Wastewater treatment plants as a pathway for microplastics: Development of a new approach to sample wastewater-based microplastics

Innovating Ferro-sonication approach for extracting microplastics from wastewater

For accurate and reliable analysis of microplastics (MPs) in wastewater (WW), it is imperative to comprehend the significance of pre-treating WW before analysis. The suspended solids (SS) in the matrix tend to adhere to the MPs during filtration, which interferes with the detection of the MPs. In this regard, the present study aims to develop and optimize a pretreatment method to improve the extraction efficiency of MPs from WW by reducing the SS. A combination of the Fenton reaction and ultrasonication, ferro-sonication (Fe-UlS), was proposed to digest and eliminate the SS from WW. This hybrid pretreatment, Fe-UlS, was optimized for ultrasonication amplitude, treatment time, and hydrogen peroxide dose using response surface methodology (RSM) with a Box-Behnken design, achieving a desirability of 0.984. The optimum conditions for the Fe-UlS, such as the (1:1) Fenton reagent ratio (0.05 M FeSO4: 30 % H2O2), ultrasonication amplitude (31 %), and total process time (30 min) were found to be statistically significant (p < 0.05). The developed method was then employed for the extraction of spiked polyethylene (PE), polypropylene (PP) and polyethylene terephthalate (PET) MPs in real WW and found efficient in removing 83 % of the TSS present in the primary influent were in 30 min at a temperature of 45 °C. Also, the method did not affect the physio-chemical characteristics of the MPs; however, the thermal analysis of PE and PP MPs showed a statistically significant decrease in the melting temperature, as proven by paired t-test analysis. Further, a non-targeted liquid chromatography-mass spectrometry (LC-MS) analysis proved that Fe-UlS is a stable process, as it did not cause any leaching of MPs under the optimum pretreatment conditions. Finally, Laser Direct-Infrared Imaging (LD-IR) analysis was conducted to validate the developed Fe-UlS pretreatment approach for MP analysis in real WW. About 3434 MPs were detected in 100 mL of WW primary influent, within the size range of 9 to 500 μm. This hybrid pretreatment approach not only streamlines WW sample processing but also reduces the required concentration of Fenton reagent and processing time, yielding accurate and reliable results for monitoring MPs in WW.

Assessment of microplastic pollution and polymer risk in the sediment compartment of the Limfjord, Denmark

Estuarine sediments intercept and temporarily retain microplastics before they reach the marine seafloor, impacting various organisms, including key commercial species. This highlights the critical need for research on microplastic exposure in these transitional environments. This study provides a detailed assessment of microplastic pollution in the sediment compartment of the Limfjord, a 1500 km2 large Danish fjord, and introduces the Polymer Hazard Index (PHI) as a tool for evaluating polymer-specific risks. Thirteen sediment samples were collected, covering an anthropogenic gradient along the fjord. State-of-the-art methods were applied for extracting and identifying (FPA-μFT-IR imaging) microplastics (10-5000 μm). Our results indicate that microplastic contamination is pervasive across all sampled locations with concentrations ranging from 273 to 4288 particles kg-1, with a predominance of small microplastics (<100 μm). The estimated mass-based concentrations ranged between 2.60 × 104-1.11 × 106 ng kg-1. Overall, we estimated a microplastic stock of 3.8 × 103-1.65 × 105 kg in the surface sediments of the Limfjord, i.e., some 2.5-110 kg km-2. The application of the PHI revealed significant risks associated with specific polymers, such as polyacrylonitrile (PAN) and acrylonitrile butadiene styrene (ABS), underscoring the importance of considering polymer-specific hazards in environmental assessments.

Assessing the presence of microplastic in agriculture soils irrigated with treated waste waters using Lumbricus sp.: Ecotoxicological effects

Global water scarcity entailed the use of treated wastewater (TWW) in agriculture, however, this water can vehiculate numerous pollutants into soil and further crops such as microplastics (MPs). To date, few studies had quantified the accumulation of MPs in soils and earthworms after irrigation with TWW as well as their toxicological effects. Hence, the main objective of the present work is to evaluate the toxicity of MPs using Lumbricus sp. earthworms collected from TWW irrigated soils with an increasing gradient of time (5 years, 16 years and 24 years). MPs determination in soil, as well as in earthworms were performed. The intestinal mucus was quantified, and cytotoxicity (Lysosomal membrane stability (LMS), Catalase (CAT) and glutathione-S-Transferase (GST) activities), neurotoxicity (Acetylcholinesterase activity (AChE)) and genotoxicity (Micronuclei frequency (MNi)) biomarker were assessed. Our results revealed that the use of TWW rendered MPs accumulation in earthworms' tissues and induce alteration on the intestinal mucus. An important cytotoxicity time-depending was observed being associated with an increase on genotoxicity. Overall, the present investigation highlights the ecotoxicological risk associated with the use of TWWs as an important driver of MPs and consequently measures are necessary to reduce MPs in wastewater treatment plans to improve this non-conventional water quality.

Effect of shape on the transport and retention of nanoplastics in saturated quartz sand

Nanoplastics (NPs) pose great challenges to soil-groundwater systems. This study investigated the transport and retention of self-synthesized 0.5-μm polystyrene NPs with different shapes using column experiments. The regular NPs were with spherical shapes, while the irregular NPs were with toroid-like shapes. The toroid-like shapes were the irregular shapes (with low aspect ratio) which have not been studied yet. The explorations were carried out in both 5-25 mM NaNO3 and 1-10 mM Ca(NO3)2 solutions. Both breakthrough curves (BTCs) and retained profiles (RPs) were monitored. Our findings uncovered a clear disparity in the transport of irregular and regular NPs, with irregular particles exhibiting lower transport ability compared to the regular ones. For example, the average breakthrough plateaus of the regular and irregular NPs were ∼0.9 and ∼0.5, respectively, in 10 mM NaNO3. In-depth theoretical analysis indicated that the lower XDLVO interaction energy barrier between the irregular NPs and quartz sand was one factor, and the greater margination of irregular NPs on quartz sand, as verified by the numerical simulation, was another factor leading to the decreased transport and increased retention of the irregular NPs. The obtained results highlighted the significance of considering particle shape in future modelling and predicting the fate of NPs in real environmental circumstances.

Spatial distribution and risk assessment of microplastics in surface waters of the St. Lawrence Estuary

Development of effective prevention and mitigation strategies for marine plastic pollution requires a better understanding of the pathways and transport mechanisms of plastic waste. Yet the role of estuaries as a key interface between riverine inputs of plastic pollution and delivery to receiving marine environments remains poorly understood. This study quantified the concentration and distribution of microplastics (MPs) (50-3200 μm) in surface waters of the St. Lawrence Estuary (SLE) in eastern Canada. Microplastics were identified and enumerated based on particle morphology, colour, and size class. Fourier Transform Infrared (FTIR) spectroscopy was used on a subset of particles to identify polymers. Generalized linear models (Gamma distribution with log-link) examined the relationship between MP concentrations and oceanographic variables and anthropogenic sources. Finally, a risk assessment model, using MP concentrations and chemical hazards based on polymer types, estimated the MP pollution risk to ecosystem health. Mean surface MP concentration in the SLE was 120 ± 42 SD particles m-3; MP concentrations were highest in the fluvial section and lowest in the Northwest Gulf of St. Lawrence. However, MP concentrations exhibited high heterogeneity along the length and width of the SLE. Microplastics were elevated at stations located closer to wastewater treatment plant outflows and downstream sites with more agricultural land. Black, blue, and transparent fibers and fragments ≤250 μm were most commonly encountered. Predominant polymer types included polyethylene terephthalate, regenerated cellulose, polyethylene, and alkyds. While the overall risk to ecosystem health in the entire estuary was considered low, several stations, particularly near urban centres were at high or very high risk. This study provides new insights into the quantification and distribution of MPs and first estimates of the risk of MP pollution to ecosystem health in one of the world's largest estuaries.

Nationwide evaluation of microplastic properties in municipal wastewater treatment plants in South Korea

Wastewater treatment plants (WWTPs) are considered a significant microplastic discharge source. To evaluate the amount and characteristics of microplastics discharged from WWTPs in South Korea, we selected 22 municipal WWTPs nationally and investigated microplastics at each treatment stage. The mean microplastic removal efficiency by WWTPs was >99%, and most of the microplastics were removed by sedimentation with the second clarifier during wastewater treatment. Consequently, the microplastic removal efficiency of WWTPs did not significantly differ from that of the adopted wastewater treatment technology because a second clarifier was applied in most WWTPs. However, for WWTPs operating a tertiary treatment process, the removal efficiency was enhanced compared with that of WWTPs discharging after a second clarifier. Although the microplastic removal efficiency was high by WWTP, the discharge contribution to the water environment could not be ignored because of the amount of treated wastewater, resulting in an increase of 5.8-270.9 items/m3 of microplastics in the receiving water. The characteristics of microplastics in WWTPs, including their components, shape, and size, were also evaluated. The most detected components included polytetrafluoroethylene and polyester. Most microplastics detected were categorized as fragments and fibers, while other types were hardly detected. The size of more than 70% of the microplastics detected in WWTPs was under 300 μm, implying that the size of microplastics required to control in WWTPs was much smaller than the defined size of microplastics. An evaluation of the correlation between other pollution factors and microplastic abundance did not reveal positive correlations, and microplastic occurrence was not affected by changing seasons, which may need to be evaluated with further studies. Research should also be performed on the effect of influent sources on the level of microplastic abundance and fate of ultrafine plastics in WWTPs.

Microplastic characterization and assessment of removal efficiency in an urban and industrial wastewater treatment plant with submarine emission discharge

Wastewater treatment plants (WWTPs) are significant contributors to microplastic (MP) pollution in marine ecosystems when they are inefficient. This study aimed to evaluate the effectiveness of microplastic removal from the effluent of the Anza WWTP (Morocco), which processes industrial and urban wastewater using a lamellar decantation system combined with a submarine emissary for treated water discharge. Additionally, this study investigated the presence of microplastics in the Atlantic seawater where treatment plant effluent is released. Microplastics were collected and extracted from wastewater and seawater samples to assess their abundance, shape, size, polymer type, and removal rates in the treatment plant. The findings revealed an average MP concentration of 1114 ± 90 MPs/L in the influent and 607 ± 101 MPs/L in the effluent, indicating a removal efficiency of 46 %. Seasonal analysis revealed the highest MP concentrations during the summer, with 2181.33 MPs/L in the influent and 1209 MPs/L in the effluent. Seawater samples from the discharge zone of the submarine emissary had an average MP concentration of 1600 MPs/m3. Characterization of the MPs revealed that fibers were the most common form of MPs in all the samples. The 500-100 μm size fraction was predominant in the WWTP samples, while MPs smaller than 1 mm were more abundant in the seawater samples. Seven polymer types were identified using attenuated total reflection fourier transform infrared spectroscopy (ATR-FTIR), with PET, PE, PVC, PA, PS, PP, and EVA being the most prevalent. Scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM/EDX) revealed various degrees of weathering and chemical elements adhering to the MP surfaces. The results of this study provide valuable insights into the effectiveness of conventional treatment systems in removing microplastics and offer a reference for developing management strategies to mitigate MP pollution in Morocco's marine ecosystems.

Removal of microplastics from aqueous media using activated jute stick charcoal

Microplastics (MPs), which are repositories of various pollutants, have significant effects on the people and the environment. Therefore, there is an urgent need for efficient and eco-friendly techniques to eliminate microplastics from water-based environments. This study introduces a new method for producing jute stick-activated charcoal (JSAC) by placing jute sticks on high-temperature pyrolysis without oxygen, followed by chemical activation with HCl. This process greatly enhances the adsorption capacity of JSAC for polyvinylchloride-based microplastics (PVC-MPs). JSAC was characterized using UV-Vis, FT-IR, XRD, and SEM studies both before and after adsorption. The study investigated the influence of pH, adsorbent quantity, and contact time on the optimization of the JSAC process. The PVC-MPs exhibited a maximum adsorption capacity of 94.12 % for the target MPs (5 g L-1) within 120 min when 10 g L-1 of JSAC was added at pH 7. This work also examined adsorption rate and various isotherm models. Adsorption kinetics analysis reveals electrostatic, hydrogen bond, π-π, and hydrophobic interactions are the combined forces responsible for MPs adsorption onto JSAC. However, the decrease in hydrophobicity in acidic or basic media led to a decrease in adsorption. The isotherm analysis was conducted using the Langmuir isotherm model, and predicted the maximum adsorption capacity of PVC-MPs to be 4.4668 mg/g. Furthermore, by employing density functional theory, the interaction energy after PVC-MP adsorption was calculated to be -269 kcal/mol, demonstrating robust adsorption and agreement with the experimental findings. Due to its large surface area and porous structure containing many functional groups, JSAC can potentially be used to treat MP contamination in water.

Plastic pollution in agricultural landscapes: an overlooked threat to pollination, biocontrol and food security

Ecosystem services such as pollination and biocontrol may be severely affected by emerging nano/micro-plastics (NMP) pollution. Here, we synthesize the little-known effects of NMP on pollinators and biocontrol agents on the organismal, farm and landscape scale. Ingested NMP trigger organismal changes from gene expression, organ damage to behavior modifications. At the farm and landscape level, NMP will likely amplify synergistic effects with other threats such as pathogens, and may alter floral resource distributions in high NMP concentration areas. Understanding exposure pathways of NMP on pollinators and biocontrol agents is critical to evaluate future risks for agricultural ecosystems and food security.

Topic modeling discovers trending topics in global research on the ecosystem impacts of microplastics

The ecological threats of microplastics (MPs) have sparked research worldwide. However, changes in the topics of MP research over time and space have not been evaluated quantitatively, making it difficult to identify the next frontiers. Here, we apply topic modeling to assess global spatiotemporal dynamics of MP research. We identified nine leading topics in current MP research. Over time, MP research topics have switched from aquatic to terrestrial ecosystems, from distribution to fate, from ingestion to toxicology, and from physiological toxicity to cytotoxicity and genotoxicity. In most of the nine leading topics, a disproportionate amount of independent and collaborative research activity was conducted in and between a few developed countries which is detrimental to understanding the environmental fates of MPs in a global context. This review recognizes the urgent need for more attention to emerging topics in MP research, particularly in regions that are heavily impacted but currently overlooked.

Coagulation performance and mechanism of different novel covalently bonded organic silicon-aluminum/iron composite coagulant for As(V) removal from water: The role of hydrolysate species and the effect of coexisting microplastics

Arsenate [As(V)] pollution is a challenge for water treatment, and the effect of coexisting microplastics (MPs) on As(V) removal is still not clear. In this study, series novel covalently bonded organic silicon-aluminum/iron composite coagulants (CSA/F) with different Al/Fe molar ratios were prepared for enhancing As(V) removal. The effect mechanism of MPs (PS MPs and PS-COOH MPs) on As(V) removal by using CSAF coagulation was analyzed. CSAF and CSF showed significantly better As(V) removal performance than other coagulants under the same conditions, especially CSF, more than 90 % As(V) removal was achieved at dosage of 20 mg/L and pH of 4.0-8.0. Interestingly, the introduction of silane coupling agent and the increase of Fe content in CSA/F changed the Al/Fe species distribution. Charge neutralization dominant in As(V) removal by using CSA, whereas adsorption and net sweeping contributed to As(V) coagulation by using CSAF and CSF with higher iron proportion at neutral pH. 3 µm MPs were removed by net sweeping of amorphous Al/Fe hydroxides, while 26 µm MPs were charge-neutralized or surface adsorbed by coagulant hydrolysates. The aliphatic C-H and -COOH functional groups of MPs were the main sites of hydrogen bonding adsorption with the hydroxyl groups of coagulant hydrolysates. This study is conducive to mitigating the environmental toxicity of arsenic and provides new insights into the interaction mechanism between composite pollutants and coagulants in waters.

Beyond microbeads: Examining the role of cosmetics in microplastic pollution and spotlighting unanswered questions

The presence of microplastics in cosmetics and personal care products (C&PCPs) has been increasingly in the public eye since the early 2010s. Despite increasing research into the potential environmental and health effects of microplastics, most research to date on microplastics in C&PCPs has investigated "rinse-off" products, while the potential impacts of "leave-on" C&PCPs have been largely neglected, despite these products being purchased in greater volumes and often having two or more microplastic ingredients in their formulations(CosmeticsEurope, 2018b). This review aims to synthesize the current knowledge of microplastic in C&PCPs, assessing the potential environmental and human health impacts of C&PCPs and discussing the regulatory implications. The lack of studies on leave-on C&PCPs is significant, suggesting a severe knowledge gap regarding microplastic presence in, and emissions from, C&PCPs. There is a noticeable lack of studies on the (eco)toxicological consequences of microplastic exposure from C&PCPs. As a result, significant aspects of microplastic contamination may be overlooked in the microplastic legislations emerging globally (including from the European Commission), which intend to restrict microplastic use in C&PCPs but focus on rinse-off C&PCPs only. This review highlights the potential consequences of microplastics in leave-on C&PCPs for regulatory decision-making, particularly as alternatives to microplastics are considered during the phase-out periods and spotlights the need for sufficient monitoring and research on these alternatives, to avoid unforeseen consequences.

Innovative solutions for the removal of emerging microplastics from water by utilizing advanced techniques

Microplastic pollution is one of the most pressing global environmental problems due to its harmful effects on living organisms and ecosystems. To address this issue, researchers have explored several techniques to successfully eliminate microplastics from water sources. Chemical coagulation, electrocoagulation, magnetic extraction, adsorption, photocatalytic degradation, and biodegradation are some of the recognized techniques used for the removal of microplastics from water. In addition, membrane-based techniques encompass processes propelled by pressure or potential, along with sophisticated membrane technologies like the dynamic membrane and the membrane bioreactor. Recently, researchers have been developing advanced membranes composed of metal-organic frameworks, MXene, zeolites, carbon nanomaterials, metals, and metal oxides to remove microplastics. This paper aims to analyze the effectiveness, advantages, and drawbacks of each method to provide insights into their application for reducing microplastic pollution.

Understanding and addressing microplastic pollution: Impacts, mitigation, and future perspectives

Improper disposal of household and industrial waste into water bodies has transformed them into de facto dumping grounds. Plastic debris, weathered on beaches degrades into micro-particles and releases chemical additives that enter the water. Microplastic contamination is documented globally in both marine and freshwater environments, posing a significant threat to aquatic ecosystems. The small size of these particles makes them susceptible to ingestion by low trophic fauna, a trend expected to escalate. Ingestion leads to adverse effects like intestinal blockages, alterations in lipid metabolism, histopathological changes in the intestine, contributing to the extinction of vulnerable species and disrupting ecosystem balance. Notably, microplastics (MPs) can act as carriers for pathogens, potentially causing impaired reproductive activity, decreased immunity, and cancer in various organisms. Studies have identified seven principal sources of MPs, including synthetic textiles (35%) and tire abrasion (28%), highlighting the significant human contribution to this pollution. This review covers various aspects of microplastic pollution, including sources, extraction methods, and its profound impact on ecosystems. Additionally, it explores preventive measures, aiming to guide researchers in selecting techniques and inspiring further investigation into the far-reaching impacts of microplastic pollution, fostering effective solutions for this environmental challenge.

Antarctic wastewater: A local source of microplastic pollution

Microplastic (MP) particles can be found all around the planet, even in Antarctica where they can be locally originated or transported by marine currents and winds. In this communication, we identify and report for the first time the contribution of a wastewater treatment plant (WWTP) as a local source of MP particles in the region. The analysis of the entire sample using micro-Raman spectroscopy revealed an MP concentration that ranged from 64 to 159 particles per liter of wastewater. >90 % of the identified particles were smaller than 50 μm. Among those analyzed, microplastics were identified as polyethylene, polypropylene, polyvinyl chloride, polytetrafluoroethylene, polyethylene terephthalate, and polystyrene. These findings demonstrate the need for urgent policies and technologies to mitigate this MP contamination source.

Enhancing microplastic removal from natural water using coagulant aids

Microplastic (MP) pollution poses a significant environmental challenge, underscoring the need for improved water treatment methods. This study investigates the effectiveness of coagulation, flocculation, and sedimentation processes for removing microbeads, focusing on key factors that influence removal efficiency. Among the coagulants tested, polyaluminium chloride (PAC) demonstrated superior performance by enhancing the aggregation of microplastics with flocs. Optimal treatment conditions were determined to be 0.4 mmol/L PAC and 3 mg/L polyacrylamide (PAM) at pH 8 (before adding PAC), with rapid stirring at 240 rpm for 1 min, followed by slow stirring at 35 rpm for 13 min, and a sedimentation period of 25 min. Under these conditions, removal efficiencies exceeded 95 % for a range of microbeads (10-1000 μm: Polystyrene (PS), Polypropylene (PP), Polyvinyl chloride (PVC), Polyamide (PA), Polyethylene (PE), and Polyurethane (PU)) from natural water samples. Without PAM, PAC alone achieved a 97 % removal rate for PS microbeads. The addition of PAM maintained high removal efficiency, while aluminium sulphate and ferric chloride were less effective, with removal rates of 67 % and 48 % for PS microbeads, respectively. PAM enhanced MP removal across various coagulants and microbead types, with maximum efficiency observed at PAM concentrations of ≥3 mg/L. The treatment also demonstrated that organic matter in Regent's Park pond water could further improve MP removal. Size significantly impacts removal efficiency: larger microbeads (1 mm to >250 μm) were removed more effectively (95 %) compared to smaller ones (10 to <250 μm), which had a lower removal rate of 49 %. Denser microbeads like PVC (density 1.38 g/cm³) settled more efficiently than lighter microbeads such as PE (density 0.97 g/cm³). These findings suggest a need for advanced technologies to better remove lighter, smaller MPs from water.

The significant impact of MPs in the industrial/municipal effluents on the MPs abundance in the Nakdong River, South Korea

Owing to extensive plastic consumption, wastewater from households, business establishments, and industrial activities have been recognised as a significant contributor to microplastics (MPs) in aquatic environments. This case study represents the first investigation of MPs in the Nakdong River, Republic of Korea, that traverses through the largest industrial complex midstream and densely populated cities of Daegu and Busan downstream before flowing into the sea. Monitoring of MP abundance in effluents discharged from three municipal, two industrial, and one livestock wastewater treatment plant (WWTP) into the Nakdong River was conducted over four seasons from August 2022 to April 2023. Identification and quantification of MPs were performed using micro-Fourier transform infrared spectrometry. Seasonal variation in MPs in the Nakdong River was found to be strongly influenced by the nearest upstream WWTPs and rivers, exhibiting a linear relationship that decreased gradually with increasing distance from the WWTPs. The average concentrations of MPs in the six effluent sources ranged from 101 ± 13 to 490 ± 240 particles/L during the yearly monitoring period, while MP concentrations in the river ranged between 79 ± 25 and 120 ± 43 particles/L. Industrial effluents contained higher amounts of discharged MPs (314 ± 78 particles/L) than municipal sources (201 ± 61 particles/L). Notably, two municipal WWTPs, located in the highly densely populated city, discharged the highest total MP amounts per day and released the greatest volumes of effluents. This study provides valuable insights into the monitoring and impact of effluents on MPs in rivers, which could inform MP treatment and management strategies for in river and marine environments.

Microplastics are effective carriers of bisphenol A and facilitate its escape from wastewater treatment systems

Microplastics (MPs) pollution is a major issue in aquatic environments. Wastewater treatment plants are significant point sources of MPs, which may also be carriers of organic pollutants. We analyzed MP number, shape, color, and polymer type distribution in sewage wastewater treatment plants. The potential of MPs to act as carriers for typical organic pollutants in sewage, such as bisphenol A (BPA), was also assessed. The predominant MPs in the influent were fibers, primarily transparent and black in color, and composed of polyethylene, polypropylene, and polystyrene. During wastewater treatment, the concentration of MPs decreased from 10.89 items per L in the influent to 0.89 items per L in the treated effluent, with significant differences in treatment efficiency at different stages. In the simulated wastewater, the three predominant MPs exhibited certain adsorption capacities for bisphenol A. Changing the temperature and pH within the range expected for wastewater could interfere with the interactions between MPs and bisphenol A, with a limited impact on adsorption. The results show that although wastewater treatment plants intercept a significant amount of MP, a considerable number of them enter the aquatic environment daily because of the high volume of wastewater discharge. These MPs, which carry pollutants such as bisphenol A, may threaten the health of fish and other aquatic organisms. However, by scientifically adjusting operational parameters, wastewater treatment plants could become "controllable sources" of MP compound pollutants.

A Scalable and Surfactant-Free Emulsion Method for Producing Microbeads from Varied Biomass Feedstocks

Despite national and international regulations, plastic microbeads are still widely used in personal care and consumer products (PCCPs). These exfoliants and rheological modifiers cause significant microplastic pollution in natural aquatic environments. Microbeads from nonderivatized biomass like cellulose and lignin can offer a sustainable alternative to these nondegradable microplastics, but processing this biomass into microbeads is challenging due to limited viable solvents and high biomass solution viscosities. To produce biomass microbeads of the appropriate size range for PCCPs (ca. 200-800 μm diameter) with shapes and mechanical properties comparable to those of commercial plastic microbeads, we used a surfactant-free emulsion/precipitation method, mixing biomass solutions in 1-ethyl-3-methylimidazolium acetate (EMImAc) with various oils and precipitating with ethanol. While yield of microbeads within the target size range highly depends on purification conditions, optimized protocols led to >90% yield of cellulose microbeads. Kraft lignin was then successfully incorporated into beads at up to 20 wt %; however, higher lignin contents result in emulsion destabilization unless surfactant is added. Finally, the microbead shape and surface morphology can be tuned using oils of varying viscosities and interfacial tensions. Dripping measurements and pendant drop tensiometry confirmed that the higher affinity of cellulose for certain oil/IL interfaces largely controlled the observed surface morphology. This work thus outlines how biomass composition, oil viscosity, and interfacial properties can be altered to produce more sustainable microbeads for use in PCCPs, which have desirable mechanical properties and can be produced over a wide range of shapes and surface morphologies.

Unraveling the effects and mechanisms of microplastics on anaerobic fermentation: Exploring microbial communities and metabolic pathways

To investigate the effects of microplastics (MPs) on hydrolysis, acidification and microbial characteristics during waste activated sludge (WAS) anaerobic fermentation process, five different kinds of MPs were added into the WAS fermentation system and results indicated that, compared to the control group, the addition of polyvinyl chloride (PVC)-MPs exhibited the least inhibition on volatile fatty acids (VFAs), reducing them by 13.49 %. Conversely, polyethylene (PE)-MPs resulted in the greatest inhibition, with a reduction of 29.57 %. MPs, while accelerated the dissolution of WAS that evidenced by an increase of lactate dehydrogenase (LDH) release, concurrently inhibited the activities of relevant hydrolytic enzymes (α-Glucosidase, protease). For microbial mechanisms, MPs addition affected the proliferation of key microorganisms (norank_f_Bacteroidetes_vadinHA17, Ottowia, and Propioniclava) and reduced the abundance of genes associated with hydrolysis and acidification (pfkb, gpmI, ilvE, and aces). Additionally, MPs decreased the levels of key hydrolytic and acidogenic enzymes to inhibit hydrolysis and acidification processes. This research provides a basis for understanding and unveils impact mechanisms of the impact of MPs on sludge anaerobic fermentation.

Microplastics in Hong Kong's marine waters: Impact of rainfall and Pearl River discharge

This study provided a systematic investigation of microplastics in Hong Kong's surface marine waters during the pandemic from 2019 to 2021. Microplastics (2.07 ± 4.00 particles/m3) exhibited significant temporal variations with higher abundance in the wet season, without a consistent trend after the mandatory mask-wearing requirement was announced. The impact of pandemic restrictions on microplastic distribution was found to be relatively minor. However, significant correlations between microplastic abundances and rainfall highlighted the substantial contribution of local emissions through surface runoff. Notably, sites in closer proximity to the Pearl River Delta exhibited higher microplastic abundances, indicating their association with emission sources. The influence of rainfall and adverse weather on marine microplastic loads demonstrated different sensitivities among various locations but can generally last for one month. These results revealed the impact of seasonal rainfall on coastal microplastics and emphasized the need for efforts to reduce microplastic discharge from land-based sources.

Seasonal variation in abundance and characteristics of microplastic in sewage sludge from major cities across the upper stretch of River Ganga, India

Microplastic (MP) load in urban sewage sludge could vary annually in wastewater treatment plants (WWTPs) depending on seasonal precipitation and human activities. We investigated the seasonal dynamics in abundance and characterization of MP loading in WWTPs located in two cities across River Ganga, India's ecologically sensitive upper stretch. During a 12-month seasonal sampling (pre-monsoon, monsoon, and post-monsoon), sludge samples (n = 36) (primary sludge, PS; drying bed sludge, DBS) were collected and analyzed for load, polymer types, shape, colour, and size (20-1000 µm). Across the three seasons, MP concentrations (particles/kg) were found to be in the ranges of 93.4 ± 5.0 × 103-189.4 ± 11 × 103 in the PS and 39.6 ± 4.0 × 103-152.0 ± 7 × 103 in the DBS. The trend of MP loading was in the following order: monsoon > post-monsoon > pre-monsoon. The dominant MP size was 50-200 µm (36.22%) followed by 20-50 µm (27.65%), 200-500 µm (24.55%) and 500-1000 µm (11.58%). ATR-FTIR results revealed polypropylene, polyethylene terephthalate, polyvinyl chloride, and nylon dominating MP in sludge. This study highlights the importance of long-term monitoring of MP loading in sewage sludge to offer a more accurate estimate of MP contamination in sludge from WWTPs and develop a possible mechanism for its elimination to safeguard the environment.

The aging of microplastics exacerbates the damage to photosynthetic performance and bioenergy production in microalgae (Chlorella pyrenoidosa)

The toxicity of microplastics (MPs) on freshwater plants has been widely studied, yet the influence of aged MPs remains largely unexplored. Herein, we investigated the influence of polyvinyl chloride (PVC) MPs, both before and after aging, at different environmentally relevant concentrations on Chlorella pyrenoidosa, a freshwater microalgae species widely recognized as a valuable biomass resource. During a 96-h period, both virgin and aged MPs hindered the growth of C. pyrenoidosa. The maximum growth inhibition rates were 32.40 % for virgin PVC at 250 mg/L and 44.72 % for aged PVC at 100 mg/L, respectively. Microalgae intracellular materials, i.e., protein and carbohydrate contents, consistently decreased after MP exposure, with more pronounced inhibition observed with aged PVC. Meanwhile, the MP aging significantly promoted the nitrogen uptake of C. pyrenoidosa, i.e., 1693.45 ± 42.29 mg/L (p < 0.01), contributing to the production of humic acid-like substances. Additionally, aged PVC induced lower chlorophyll a and Fv/Fm when compared to virgin PVC, suggesting a more serious inhibition of the photosynthesis process of microalgae. The toxicity of MPs to C. pyrenoidosa was strongly associated with intercellular oxidative stress levels. The results indicate that MP aging exacerbates the damage to photosynthetic performance and bioenergy production in microalgae, providing critical insights into the toxicity analysis of micro(nano)plastics on freshwater plants.

Characterization of HDPE microparticles in sludge aerobic digestion and their influence on the process

The occurrence of microplastics (MPs) in wastewater has been studied in the last years. The high efficiency of their removal from wastewater is linked to their transfer to the sludge. In this work, the effect of high-density polyethylene (HDPE) on aerobic digestion was evaluated and these MPs were monitored, characterizing them by three different techniques. Two parallel batch digesters were monitored. AD-Control (meaning Aerobic Digester) operated as a reference, with no external HDPE particles, whereas these polymeric fragments were introduced to the second aerobic digester (AD-HDPE) using ring pulls as microplastic support. FTIR, Raman spectroscopies and fluorescence analysis of these microparticles showed some relevant results that should be highlighted. Higher fluorescence appeared after 7 days in the digester. It coincided with an increase of active volatile suspended solids (AVSS) in the AD-HDPE, which means that an increase of the microbial activity took place. Despite the presence of HDPE particles in the sludge, the digester performance was not compromised. Besides, the HDPE particles did not affect the microbial diversity (Shannon index) of the bacterial community at the end of the experiment compared to the bacterial community of the aerobic digester control tank. Based on the analysis of the relative abundances of microbial taxa, it was concluded that HDPE had selective effects on sludge microbial community, increasing the relative abundance of Bacteroridota phylum.

Microplastics in aquatic systems: An in-depth review of current and potential water treatment processes

Plastic products, despite their undeniable utility in modern life, pose significant environmental challenges, particularly when it comes to recycling. A crucial concern is the pervasive introduction of microplastics (MPs) into aquatic ecosystems, with deleterious effects on marine organisms. This review presents a detailed examination of the methodologies developed for MPs removal in water treatment systems. Initially, investigating the most common types of MPs in wastewater, subsequently presenting methodologies for their precise identification and quantification in aquatic environments. Instruments such as scanning electron microscopy, dynamic light scattering, Fourier transform infrared spectroscopy, Raman spectroscopy, surface-enhanced Raman spectroscopy, and Raman tweezers stand out as powerful tools for studying MPs. The discussion then transitions to the exploration of both existing and emergent techniques for MPs removal in wastewater treatment plants and drinking water treatment plants. This includes a description of the core mechanisms that drive these techniques, with an emphasis on the latest research developments in MPs degradation. Present MPs removal methodologies, ranging from physical separation to chemical and biological adsorption and degradation, offer varied advantages and constraints. Addressing the MPs contamination problem in its entirety remains a significant challenge. In conclusion, the review offers a succinct overview of each technique and forwards recommendations for future research, highlighting the pressing nature of this environmental dilemma.

Occurrence Characteristics and Ecotoxic Effects of Microplastics in Environmental Media: a Mini Review

The issue of environmental pollution caused by the widespread presence of microplastics (MPs) in environmental media has garnered significant attention. However, research on MPs pollution has mainly focused on aquatic ecosystems in recent years. The sources and pollution characteristics of MPs in the environment, especially in solid waste, have not been well-described. Additionally, there are few reports on the ecotoxicity of MPs, which highlights the need to fill this gap. This review first summarizes the occurrence characteristics of MPs in water, soil, and marine environments, and then provides an overview of their toxic effects on organisms and the relevant mechanisms. This paper also provides an outlook on the hotspots of research on pollution characterization and ecotoxicity of MPs. Finally, this review aims to provide insights for future ecotoxicity control of MPs. Overall, this paper expands our understanding of the pollution characteristics and ecological toxicity of MPs in current environmental media, providing forward-looking guidance for future research.

Research priorities on microplastics in marine and coastal environments: An Australian perspective to advance global action

Plastic and microplastic contamination in the environment receive global attention, with calls for the synthesis of scientific evidence to inform actionable strategies and policy-relevant practices. We provide a systematic literature review on microplastic research across Australian coastal environments in water, sediment and biota, highlighting the main research foci and gaps in information. At the same time, we conducted surveys and workshops to gather expert opinions from multiple stakeholders (including researchers, industry, and government) to identify critical research directions to meet stakeholder needs across sectors. Through this consultation and engagement process, we created a platform for knowledge exchange and identified three major priorities to support evidence-based policy, regulation, and management. These include a need for (i) method harmonisation in microplastic assessments, (ii) information on the presence, sources, and pathways of plastic pollution, and (iii) advancing our understanding of the risk of harm to individuals and ecosystems.

Occurrence, detection and ecotoxicity of microplastics in selected environments-a systematic appraisal

Microplastics (MPs) are being released into the environment in large quantities, especially in less developed parts of the world. This group of pollutants is mostly leached into the environment through heavy plastic dumpsites, pharmaceutical and personal care product containers, hospital wastes, plastic package accessories, and litter from food packaging. Consequently, these compounds are found in different compartments of the ecosystem, such as soils, sediments, biota, and, surprisingly, drinking water. The present study systematically appraised recent studies on MP pollution in the Asian and African environments. It also summarized the trends in the methods for the environmental monitoring of MPs and the removal strategies that have been employed. From the data gathered, the two key instrumentations involved are the microscopes for visualization and the Fourier transform-infra-red (FT-IR) spectrometer to classify or characterize the MPs. Based on the surveyed works of literature, China and South Africa have relatively more information on MP contamination of diverse matrices within their countries. Meanwhile, studies on the status of MP contamination should be conducted across all countries. Hence, this study becomes an eye-opener regarding the commencement of research works on the MP contamination of the environment, especially in other Asian and African countries with little or no information. Furthermore, the literature on ecotoxicity studies of MPs was investigated to ascertain the toxic nature of these compounds. This aspect of research is vital because it serves as a prerequisite for the remediation of these compounds. Microplastics have been declared lethal to biotic components, so all hands must be on deck to continuously remove them from the environment.

Characterization and removal of microplastics in the Guheshwori Wastewater Treatment Plant, Nepal

Contamination of river water systems by microplastic particles (MPPs) is one of the emerging global environmental concerns with potentially widespread ecological, socioeconomic, and health implications. A wastewater treatment plant (WWTP) processes and treats wastewater to remove pollutants and release safe water into the environment. There has been limited research on the characterization of microplastics and their removal in WWTP in South Asia. In this work, we report on the characterization of microplastics in wastewater and sludge samples (n = 300) from Guheshwori WWTP located on the bank of the Bagmati River in Kathmandu city, Nepal representing inlet, secondary aeration tank (SAT), outlet, and sludge from November 2021 to November 2022. On average, we detected 31.2 ± 17.3 MPPs/L, 11.2 ± 9.4 MPPs/L, 8.5 ± 5.6 MPPs/L, and 6.6 ± 4.8 MPPs/g in the samples collected from inlet, SAT, outlet, and sludge, respectively. Commonly found MPPs were in the form of fiber, fragments, foam, and pellets. Largely, MPPs were red, yellow, white, blue, and black. Among the 44 μm - 150 μm, 150 μm - 500 μm and 500 μm - 5 mm categories of size fractions, the most dominant fractions were 500 μm - 150 μm in inlet, SAT, and sludge, and 150 μm - 44 μm in the outlet sampling unit. The Guheshwori WWTP was able to remove 72.5 % of MPPs on average, that mostly occurred in the inlet. The effluent released into the river and the sludge still contained a significant number of MPPs.

Accumulation of antibiotics in the environment: Have appropriate measures been taken to protect Canadian human and ecological health?

In Canada, every day, contaminants of emerging concern (CEC) are discharged from waste treatment facilities into freshwaters. CECs such as pharmaceutical active compounds (PhACs), personal care products (PCPs), per- and polyfluoroalkyl substances (PFAS), and microplastics are legally discharged from sewage treatment plants (STPs), water reclamation plants (WRPs), hospital wastewater treatment plants (HWWTPs), or other forms of wastewater treatment facilities (WWTFs). In 2006, the Government of Canada established the Chemicals Management Plan (CMP) to classify chemicals based on a risk-priority assessment, which ranked many CECs such as PhACs as being of low urgency, therefore permitting these substances to continue being released into the environment at unmonitored rates. The problem with ranking PhACs as a low priority is that CMP's risk management assessment overlooks the long-term environmental and synergistic effects of PhAC accumulation, such as the long-term risk of antibiotic CEC accumulation in the spread of antibiotic resistance genes. The goal of this review is to specifically investigate antibiotic CEC accumulation and associated environmental risks to human and environmental health, as well as to determine whether appropriate legislative strategies are in place within Canada's governance framework. In this research, secondary data on antibiotic CEC levels in Canadian and international wastewaters, their potential to promote antibiotic-resistant residues, associated environmental short- and long-term risks, and synergistic effects were all considered. Unlike similar past reviews, this review employed an interdisciplinary approach to propose new strategies from the perspectives of science, engineering, and law.

Harnessing Magnetic Nanoparticles for the Effective Removal of Micro- and Nanoplastics: A Critical Review

The spread of micro- (MPs) and nanoplastics (NPs) in the environment has become a significant environmental concern, necessitating effective removal strategies. In this comprehensive scientific review, we examine the use of magnetic nanoparticles (MNPs) as a promising technology for the removal of MPs and NPs from water. We first describe the issues of MPs and NPs and their impact on the environment and human health. Then, the fundamental principles of using MNPs for the removal of these pollutants will be presented, emphasizing that MNPs enable the selective binding and separation of MPs and NPs from water sources. Furthermore, we provide a short summary of various types of MNPs that have proven effective in the removal of MPs and NPs. These include ferromagnetic nanoparticles and MNPs coated with organic polymers, as well as nanocomposites and magnetic nanostructures. We also review their properties, such as magnetic saturation, size, shape, surface functionalization, and stability, and their influence on removal efficiency. Next, we describe different methods of utilizing MNPs for the removal of MPs and NPs. We discuss their advantages, limitations, and potential for further development in detail. In the final part of the review, we provide an overview of the existing studies and results demonstrating the effectiveness of using MNPs for the removal of MPs and NPs from water. We also address the challenges that need to be overcome, such as nanoparticle optimization, process scalability, and the removal and recycling of nanoparticles after the completion of the process. This comprehensive scientific review offers extensive insights into the use of MNPs for the removal of MPs and NPs from water. With improved understanding and the development of advanced materials and methods, this technology can play a crucial role in addressing the issues of MPs and NPs and preserving a clean and healthy environment. The novelty of this review article is the emphasis on MNPs for the removal of MPs and NPs from water and a detailed review of the advantages and disadvantages of various MNPs for the mentioned application. Additionally, a review of a large number of publications in this field is provided.

Decoding the molecular concerto: Toxicotranscriptomic evaluation of microplastic and nanoplastic impacts on aquatic organisms

The pervasive and steadily increasing presence of microplastics/nanoplastics (MPs/NPs) in aquatic environments has raised significant concerns regarding their potential adverse effects on aquatic organisms and their integration into trophic dynamics. This emerging issue has garnered the attention of (eco)toxicologists, promoting the utilization of toxicotranscriptomics to unravel the responses of aquatic organisms not only to MPs/NPs but also to a wide spectrum of environmental pollutants. This review aims to systematically explore the broad repertoire of predicted molecular responses by aquatic organisms, providing valuable intuitions into complex interactions between plastic pollutants and aquatic biota. By synthesizing the latest literature, present analysis sheds light on transcriptomic signatures like gene expression, interconnected pathways and overall molecular mechanisms influenced by various plasticizers. Harmful effects of these contaminants on key genes/protein transcripts associated with crucial pathways lead to abnormal immune response, metabolic response, neural response, apoptosis and DNA damage, growth, development, reproductive abnormalities, detoxification, and oxidative stress in aquatic organisms. However, unique challenge lies in enhancing the fingerprint of MPs/NPs, presenting complicated enigma that requires decoding their specific impact at molecular levels. The exploration endeavors, not only to consolidate existing knowledge, but also to identify critical gaps in understanding, push forward the frontiers of knowledge about transcriptomic signatures of plastic contaminants. Moreover, this appraisal emphasizes the imperative to monitor and mitigate the contamination of commercially important aquatic species by MPs/NPs, highlighting the pivotal role that regulatory frameworks must play in protecting all aquatic ecosystems. This commitment aligns with the broader goal of ensuring the sustainability of aquatic resources and the resilience of ecosystems facing the growing threat of plastic pollutants.

Primary Microplastics in the Ecosystem: Ecological Effects, Risks, and Comprehensive Perspectives on Toxicology and Detection Methods

Recent discoveries of microplastics in cities, suburbs, and even remote locations, far from microplastic source regions, have raised the possibility of long-distance transmission of microplastics in many ecosystems. A little is known scientifically about the threat that it posed to the environment by microplastics. The problem's apparent size necessitates the rapid development of reliable scientific advice regarding the ecological risks of microplastics. These concerns are brought on by the lack of consistent sample and identification techniques, as well as the limited physical analysis and understanding of microplastic pollution. This review provides insight regarding some unaddressed issues about the occurrence, fate, movement, and impact of microplastics, in general, with special emphasis on primary microplastics. The approaches taken in the earlier investigations have been analyzed and different recommendations for future research have been suggested.

Flow cytometry as a tool for the rapid enumeration of 1-μm microplastics spiked in wastewater and activated sludge after coagulation-flocculation-sedimentation

Considering the limited literature and the difficulty of quantifying 1-μm micro-nanoplastics (1-μm MNP) in complex aqueous matrices such as wastewater and sludge, the removal rate of these very small particles in wastewater treatment plants (WWTP) represents a major challenge. In this study, coagulation-flocculation-sedimentation (CFS) with aluminum salts was investigated to evaluate the removal of 1-μm MNPs spiked in tap water, raw wastewater, pre-settled wastewater, and activated sludge. Quantification of 1-μm MNP was performed using the high-throughput flow cytometry (FCM) analysis which takes only a few minutes and produces results with high accuracy and reproducibly. The results indicated that the 1-μm MNPs were highly stable in pure water and unable to settle rapidly. In raw wastewater, sedimentation without coagulants removed less than 4% of 1-μm MNP. Conversely, CFS treatment showed a significant improvement in the removal of 1-μm MNP from wastewater. At dosages of 0.3-3 mg Al3+/L, the removal of MNPs in wastewater reached 30% and no flocs were observed, while floc formation was visible with increased dosages of 3-12 mg Al3+/L, obtaining MNP removal greater than 90%. CFS in activated sludge with a solids content of 5800 mg MLSS/L registered the highest removal efficiency (95-99%) even for dosages of 0.3-60 mg Al3+/L and pH dropping to 5. However, activated sludge showed extremely high removal efficiency of MNPs (97.3 ± 0.9%) even without coagulants. The large, dense flocs that constitute activated sludge appear particularly efficient in capturing 1-μm MNPs during the sedimentation process even in the absence of coagulants.

Ecological risk assessment of microplastics and mesoplastics in six common fishes from the Bay of Bengal Coast

Plastic particles have emerged as a growing threat to both ecosystems and human well-being, as they are being ingested and accumulate at different trophic levels. However, microplastic and mesoplastic contamination and its risk to coastal and marine water fish have not been well studied, particularly in the northern Bay of Bengal. In this study, the presence of small-scale plastic particles (micro- and meso-sized) in the gastrointestinal tract (GIT) and muscles of six edible fish species from the northern Bay of Bengal Coast were identified and analyzed. The overall range of microplastics was 1.74 ± 0.23-3.79 ± 2.03items/g in muscle and 0.54 ± 0.22-5.96 ± 3.16 items/g in the GIT, with 16.38 ± 8.08-31.88 ± 12.09 items/individual. No mesoplastics were found in muscle tissue, but they were present in the GIT at concentrations ranging from 0.33 ± 0.27 to 0.03 ± 0.02 items/g and from 0.51 ± 0.05to 1.38 ± 1.01 items/individual. Lepturacanthus savala accumulated the most microplastics in muscle, and Harpadon nehereus had the least. In addition, the highest levels of mesoplastics were detected in the GIT of Polynemus paradiseus and the lowest was detected in the GIT of Lutjenus sanguineus. Omnivorous fish showed higher plastic concentrations than carnivorous fish, which was linked to dietary habits, feeding strategies and digestive processes. Plastic material predominantly accumulated in the GIT rather than in the muscle. The majority of ingested plastic particles were fibres (95.18 %), were violet in color (34 %), and were < 0.5 mm in size (87 %). The dominant microplastic polymers included 38 % PE, 15 % PP, 33 % PU, and 14 % CES. In contrast, the prevalent mesoplastic polymers comprised 45 % PE, 19 % PP, 13 % PS, 16 % PA, and 7 % PET. Subsequently, a hazard analysis using the polymer hazard index (PHI) revealed that plastic contamination was of distinct hazard categories for different polymer types, ranging from grade I (<1) to grade IV (100-1000). The assessment of the contamination factor (1 < CF < 3) and pollution load index (PLI > 1) indicated moderate contamination of fish by the ingestion of plastic debris. This study provides the foremost evidence for the presence of mesoplastics and microplastics in coastal and marine fish in the study region, paving the way for future investigations and policy implementation.

Investigation into the characteristics of electron beam-aged microplastics and adsorption behavior of dibutyl phthalate

Microplastics are increasingly prevalent in the environment, and their ability to adsorb various organic additives, posing harm to organisms, has attracted growing attention. Currently, there are no effective methods to age microplastics, and there is limited discussion on the subsequent treatment of aged microplastics. This study focuses on micro polyethylene (PE) and employs electron beam technology for aging treatment, investigating the adsorption and leaching behavior between PE and dibutyl phthalate (DBP) before and after aging. Experimental results indicate that with increasing doses of electron beam irradiation, the surface microstructure of PE worsens, inducing the generation of oxygen-containing functional groups on the surface of polyethylene. Comparative evaluations between electron beam aging and existing methods show that electron beam technology surpasses existing aging methods, achieving a level of aging exceeding 0.7 within an extremely short period of 1 min at doses exceeding 350 kGy. Adsorption experiments demonstrate that the adsorption between PE and DBP conforms to pseudo-second-order kinetics and the Freundlich model both before and after aging. The adsorption capacity of microplastics for DBP increases from 76.8 mg g-1 to 167.0 mg g-1 after treatment, exceeding that of conventional DBP adsorbents. Electron beam irradiation causes aging of microplastics mainly through the generation of ·OH, which lead to the formation of oxygen-containing functional groups on the microplastics' surface, thereby enhancing their adsorption capacity for DBP. This provides a new perspective for the degradation of aged microplastics and composite pollutants.

Microplastics removal efficiency and risk analysis of wastewater treatment plants in Oman

Microplastics (MPs) have recently been documented as an emerging pollutant that poses a critical threat to environment. Wastewater treatment plants (WWTPs) are commonly regarded as significant contributors to the presence of MPs. This study aimed to assess the MPs load of three wastewater treatment facilities in Oman using various treatments, including MBR, SBR, and CAS. Wastewater samples from influent, effluent, and sludge were collected and analyzed to determine the concentration, morphology, size, color, and polymer type of the MPs. A set of sieves with a mesh size range of 1 mm-45 μm was used to for filtration. Oxidation treatment was applied for all samples using Fenton's reagent, followed by density separation by sodium chloride solution. The Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy (ATR- FTIR) method was utilized to test 10% from each sampling point to confirm the polymer types of the MPs. The pollution load index (PLI) and hazard index (HI) have been employed to assess the risk associated with the chemical toxicity and concentration of detected particles. The PROMETHEE method was used to rank the risk of sampling sites based on different criteria that posed potential ecological and human health risks. The results indicate that the average concentrations of 0.99 MP/L, 1.38 MP/L, and 0.93 MP/L were detected in the final treated effluent of WWTP A, WWTP B, and WWTP C, respectively. These concentrations correspond to overall removal efficiencies of 82.5%, 77.4%, and 79.2% for WWTP A, WWTP B, and WWTP C, respectively Most MPs found in tertiary effluent were smaller particles (425 μm) and fiber-shaped. The major types of MPs were polypropylene (PP), low-density polyethylene (LDPE), polyurethane (PU), polyethylene terephthalate (PET), and Polyvinyl chloride (PVC). This study showed that treated effluent and sludge release significant MPs into the environment.

Entry pathways determined the effects of MPs on sludge anaerobic digestion system: The views of methane production and antibiotic resistance genes fates

Sludge is one of the primary reservoirs of microplastics (MPs), and the effects of MPs on subsequent sludge treatment raised attention. Given the entry pathways, MPs would exhibit different properties, but the entry pathway-dependent effect of MPs on sludge treatment performance and the fates of antibiotic resistance genes (ARGs), another high-risk emerging contaminant, were seldom documented. Herein, MPs with two predominant entry pathways, including wastewater-derived (WW-derived) and anaerobic digestion-introduced (AD-introduced), were used to investigate the effects on AD performance and ARGs abundances. The results indicated that WW-derived MPs, namely the MPs accumulated in sludge during the wastewater treatment process, exhibited significant inhibition on methane production by 22.8%-71.6%, while the AD-introduced MPs, being introduced in the sludge AD process, slightly increased the methane yield by 4.7%-17.1%. Meanwhile, MPs were responsible for promoting transmission of target ARGs, and polyethylene terephthalate MPs (PET-MPs) showed a greater promotion effect (0.0154-0.0936) than polyamide MPs (PA-MPs) (0.0013-0.0724). Compared to size, entry pathways and types played more vital roles on MPs influences. Investigation on mechanisms based on microbial community structure revealed characteristics (aging degree and types) of MPs determined the differences of AD performance and ARGs fates. WW-derived MPs with longer aging period and higher aging degree would release toxics and decrease the activities of microorganisms, resulting in the negative impact on AD performance. However, AD-introduced MPs with short aging period exhibited marginal impacts on AD performance. Furthermore, the co-occurrent network analysis suggested that the variations of potential host bacteria induced by MPs with different types and aging degree attributed to the dissemination of ARGs. Distinctively from most previous studies, the MPs with different sizes did not show remarkable effects on AD performance and ARGs fates. Our findings benefited the understanding of realistic environmental behavior and effect of MPs with different sources.

Optimization and application of pretreatment method of microplastics detection in municipal solid waste landfills

The landfill is one of the most important sources of microplastics (MPs). The pretreatment method is a precondition of microplastics study for the presence of complex substances in landfills. Therefore, it is essential to examine the impact of different pretreatment methods on the microplastics detection. A literature review and a comparison experiment on digestion solutions were performed to establish a comprehensive identification method for MPs in landfills. When exposed to of 30 % H2O2, minimal mass reduction of PE, PP and PET were 4.00 %, 3.00 % and 3.00 % respectively, and the least surface damage was observed in MPs, while exhibiting the most optimal peak value for infrared spectral characteristics. It is demonstrated that the effect of 30 % H2O2 dissolution was superior compared to 10 % KOH and 65 % HNO3. The method was subsequently utilized to investigate the distribution of MPs in a landfill. The dominant MPs were polyethylene (PE, 18.56-23.91 %), polyethylene terephthalate (PET, 8.80-18.66 %), polystyrene (PS, 10.31-18.09 %), and polypropylene (PP, 11.60-14.91 %). The comprehensive identification method of "NaCl density separation + 30 % H2O2 digestion + NaI density separation + sampling microscope + Mirco-FTIR" is suitable for the detection of MPs in landfills.

Microplastics in urban water systems, Tehran Metropolitan, Iran

Urban water systems are potential sources of secondary microplastics (MPs) as well as a distributor of MPs in the environment. In the present study, the presence of MPs in the urban water systems of the Tehran Metropolitan (Capital of Iran) was investigated. In addition, the probable relationship of MPs with different land uses (i.e., residential-commercial, forest, military, and highway) was assessed. The results showed that all parts of Tehran's urban water system in the study area were contaminated with MPs (107.1 ± 39, 37.8 ± 10.5, 48.3 ± 3.1, 46.9 ± 5.6, 59.4 ± 26.5, 1.7, 2.0 ± 0.6, 7.9 ± 1, 1.8 ± 0.2 particles/liter at the residential, integrated, military, forest, highway runoffs, drinking water, groundwater, seasonal river, and the effluent of the wastewater treatment plants; respectively). However, significant differences were found between different land uses. As expected, the residential runoff had the highest rate of MPs pollution, with 107.1 ± 39 particles/liter. According to the obtained results and our estimation, more than five million MPs/day can enter into the water bodies and soil of the study area through the wastewater treatment plants. While there are significant differences in MPs in the different land uses, our findings suggest that residential areas and highways need further attention in controlling the spread of MPs in urban areas.

The exploitation of bio-electrochemical system and microplastics removal: Possibilities and perspectives

Microplastic (MP) pollution has caused severe concern due to its harmful effect on human beings and ecosystems. Existing MP removal methods face many obstacles, such as high cost, high energy consumption, low efficiency, release of toxic chemicals, etc. Thus, it is crucial to find appropriate and sustainable methods to replace common MP removal approaches. Bio-electrochemical system (BES) is a sustainable clean energy technology that has been successfully applied to wastewater treatment, seawater desalination, metal removal, energy production, biosensors, etc. However, research reports on BES technology to eliminate MP pollution are limited. This paper reviews the mechanism, hazards, and common treatment methods of MP removal and discusses the application of BES systems to improve MP removal efficiency and sustainability. Firstly, the characteristics and limitations of common MP removal techniques are systematically summarized. Then, the potential application of BES technology in MP removal is explored. Furthermore, the feasibility and stability of the potential BES MP removal application are critically evalauted while recommendations for further research are proposed.

Meta-analysis unravels the complex combined toxicity of microplastics and antibiotics in aquatic ecosystems

The aquatic ecosystem, a repository for various pollutants, has been identified as a crucial zone where microplastics (MPs) serve as vectors for antibiotics, facilitating their spread. Despite this, the influence of MPs on the toxicity of antibiotics remains a topic of debate. In this study, we conduct a global meta-analysis, examining 730 datasets from 29 laboratory studies. Our findings reveal that the impact of MPs on antibiotic toxicity is highly dependent on biological response pathways, microplastic concentration, antibiotic properties, and exposure time. We observed that MPs amplify the accumulation of antibiotics in aquatic organisms, significantly heightening their adverse effects on growth, development, and immune functions. Intriguingly, MPs appear to mitigate the reproductive toxicity caused by antibiotics. A notable inverse relationship was identified between antibiotic toxicity and microplastic concentration and exposure time. Furthermore, antibiotic concentration predominantly affects growth, development, and reproductive health, whereas exposure time is critical in determining antibiotic accumulation and immune-related toxicity. These insights underscore that microplastic co-exposure can modify the toxicological profile of antibiotics. The outcomes of this research enhance our comprehensive understanding of the intricate combined effects of MPs and antibiotics on aquatic life, emphasizing the necessity for informed scientific management of these emerging contaminants.

Understanding microplastic presence in different wastewater treatment processes: Removal efficiency and source identification

Municipal effluents discharged from wastewater treatment plants (WWTPs) are a considerable source of microplastics in the environment. The dynamic profiles of microplastics in treatment units in WWTPs with different treatment processes remain unclear. This study quantitatively analyzed microplastics in wastewater samples collected from different treatment units in two tertiary treatment plants with distinct processes. The influents contained an average of 15.5 ± 3.5 particles/L and 38.5 ± 2.5 particles/L in the two WWTPs with in the oxidation ditch process and the integrated fixed-film activated sludge process, respectively. Interestingly, microplastic concentrations in the influent were more influenced by the population density in the served area than sewage volume or served population equivalent. Throughout the treatment process, concentrations were reduced to 1.5 ± 0.5 particles/L and 1.0 ± 1.0 particles/L in the final effluents, representing an overall decrease of 90% and 97%, in WWTPs with the oxidation ditch process and integrated fixed-film activated sludge process, respectively. A significant proportion of the microplastics were removed during the primary treatment stage in both WWTPs, with better performance for foam, film, line-shaped and large-sized microplastics. Most microplastics were accumulated in activated sludge, indicating its key role as the primary sink in WWTPs. The multiple correspondence analysis identified laundry washing and daily necessities such as packaging and containers as the major contributors to microplastics in WWTPs. The study proposed recommendations for upgrading WWTPs, modifying designs, and implementing strategies to reduce microplastic sources, aiming to minimize the release of microplastics into the environment. These findings can shed lights on the sources of microplastics in WWTPs, and advance our understanding of the mechanisms for more effective microplastic removals in wastewater treatment technologies in future applications.

Toxicological review of micro- and nano-plastics in aquatic environments: Risks to ecosystems, food web dynamics and human health

The increase of micro- and nano-plastics (MNPs) in aquatic environments has become a significant concern due to their potential toxicological effects on ecosystems, food web dynamics, and human health. These plastic particles emerge from a range of sources, such as the breakdown of larger plastic waste, consumer products, and industrial outputs. This review provides a detailed report of the transmission and dangers of MNPs in aquatic ecosystems, environmental behavior, and interactions within aquatic food webs, emphasizing their toxic impact on marine life. It explores the relationship between particle size and toxicity, their distribution in different tissues, and the process of trophic transfer through the food web. MNPs, once consumed, can be found in various organs, including the digestive system, gills, and liver. Their consumption by lower trophic level organisms facilitates their progression up the food chain, potentially leading to bioaccumulation and biomagnification, thereby posing substantial risks to the health, reproduction, and behavior of aquatic species. This work also explores how MNPs, through their persistence and bioaccumulation, pose risks to aquatic biodiversity and disrupt trophic relationships. The review also addresses the implications of MNPs for human health, particularly through the consumption of contaminated seafood, highlighting the direct and indirect pathways through which humans are exposed to these pollutants. Furthermore, the review highlights the recommendations for future research directions, emphasizing the integration of ecological, toxicological, and human health studies to inform risk assessments and develop mitigation strategies to address the global challenge of plastic pollution in aquatic environments.

Emerging pollutant in surface water bodies: a review on monitoring, analysis, mitigation measures and removal technologies of micro-plastics

Water bodies play a crucial role in supporting life, maintaining the environment, and preserving the ecology for the people of India. However, in recent decades, human activities have led to various alterations in aquatic environments, resulting in environmental degradation through pollution. The safety of utilizing surface water sources for drinking and other purposes has come under intense scrutiny due to rapid population growth and industrial expansion. Surface water pollution due to micro-plastics (MPs) (plastics < 5 mm in size) is one of the emerging pollutants in metropolitan cities of developing countries because of its utmost resilience and synthetic nature. Recent studies on the surface water bodies (river, pond, Lake etc.) portrait the correlation between the MPs level with different parameters of pollution such as specific conductivity, total phosphate, and biological oxygen demand. Fibers represent the predominant form of MPs discovered in surface water bodies, exhibiting fluctuations across seasons. Consequently, present study prioritizes understanding the adaptation, prevalence, attributes, fluctuations, and spatial dispersion of MPs in both sediment and surface water environments. Furthermore, the study aims to identify existing gaps in the current understanding and underscore opportunities for future investigation. From the present study, it has been reported that, the concentration of MPs in the range of 0.2-45.2 items/L at the Xisha Islands in the south China sea, whereas in India it was found in the range of 96 items/L in water samples and 259 items/kg in sediment samples. This would certainly assist the urban planners in achieving sustainable development goals to mitigate the increasing amount of emergent pollutant load.

Investigation of microplastics in advanced biological wastewater treatment plant effluent

In recent years, plastic pollution in the environment has also increased due to the increasing production and consumption of plastics worldwide. The presence of microplastics (MPs) in the environment from different sources is observed almost everywhere, especially in aquatic environments. A standard method for sampling, identification, and quantification of MPs in wastewater has not yet been established. In this study, it was aimed to determine the MPs and their characteristics in the effluent of an advanced biological domestic wastewater treatment plant. The seasonal changes of MPs in a year were revealed. Pre-treatments suitable for the studied wastewater were developed for visual determination of MPs. Fibers are the dominant type of MPs, with numbers ranging between 32.0 and 95.5 particle/L. MPs in five different polymer structures were determined by FTIR analysis. These are Polyethylene, Polypropylene, Polyester, Polyurethane and Polyethylene terephthalate. The results were evaluated according to QA/QC and determined to meet the standards.

Treating wastewater for microplastics to a level on par with nearby marine waters

Retention of microplastics (MPs) at the third largest wastewater treatment plant (WWTP) in Sweden was investigated. The plant is one of the most modern and advanced of its kind, with rapid sand filter for tertiary treatment in combination with mechanical, biological, and chemical treatment. It achieved a significantly high treatment efficiency, which brought the MP concentration in its discharge on par with concentrations measured in marine waters of the same region. This novel data shows that properly designed modern WWTPs can reduce the MP content of sewage down to background levels measured in the receiving aquatic environment. Opposite to current understanding of the retention of MP by WWTPs, a modern and well-designed WWTP does not have to be a significant point source for MP. MPs were quantified at all major treatment steps, including digester inlet and outlet sludge. MPs sized 10-500 µm were analyzed by a focal plane array based micro-Fourier transform infrared (FPA-µFTIR) microscopy, a hyperspectral imaging technique, while MPs above 500 µm were analyzed by Attenuated Total Reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy. Mass was estimated from the hyperspectral images for MPs <500 µm and from microscope images >500 µm. The overall treatment efficiency was in terms of MP counts 99.98 %, with a daily input of 6.42 × 1010 and output of 1.04 × 107 particles. The mass removal efficiency was 99.99 %. The mechanical part of the treatment, the pre-treatment, and primary stages, reduced both the MP counts and mass by approximately 71 %. The combined biological treatment, secondary settling, and final polishing with rapid sand filtration removed nearly all the remaining 29 %. MPs became successively smaller as they passed the different treatment steps. The digester inlet received 1.04 × 1011 MPs daily, while it discharged 9.96 × 1010 MPs, causing a small but not significant decrease in MP counts, with a corresponding MP mass reduction of 9.56 %.

The Plasticene era: Current uncertainties in estimates of the hazards posed by tiny plastic particles on soils and terrestrial invertebrates

Plastics are ubiquitous in our daily life. Large quantities of plastics leak in the environment where they weather and fragment into micro- and nanoparticles. This potentially releases additives, but rarely leads to a complete mineralization, thus constitutes an environmental hazard. Plastic pollution in agricultural soils currently represents a major challenge: quantitative data of nanoplastics in soils as well as their effects on biodiversity and ecosystem functions need more attention. Plastic accumulation interferes with soil functions, including water dynamics, aeration, microbial activities, and nutrient cycling processes, thus impairing agricultural crop yield. Plastic debris directly affects living organisms but also acts as contaminant vectors in the soils, increasing the effects and the threats on biodiversity. Finally, the effects of plastics on terrestrial invertebrates, representing major taxa in abundance and diversity in the soil compartment, need urgently more investigation from the infra-individual to the ecosystem scales.

Quantifying annual microplastic emissions of an urban catchment: Surface runoff vs wastewater sources

Urban clusters are recognized as hotspots of microplastic pollution, and the associated urban rivers convey microplastics into the global oceans. Despite this knowledge, the relative contributions of various sources to the annual microplastic emissions from urban catchments remain scarcely quantified. Here, we quantified microplastic emissions from a riverine urban catchment in Japan. The total microplastics (size range: 10-5000 μm) released from the catchment amounted to 269.1 tons/annum, of which 78.1% is contributed by surface runoff and other uncontrolled emissions (UCE), and 21.1% emerges from the regulated wastewater (controlled emissions; CE), implying that approximately one-fifth is intercepted and removed by the wastewater treatment plants (WWTPs). This further indicated higher microplastic pollution by unmanaged surface runoff compared to untreated wastewater. In the dry season, WWTPs contributed significantly to the reduction of total microplastic emissions (95%) compared to wet periods (8%). On an annual scale, the treated effluent occupies only 0.1% of the total microplastics released to the river network (212.4 tons/annum), while the remaining portion is dominated by UCE, i.e., primarily surface runoff emissions (98.9%), and trivially by the background microplastic inputs that are potentially derived through atmospheric depositions in dry days (1.0%). It was shown that moderate and heavy rainfall events which occur during 18% of the year (within the context of Japan), leading to 95% of the annual microplastic emissions, are crucial for pollution control of urban rivers. Furthermore, our study demonstrated that surface area-normalized microplastic emissions from an urban catchment (∼0.8 tons/km2/annum) is globally relevant, especially for planning microplastic interventions for developed cities.

Surface wettability control and electron transport regulation in zerovalent iron for enhanced removal of emerging polystyrene microplastics-heavy metal contaminants

Emerging microplastics-heavy metal (MPs-HM) contaminants in wastewaters pose an emerging health and environmental risk due to their persistence and increasing ecological risks (e.g., "Trojan horse" effect). Hence, removing MPs in solution and preventing secondary releases of HM has become a key challenge when tackling with MPs pollution. Leveraging the hydrophobic nature of MPs and the electron transfer efficiency from Fe0 to HM, we demonstrate an alkylated and sulfidated nanoscale zerovalent iron (AS-nZVI) featuring a delicate "core-shell-hydrophobic film" nanostructure. Exemplified by polystyrene (PS) MPs-Pb(II) removal, the three nanocomponents offer synergistic functions for the rapid separation of MPs, as well as the reduction and stabilization of Pb(II). The outmost hydrophobic film of AS-nZVI greatly improves the anticorrosion performance of nanoscale zerovalent iron and the enrichment abilities of hydrophobic MPs, achieving a maximum removal capacity of MPs to 2725.87 mgMPs·gFe-1. This MPs enrichment promotes the subsequent reductive removal of Pb(II) through the electron transfer from the iron core of AS-nZVI to Pb(II), a process further strengthened by the introduced sulfur. When considering the inevitable aging of MPs in wastewaters due to mechanical wear or microbial degradation, our study concurrently examines the efficiencies and behaviors of AS-nZVI in removing virgin-MPs-Pb(II) and aged-MPs-Pb(II). The batch results reveal that AS-nZVI has an exceptional ability to remove above 99.6 % Pb(II) for all reaction systems. Overall, this work marks a pioneering effort in highlighting the importance of MPs-toxin combinations in dealing with MPs contamination and in demonstrating the utility of nZVI techniques for MPs-contaminated water purification.