic wastewater and seawater was characterized during aging and exposure. A delayed development and subsequent mortality was observed after 6 days of exposure to aged Ag NPs, with a 2-fold decrease in EC50 (316 µg/L) compared to pristine NPs (EC50 640 µg/L) despite the similar dissolved Ag concentrations measured for aged and pristine Ag NPs (441 µg/L and 378 µg/L, respectively). In co-exposures with TiO2 NPs, higher dissolved Ag levels were measured for aged NPs (238.3 µg/L) relative to pristine NPs (98.57 µg/L). Co-exposure resulted in a slight decrease (15%) in the Ag NP EC50 (270 µg/L) with a 1.9-fold increase in Ag NP retained within the organisms after depuration (2.82% retention) compared to Ag NP single exposures as measured with sp-ICP-MS suggesting that the particles are still bioavailable despite the heteroaggregation observed between Ag, Ti NPs and wastewater components. This study shows that the presence of TiO2 NPs can affect the stability and toxicity of Ag NPs in complex media that cannot be predicted solely based on ionic, total or nanoparticulate concentrations and the need for studying NP interactions in more complex matrices is highlighted.
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s The entering of silver nanoparticles (Ag NPs) in natural environments constantly increases due to their widespread production and application. While the environmental behavior, impacts, and fate of Ag NPs were critically assessed, the main challenge represents continuous tracking and quantification of Ag NPs in environmental and biological matrices. A group of labeled Ag NPs with gold cores ([email protected] NPs) was developed for distinguishing between pristine Ag NPs and their other forms, and we comprehensively compared their physicochemical properties, environmental behavior, and biological effects with unlabeled Ag NPs. The electron transfer process from the Au core to the Ag shell gradually decreased with the increase of Ag shell thickness, then the inhibition of Ag⁺ release induced by the Au core was gradually alleviated, but the generation of superoxide radicals was intensified sharply. Then, the effect of the Au core on the dissolution capacity and free radicals’ generation significantly altered the biological toxicity of Ag NPs, and the influence degree was related to the test organism's species. Nevertheless, the Au core retained the surface properties of Ag NPs, leading to the uptake of [email protected] NPs, entirely consistent with the behavior of unlabeled Ag NPs. These findings confirmed that Au core labeling provides new opportunities for tracking Ag NPs in environmental and biological systems, and the exposure conditions and test organisms should be carefully assessed before employing the Au core labeling technology.
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We review the challenges and opportunities for biosensor research in North America aimed to accelerate translational research. We call for platform approaches based on: i) tools that can support interoperability between food, environment and agriculture, ii) open-source tools for analytics, iii) algorithms used for data and information arbitrage, and iv) use-inspired sensor design. We summarize select mobile devices and phone-based biosensors that couple analytical systems with biosensors for improving decision support. Over 100 biosensors developed by labs in North America were analyzed, including lab-based and portable devices. The results of this literature review show that nearly one quarter of the manuscripts focused on fundamental platform development or material characterization. Among the biosensors analyzed for food (post-harvest) or environmental applications, most devices were based on optical transduction (whether a lab assay or portable device). Most biosensors for agricultural applications were based on electrochemical transduction and few utilized a mobile platform. Presently, the FEAST of biosensors has produced a wealth of opportunity but faces a famine of actionable information without a platform for analytics.
Preprint
The imminent arrival of nanoparticles (NPs) to the wastewater treatment plants (WWTP) brings concern about their effects. In this work, the effects of titanium dioxide (TiO 2) NPs in the removal of carbon, nitrogen, and phosphorus by activated sludge bioreactors during the treatment of synthetic, raw and ltered wastewater were evaluated. The oc size, compaction of sludge, and morphological interactions between sludge and NPs were also evaluated. The main effect was observed in the ammoniacal nitrogen removal, which was inhibited up to 22% for all types of wastewater in the presence of TiO 2 NPs. While nitrite production de ciencies were observed for real wastewaters experiments, nitrate formation was mainly affected for synthetic wastewater. The removal of organic matter was affected by TiO 2 NPs in lower level (up to 6%) than nitrogen removal, especially during treatment of raw wastewater. The removal of orthophosphate was improved in presence of NPs 34%, 16% and 55% for synthetic, raw, and ltered wastewater, respectively. The compaction of the sludge was also a positive effect, which enhanced as the concentration of NPs increased without alterations in the oc size for all types of wastewater. Based on TEM and STEM imaging, the main interaction of TiO 2 NPs with activated sludge ocs was mainly the adsorption of NPs on the cell membrane. This means that NPs can disrupt the cell membrane during aerobic wastewater treatment. The effects of NPs on macronutrient removal depended on wastewater characteristics. The use of realistic matrices is highly encouraged for ecotoxicological experiments.
Article
Sludge generated in wastewater treatment facilities is an integral part for the introduction of silver nanoparticles (AgNPs) to the terrestrial environment, which would cause some adverse ecosystem responses. The understanding of silver release process from the sludge is important to evaluate their risks. In this study, the amount and speciation of the released silver were investigated by taking the sludge generated by wastewater coagulation with AgNPs added (denoted as sludgeC-AgNPs) an example, and kinetic analysis and density functional theory (DFT) calculations were first used to explore the controlling steps and pathways about the silver release. The results showed that sludgeC-AgNPs could release the dissolved silver and the colloidal silver. Beside Cl⁻, Ca²⁺ in the leaching solution could enhance the silver release of sludgeC-AgNPs, especially for the colloidal silver. The released colloidal silver restricted in size from 40 nm to 100 nm with irregular shape. Although the oxidative dissolution of Ag⁰ was the origin of the silver release pathways from the sludgeC-AgNPs, the silver diffusion was the controlling step due to the spontaneous binding between silver and the hydrolysates of polyaluminium chloride in sludgeC-AgNPs. However, Ca²⁺ in the leaching solution could occupy the binding site of silver on sludgeC-AgNPs, which would increase the diffusion rate of silver over the oxidative rate of Ag⁰. With this condition, the controlling step of silver release from sludgeC-AgNPs turned to the oxidative dissolution of Ag⁰. Our findings are important to assess the fate of AgNPs in wastewater treatment as well as sludge applications.
Article
Titanium dioxide (TiO2) is commonly contained in many commercial products and there are concerns about its release into the aquatic environment after use. This study was designed to characterize the distribution of Ti-containing nanoparticulates (NPs) in the water of the Tamsuei River Basin in northern Taiwan. Water samples were collected from the upstream, mid-stream, and downstream areas of the Tamsuei River Basin and analyzed with single-particle ICPMS to profile the Ti-containing NPs in terms of mass concentration, number concentration and particulate size. The lowest mass concentration of Ti-containing NPs, 1.04 ± 0.04 μg/L, was found in the upstream water samples, while the highest mass concentration, 31.7 ± 0.6 μg/L, was observed in downstream samples; there was an increasing trend from upstream to downstream. The highest particulate number concentration, 479 ± 163 × 10³/mL, was observed for the downstream samples, but the lowest concentration, 45.4 ± 5.6 × 10³/mL, was found in the mid-stream water samples taken from Site C. Moreover, the average mode values for particulate sizes were approximately 50 nm for all samples, although a relatively larger average mode value of 62 ± 5.7 nm was observed in the mid-stream samples from Site A. Increasing mass concentrations and particulate number concentrations from upstream to downstream implied that these NPs might have originally resulted from anthropogenic activities involving the use of TiO2 NPs–containing products. Surprisingly, however, the lowest number concentrations for Ti-containing NPs in the mid-stream samples can probably be attributed to the fact that the corresponding sampling sites were located in the water preservation zone, which exhibits a particle-settling effect. Additionally, the sizes of Ti-containing NPs in downstream samples were not significantly larger than those in the upstream and mid-stream samples, as expected, which was probably due to the steric effects resulting from the presence of large amounts of macromolecule polymers in aquatic environments.
Article
Sludge is an integral part in the migration pathway of silver nanoparticles (AgNPs) from manufacture to the terrestrial environment. However, the detailed information on the role of natural organic matters (NOMs) remains limited. In this study, the sludge generated from coagulation of wastewater spiked with AgNPs (denoted as sludgeC-AgNPs) was taken as the model. Effects of humic acid (HA), alginate (AA) and bovine serum albumin (BSA) on the release amount, dynamics and speciation of silver from the sludgeC-AgNPs were investigated by a series of leaching experiments. The results showed that HA, AA and BSA in the leaching solution could enhance the silver release from the sludgeC-AgNPs. The concentrations of the dissolved and colloidal silver in the BSA solution were the highest at the initial stage of dynamic leaching. The controlling step of the silver release was internal diffusion in the HA and AA solution, while the release of dissolved silver was controlled by both chemical reaction and internal diffusion in the BSA solution. In addition, the released colloidal silver fractions in the BSA solution contained more particles with size >50 nm compared with the HA and AA solutions. The results suggested that the properties of NOMs may be the key factor affecting the transfer of AgNPs from the sludge to the terrestrial environment.
Article
Full-text available
The imminent arrival of nanoparticles (NPs) to the wastewater treatment plants (WWTP) brings concern about their effects, which can be related to the wastewater composition. In this work, the effects of titanium dioxide (TiO2) NPs in the removal of carbon, nitrogen, and phosphorus by activated sludge bioreactors during the treatment of synthetic, raw, and filtered wastewaters were evaluated. Floc size, compaction of sludge, and morphological interactions between sludge and NPs were also determined. The main effect of TiO2 NPs was the inhibition of up to 22% in the removal of ammonia nitrogen for all types of wastewaters. This effect is strong dependent on combined factors of TiO2 NPs concentration and content of organic matter and ammonia in wastewater. The removal of dissolved organic carbon was affected by TiO2 NPs in lower level (up to 6%) than nitrogen removal for all types of wastewaters. Conversely to adverse effects, the removals of orthophosphate in the presence of TiO2 NPs were improved by 34%, 16%, and 55% for synthetic, raw, and filtered wastewater, respectively. Compaction of the sludge was also enhanced as the concentrations of NPs increased without alterations in the floc size for all types of wastewaters. Based on TEM and STEM imaging, the main interaction between TiO2 NPs and the activated sludge flocs was the adsorption of NPs on cell membrane. This means that NPs can be attached to cell membrane during aerobic wastewater treatment, and potentially disrupt this membrane. The effects of TiO2 NPs on macronutrient removal clearly depended on wastewater characteristics; hence, the use of realistic media is highly encouraged for ecotoxicological experiments involving NPs.
Chapter
The rapid expansion of nanotechnology has led to the incorporation of engineered nanomaterials in consumer products, including personal care products, electronics, food and agricultural products. Increased production, usage and disposal of these products increased nanomaterial release in the environment, where wastewater treatment plants serve as important intermediate points receiving nanomaterial-containing wastewater. This chapter describes the type and behaviour of nanoparticles in wastewater treatment plants, how it affects the treatment process and their removal from wastewater treatment plants. In different treatment stages, the nanoparticle concentration, size and shape vary with the type of consumer products, season, and interaction with the materials existing in treatment plants. The majority of the nanoparticles are removed via primary treatment or secondary treatment, only a few escape to the effluent leading to its presence in the receiving aquatic streams.
Article
In this study, a lab-scale wastewater treatment plant (WWTP), simulating biological treatment, received 10 µg/L Ag and 100 µg/L TiO2 nanoparticles (NPs) for five weeks. NP partitioning was evaluated by size fractionation (>0.7 µm, 0.1-0.7 µm, 3 kDa-0.1 µm, <3 kDa) using inductively coupled plasma mass spectrometry (ICP-MS), single particle ICP-MS and transmission electron microscopy. The ecotoxicological effects of the transformed NPs in the effluent were assessed using a battery of marine and freshwater bioassays (algae and crustaceans) and an in vitro gill cell line model (RTgill-W1). TiO2 aggregates were detected in the effluent, while Ag NPs (0.1 to 0.22 µg/L) were associated with S, Cu, Zn. Fractionation showed that >80% of Ag and Ti were associated with the effluent solids. Increased toxicity was observed during weeks 2-3 and the effects were species-dependent; with marine epibenthic copepods and algae being the most sensitive. Increased reactive oxygen species formation was observed in vitro followed by an increase in epithelial permeability. The effluent affected the gill epithelium integrity in vitro and impacted defense pathways (upregulation of multixenobiotic resistance genes). To our knowledge, this is the first study to combine a lab-scale activated sludge WWTP with extensive characterization techniques and ecotoxicological assays to study the effects of transformed NPs in the effluent.
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Questions about how to regulate nano-enhanced products regularly arise as researchers determine possible nanoparticle transformation(s). Focusing concern on the incorporation and subsequent release of nano-Ag in the fabrics often overshadows the fact that many "conventional silver" antimicrobials such as ionic silver, AgCl, metallic Ag and other forms will also form different species of silver. In this study we used a laboratory washing machine to simulate the household laundering of a number of textiles prepared with known conventional Ag or nano-Ag treatments and a commercially available fabric incorporating yarns coated with bulk metallic Ag. Serial filtration allowed for quantification of total Ag released in various size fractions (> 0.45 µm, < 0.45 µm, < 0.1 µm and < 10 kDa) while characterization of particles with TEM/EDX provided insight on Ag transformation mechanisms. Most conventional Ag-additives yielded more total Ag and more nano-particulate sized Ag in washing liquid than fabrics that used nano-Ag treatments. Incorporating the nanosilver into the fiber (opposed to surface treatments) yielded less total Ag during fabric washing. A variety of metallic Ag, AgCl, and Ag/S particles were observed in washing solution by TEM/EDX to various extents depending on the initial Ag speciation in the fabrics. Very similar particles were also observed when dissolved ionic Ag was added directly into the washing liquid. Based on the present study, we can state that all silver-treated textiles, regardless if the treatment is "conventional" or "nano", can be a source of silver nanoparticles in washing solution when laundering fabrics. Indeed, in this study we observed that textiles treated with "conventional" silver have equal or greater propensity to form nano-silver particles during washing conditions than those treated with "nano" silver. This fact needs to be strongly considered when addressing the risks of nano-silver and emphasizes that regulatory assessment of nanosilver warrants a similar approach to conventional silver.
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Titanium dioxide (TiO2) is a common food additive used to enhance the white colour, brightness and sometimes flavour of a variety of food products. In this study seven food grade TiO2 materials (E171), 24 food products and three personal care products were investigated for their TiO2 content and the number-based size distribution of TiO2 particles present in these products. We used three principally different methods to determine the number-based size distribution of TiO2 particles: e.g. electron microscopy, asymmetric flow field-flow fractionation combined with inductively coupled mass spectrometry and single-particle inductively coupled mass spectrometry. We show that all E171 materials have similar size distributions with primary particles in the range of 60 to 300 nm. 10-15% of the particles in these materials had sizes below 100 nm depending on the analytical method used. 24 of the 27 food and personal care samples showed detectable amounts of titanium with a highest concentration of 9.0 mg TiO2/g product in a chewing gum. Number-based size distributions for TiO2 particles in the food and personal care products were determined and 5-10% of the particles in these products had sizes below 100 nm depending on the analytical method used, comparable as to that in the TiO2 materials. We successfully used three principally different methods to determine the number-based size distribution of TiO2 particles in TiO2 materials and Ti containing food and personal care products. Comparable size distributions were found, however, each of the applied methods shows practical size limits for TiO2 particles of 20 and 50 nm which shows the inability of current methods to support the EU recommendation for the definition of nanomaterials.
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In recent years, exterior thermal insulation systems became more and more important leading to an increasing amount of houses equipped with biocide-containing organic façade coatings or fungicide treated wood. It is known that these biocides, e.g. terbutryn, carbendazim, and diuron, as well as wood preservatives as propiconazole, leach out of the material through contact with wind driven rain. Hence, they are present in combined sewage during rain events in concentrations up to several hundred ng L(-1). The present study focused on the occurrence of these biocides in five wastewater treatment plants in Denmark and Sweden during dry and wet weather. It was discovered, that biocides are detectable not only during wet weather but also during dry weather when leaching from façade coatings can be excluded as source. In most cases, the concentrations during dry weather were in the same range as during wet weather (up to 100 ng L(-1)); however, for propiconazole noteworthy high concentrations were detected in one catchment (4.5 μg L(-1)). Time resolved sampling (12 × 2 h) enabled assessments about possible sources. The highest mass loads during wet weather were detected when the rain was heaviest (e.g. up to 116 mg h(-1) carbendazim or 73 mg h(-1) mecoprop) supporting the hypothesis that the biocides were washed off by wind driven rain. Contrary, the biocide emissions during dry weather were rather related to household activities than with emissions from buildings, i.e., emissions were highest during morning and evening hours (up to 50 mg h(-1)). Emissions during night were significantly lower than during daytime. Only for propiconazole a different emission behaviour during dry weather was observed: the mass load peaked in the late afternoon (3 g h(-1)) and declined slowly afterwards. Most likely this emission was caused by a point source, possibly from inappropriate cleaning of spray equipment for agriculture or gardening.
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Differential filtration was used to measure silver (>2nm) entering and leaving nine sewage treatment plants (STPs). The mean concentration of colloidal (2-450nm) silver, which includes nanosilver, was found to be 12ngL(-1) in the influent and 6ngL(-1) in the effluent. For particulate silver (>450nm) the mean values were 3.3μgL(-1) for influent and 0.08μgL(-1) for effluent. Thus, removal was around 50% and 98% for colloidal and particulate silver respectively. There was no significant difference in performance between the different types of STP investigated (three examples each of activated sludge, biological filter and biological filter with tertiary treatment located across England, UK). In addition, treated sewage sludge samples (biosolids) were taken from several STPs to measure the total silver likely to be discharged to soils. Total silver was 3-14mgkg(-1) DW in the sludge (median 3.6), which if the sludge were added at the recommended rate to soil, would add 11μgkg(-1)yr(-1) to the top 20cm soil layer. Predicted concentrations using the LF2000-WQX model for all the rivers of England and Wales for nanosilver were typically in the 0-1ngL(-1) range but levels up to 4ngL(-1) are possible in a high discharge and low flow scenario. Predicted concentrations for the total particulate forms were mostly below 50ngL(-1) except for a high discharge and low flow scenario where concentrations could reach 135ngL(-1).
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The objective of this paper is to demonstrate the full-scale feasibility of the phenomenological dynamic influent pollutant disturbance scenario generator (DIPDSG) that was originally used to create the influent data of the International Water Association (IWA) Benchmark Simulation Model No. 2 (BSM2). In this study, the influent characteristics of two large Scandinavian treatment facilities are studied for a period of two years. A step-wise procedure based on adjusting the most sensitive parameters at different time scales is followed to calibrate/validate the DIPDSG model blocks for: 1) flow rate; 2) pollutants (carbon, nitrogen); 3) temperature; and, 4) transport. Simulation results show that the model successfully describes daily/weekly and seasonal variations and the effect of rainfall and snow melting on the influent flow rate, pollutant concentrations and temperature profiles. Furthermore, additional phenomena such as size and accumulation/flush of particulates of/in the upstream catchment and sewer system are incorporated in the simulated time series. Finally, this study is complemented with: 1) the generation of additional future scenarios showing the effects of different rainfall patterns (climate change) or influent biodegradability (process uncertainty) on the generated time series; 2) a demonstration of how to reduce the cost/workload of measuring campaigns by filling the gaps due to missing data in the influent profiles; and, 3) a critical discussion of the presented results balancing model structure/calibration procedure complexity and prediction capabilities.
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The majority of pure silver nanoparticles in consumer products are likely released into sewer systems and usually end up in wastewater treatment plants (WWTPs). Research investigating the reduction in nanoscale silver particles (n-Ag-Ps) has focused on the biological treatment process, generally in controlled laboratory experiments. This study, analyzing the field-collected samples from nine municipal WWTPs in Germany, is the first to evaluate the reduction in n-Ag-Ps by mechanical and biological treatments in sequence in the WWTPs. Additionally, the concentration of n-Ag-Ps in effluent was determined through two different methods that are presented here, a novel ionic exchange resin (IER) and cloud point extraction (CPE) methods. The n-Ag-Ps concentrations in influent were all low (< 1.5 g/L), and decreased (average removal efficiency: ~35%) significantly after mechanical treatment, indicating that the mechanical treatment contributes to the n-Ag-Ps removal. Afterwards, more than 72% of the remaining n-Ag-Ps in the semi-treated wastewater (i.e., wastewater after mechanical treatment) were reduced by biological treatment. Together, these processes reduced 95% of the n-Ag-Ps that entered WWTP, which resulted in low concentration of n-Ag-Ps in the effluents (< 12 ng/L). For a WWTP with 520000 t/d treatment capacity, we estimated that the daily n-Ag-Ps load in effluent discharge equated to about 4.4 g/d. Obviously, WWTP is not a potential point source for n-Ag-Ps in aquatic environment.
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Discharge of silver nanoparticles (Ag-NP) from textiles and cosmetics, todays major application areas for metallic Ag-NP, into wastewater is inevitable. Transformation and removal processes in sewers and wastewater treatment plants (WWTP) will determine the impact of Ag-NP on aquatic and terrestrial environments, via the effluents of the WWTP and via the use of digested sludge as fertilizer. We thus conducted experiments addressing the behavior of Ag-NP in sewers and in WWTP. We spiked Ag-NP to a 5 km long main trunk sewer and collected 40 wastewater samples after 500 m, 2400 m and 5000 m each according to the expected travel times of the Ag-NP. Excellent mass closure of the Ag derived by multiplying the measured Ag concentrations times the volumetric flow rates indicate an efficient transport of the Ag-NP without substantial losses to the sewer biofilm. Ag-NP reacted with raw wastewater in batch experiments were sulfidized to roughly 15% after 5 h reaction time as revealed by X-ray absorption spectroscopy (XAS). However, acid volatile sulfide (AVS) concentrations were substantially higher in the sewer channel (100 μM) compared to the batch experiments (3 μM; still sufficient to sulfidize spiked 2 μM Ag) possibly resulting in a higher degree of sulfidation in the sewer channel. We further investigated the removal efficiency of 10 nm and 100 nm Ag- and gold (Au)-NP coated with citrate or polyvinylpyrrolidone in activated sludge batch experiments. We obtained very high removal efficiencies (∼99%) irrespective of size and coating for Ag- and Au-NP, the latter confirming that the particle type was of minor importance with respect to the degree of NP removal. We observed a strong size dependence of the sulfidation kinetics. We conclude that Ag-NP discharged to the wastewater stream will become sulfidized to various degrees in the sewer system and are efficiently transported to the WWTP. The sulfidation of the Ag-NP will continue in the WWTP, but primarily depending on the size the Ag-NP, may not be complete. Very high removal efficiencies in the WWTP will divert most of the Ag-NP mass flow to the digester and only a small fraction of the Ag will be released to surface waters.
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We investigated the removal of silver in five publicly owned treatment works (POTWs) and the fate of Ag in effluent receiving streams. Comparisons were made to several other metals. Silver was removed efficiently (>94%) in all POTWs. The percentage of total Ag removed was independent of the influent Ag concentration, while the concentration of Ag in effluents was directly related to influent concentration. A good correlation (r2 = 0.77) between metal removal (%) and partition coefficient (Kd) indicated that differences among metals in removal efficiency were controlled mainly by metal partitioning (sorption) to particles removed by settling and/or filtration. A large fraction (19–53%) of Ag in the filterable (< 1.0-μm) fraction of POTW effluents was associated with submicron particles or colloids (>0.05 μm), and the percentage filterable Ag was directly related to DOC concentration (r2 = 0.96). Effluent Ag concentrations (0.06–2.6 μg/L) were several orders of magnitude higher that typical “background” stream levels (1–2 ng/L), but Ag discharged to streams was rapidly dissipated by dilution and incorporation into stream sediments.
Article
Activated Sludge Models are widely used for simulation-based evaluation of wastewater treatment plant (WWTP) performance. However, due to the high workload and cost of a measuring campaign on a full-scale WWTP, many simulation studies suffer from lack of sufficiently long influent flow rate and concentration time series representing realistic wastewater influent dynamics. In this paper, a simple phenomenological modelling approach is proposed as an alternative to generate dynamic influent pollutant disturbance scenarios. The presented set of models is constructed following the principles of parsimony (limiting the number of parameters as much as possible), transparency (using parameters with physical meaning where possible) and flexibility (easily extendable to other applications where long dynamic influent time series are needed). The proposed approach is sub-divided in four main model blocks: 1) model block for flow rate generation, 2) model block for pollutants generation (carbon, nitrogen and phosphorus), 3) model block for temperature generation and 4) model block for transport of water and pollutants. The paper is illustrated with the results obtained during the development of the dynamic influent of the Benchmark Simulation Model no. 2 (BSM2). The series of simulations show that it is possible to generate a dry weather influent describing diurnal flow rate dynamics (low rate at night, high rate during day time), weekend effects (with different flow rate during weekends, compared to weekdays), holiday effects (where the wastewater production is assumed to be different for a number of weeks) and seasonal effects (with variations in the infiltration and thus also the flow rate to the WWTP). In addition, the dry weather model can be extended with a rain and storm weather generator, where the proposed phenomenological model can also mimic the “first flush” effect from the sewer network and the influent dilution phenomena that are typically observed at full-scale WWTPs following a rain event. Finally, the extension of the sewer system can be incorporated in the influent dynamics as well: the larger the simulated sewer network, the smoother the simulated diurnal flow rate and concentration variations. In the discussion, it is pointed out how the proposed phenomenological models can be expanded to other applications, for example to represent heavy metal or organic micro-pollutant loads entering the treatment plant.
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Titanium dioxide is a common additive in many food, personal care, and other consumer products used by people, which after use can enter the sewage system and, subsequently, enter the environment as treated effluent discharged to surface waters or biosolids applied to agricultural land, incinerated wastes, or landfill solids. This study quantifies the amount of titanium in common food products, derives estimates of human exposure to dietary (nano-) TiO(2), and discusses the impact of the nanoscale fraction of TiO(2) entering the environment. The foods with the highest content of TiO(2) included candies, sweets, and chewing gums. Among personal care products, toothpastes and select sunscreens contained 1% to >10% titanium by weight. While some other crèmes contained titanium, despite being colored white, most shampoos, deodorants, and shaving creams contained the lowest levels of titanium (<0.01 μg/mg). For several high-consumption pharmaceuticals, the titanium content ranged from below the instrument detection limit (0.0001 μg Ti/mg) to a high of 0.014 μg Ti/mg. Electron microscopy and stability testing of food-grade TiO(2) (E171) suggests that approximately 36% of the particles are less than 100 nm in at least one dimension and that it readily disperses in water as fairly stable colloids. However, filtration of water solubilized consumer products and personal care products indicated that less than 5% of the titanium was able to pass through 0.45 or 0.7 μm pores. Two white paints contained 110 μg Ti/mg while three sealants (i.e., prime coat paint) contained less titanium (25 to 40 μg Ti/mg). This research showed that, while many white-colored products contained titanium, it was not a prerequisite. Although several of these product classes contained low amounts of titanium, their widespread use and disposal down the drain and eventually to wastewater treatment plants (WWTPs) deserves attention. A Monte Carlo human exposure analysis to TiO(2) through foods identified children as having the highest exposures because TiO(2) content of sweets is higher than other food products and that a typical exposure for a US adult may be on the order of 1 mg Ti per kilogram body weight per day. Thus, because of the millions of tons of titanium-based white pigment used annually, testing should focus on food-grade TiO(2) (E171) rather than that adopted in many environmental health and safety tests (i.e., P25), which is used in much lower amounts in products less likely to enter the environment (e.g., catalyst supports, photocatalytic coatings).
Article
Dynamic priority pollutant (PP) fate models are being developed to assess appropriate strategies for limiting the release of PPs from urban sources and for treating PPs on a variety of spatial scales. Different possible sources of PP releases were mapped and both their release pattern and release factors were quantified as detailed as possible.This paper focuses on the link between the gathered PP sources data and the dynamic models of the urban environment. This link consists of (1) a method for the quantitative and structured storage of temporal emission pattern information, (2) the retrieval of spatial emission source data from a GIS covering the studied urban area, (3) the coupling of the (GIS-based) spatial emission source data with temporal emission pattern information and (4) the generation of PP release time series to feed the dynamic sewer catchment model.Steps 3 and 4 were included as the main features of a dedicated software tool. Finally, this paper also illustrates the method's applicability to generate model input time series for generic pollutants (N, P and COD/BOD) in addition to priority pollutants.
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As engineered nanomaterials (NMs) become used in industry and commerce their loading to sewage will increase. In this research, sequencing batch reactors (SBRs) were operated with hydraulic (HRT) and sludge (SRT) retention times representative of full-scale biological WWTPs for several weeks. Under environmentally relevant NM loadings and biomass concentrations, NMs had negligible effects on ability of the wastewater bacteria to biodegrade organic material, as measured by chemical oxygen demand (COD). Carboxy-terminated polymer coated silver nanoparticles (fn-Ag) were removed less effectively (88% removal) than hydroxylated fullerenes (fullerols; >90% removal), nano TiO(2) (>95% removal) or aqueous fullerenes (nC(60); >95% removal). Experiments conducted over 4 months with daily loadings of nC(60) showed that nC(60) removal from solution depends on the biomass concentration. Under conditions representative of most suspended growth biological WWTPs (e.g., activated sludge), most of the NMs will accumulate in biosolids rather than in liquid effluent discharged to surface waters. Significant fractions of fn-Ag were associated with colloidal material which suggests that efficient particle separation processes (sedimentation or filtration) could further improve removal of NM from effluent.
Article
The increasing number of nanomaterial based consumer products raises concerns about their possible impact on the environment. This study provides an assessment of the effluent from a commercially available silver nanowashing machine. The washing machine released silver in its effluent at an average concentration of 11μgL(-1), as determined by inductive coupled mass spectrometry (ICP-MS). The presence of silver nanoparticles (AgNPs) was confirmed by single particle ICP-MS as well as ion selective electrode measurements and filtration techniques. Size measurements showed particles to be in the defined nanosize range, with an average size of 10nm measured with transmission electron microscopy (TEM) and 60-100nm determined with nanoparticle tracking analysis (NTA). The effluent was shown to have negative effects on a natural bacterial community as its abundance was clearly reduced when exposed to the nanowash water. If washing machines capable of producing AgNPs become a common feature of households in the future, wastewater will contain significant loadings of AgNPs which might be released into the environment.
Article
We investigated the behavior of metallic silver nanoparticles (Ag-NP) in a pilot wastewater treatment plant (WWTP) fed with municipal wastewater. The treatment plant consisted of a nonaerated and an aerated tank and a secondary clarifier. The average hydraulic retention time including the secondary clarifier was 1 day and the sludge age was 14 days. Ag-NP were spiked into the nonaerated tank and samples were collected from the aerated tank and from the effluent. Ag concentrations determined by inductively coupled plasma-mass spectrometry (ICP-MS) were in good agreement with predictions based on mass balance considerations. Transmission electron microscopy (TEM) analyses confirmed that nanoscale Ag particles were sorbed to wastewater biosolids, both in the sludge and in the effluent. Freely dispersed nanoscale Ag particles were only observed in the effluent during the initial pulse spike. X-ray absorption spectroscopy (XAS) measurements indicated that most Ag in the sludge and in the effluent was present as Ag(2)S. Results from batch experiments suggested that Ag-NP transformation to Ag(2)S occured in the nonaerated tank within less than 2 h. Physical and chemical transformations of Ag-NP in WWTPs control the fate, the transport and also the toxicity and the bioavailability of Ag-NP and therefore must be considered in future risk assessments.
Article
Nanosized silver sulfide (α-Ag(2)S) particles were identified in the final stage sewage sludge materials of a full-scale municipal wastewater treatment plant using analytical high-resolution transmission electron microscopy. The Ag(2)S nanocrystals are in the size range of 5-20 nm with ellipsoidal shape, and they form very small, loosely packed aggregates. Some of the Ag(2)S nanoparticles (NPs) have excess S on the surface of the sulfide minerals under S-rich environments, resulting in a ratio of Ag to S close to 1. Considering the current extensive production of Ag NPs and their widespread use in consumer products, it is likely that they are entering wastewater streams and the treatment facilities that process this water. This study suggests that in a reduced, S-rich environment, such as the sedimentation processes during wastewater treatment, nanosized silver sulfides are being formed. This field-scale study provides for the first time nanoparticle-level information of the Ag(2)S present in sewage sludge products, and further suggests the role of wastewater treatment processes on transformation of Ag nanoparticles and ionic Ag potentially released from them.
Article
Sorption to activated sludge is a major removal mechanism for pollutants, including manufactured nanoparticles (NPs), in conventional activated sludge wastewater treatment plants. The objectives of this work were to (1) image sorption of fluorescent NPs to wastewater biomass; (2) quantify and compare biosorption of different types of NPs exposed to wastewater biomass; (3) quantify the effects of natural organic matter (NOM), extracellular polymeric substances (EPS), surfactants, and salt on NP biosorption; and (4) explore how different surface functionalities for fullerenes affect biosorption. Batch sorption isotherm experiments were conducted with activated sludge as sorbent and a total of eight types of NPs as sorbates. Epifluorescence images clearly show the biosorption of fluorescent silica NPs; the greater the concentration of NPs exposed to biomass, the greater the quantity of NPs that biosorb. Furthermore, biosorption removes different types of NPs from water to different extents. Upon exposure to 400 mg/L total suspended solids (TSS) of wastewater biomass, 97% of silver nanoparticles were removed, probably in part by aggregation and sedimentation, whereas biosorption was predominantly responsible for the removal of 88% of aqueous fullerenes, 39% of functionalized silver NPs, 23% of nanoscale titanium dioxide, and 13% of fullerol NPs. Of the NP types investigated, only aq-nC(60) showed a change in the degree of removal when the NP suspension was equilibrated with NOM or when EPS was extracted from the biomass. Further study of carbonaceous NPs showed that different surface functionalities affect biosorption. Thus, the production and transformations in NP surface properties will be key factors in determining their fate in the environment.
Article
Engineered nanomaterials (ENM) are already used in many products and consequently released into environmental compartments. In this study, we calculated predicted environmental concentrations (PEC) based on a probabilistic material flow analysis from a life-cycle perspective of ENM-containing products. We modeled nano-TiO(2), nano-ZnO, nano-Ag, carbon nanotubes (CNT), and fullerenes for the U.S., Europe and Switzerland. The environmental concentrations were calculated as probabilistic density functions and were compared to data from ecotoxicological studies. The simulated modes (most frequent values) range from 0.003 ng L(-1) (fullerenes) to 21 ng L(-1) (nano-TiO(2)) for surface waters and from 4 ng L(-1) (fullerenes) to 4 microg L(-1) (nano-TiO(2)) for sewage treatment effluents. For Europe and the U.S., the annual increase of ENMs on sludge-treated soil ranges from 1 ng kg(-1) for fullerenes to 89 microg kg(-1) for nano-TiO(2). The results of this study indicate that risks to aquatic organisms may currently emanate from nano-Ag, nano-TiO(2), and nano-ZnO in sewage treatment effluents for all considered regions and for nano-Ag in surface waters. For the other environmental compartments for which ecotoxicological data were available, no risks to organisms are presently expected.
Article
The widespread use of silver nanoparticles (Ag-NPs) in commercial products, especially textiles, will likely result in an unknown spread of Ag into the environment. The quantification and characterization of the Ag released from nano-Ag-products is an important parameter needed to predict the effect of Ag-NPs on the environment. The aim of this study was to determine the amount and the form of Ag released during washing from nine fabrics with different ways of silver incorporation into or onto the fibers. The effect of pH, surfactants, and oxidizing agents was evaluated. The results show that little dissolution of Ag-NPs occurs under conditions relevant to washing (pH 10) with dissolved concentrations 10 times lower than at pH 7. However, bleaching agents such as hydrogen peroxide or peracetic acid (formed by the perborate/TAED system) can greatly accelerate the dissolution of Ag. The amount and form of Ag released from the fabrics as ionic and particulate Ag depended on the type of Ag-incorporation into the textile. The percentage of the total silver emitted during one washing of the textiles varied considerably among products (from less than 1 to 45%). In the washing machine the majority of the Ag (at least 50% but mostly >75%) was released in the size fraction >450 nm, indicating the dominant role of mechanical stress. A conventional silver textile did not show any significant difference in the size distribution of the released silver compared to many of the textiles containing nano-Ag. These results have important implications for the risk assessment of Ag-textiles and also for environmental fate studies of nano-Ag, because they show that under conditions relevant to washing, primarily coarse Ag-containing particles are released.
Article
Titanium (Ti) occurs naturally in soils and as highly purified titanium dioxide (Ti5O2) in many commercial products that have been used for decades. We report for the first time the occurrence, characterization, and removal of nano- and larger-sized Ti at wastewater treatment plants (WWTPs). At one WWTP studied in detail, raw sewage contained 100 to nearly 3000 microg TVL Ti larger than 0.7 microm accounted for the majority of the Ti in raw sewage, and this fraction was well removed by WWTP processes. Ti concentrations in effluents from this and several other WWTPs ranged from <5 to 15 microg/L and were nearly all present in the < 0.7 microm size fraction. As Ti was removed, it accumulated in settled solids at concentrations ranging from 1 to 6 microg Ti/mg. Ti-containing solids were imaged in sewage, biosolids, and liquid effluent as well as in commercial products containing engineered TiO2. Single nanoparticles plus spherical aggregates (50 nm to a few hundred nanometer in size) composed of sub-50 nm spheres of Ti and oxygen only (presumably TiO2) were observed in all samples. Significantly larger silicate particles containing a mixture of Ti and other metal atoms were also observed in the samples. To support the field work, laboratory adsorption batch and sequencing batch reactor experiments using TiO2 and activated sludge bacteria verified that adsorption of TiO2 onto activated sludge biomass occurs. Monitoring for TiO2 in the environment where WWTP liquid effluent is discharged (rivers, lakes, oceans) or biomass disposed (landfills, agriculture and soil amendments, incinerator off-gas or residuals) will increase our knowledge on the fate and transport of other nanomaterials in the environment
Article
A new method for determining the size of titanium dioxide particles is proposed and assayed in a commercial sunscreen product. Today many sun protection cosmetics incorporate physical UV filters as active ingredients, and there are no official methods for determining these compounds in sunscreen cosmetics. Here flow field-flow fractionation (FlFFF) has been tested, first to sort two different types of TiO2 nano- and microstandard materials (AeroxideTiO2 Degussa P-25 and TiO2 rutile 0.1-0.2-microm size) and then to fractionate TiO2 particles, extracted from a commercial sunscreen lotion. All the TiO2 FlFFF separations were detected by UV but during elution fractions were collected and their Ti content measured by inductively coupled plasma-atomic emission spectrometer (ICP-AES); the Ti concentration profiles obtained by ICP-AES were well correlated with the UV signals. The TiO2 particle mass-size distribution were calculated from the UV profiles. This methodology is relatively simple and rapid, and the sample treatment is as a whole easy and low cost.
Article
The contribution of atmospheric deposition to emissions of trace metals in stormwater runoff was investigated by quantifying wet and dry deposition fluxes and stormwater discharges within a small, highly impervious urban catchment in Los Angeles. At the beginning of the dry season in spring 2003, dry deposition measurements of chromium, copper, lead, nickel, and zinc were made monthly for 1 year. Stormwater runoff and wet deposition samples also were collected, and loading estimates of total annual deposition (wet+dry) were compared with annual stormwater loads. Wet deposition contributed 1-10% of the total deposition inside the catchment, indicating the dominance of dry deposition in semi-arid regions such as Los Angeles. Based on the ratio of total deposition to stormwater, atmospheric deposition potentially accounted for as much as 57-100% of the total trace metal loads in stormwater within the study area. Despite potential bias attributable to processes that were not quantified in this study (e.g., resuspension out of the catchment or sequestration within the catchment), these results demonstrate atmospheric deposition represents an important source of trace metals in stormwater to waterbodies near urban centers.
Article
In Norway the combined hydraulic capacity of all domestic wastewater treatment plants is relatively equally distributed between three major treatment plant types; mechanical, chemical, and combined chemical and biological. The Western coast from Lindesnes in the south to the Russian boarder in the North is dominated by mechanical treatment plants, constituting approximately 68% of the treatment capacity in that area. In the present study we report concentrations and removal efficiencies of polycyclic aromatic hydrocarbons (PAHs), nonylphenols, phthalates, polybrominated diphenyl ethers (PBDEs) and polychlorinated biphenyls (PCBs) found in five Norwegian wastewater treatment plants (WWTPs) applying different levels of treatment. Concentrations of organic micropollutants in the influents to the WWTPs were generally in the low range of what have been reported by others for domestic wastewater in Europe and North-America. More than 90% removal could be obtained for nonylphenols, PBDEs, and the more hydrophobic 4-6 ring PAHs by chemical precipitation, however, biological treatment appeared to be necessary for efficient removal of the less lipophilic 2 and 3 ring PAHs, the medium- to short-chained nonylphenol ethoxylates and diethyl phthalate. SigmaPCB(7) was removed by more than 90% by combined biological/chemical treatment, while removal efficiency by chemical treatment was not possible to estimate due to low inlet concentrations. Low or insignificant removals of PAHs, phthalates and nonylphenols with their ethoxylates were observed at the mechanical WWTP, which was in accordance with the minuscule removal of TOC.
Article
Manufacturers of clothing articles employ nanosilver (n-Ag) as an antimicrobial agent, but the environmental impacts of n-Ag release from commercial products are unknown. The quantity and form of the nanomaterials released from consumer products should be determined to assess the environmental risks of nanotechnology. This paper investigates silver released from commercial clothing (socks) into water, and its fate in wastewater treatment plants (WWTPs). Six types of socks contained up to a maximum of 1360 microg-Ag/g-sock and leached as much as 650 microg of silver in 500 mL of distilled water. Microscopy conducted on sock material and wash water revealed the presence of silver particles from 10 to 500 nm in diameter. Physical separation and ion selective electrode (ISE) analyses suggest that both colloidal and ionic silver leach from the socks. Variable leaching rates among sock types suggests that the sock manufacturing process may control the release of silver. The adsorption of the leached silver to WWTP biomass was used to develop a model which predicts that a typical wastewater treatment facility could treat a high concentration of influent silver. However, the high silver concentration may limitthe disposal of the biosolids as agricultural fertilizer.
Modelling Illicit Drug Fate in Sewers for Wastewater-based Epidemiology
  • P Ramin
Ramin, P., 2016. Modelling Illicit Drug Fate in Sewers for Wastewater-based Epidemiology. PhD. Technical University of Denmark.
Diurnal variations in the occurrence and the fate of hormones and antibiotics in activated sludge wastewater treatment in Oslo
  • R J B Peters
  • G Van Bemmel
  • Z Herrera-Rivera
  • H P F G Helsper
  • H J P Marvin
  • S Weigel
  • P C Tromp
  • A G Oomen
  • A G Rietveld
  • H Bouwmeester
  • H Leknes
  • H Liltved
  • K V Thomas
Peters, R.J.B., van Bemmel, G., Herrera-Rivera, Z., Helsper, H.P.F.G., Marvin, H.J.P., Weigel, S., Tromp, P.C., Oomen, A.G., Rietveld, A.G., Bouwmeester, H., 2014. Characterization of titanium dioxide nanoparticles in food products: analytical methods to define nanoparticles. J. Agric. Food Chem. 62 (27), 6285e6293. Pl osz, B.G., Leknes, H., Liltved, H., Thomas, K.V., 2010. Diurnal variations in the occurrence and the fate of hormones and antibiotics in activated sludge wastewater treatment in Oslo, Norway. Sci. Total Environ. 408 (8), 1915e1924.