Removal of polystyrene and polyethylene microplastics using PAC and FeCl3 coagulation: Performance and mechanism

Fibrous microplastics released from textiles: Occurrence, fate, and remediation strategies

Microplastics (MP), i.e., particles measuring less than 5 mm in size, are considered emerging pollutants. The ubiquity of MP is causing great concern among environmental and public health agencies. Anthropogenic activities are responsible for the extensive dispersal of MP in nature. Adverse effects on living organisms, interactions with other contaminants occurring in the environment, and the lack of effective degradation/removal techniques are significant issues related to MP. Most MP found in nature are fibrous (FMP). FMP originate from textile products, mainly synthetic fibers (e.g., polyester). Synthetic fibers are intensively used to produce countless goods due to beneficial characteristics such as high mechanical resistance and economic feasibility. FMP are ubiquitous on the planet and impart lasting adverse effects on biodiversity. Data on the consequences of long-term exposure to these pollutants are scarce in the literature. In addition, few studies address the main types of synthetic microfibers released from textiles, their occurrence, adverse effects on organisms, and remediation strategies. This review discusses the relevant topics about FMP and alerts the dangers to the planet. Furthermore, future perspectives and technological highlights for the FMP mitigation/degradation are presented.

Efficiency and mechanism of micro- and nano-plastic removal with polymeric Al-Fe bimetallic coagulants: Role of Fe addition

The occurrence of microplastics (MPs) and even nanoplastics (NPs) in tap water has raised considerable attention. As a pre-treatment and also the most important process in drinking water treatment plants, coagulation has been widely studied to remove MPs, but few studies focused on the removal pattern and mechanism of NPs, especially no study paid attention to the coagulation enhanced by prehydrolysed Al-Fe bimetallic coagulants. Therefore, in this study, polymeric species and coagulation behaviour of MPs and NPs influenced by Fe fraction in polymeric Al-Fe coagulants were investigated. Special attention was given to the residual Al and the floc formation mechanism. The results showed that asynchronous hydrolysis of Al and Fe sharply decreases the polymeric species in coagulants and that the increase of Fe proportion changes the sulfate sedimentation morphology from dendritic to layered structures. Fe weakened the electrostatic neutralization effect and inhibited the removal of NPs but enhanced that of MPs. Compared with monomeric coagulants, the residual Al decreased by 17.4 % and 53.2 % in the MP and NP systems (p < 0.01), respectively. With no new bonds detected in flocs, the interaction between micro/nanoplastics and Al/Fe was merely electrostatic adsorption. According to the mechanism analysis, sweep flocculation and electrostatic neutralization were the dominant removal pathways of MPs and NPs, respectively. This work provides a better coagulant option for removing micro/nanoplastics and minimizing Al residue, which has promising potential for application in water purification.

Mechanism of nanoplastics capture by jellyfish mucin and its potential as a sustainable water treatment technology

The accumulation of nanoplastics (NPs) in the environment has raised concerns about their impact on human health and the biosphere. The main aim of this study is to understand the mechanism that governs the capture of NPs by jellyfish mucus extracted from the jellyfish Aurelia sp. (A.a.) and compare the capture/removal efficiency to that of conventional coagulants and mucus from other organisms. The efficacy of A.a mucus to capture polystyrene and acrylic NPs (∼100 nm) from spiked wastewater treatment plant (WWTP) effluent was evaluated. The mucus effect on capture kinetics and destabilization of NPs of different polymer compositions, sizes and concentrations was quantified by means of fluorescent NPs, dynamic light scattering and zeta potential measurements and visualized by scanning electron microscopy. A dosing of A.a. mucus equivalent to protein concentrations of ∼2-4 mg L^-1 led to a rapid change in zeta potential from a baseline of -30 mV to values close to 0 mV, indicating a marked change from a stable to a non-stable dispersion leading to a rapid (<10 min) and significant removal of NPs (60 %-90 %) from a stable suspension. The A.a. mucus outperformed all other mucus types (0-37 %) and coagulants (0 %-32 % for ferric chloride; 23-40 % for poly aluminum chlorohydrate), highlighting the potential for jellyfish mucus to be used as bio-flocculant. The results indicate a mucus-particle interaction consisting of adsorption-bridging and "mesh" filtration. Further insight is provided by carbohydrate composition and protein disruption analysis. Total protein disruption resulted in a complete loss of the A.a. mucus capacity to capture NPs, while the breaking of disulfide bonds and protein unfolding resulted in improved capture capacity. The study demonstrates that natural jellyfish mucin can capture and remove NPs in water and wastewater treatment systems more efficiently than conventional coagulants, highlighting the potential for development of a new type of bio-flocculant.

Microplastic remediation technologies in water and wastewater treatment processes: Current status and future perspectives

Microplastics (MPs) are a type of contaminants produced during the use and disposal of plastic products, which are ubiquitous in our lives. With the high specific surface area and strong hydrophobicity, MPs can adsorb various hazardous microorganisms and chemical contaminants from the environment, causing irreversible damage to our humans. It is reported that the MPs have been detected in infant feces and human blood. Therefore, the presence of MPs has posed a significant threat to human health. It is critically essential to develop efficient, scalable and environmentally-friendly methods to remove MPs. Herein, recent advances in the MPs remediation technologies in water and wastewater treatment processes are overviewed. Several approaches, including membrane filtration, adsorption, chemically induced coagulation-flocculation-sedimentation, bioremediation, and advanced oxidation processes are systematically documented. The characteristics, mechanisms, advantages, and disadvantages of these methods are well discussed and highlighted. Finally, the current challenges and future trends of these methods are proposed, with the aim of facilitating the remediation of MPs in water and wastewater treatment processes in a more efficient, scalable, and environmentally-friendly way.

Microplastic sources, formation, toxicity and remediation: a review

Microplastic pollution is becoming a major issue for human health due to the recent discovery of microplastics in most ecosystems. Here, we review the sources, formation, occurrence, toxicity and remediation methods of microplastics. We distinguish ocean-based and land-based sources of microplastics. Microplastics have been found in biological samples such as faeces, sputum, saliva, blood and placenta. Cancer, intestinal, pulmonary, cardiovascular, infectious and inflammatory diseases are induced or mediated by microplastics. Microplastic exposure during pregnancy and maternal period is also discussed. Remediation methods include coagulation, membrane bioreactors, sand filtration, adsorption, photocatalytic degradation, electrocoagulation and magnetic separation. Control strategies comprise reducing plastic usage, behavioural change, and using biodegradable plastics. Global plastic production has risen dramatically over the past 70 years to reach 359 million tonnes. China is the world's top producer, contributing 17.5% to global production, while Turkey generates the most plastic waste in the Mediterranean region, at 144 tonnes per day. Microplastics comprise 75% of marine waste, with land-based sources responsible for 80-90% of pollution, while ocean-based sources account for only 10-20%. Microplastics induce toxic effects on humans and animals, such as cytotoxicity, immune response, oxidative stress, barrier attributes, and genotoxicity, even at minimal dosages of 10 μg/mL. Ingestion of microplastics by marine animals results in alterations in gastrointestinal tract physiology, immune system depression, oxidative stress, cytotoxicity, differential gene expression, and growth inhibition. Furthermore, bioaccumulation of microplastics in the tissues of aquatic organisms can have adverse effects on the aquatic ecosystem, with potential transmission of microplastics to humans and birds. Changing individual behaviours and governmental actions, such as implementing bans, taxes, or pricing on plastic carrier bags, has significantly reduced plastic consumption to 8-85% in various countries worldwide. The microplastic minimisation approach follows an upside-down pyramid, starting with prevention, followed by reducing, reusing, recycling, recovering, and ending with disposal as the least preferable option.

Efficiency of Coagulation/Flocculation for the Removal of Complex Mixture of Textile Fibers from Water

Synthetic fibers enter wastewater treatment plants together with natural fibers, which may affect treatment efficiency, a fact not considered in previous studies. Therefore, the aim of the present study was to evaluate the efficiency of the coagulation/flocculation process for the removal of a mixture of textile fibers from different water matrices. Natural and synthetic fibers (100 mg/L; cotton, polyacrylonitrile, and polyamide) were added to a synthetic matrix, surface water and laundry wastewater and subjected to coagulation/flocculation experiments with ferric chloride (FeCl3) and polyaluminum chloride (PACl) under laboratory conditions. In the synthetic matrix, both coagulants were found to be effective, with FeCl3 having a lesser advantage, removing textile fibers almost completely from the water (up to 99% at a concentration of 3.94 mM). In surface water, all dosages had approximately similar high values, with the coagulant resulting in complete removal. In laundry effluent, the presence of surfactants is thought to affect coagulation efficiency. PACl was found to be effective in removing textile fibers from laundry wastewater, with the lowest removal efficiency being 89% and all dosages having similar removal efficiencies. Natural organic matter and bicarbonates showed a positive effect on the efficiency of FeCl3 in removing textile fibers from surface water. PACl showed better performance in coagulating laundry wastewater while surfactants had a negative effect on FeCl3 coagulation efficiency.

Unaccounted Microplastics in the Outlet of Wastewater Treatment Plants—Challenges and Opportunities

Since the 1950s, plastic production has skyrocketed. Various environmental and human activities are leading to the formation and accumulation of microplastics (MPs) in aquatic and terrestrial ecosystems, causing detrimental effects on water, soil, plants, and living creatures. Wastewater treatment plants (WWTPs) are one of the primary MP management centers meant to check their entry into the natural systems. However, there are considerable limitations in effectively capturing, detecting, and characterizing these MPs in the inlet and outlet of WWTPs leading to “unaccounted MPs” that are eventually discharged into our ecosystems. In order to assess the holistic picture of the MPs’ distribution in the ecosystems, prevent the release of these omitted MPs into the environment, and formulate regulatory policies, it is vital to develop protocols that can be standardized across the globe to accurately detect and account for MPs in different sample types. This review will cover the details of current WWTP adoption procedures for MP management. Specifically, the following aspects are discussed: (i) several processes involved in the workflow of estimating MPs in the outlet of WWTPs; (ii) key limitations or challenges in each process that would increase the uncertainty in accurately estimating MPs; (iii) favorable recommendations that would lead to the standardization of protocols in the workflow and facilitate more accurate analysis of MPs; (iv) research opportunities to tackle the problem of ‘missing MPs’; and (v) future research directions for the efficient management of MPs. Considering the burgeoning research interest in the area of MPs, this work would help early scientists in understanding the current status in the field of MP analysis in the outlet of WWTPs.

Plastic waste management for sustainable environment: techniques and approaches

Excessive exploitation, negligence, non-degradable nature, and physical and chemical properties of plastic waste have resulted in a massive pollution load into the environment. Consequently, plastic entres the food chain and can cause serious health issues in aquatic animals and humans. The present review summarizes currently reported techniques and approaches for the removal of plastic waste. Many techniques, such as adsorption, coagulation, photocatalysis, and microbial degradation, and approaches like reduction, reuse and recycling are potentially in trend and differ from each other in their efficiency and interaction mechanism. Moreover, substantial advantages and challenges associated with these techniques and approaches are highlighted to develop an understanding of the selection of possible ways for a sustainable future. Nevertheless, in addition to the reduction of plastic waste from the ecosystem, many alternative opportunities have also been explored to cash plastic waste. These fields include the synthesis of adsorbents for the removal of pollutants from aqueous and gaseous stream, their utility in clothing, waste to energy and fuel and in construction (road making). Substantial evidence can be observed in the reduction of plastic pollution from various ecosystems. In addition, it is important to develop an understanding of factors that need to be emphasized while considering alternative approaches and opportunities to cash plastic waste (like adsorbent, clothing, waste to energy and fuel). The thrust of this review is to provide readers with a comprehensive overview of the development status of techniques and approaches to overcome the global issue of plastic pollution and the outlook on the exploitation of this waste as resources.

In Vitro Viral Recovery Yields under Different Re-Suspension Buffers in Iron Flocculation to Concentrate Viral Hemorrhagic Septicemia Virus Genotype IVa in Seawater

Iron flocculation is widely used to concentrate viruses in water, followed by Fe-virus flocculate formation, collection, and elution. In the elution stage, an oxalic or ascorbic acid re-suspension buffer dissolved iron hydroxide. After the concentration of viral hemorrhagic septicemia virus (VHSV) in seawater (1 × 10¹ to 1 × 10⁵ viral genome copies or plaque-forming unit (PFU)/mL), the recovery yield of the viral genome using quantitative real-time PCR (qRT-PCR) and viral infectivity using the plaque assay were investigated to evaluate the validity of the two re-suspension buffers to concentrate VHSV. The mean viral genome recovery yield with oxalic and ascorbic acid was 71.2 ± 12.3% and 81.4 ± 9.5%, respectively. The mean viral infective recovery yields based on the PFU were significantly different between the two buffers at 23.8 ± 22.7% (oxalic acid) and 4.4 ± 2.7% (ascorbic acid). Notably, although oxalic acid maintains viral infectivity over 60% at a viral concentration above 10⁵ PFU/mL, the infective VHSVs were not sufficiently recovered at a low viral concentration (10² PFU/mL, <10%). To support this result, concentrated VHSV was inoculated in Epithelioma papulosum cyprini (EPC) cells to confirm cell viability, viral gene expression, and extracellular viral titer. All results demonstrated that oxalic acid buffer was superior to ascorbic acid buffer in preserving viral infectivity.

Highly selective electrochemical impedance spectroscopy-based graphene electrode for rapid detection of microplastics

The widespread occurrence of microplastics (MPs) in aquatic ecosystems that caused environmental pollution has attracted worldwide attention. Herein, graphene electrode was initially derived from petroleum waste. Then the electrochemical responses of the electrode were evaluated using electrochemical impedance spectroscopy (EIS) toward polystyrene (PS) under various optimum conditions. For the quantitative measurement of PS concentration, principal component analysis (PCA) score images displayed that the data points offered the best discrimination of the classes, and singular value decomposition (SVD) showed that a good linearity was achieved between Z"u(1) and lgC_ps in the concentration range of 0.01-25 mg L^-1. Especially for PS with particle size of 1 μm, the highest correlation coefficient (R² = 0.9914) was obtained. The sensor ability to determine the polystyrene concentration in real samples was evaluated with the recovery of 98.4-113.3 % and reliable reproducibility (RSD < 9.72 %). For the quantitative measurement of the particle size of PS, SVD images exhibited that a linearity was obtained between Z'u(1)and lgD_ps in the particle size range of 0.08-20 μm. A good linearity with R² = 0.9877 was obtained when the concentration was 1 mg L^-1. The recovery was in the range of 100.8-118.0 % with the RSD < 6.38 %. Therefore, a novel method is established for the rapid detection of PS MPs.

Effects of electrostatic neutralization of Keggin Fe13 on the removal of micro and nano plastic

The successful preparation and identification of Keggin-structure Fe₁₃ clusters in recent years further enriched the potential application scenarios of ferric coagulants. Comparing the coagulation efficiencies and mechanisms of Fe₁₃ in the removal of nano/microplastics with conventional polymeric Al₁₃ and monomeric Al/Fe, this work aimed to elucidate the coagulation behaviour of Fe₁₃ compared with the traditional mono ferric coagulant, which has the coagulation applied bottleneck of quick and violet hydrolysis. The results showed that Fe₁₃ has a similar electrostatic neutralization potential to Al₁₃, which could keep a positively charged species, especially in acid conditions. The Fe₁₃ species has a selective removal potential toward the microplastics with a polar functional group like ester. Moreover, Fe₁₃ could hydrolyze to form active sol-gel hydroxides in neutral and alkalinity conditions, which is like the behaviour of traditional monomeric Fe coagulants but seldom restabilization. The electrostatic neutralization of Fe₁₃ could enhance the removal of nano plastic from - 25-75% compared with monomeric Fe at pH 4. The higher floc density as a monomeric Fe coagulant and better electrostatic neutralization potential of Keggin Fe₁₃ posed a good prospect for Fe₁₃ to replace the monomeric Fe coagulants in conventional coagulation.

Adsorptive behavior of micro(nano)plastics through biochar: Co-existence, consequences, and challenges in contaminated ecosystems

The abundance of micro(nano)plastics in natural ecosystems is a crucial global challenge, as these small-sized plastic particles originate from land-based and marine-based activities and are widely present in marine, freshwater, and terrestrial ecosystems. Micro(nano)plastics can significantly be reduced through various methods, such as biological, chemical, and physical techniques. Biochar is a low-cost adsorbent and is considered an efficient material and its application is ecologically effective carbon-negative for remediation of organic and inorganic pollutants. Therefore, this review critically discusses the fate and transport of micro(nano)plastics and their interactions with different biochar in aqueous and column porous media. This review outlines the implications of biochar with the co-existence of micro(nano)plastics in efforts to understand their coupled effects on soil physicochemical properties, microbial communities, and plant growth, along with the removal of heavy metals and other toxic contaminants. In batch experiments, biochar synthesized from various biomasses such as corn straw, hardwood, pine and spruce bark, corncob, and Prosopis juliflora had shown high level of removal efficiency (>90 %) for microplastic adsorption under varying environmental conditions viz., pH, temperature, ionic strength, particle size, and dose due to chemical bonding and electrostatic attractions. Increased temperature of the aqueous solutions encouraged higher adsorption, while higher pH and dissolved organic matter and nutrients may show decreased adsorption capacities for micro(nano)plastics using biochar. Compared to other available physical, chemical, and biological methods, biochar-amended sand filters in column experiments have been very efficient in removing micro(nano)plastics. In saturated column porous media, various microplastics could be inhibited using biochar due to decreased electrostatic repulsion, steric hindrance, and competitive sorption due to humic acid, ionic strength, and cations. Finally, this review provides in-depth insights on further investigations and recommendations for overall micro(nano)plastics removal using biochar-based materials.

Surface characteristics of polystyrene microplastics mainly determine their coagulation performances

In this study, polyaluminum sulfate (PAS) coagulant was selected to evaluate the coagulation performance of polystyrene microplastics. Overall, polystyrene removal efficiency was 90.4 % at the optimal dosage of 7.5 g/L of PAS. In addition to the type of coagulants (e.g. polyaluminum chloride, iron(III) chloride, and polyferric sulfate), surface characteristics such as densities, particle sizes, morphologies, adsorbed substances, and functional groups can also significantly impact the coagulation performance. The coagulation ratios are reduced to (2.6 ± 0.1)% when the densities of microplastics decrease. Aging treatments involving NaOH, H₂SO₄, NaClO, CH₃OH, and O₃ promoted coagulation, whereas UV and Na₂S₂O₃ treatments inhibited (64.1 ± 9.7)% and (79.3 ± 8.0)% of polystyrene removals, respectively. In contrast, Fe(NO₃)₃ treatment did not affect the removal ratio. Further characterization of polystyrene before and after coagulation exemplified that the functional groups (CO, CO, and CH) and the rough surfaces of PAS provided adsorption and interception sites for hydrolysis products of the PAS.

Effect of Fe and Al based coagulants and disinfectants on polyethylene microplastics removal in coagulation process through response surface methodology

Microplastic (MP) pollution has been rising as a threatening risk and recently has appealed to the attention of more researchers. In this study, influential parameters affecting the removal rate of polyethylene microplastics (PEMPs) were optimized through response surface methodology (RSM). In Box Behnken Design (BBD), independent parameters were pH, PEMP size, coagulant dosage and polyacrylamide dosage. Two experimental sets were conducted, one with ferric chloride and the second with poly aluminum chloride as two commonly applied coagulants in drinking water treatment plants (DWTPs). Comparing the results of optimized parameters, PAC was a better coagulant with the predicted removal rate of 58.19%, while the removal rate with ferric chloride as a coagulant was predicted to be 56.37%. Moreover, some experiments were conducted to analyze the effect of ozone gas and sodium hypochlorite as disinfectants on removal rate. The highest removal rate was observed when 2 ppm of O₃ was added to the solution coagulated with optimal dosage of PAC, reaching the removal rate of 76.8%.

Enhanced coagulation process for removing dissolved organic matter, microplastics, and silver nanoparticles

Dissolved organic carbon (DOC), microplastics (MPs), and silver nanoparticles (AgNPs) in water are of major concern because of their direct and indirect toxic effects on aquatic organisms and human exposure via water. This work investigated the effect of poly aluminum chloride (PACl) coagulation for reducing DOC, MPs, and AgNPs. This work used water from a canal in Thailand with a DOC of 5.2 mg/L in the experiment. AgNPs of 5-20 mg/L were added to canal water to create synthetic water for the PACl coagulation. Polyethylene and polypropylene (PP) type MPs were identified in the raw water with Fourier transform infrared spectroscopy. Coagulation with 15 mg/L of PACl performed better in the PP removal. The PACl coagulation at dosages of 15, 40, and 70 mg/L removed DOC by 16-20%, 44-52%, and 46-63% and AgNPs by 34-90%, 53-93%, and 81-95%, respectively. The presence of AgNPs at high levels could inhibit the efficiency of DOC reduction by the PACl coagulation. The FESEM identified the adsorption of silver-containing nanoparticles onto the flocs with increased dosages of PACl. So, PACl is a coagulant in the removal of AgNPs that can reduce health hazards and eco-toxicological risks in water sources due to the release of silver.

The removal of microplastics from water by coagulation: A comprehensive review

Drinking water treatment plants (DWTPs) and wastewater treatment plants (WWTPs) are the first and last hurdles for the prevention of microplastics (MPs) pollution, respectively. With coagulation as one of the most critical technologies for the removal of MPs in water treatment plants, there is an urgent need to gain an in-depth understanding of the mechanisms and influencing factors of MPs removal during coagulation. In this paper, the research progress of adopting coagulation in MPs removal in recent years is reviewed, the removal effect of coagulation in water treatment plants are compared, and the role of three coagulation mechanisms, i.e., charge neutralization, adsorption bridging, and sweep flocculation in MPs removal process are identified. The effect of coagulant performance, MPs characteristics, operation conditions and other parameters on the removal of MPs are systematically analyzed. It is found that the combined coagulation techniques have better removal efficiency, can better decrease MP pollution and meet strict discharge standards. Moreover, flaws in the application of coagulation technology are pointed out, and strategies to deal with them are also proposed. Hopefully, this review can not only contribute to a better understanding of the mechanism of MPs removal by coagulation technology, but also serve as a useful guide for future research on MPs removal.

Current status of microplastics and nanoplastics removal methods: Summary, comparison and prospect

In modern society, plastics also play an indispensable role in people's lives due to their various excellent properties. However, when these plastic products are discarded after being used, after being subjected to external influences, they will continue to be worn, damaged and degraded into micro- and nano-scale plastics, which are microplastics and nanoplastics (M/NPs). Although people's attention has been paid to M/NPs at present, the focus is still mainly on the detection and hazard of M/NPs, and how to remove M/NPs is relatively less popular. This review was written in order to draw the attention of more researchers to remove M/NPs. This review first briefly introduces the research background of M/NPs, and also shows the main analytical methods currently used for qualitative and quantitative M/NPs. Then, most of the current literature on the removal of M/NPs was collected, and they were classified, summarized, and introduced according to the classification of physical, physicochemical, and biological methods. The advantages and disadvantages of various methods are summarized, and they are also compared, which can help more researchers choose the appropriate method for research. In addition, the application scenarios of these methods are briefly introduced. Finally, some future research directions are proposed for the current research status of M/NPs removal. It is hoped that this will further promote the development on the method of removing M/NPs.

Efficient removal of nano- and micro- sized plastics using a starch-based coagulant in conjunction with polysilicic acid

Microplastic (MP) pollution has increasingly become an enormous global challenge due to the ubiquity and uncertain environmental performance, especially for nano- and micro- sized MPs. In this work, the performance and mechanisms in coagulation of 100 nm-5.0 μm sized polystyrene particles using an etherified starch-based coagulant (St-CTA) assisted by polysilicic acid (PSA) were systematically studied on the basis of the changes in MPs removal rates under various pH levels and in the presence of different coexisting inorganic and organic substances, zeta potentials of supernatants, and floc properties. St-CTA in conjunction with PSA had a high performance in coagulation of nano- and micro- sized MPs from water with a lower optimal dose and larger and compacter flocs. Besides, the MPs removal rate can be improved in acidic and coexisting salt conditions. The efficient performance in removal of MPs by this enhanced coagulation was owing to the synergic effect, that is, the effective aggregation of MPs through the charge neutralization of St-CTA followed by the efficient netting-bridging effect of PSA. The effectiveness of this enhanced coagulation was further confirmed by removal of two other typical nano-sized MPs, such as poly(methyl methacrylate) and poly(vinyl chloride), from different water sources including tap water, river water, and sludge supernatant from a sewage treatment plant. This work provided a novel enhanced coagulation technique that can effectively remove nano- and micro- sized MPs from water.

Self-driven magnetorobots for recyclable and scalable micro/nanoplastic removal from nonmarine waters

Micro/nanoplastic (MNP) contamination in nonmarine waters has evolved into a notable ecotoxicological threat to the global ecosystem. However, existing strategies for MNP removal are typically limited to chemical flocculation or physical filtering that often fails to decontaminate plastic particulates with ultrasmall sizes or ultralow concentrations. Here, we report a self-driven magnetorobot comprising magnetizable ion-exchange resin sphere that can be used to dynamically remove or separate MNPs from nonmarine waters. As a result of the long-range electrophoretic attraction established by recyclable ion-exchange resin, the magnetorobot shows sustainable removal efficiency of >90% over 100 treatment cycles, with verified broad applicability to varying plastic compositions, sizes, and shapes as well as nonmarine water samples. Our work may facilitate industry-scale MNP removal with affordable cost and minimal secondary pollution and suggests an appealing strategy based on self-propelled micro/nanorobots to sample and assess nanoplastics in aqueous environment.

Photochlorination-induced degradation of microplastics and interaction with Cr(VI) and amlodipine

Wastewater treatment plants (WWTPs) are the important source of microplastics (MPs) in the environment, and disinfection processes bear high potential to degrade MPs. This study investigated the physicochemical degradation, dissolved organic products and interaction with co-existed pollutants (heavy metal and pharmaceutical) on polyethylene (PE), polypropylene (PP) and polystyrene (PS) MPs during simulated disinfection processes. Compared to photo or chlorination, photochlorination significantly resulted in the physicochemical degradation, including morphology alteration, fragmentation, and chemical oxidation on PP and PS MPs, but showed relatively low effect on PE, indicating the different resistance among polymers to disinfected treatment. Photochlorination also caused the formation of chain-scission organic compounds and even chlorinated products from MPs (e.g. C₁₁H₁₉O₄Cl for PP and monochlorophenol, dichlorophenol, chloroacetophenone and chlorobenzoic acid for PS), which may form disinfection byproducts to induce healthy risk. The adsorption potentials of MPs for Cr(VI) or amlodipine were enhanced by photochlorination since the cracking and formed oxygen functional groups enhanced the pore filling and surface precipitation of Cr(VI), and the electrostatic attraction and hydrogen bonding with amlodipine. The findings indicated the physicochemical degradation of MPs and the combined pollution with co-existed pollutants, highlighting the health risks of MP-derived organic products during the disinfection treatments (even in normal dosage) in WWTPs.

Removal of microplastics and nanoplastics from urban waters: Separation and degradation

The omnipresent micro/nanoplastics (MPs/NPs) in urban waters arouse great public concern. To build a MP/NP-free urban water system, enormous efforts have been made to meet this goal via separating and degrading MPs/NPs in urban waters. Herein, we comprehensively review the recent developments in the separation and degradation of MPs/NPs in urban waters. Efficient MP/NP separation techniques, such as adsorption, coagulation/flocculation, flotation, filtration, and magnetic separation are first summarized. The influence of functional materials/reagents, properties of MPs/NPs, and aquatic chemistry on the separation efficiency is analyzed. Then, MP/NP degradation methods, including electrochemical degradation, advanced oxidation processes (AOPs), photodegradation, photocatalytic degradation, and biological degradation are detailed. Also, the effects of critical functional materials/organisms and operational parameters on degradation performance are discussed. At last, the current challenges and prospects in the separation, degradation, and further upcycling of MPs/NPs in urban waters are outlined. This review will potentially guide the development of next-generation technologies for MP/NP pollution control in urban waters.

Understanding and characteristics of coagulation removal of composite pollution of microplastic and norfloxacin during water treatment

Water composite pollution is still a great challenge in the field of water treatment. Especially for microplastic (MP), as an emerging pollutant, its wide distribution in water and persistent eco-environmental influence have received great concerns in recent years. Nevertheless, the removal characteristics and mechanism of conventional coagulation on MP composite pollution is quite insufficient. In this study, the coagulation removal performance and mechanisms of MP (polyethylene, PE) and norfloxacin (NOR) was investigated by polyaluminium chloride (PAC) and anionic polyacrylamide (APAM). Compared with single system, the removal efficiency of PE was significantly improved (>99.0%) under plateau stage in composite system, while the removal efficiency of NOR was slightly decreased to around 42% regardless of the addition of APAM. The scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), zeta potential and One-way analysis of variance (ANOVA) of experimental data were used to explore the coagulation mechanisms. The results demonstrated that the removal of individual PE and NOR was mainly controlled by charge neutralization and sweep flocculation by PAC and APAM, and adsorption by formation of Al-NOR complex, respectively. Importantly, in composite system, the removal of PE was enhanced not only by the stronger charge neutralization but also the adsorption via the formation of PE-NOR-Al complex. Furthermore, the removal efficiency of PE and NOR in neutral and weak alkaline conditions was higher than that in weak acidic or strong alkaline conditions. The presence of metal ions and humic acid had obvious inhibition and promoting effects on the removal efficiency of PE and NOR. This study can provide a new perspective on fundamental understanding in characteristics and mechanisms of MP composite pollutants removed by coagulation.

Nanomaterials for microplastic remediation from aquatic environment: Why nano matters?

The contamination of microplastics in aquatic environment is regarded as a serious threat to ecosystem especially to aquatic environment. Microplastic pollution associated problems including their bioaccumulation and ecological risks have become a major concern of the public and scientific community. The removal of microplastics from their discharge points is an effective way to mitigate the adverse effects of microplastic pollution, hence has been the central of the research in this realm. Presently, most of the commonly used water or wastewater treatment technologies are capable of removing microplastic to certain extent, although they are not intentionally installed for this reason. Nevertheless, recognizing the adverse effects posed by microplastic pollution, more efforts are still desired to enhance the current microplastic removal technologies. With their structural multifunctionalities and flexibility, nanomaterials have been increasingly used for water and wastewater treatment to improve the treatment efficiency. Particularly, the unique features of nanomaterials have been harnessed in synthesizing high performance adsorbent and photocatalyst for microplastic removal from aqueous environment. This review looks into the potentials of nanomaterials in offering constructive solutions to resolve the bottlenecks and enhance the efficiencies of the existing materials used for microplastic removal. The current efforts and research direction of which studies can dedicate to improve microplastic removal from water environment with the augmentation of nanomaterial-enabled strategies are discussed. The progresses made to date have witnessed the benefits of harnessing the structural and dimensional advantages of nanomaterials to enhance the efficiency of existing microplastic treatment processes to achieve a more sustainable microplastic cleanup.

Removal of polystyrene nanoplastics from water by CuNi carbon material: The role of adsorption

Nanoplastics have attracted wide attention worldwide as a new potentially threatening pollutant, and they can cause harm to the organisms and pose threat to the water environment. Therefore, efficient removal techniques for nanoplastics are urgently needed. In this study, CuNi carbon material (CuNi@C) was prepared by hydrothermal method for the removal of polystyrene (PS) nanoplastics from water. CuNi@C was effectively adsorbed on PS nanoplastics. When the CuNi@C dosage increased from 0.1 g/L to 0.3 g/L, the removal efficiency of PS nanoplastics (10 mg/L) elevated from 32.72% to 99.18%. The images of the scanning electron microscope (SEM) and the Fourier transform infrared spectroscopy (FTIR) spectra of CuNi@C confirmed the adsorption of PS nanoplastics on the CuNi@C. The fitting results of adsorption kinetic models and isotherms equations demonstrated that physical adsorption and monolayer coverage were the predominant mechanisms of the PS nanoplastics adsorption on CuNi@C. Thermodynamics analysis illustrated the adsorption of PS nanoplastics on CuNi@C was a spontaneous and endothermic process. The electrostatic attraction occurred in adsorption progress, and the removal efficiency of PS nanoplastics in the acidic system was generally higher than that in the alkaline system. CuNi@C can be recycled via washing and drying treatment and these CuNi@C comparable PS nanoplastics removal performance to the original ones. After four times cycles, CuNi@C can still remove ~75% of total PS nanoplastics from water. This study reveals that CuNi@C can be used as promising techniques for the removal of PS nanoplastics from the aqueous environment.

Application of a combined response surface methodology (RSM)-artificial neural network (ANN) for multiple target optimization and prediction in a magnetic coagulation process for secondary effluent from municipal wastewater treatment plants

In this study, an enhanced coagulation-flocculant process incorporating magnetic powder was used to further treat the secondary effluent of domestic wastewater from a municipal wastewater treatment plant. The purpose of this work was to improve the discharged water quality to the surface water class IV standard of China. A novel approach using a combination of the response surface methodology and an artificial neural network (RSM-ANN) was used to optimize and predict the total phosphorus (TP) pollutant removal and turbidity. This work was first evaluated by RSM using the concentrations of coagulant, magnetic powder, and flocculant as the controllable operating variables to determine the optimal TP removal and turbidity. Next, an ANN model with a back-propagation algorithm was constructed from the RSM data along with the non-controllable variables, raw TP concentration, and raw water turbidity. Under the optimized experimental conditions (28.42 mg/L coagulant, 623 mg/L magnetic powder, and 0.18 mg/L flocculant), the TP and turbidity removal reached 88.79 ± 5.45% and 63.48 ± 9.60%, respectively, compared with 83.28% and 59.80%, predicted by the single RSM model, and 87.71 ± 5.74% and 64.62 ± 10.75%, predicted by the RSM-ANN model. The treated water were 0.17 ± 6.69% mg/L of TP and 2.46 ± 5.09% NTU of turbidity, respectively, which completely met the surface water class IV standard (TP < 0.3 mg/L; turbidity < 3 NTU). Therefore, this work demonstrated that the discharged water quality was completely improved using the magnetic coagulation process. In addition, the combined RSM-ANN approach could have potential application in municipal wastewater treatment plants.

Improving nanoplastic removal by coagulation: Impact mechanism of particle size and water chemical conditions

Plastic particles may bring potential threats to the ecosystem. Coagulation, as a widely used method to remove particles, has been rarely studied for plastic particles in the nanometer range. In this work, the coagulation removal of polystyrene nanoplastic particles (PSNPs, 50-1000 nm) was conducted in a model system containing coagulants aluminum chlorohydrate (PAC) and polyacrylamide (PAM). The optimal removal efficiency (98.5%) was observed in the coagulation process at pH= 8.0, 0.4 g·L^-1 PAC and 20 mg·L^-1 PAM. The inhibition impact of humic acid was also noticed, due to its competitive adsorption with PSNPs onto flocs. The interaction energies between PSNPs and PAC were calculated by the extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) theory, which showed that electrical neutralization resulted in the difference of the remove efficiency in different sizes and coagulant concentrations. The formation of Al-O bond between PSNPs and PAC/PAM flocs promoted the removal of PSNPs. Excessive PAM (> 20 mg·L^-1) increased clusters size and solution viscosity, which resulted in the settling of clusters being controlled by buoyancy and the reduced remove efficiency. The findings suggest that the chemical coagulation dominants the removal of NPs, and the coagulation efficiency can be optimized by choosing suitable coagulant and water chemical conditions.

Microplastics and nanoplastics: Recent literature studies and patents on their removal from aqueous environment

The presence of microplastics (MP) and nanoplastics (NP) in the environment poses significant hazards towards microorganisms, humans, animals and plants. This paper is focused on recent literature studies and patents discussing the removal process of these plastic pollutants. Microplastics and nanoplastics can be quantified by counting, weighing, absorbance and turbidity and can be further analyzed using scanning electron microscopy (SEM), dynamic light scattering (DLS), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, surface-enhanced Raman spectroscopy and Raman tweezers. Mitigation methods reported are categorized depending on the removal characteristics: (i) Filtration and separation method: Filtration and separation, electrospun nanofiber membrane, constructed wetlands; (ii) Capture and surface attachment method: coagulation, flocculation and sedimentation (CFS), electrocoagulation, adsorption, magnetization, micromachines, superhydrophobic materials and microorganism aggregation; and (iii) Degradation method: photocatalytic degradation, microorganism degradation and thermal degradation; where removal efficiency between 58 and 100% were reported. As these methods are significantly distinctive, the parameters which affect the MP/NP removal performance e.g., pH, type of plastics, presence of interfering chemicals or ions, surface charges etc. are also discussed. 42 granted international patents related to microplastics and nanoplastics removal are also reviewed where the majority of these patents are focused on separation or filtration devices. These devices are efficient for microplastics up to 20 μm but may be ineffective for nanoplastics or fibrous plastics. Several patents were found to focus on methods similar to literature studies e.g., magnetization, CFS, biofilm and microorganism aggregation; with the addition of another method: thermal degradation.

Aggregation of carboxyl-modified polystyrene nanoplastics in water with aluminum chloride: Structural characterization and theoretical calculation

Nanoplastics (NPs) pollution of aquatic systems is becoming an emerging environmental issue due to their stable structure, high mobility, and easy interactions with ambient contaminants. Effective removal technologies are urgently needed to mitigate their toxic effects. In this study, we systematically investigated the removal effectiveness and mechanisms of a commonly detected nanoplastics, carboxyl-modified polystyrene (PS-COOH) via coagulation and sedimentation processes using aluminum chloride (AlCl₃) as a coagulant. PS-COOH appeared as clearly defined and discrete spherical nanoparticles in water with a hydrodynamic diameter of 50 nm. The addition of 10 mg/L AlCl₃ compressed and even destroyed the negatively charged PS-COOH surface layer, decreased the energy barrier, and efficiently removed 96.6% of 50 mg/L PS-COOH. The dominant removal mechanisms included electrostatic adsorption and intermolecular interactions. Increasing the pH from 3.5 to 8.5 sharply enhanced the PS-COOH removal, whereas significant loss was observed at pH 10.0. High temperature (23 °C) favored the removal of PS-COOH compared to lower temperature (4 °C). High PS-COOH removal efficiency was observed over the salinity range of 0 - 35‰. The presence of positively charged Al₂O₃ did not affect the PS-COOH removal, while negatively charged SiO₂ reduced the PS-COOH removal from 96.6% to 93.2%. Moreover, the coagulation and sedimentation process efficiently removed 90.2% of 50 mg/L PS-COOH in real surface water even though it was rich in inorganic ions and total organic carbon. The fast and efficient capture of PS-COOH by AlCl₃ via a simple coagulation and sedimentation process provides a new insight for the treatment of NPs from aqueous environment.

Highly efficient removal of DEET by UV-LED irradiation in the presence of iron-containing coagulant

N,N-Diethyl-3-methyl benzoyl amide (DEET) has been detected as an emerging pollutant in various water bodies because of its widespread use as an insect repellent. In this study, the combination of UV-LED₂₇₅ and iron-containing coagulant (FeCl₃) was used for the elimination of DEET in water. It was found that UV-LED₂₇₅/FeCl₃ (98 %) system presented a favorable removal of DEET compared with UV₂₅₄/FeCl₃ (59 %) and UV-LED₂₇₅/Fe₂(SO₄)₃ (81 %) processes at initial pH 3.5. DEET degradation by both UV-LED₂₇₅/FeCl₃ and UV-LED₂₇₅/Fe₂(SO₄)₃ processes followed pseudo-first-order kinetics with the calculated pseudo-first-order rate constants (k_obs) of 0.0105 and 0.0046 cm² mJ^-1, respectively. The results of ESR analysis and radicals quenching experiments indicated that hydroxyl radicals (OH) and superoxide radicals (O₂^-) were responsible for DEET degradation in UV-LED₂₇₅/FeCl₃ process, and the former played the major role. An increase in FeCl₃ dosage was beneficial to the degradation. In the UV-LED₂₇₅/FeCl₃ process, DEET degradation increased with a decrease in pH from 3.5 to 3.0, whereas it was almost completely suppressed with an increase in pH from 4.3 to 6.3. DEET degradation was almost unchanged after the introduction of NO₃^-, and it impeded after the addition of humic acid (HA), HCO₃^-, and SO₄^2-. The plausible degradation pathway mainly involved hydroxylation, cleavage of the C-N bond, acetylation, and dealkylation. Among the disinfection by-products (DBPs) evaluated, UV-LED₂₇₅/FeCl₃ pretreatment generally increased the generation of trichloromethane, chloral hydrate, dichloroacetic acid, and trichloroacetic acid, which implied that further assessment of environmental risk was needed during its practical applications.

Enhanced removal of polyethylene terephthalate microplastics through polyaluminum chloride coagulation with three typical coagulant aids

Given the discovery and hazard of microplastics in freshwater environments, the removal of microplastics in drinking water deserves more attention. Nevertheless, in the light of existing literature, the effectiveness of conventional coagulation on microplastics removal is insufficient. Hence, enhanced coagulation is worth being explored. This study investigated the improving performance of anionic polyacrylamide (PAM), sodium alginate (SA), and activated silicic acid (ASA) when using poly‑aluminum chloride (PAC) to remove polyethylene terephthalate (PET) microplastics. The experimental results showed that ASA had the highest removal efficiency (54.70%) under conventional dosage, while PAM achieved the best removal effect (91.45%) at high dosage. Mechanism of coagulation was studied by scanning electron microscope (SEM), Fourier transform infrared spectroscope (FTIR), X-ray photoelectron spectroscopy (XPS), and the results illustrated that when only PAC existed or the dosage of coagulant aids was low, double layer compression was the main principle. The increase of coagulant aids dosage improved the effect of adsorption and sweep flocculation significantly. Moreover, jar tests carried in different conditions demonstrated that the current coagulation systems were highly adaptable.

Understanding the fragmentation of microplastics into nano-plastics and removal of nano/microplastics from wastewater using membrane, air flotation and nano-ferrofluid processes

Nano/microplastics (NPs/MPs), a tiny particle of plastic pollution, are known as one of the most important environmental threats to marine ecosystems. Wastewater treatment plants can act as entrance routes for NPs/MPs to the aquatic environment as they breakdown of larger fragments of the plastic component during the treatment process; therefore, it is necessary to remove NPs/MPs during the wastewater treatment process. In this study, understanding the effect of water shear force on the fragmentation of larger size MPs into smaller MPs and NPs and their removal by air flotation and nano-ferrofluid (i.e., magnetite and cobalt ferrite particle as a coagulant) and membrane processes were investigated as a proof-of-concept study. It is found that a two-blade mechanical impeller could fragment MPs from 75, 150 and 300 μm into mean size NPs/MPs of 0.74, 1.14 and 1.88 μm, respectively. Results showed that the maximum removal efficiency of polyethylene, polyvinyl chloride and polyester was 85, 82 and 69%, respectively, in the air flotation process. Increasing the dose of behentrimonium chloride surfactant from 2 to 10 mg/L improved the efficiency of the air flotation process for NPs/MPs removal. It is also found that the removal efficiency of NPs/MPs by the air flotation system depends on solution pH, size, and types of NPs/MPs. This study also found a less significant removal efficiency of NPs/MPs by both types of ferrofluid used in this study with an average removal of 43% for magnetite and 55% for cobalt ferrite. All three plastics tested had similar removal efficiency by the nano-ferrofluid particles, meaning that this removal technique does not rely on the plastic component type. Among all the process tested, both ultrafiltration and microfiltration membrane processes were highly effective, removing more than 90% of NPs/MPs fragment particles. Overall, this study has confirmed the effectiveness of using air flotation and the membrane process to remove NPs/MPs from wastewater.

Is froth flotation a potential scheme for microplastics removal? Analysis on flotation kinetics and surface characteristics

Increasing microplastics (MPs) cause significant threats to the ecosystem and society. The tremendous advances concerning the sources, occurrence, chemical behavior, toxicology, and ecological effects contribute to the emerging MPs removal. Based on the intrinsic hydrophobicity of MPs, froth flotation can remove MPs from water environments via bubble attachment on hydrophobic surfaces. This study comprehensively investigated plastic, aqueous, and operating variables in the flotation removal of polyethylene terephthalate (PET) and polystyrene (PS) MPs, assisted by numerous bench-scale experiments and a first-order model with rectangular distribution of floatability. Froth flotation performed better to remove MPs with higher density, larger size, and lower concentration. K⁺ (0-50 mM), Na⁺ (0-150 mM), and Ca²⁺ (0-10 mM) did not affect the flotation recovery of MPs. MPs particles could be thoroughly removed by froth flotation when humic acid (HA) and Al³⁺ concentrations were less than 30 mg/L and 0.05 mM, respectively. 100% of MPs could be removed at a rapid flotation rate under aeration volume of 5.4 mL/min and frother dosage of 28 mg/L. Non-covalent interactions and near-surface water film might favor the adhesion of hydrophilic species and obstruct the flotation removal of MPs. The froth flotation-based MPs removal had potential application in multiple flow systems due to its simplicity and continuity.

What have we known so far about microplastics in drinking water treatment? A timely review

Microplastics (MPs) have been widely detected in drinking water sources and tap water, raising the concern of the effectiveness of drinking water treatment plants (DWTPs) in protecting the public from exposure to MPs through drinking water. We collected and analyzed the available research articles up to August 2021 on MPs in drinking water treatment (DWT), including laboratory- and full-scale studies. This article summarizes the major MP compositions (materials, sizes, shapes, and concentrations) in drinking water sources, and critically reviews the removal efficiency and impacts of MPs in various drinking water treatment processes. The discussed drinking water treatment processes include coagulation-flocculation (CF), membrane filtration, sand filtration, and granular activated carbon (GAC) filtration. Current DWT processes that are purposed for particle removal are generally effective in reducing MPs in water. Various influential factors to MP removal are discussed, such as coagulant type and dose, MP material, shape and size, and water quality. It is anticipated that better MP removal can be achieved by optimizing the treatment conditions. Moreover, the article framed the major challenges and future research directions on MPs and nanoplastics (NPs) in DWT.

Differences in removal rates of virgin/decayed microplastics, viruses, activated carbon, and kaolin/montmorillonite clay particles by coagulation, flocculation, sedimentation, and rapid sand filtration during water treatment

One of the main purposes of drinking water treatment is to reduce turbidity originating from clay particles. Relatively little is known about the removal of other types of particles, including conventionally sized powdered activated carbon (PAC) and superfine PAC (SPAC), which are intentionally added during the treatment process; microplastic particles; and viruses. To address this knowledge gap, we conducted a preliminary investigation in full-scale water treatment plants and then studied the removal of these particles during coagulation-flocculation, sedimentation, and rapid sand filtration (CSF) in bench-scale experiments in which these particles were present together. Numbers of all target particles were greatly decreased by coagulation-flocculation and sedimentation (CS). Subsequent rapid sand filtration greatly reduced the concentrations of PAC and SPAC but not the concentrations of viruses, microplastic particles, and clay particles. Overall removal rates by CSF were 4.6 logs for PAC and SPAC, 3.5 logs for viruses, 2.9 logs for microplastics, and 2.8 logs for clay. The differences in removals were not explained by particle sizes or zeta potentials. However, for clays, PAC and SPAC, for which the particle size distributions were wide, smaller particles were less efficiently removed. The ratios of both clay to PAC and clay to SPAC particles increased greatly after rapid sand filtration because removal rates of PAC and SPAC particles were about 2 logs higher than removal rates of clay particles. The trend of greater reduction of PAC concentrations than turbidity was confirmed by measurements made in 14 full-scale water purification plants in which residual concentrations of PAC in treated water were very low, 40-200 particles/mL. Clay particles therefore accounted for most of the turbidity in sand filtrate, even though PAC was employed. The removal rate of microplastic particles was comparable to that of clays. Sufficient turbidity removal would therefore provide comparable removal of microplastics. We investigated the effect of mechanical/photochemical weathering on the removal of microplastics via CSF. Photochemical weathering caused a small increment in the removal rate of microplastics during CS but a small reduction in the removal rate of microplastics during rapid sand filtration; mechanical weathering decreased the removal rate via CS but increased the removal rate via rapid sand filtration. The changes of removal of microplastics might have been caused by changes of their zeta potential.

Microplastic contaminants in the aqueous environment, fate, toxicity consequences, and remediation strategies

Microplastic is a fragmented plastic part that emerges as a potential marine and terrestrial contaminant. The microplastic wastes in marine and soil environments cause severe problems in living systems. Microplastic wastes have been linked to various health problems, including reproductive harm and obesity, plus issues such as organ problems and developmental delays in children. Recycling plastic/microplastics from the environment is very low, so remediating these polymers after their utilization is of paramount concern. The microplastic causes severe toxic effects and contaminates the environment. Microplastic affects marine life, microorganism in soil, soil enzymes, plants system, and physicochemical properties. Ecotoxicology of the microplastic raised many questions about its use and development from the environment. Various physicochemical and microbial technologies have been developed for their remediation from the environment. The microplastic effects are linked with its concentration, size, and shape in contaminated environments. Microplastic is able to sorb the inorganic and organic contaminants and affect their fate into the contaminated sites. Microbial technology is considered safer for the remediation of the microplastics via its unique metabolic machinery. Bioplastic is regarded as safer and eco-friendly as compared to plastics. The review article explored an in-depth understanding of the microplastic, its fate, toxicity to the environment, and robust remediation strategies.

Microplastic removal in conventional drinking water treatment processes: Performance, mechanism, and potential risk

The effectiveness of traditional drinking water treatment plants for the removal of Microplastics (MPs) in the size range of tens of micrometers is currently uncertain. This study investigated the behavior and removal efficiency of four different sized polystyrene MPs (10-90 μm in diameter) in a simulated cascade of coagulation/sedimentation, sand filtration, and UV-based oxidation over technically relevant time frames. In the coagulation and sand filtration steps, the larger the MP size, the better it was removed. The coagulant type and water characteristics (i.e., pH and the presence of natural organic matter) influenced the coagulation efficiency for MPs. X-ray microcomputed tomography technique and two-site kinetic modeling were used to identify the mechanisms involved in sand filtration. The MPs > 20 μm could be completely retained in sand by straining, while the attachment to the sand surface was likely responsible for the retention of MPs < 20 μm. However, approximately 16% of 10 μm MPs injected passed through the sand, which were further fragmented by UV oxidation. UV/H₂O₂ treatment promoted the MP fragmentation and chemical leaching more significantly than UV treatment, resulting in a higher toxicity for UV/H₂O₂-treated water. Our findings pave the way for deeper understanding of how MPs behave and transform in a sequential drinking water treatment process.

Treatment processes for microplastics and nanoplastics in waters: State-of-the-art review

In this work, established treatment processes for microplastics (MPs) and nanoplastics (NPs) in water as well as developed analytical techniques for evaluation of the operation of these processes were reviewed. In this regard, the strengths and limitations of different qualitative and quantitative techniques for the analysis of MPs and NPs in water treatment processes were first discussed. Afterward, the MPs and NPs treatment processes were categorized into the separation and degradation processes and the challenges and opportunities in their performance were analyzed. The evaluation of these processes revealed that the MPs or NPs removal efficiency of the separation and degradation processes could reach up to 99% and 90%, respectively. It can be concluded from this work that the combination of separation and degradation processes could be a promising approach to mineralize MPs and NPs in water with high efficiency.