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Rapid sand filtration for <10 μm-sized microplastic removal in tap water treatment: Efficiency and adsorption mechanisms
Abstract
The omnipresence of microplastics (MPs) in potable water has become a major concern due to their potential disruptive effect on human health. Therefore, the effective removal of MPs in drinking water is essential for life preservation. In this study, tap water containing microplastic <10 μm in size was treated using constructed pilot-scale rapid sand filtration (RSF) system to investigate the removal efficiency and the mechanisms involved. The results show that the RSF provides significant capacity for the removal and immobilization of MPs < 10 μm diameter (achieving 98 %). Results showed that silicate sand reacted with MPs through a cooperative assembly process, which mainly involved interception, trapping, entanglement, and adsorption. The MPs were quantified by Flow cytometry instrument. A kinetics study underlined the pivotal role of physio-chemisorption in the removal process. MP particles smaller than absorbents, saturation of adsorbents, and reactor hydrodynamics were identified as limiting factors, which were alleviated by backwashing. Backwashing promoted the desorption of up to 97 % MPs, conducive for adsorbent active site regeneration. These findings revealed the critical role of RSF and the importance of backwashing in removing MPs. Understanding the mechanisms involved in removing microplastics from drinking water is crucial in developing more efficient strategies to eliminate them.
... Sludge generation from filtration processes occurs due to the accumulation of captured solids and particulates on the filtration media, such as sand, gravel, or various filter media [66,67]. In wastewater treatment plants, filtration processes may include rapid sand filtration, multimedia filtration, or membrane filtration techniques like microfiltration, ultrafiltration, or reverse osmosis [68][69][70]. Regardless of the specific method used, the accumulation of captured solids on the filtration media gradually reduces the effectiveness of the filtration process, necessitating periodic cleaning or replacement of the media [50]. The sludge generated from filtration processes, often referred to as filter cake, consists of the captured solids, particulates, and organic matter [71]. ...
... This suggests that GAC (Granular Activated Carbon) biofilters employed at the treatment plant serve the purpose of eliminating emerging contaminants and controlling opportunistic pathogens. However, there are concerns regarding the potential saturation of the granular media's pores during the water treatment process, coupled with suboptimal backwashing procedures [51]. These factors may lead to the detachment of bacterial contaminants into the granular filters, ultimately allowing them to enter the treated water. ...
... Filtration is a process by which particles and microorganisms dispersed in an aqueous medium are retained through membranes or granular materials. This retention occurs owing to the transport mechanisms (diffusion, interception, and sedimentation) and adhesion (through physisorption or chemisorption), as shown in Fig. 4. Filtration transport mechanisms have been elucidated and correlated with the efficiency of filter materials (Chabi et al., 2024;. Regarding microplastic pollution, the efficiency of filtration depends on both the filter material (i.e. ...
Microplastics (MPs) composed of different polymers with various shapes, within a vast granulometric distribution (1 μm - 5 mm) and with a wide variety of physicochemical surface and bulk characteristics spiral around the globe, with different atmospheric, oceanic, cryospheric, and terrestrial residence times, while interacting with other pollutants and biota. The challenges of microplastic pollution are related to the complex relationships between the microplastic generation mechanisms (physical, chemical, and biological), their physicochemical properties, their interactions with other pollutants and microorganisms, the changes in their properties with aging, and their small sizes that facilitate their diffusion and transportation between the air, water, land, and biota, thereby promoting their ubiquity. Early career researchers (ERCs) constitute an essential part of the scientific community committed to overcoming the challenges of microplastic pollution with their new ideas and innovative scientific perspectives for the development of remediation technologies. However, because of the enormous amount of scientific information available, it may be difficult for ERCs to determine the complexity of this environmental issue. This mini-review aims to provide a quick and updated overview of the essential insights of microplastic pollution to ERCs to help them acquire the background needed to develop highly innovative physical, chemical, and biological remediation technologies, as well as valorization proposals and environmental education and awareness campaigns. Moreover, the recommendations for the development of holistic microplastic pollution remediation strategies presented here can help ERCs propose technologies considering the environmental, social, and practical dimensions of microplastic pollution while fulfilling the current government policies to manage this plastic waste.
Adsorption isotherm is the most important calculation to predict and analyze the various possible mechanisms that occur in adsorption process. However, until now, most studies only presented the adsorption isotherm theory, and there are no studies that explain the adsorption isotherm thoroughly and in detail from theory to calculation. Therefore, this study contains guidelines for selecting the type of adsorption isotherm to describe the entire adsorption data set, which is featured by the ten most common adsorption isotherms. The steps of how to analyze the two-parameter monolayer adsorption are presented. This study is expected to provide clear and useful information for researchers who are working and studying on the adsorption process.
Microplastic pollution has become a global environmental concern with detrimental effects on ecosystems and human health. Effective removal of microplastics from water sources is crucial to mitigate their impacts. Advanced oxidative processes (AOPs) have emerged as promising strategies for the degradation and elimination of microplastics. This review provides a comprehensive overview of the application of AOPs in the removal of microplastics from water. Various AOPs, such as photocatalysis, ozonation, and Fenton-like processes, have shown significant potential for microplastic degradation. These processes generate highly reactive species, such as hydroxyl radicals, which can break down microplastics into smaller fragments or even mineralize them into harmless byproducts. The efficiency of photocatalytic oxidation depends on several factors, including the choice of photocatalysts, reaction conditions, and the physicochemical properties of microplastics. Furthermore, this review discusses the challenges associated with photocatalytic oxidation, such as the need for optimization of operating parameters and the potential formation of harmful byproducts. Overall, photocatalytic oxidation offers a promising avenue for the removal of microplastics from water, contributing to the preservation of aquatic ecosystems and safeguarding human health. However, further research is needed to address the limitations and optimize the implementation of this process for effective and sustainable microplastic remediation.
Human exposure to microplastics (MPs) through drinking water has drawn serious concern recently because of the potential adverse health effects. Although there are reports on the occurrence of MPs in bottled water, little is known about the abundance of a whole spectrum of MPs with sizes ranging from 1 µm to 5 mm due to the restrictions of conventional MPs detection methods. Some studies using micro-Raman spectroscopy can achieve MPs with a size of <10 µm, however, quantitation of all MPs was extremely time consuming and only a small portion (<10%) of MPs would be analyzed. The present study quantified MPs from nine brands of bottled water using fluorescence microscopy and flow cytometry for MPs with a size of ≥50 µm and a size of <50 µm, respectively. The average abundance of MPs with a size of ≥50 µm in bottled water samples was found ranging from 8–50 particles L−1, while MPs with a size of <50 µm were found to be 1570–17,817 particles L−1, where the MPs abundance from mineral water samples were significantly more than distilled and spring water samples. The modal size and shape of MPs were found at 1 µm and fragments, respectively. Besides, three tap water samples obtained locally were analyzed and compared with the bottled water samples, where less MPs were found in tap water samples. In addition, contamination of MPs from bottle and cap and interference by addition of mineral salts were studied, where no significant difference from all these processes to the control sample was found, suggesting the major contamination of MPs was from other manufacturing processes. Estimated daily intake (EDI) of MPs increased substantially when data of small MPs are included, suggesting that previously reports on exposure of MPs from drinking water might be underestimated, as only large MPs were considered.
The effects of microalgal biofouling on microplastic (MP) may differ from bacterial biofouling. In this study, the influence of microalgae on MP surface alteration, structural change, and adsorption of organic micropollutants was evaluated. Virgin polyethylene (PE), polyvinyl chloride (PVC), and polyamide (PA) were each immersed in algal photobioreactor and river freshwater for 30 days to simulate algal and river microbe biofouling respectively. Consequently, their physicochemical changes and adsorption potential of a mixture of six bisphenol analogues (BPA, BPS, BPE, BPB, BPF, BPAF) and two parabens (propyl–paraben, benzyl–paraben) were investigated. Owing to the algal bioactive compounds, major microalgae-induced biofouling and more MP aging than the river microbe aging were observed through fractures, pits, cracks, and algal attachments. Intrusion of algal organic matter and scission of polymeric functional groups were revealed during microalgal immersion and the potential MP aging pathways were proposed. Algal biofouling considerably altered the intrinsic properties of the MPs, consequently the adsorption capacity of PE and PVC was enhanced by 3.04–6.72 and 2.14–8.72 times, respectively. Adsorption process onto algal-aged MPs was pH-dependent, endothermic, non-spontaneous, and favored by hydrogen bonds. Meanwhile, the amide group in PA structure was conducive to organic micropollutant adsorption, which was likely reduced by algal aging and the erosion of the N-H stretching. Moreover, higher adsorption capacities of organic micropollutants were shown by the algal-biofilm PE and PVC than virgin and river microbial biofilm MPs. This study discloses that, biofouling and aging of MPs by microalgae through their bioactive components would engender more incidences on MPs properties, organic micropollutants adsorption with associated environmental and health hazards.
Microplastics are the new emerging pollutants ubiquitously detectable in aquatic and terrestrial ecosystems. Fate and behavior, as well as ecotoxicity, are of increasing environmental concern, particularly in sediments and soils as natural sinks. For a global environmental risk assessment, reliable and easy to apply analytical methods are mandatory to obtain comparable data. This is based on the isolation of microplastics out of the solid sample matrices prior to instrumental detection. Thus, this study provides an easy to apply approach for density separation. The technique emerged from a comparative study using different salt solutions to isolate conventional, and for the first time biodegradable, microplastics from different solid sample matrices, i.e., sand, artificial soil, and compost. Four solutions (water, sodium chloride, sodium hexametaphosphate, and sodium bromide) of different densities were applied followed by oxidizing digestion. Finally, the impact of the procedures on size and surface properties of microplastics was tested. Dependent on the sample matrix, the highest recovery rates of 87.3–100.3% for conventional polymers, and 38.2–78.2% for biodegradable polymers, were determined with sodium bromide. It could be shown that the type of solid sample matrix influences the recovery rates and has to be considered when choosing a sample preparation technique.
Graphical abstract
The prevalence of micro and nanoplastics (MNPs) across the various environments and their negative impact on ecosystems have become a serious global threat and are currently a subject of many environmental concerns. Studies have provided evidence that MNPs have the potential to leach toxic plastic chemical additives and can adsorb a variety of persistent organic environmental pollutants, thereby enhancing their bioavailability, toxicity, and dispersion. Moreover, these MNPs easily penetrate the food chain and might cause health problems when ingested by humans and other organisms. Currently, there is complexity in understanding the mechanisms by which these toxic chemicals adsorb/desorb onto/from MNPs, and the physical and biological impacts of these chemical additives. To date, there is a considerable lack of knowledge on the major chemical additives of concern used in the plastic industry, their fate once MNPs dispose into the environment, the factors that affect their degradation, and their consequent impacts on human health. This review critically analyzes the current knowledge concerning the physical, chemical, and biological impacts of MNPs, and the various chemical and organic pollutants associated with MNPs. Emphasis was laid on their types, occurrence, fate, and distribution in the environment. The different techniques used in their identification, characterization, and removal were also elucidated. Furthermore, the consequent harmful effects of MNPs on human health were discussed to spur more future studies and fill knowledge gaps in this area.
Occurrence of microplastics and nanoplastics in aquatic systems, as well as in water compartments used to produce drinking water have become a major concern due to their impact on the environment and public health. Nanoplastics in particular, in regard to their fate and removal efficiency in drinking water treatment plants (DWTP), which ensure water quality and supply drinking water for human consumption have been, by far, rarely investigated. This study investigates the removal efficiency of polystyrene (PS) nanoplastics in a conventional water treatment plant providing drinking water for 500′000 consumers. For that purpose, a pilot-scale DWTP, located within the main treatment plant station, reproducing at a reduced scale the different processes and conditions of the main treatment plant is used. The results show that filtration process through sand and granular activated carbon (GAC) filters in the absence of coagulation achieves an overall nanoplastic removal of 88.1%. The removal efficiency of filtration processes is mainly attributed to physical retention and adsorption mechanisms. On the other hand, it is found that coagulation process greatly improves the removal efficiency of nanoplastics with a global removal efficiency equal to 99.4%. The effective removal efficiency of sand filtration increases considerably from 54.3% to 99.2% in the presence of coagulant, indicating that most of PS nanoplastics are removed during sand filtration process. The higher removal efficiency with the addition of coagulant is related to nanoplastics surface charge reduction and aggregation thus significantly increasing their retention in the filter media.
Microplastic contamination has become a problem, as plastic production has increased worldwide. Microplastics are plastics with particles of less than 5 mm and are absorbed through soil, water, atmosphere, and living organisms and finally affect human health. However, information on the distribution, toxicity, analytical methods, and removal techniques for microplastics is insufficient. For clear microplastic analytical methods and removal technologies, this article includes the following: (1) The distribution and contamination pathways of microplastics worldwide are reviewed. (2) The health effects and toxicity of microplastics were researched. (3) The sampling, pretreatment, and analytical methods of microplastics were all reviewed through various related articles. (4) The various removal techniques of microplastics were categorized by wastewater treatment process, physical treatment, chemical treatment, and biological treatment. This paper will be of great help to microplastic analysis and removal techniques.
Although plastic materials play an essential role in life, the intensive production of plastic products and mismanagement of plastic waste worldwide have resulted in microplastic pollution. The two major characteristics of environmental microplastics are having small size and resistance to degradation, which make microplastics a persistent organic pollutant. As microplastic pollution has been observed in diverse environmental matrices, it has attracted great attention of scholars globally. Over the last decade, scholars have mainly documented the particle properties of microplastics, such as size, shape or color and their adverse effects on organisms. However, no research has updated on environmental microplastics from the perspective of multi-media. Our review first summarized the literature in the occurrence, distribution, and characteristics of microplastics in three kinds of environmental matrices (water, soil, and air) to the public. We then identify the methodological challenges in researches and discuss the advantages and limitations of popular methods to analyze environmental microplastics. Eventually, our paper highlights the current challenges and proposes suggestions for the future research on microplastic pollution.
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.
Microplastics (MPs), tiny particles broken down from larger pieces of plastics, have accumulated everywhere on the earth. As an inert carbon stream in aquatic environment, they have been reported as carriers for heavy metals and exhibit diverse interactive effects. However, these interactions are still poorly understood, especially mechanisms driving these interactions and how they pose risks on living organisms. In this mini review, a bibliometric analysis in this field was conducted and then the mechanisms driving these interactions were examined, especially emphasizing the important roles of microorganisms on the interactions. Their combined toxic effects and the potential hazards to human health were also discussed. Finally, the future research directions in this field were suggested. This review summarized the recent research progress in this field and highlighted the essential roles of the microbes on the interactions between MPs and heavy metals with the hope to promote more studies to unveil action mechanisms and reduce/eliminate the risks associated with MP presence.
Microplastics (MPs) have been detected in drinking water and raw water sources. Therefore, it is important to know the performance of drinking water treatment process. The rapid sand filter (RSF) is one of the water treatments that can be an alternative treatment in removing MPs after several configuration processes (pre-sedimentation, coagulation-flocculation, and sedimentation). This study aims to determine the effectiveness of RSF to remove MPs. The artificial samples were made from plastics bags and tyre flakes, with sizes from 10 μm to more than 500 μm. Bentonite was added to represent turbidity in the water. The average removal efficiency of plastics flakes before entering the filter was 50.48% (using bentonite) and 47.78% (without bentonite). Overall, the removal efficiency for the tyre flakes was 90.72% (using bentonite) and 93.03% (without bentonite). The filtration used in this study was varied between 4 and 10 m/h. Removal efficiency using RSF for plastic flakes on which the Effective Size (ES) filter media 0.39 mm was 97.7% and on which ES 0.68 mm was 94.3%. Meanwhile, the removal efficiency of the tyre flakes for ES 0.39 mm were 90.6% and ES 0.68 mm was 85.2%. However, in this study, RSF mostly removed MPs particles greater than 200 μm in size. HIGHLIGHTS
Mostly MPs >= 200 μm can be removed by using a conventional rapid sand filter.;
Increased turbidity will not increase the efficiency of MPs removal.;
Part of the MPs can also be removed in coagulation and flocculation.;
Size of MPs is important for the surface screening mechanism.;
Plastics have enormous impacts to every aspect of daily life including technology, medicine and treatments, and domestic appliances. Most of the used plastics are thrown away by consumers after a single use, which has become a huge environmental problem as they will end up in landfill, oceans and other waterways. These plastics are discarded in vast numbers each day, and the breaking down of the plastics from micro- to nano-sizes has led to worries about how toxic these plastics are to the environment and humans. While, there are several earlier studies reported the effects of micro- and nano-plastics have on the environment, there is scant research into their impact on the human body at subcellular or molecular levels. In particular, the potential of how nano-plastics move through the gut, lungs and skin epithelia in causing systemic exposure has not been examined thoroughly. This review explores thoroughly on how nanoplastics are created, how they behave/breakdown within the environment, levels of toxicity and pollution of these nanoplastics, and the possible health impacts on humans, as well as suggestions for additional research. This paper aims to inspire future studies into core elements of micro- and nano-plastics, the biological reactions caused by their specific and unusual qualities.
Adsorption for water and wastewater treatment has been the subject of many research in the scientific community, focusing mainly on either equilibrium or kinetic studies. Adsorption kinetics are commonly modeled using pseudo-first and pseudo-second order rate laws. Analyses of published works in the past two decades indicated that the pseudo-second order is considered to be the superior model as it can represent many adsorption systems. However, critical assessment of modeling techniques and practices suggests that its superiority could be a consequence of currently acceptable modeling norms which tend to favor the pseudo-second order model. The partiality was due to several modeling pitfalls that are often neglected. In addition, commonly used model validation tools are often used haphazardly and redundantly. As such, they cannot sufficiently provide any kind of certainty on the validity of a model. To eliminate modeling biasness, a new validation method was proposed and was then employed to re-examine previously published adsorption kinetic data.
Backwashing rapid sand filters causes inadvertent displacement of filter media grains from their previous depths. This displacement can affect the hydraulic function of filters by segregating media grains, and the function of biofilters through displacement of active biomass and coatings from proper depths. This study quantifies grain displacement in a pilot-scale filter using tracer grains of colored sand, glass beads, anthracite and garnet to determine the effect of grain size, density and shape on grain displacement.
Microplastics are particles smaller than five millimeters deriving from the degradation of plastic objects present in the environment. Microplastics can move from the environment to living organisms, including mammals. In this study, six human placentas, collected from consenting women with physiological pregnancies, were analyzed by Raman Microspectroscopy to evaluate the presence of microplastics. In total, 12 microplastic fragments (ranging from 5 to 10 μm in size), with spheric or irregular shape were found in 4 placentas (5 in the fetal side, 4 in the maternal side and 3 in the chorioamniotic membranes); all microplastics particles were characterized in terms of morphology and chemical composition. All of them were pigmented; three were identified as stained polypropylene a thermoplastic polymer, while for the other nine it was possible to identify only the pigments, which were all used for man-made coatings, paints, adhesives, plasters, finger paints, polymers and cosmetics and personal care products.
The adventitious carbon located at 284.8 eV was used to calibrate samples without the carbon themselves. When the carbon is as a major part of the inorganic material, the adventitious carbon should be identified and used as the reference. There is no adventitious carbon on the surfaces of the polymer materials, so using C1s of the carbon in the polymer itself to calibrate the charging effect is reasonable. Furthermore, compared with gold and argon, a more practical and convenient method based on C1s is proposed to get the right positions for binding energy peaks.
Microplastic pollution of water and ecosystem is attracting continued attention worldwide. Due to their small sizes (≤ 5 mm) microplastic particles can be discharged to the environment from treated wastewater effluents. As microplastics have polluted most of our aquatic ecosystems, often finding its way into drinking water, there is urgent need to find new solutions for tackling the menace of microplastic pollution. In this work, sustainable green photocatalytic removal of microplastics from water activated by visible light is proposed as a tool for the removal of microplastics from water. We propose a novel strategy for the elimination of microplastics using glass fiber substrates to trap low density microplastic particles such as polypropylene (PP) which in parallel support the photocatalyst material. Photocatalytic degradation of PP microplastics spherical particles suspended in water by visible light irradiation of zinc oxide nanorods (ZnO NRs) immobilized onto glass fibers substrates in a flow through system is demonstrated. Upon irradiation of PP microplastics for two weeks under visible light reduced led to a reduction of the average particle volume by 65%. The major photodegradation by-products were identified using GC/MS and found to be molecules that are considered to be mostly nontoxic in the literature.
Microplastics are globally recognized as contaminants in freshwater and marine aquatic systems. To date there is no universally accepted protocol for isolation and quantification of microplastics from aqueous media. Various methodologies exist, many of which are time consuming and have the potential to introduce contaminants into samples, thereby obscuring characterization of the environmental microplastic load. Here, we present first steps in the detection of microplastics in liquid samples, based on their fluorescent staining followed by high throughput analysis and quantification using Flow Cytometry. Using controlled laboratory settings nine polymer types [polystyrene (PS); polyethylene (PE); polyethylene terephthalate (PET/PETE); high density polyethylene (HDPE); low density polyethylene (LDPE); polyvinyl chloride (PVC); polypropylene (PP); nylon (PA); polycarbonate (PC)] were tested for identification and quantification in freshwater. All nine plastic types were stained with 10 μg/mL Nile Red in 10% dimethyl sulfoxide with a 10 min incubation time. The lowest spatial detectable limit for plastic particles was 200 nm. Out of the nine polymer types chosen for the study PS, PE, PET, and PC were well-identified; however, results for other plastic types (PVC, PP, PA, LDPE, and HDPE) were masked to certain extent by Nile Red aggregation and precipitation. The methodology presented here permits identification of a range of particle sizes and types. It represents a significant step in the quantification of microplastics by replacing visual data interpretation with a sensitive and automated method.
Background
Microplastics (MPs) are omnipresent in the environment, including the human food chain; a likely important contributor to human exposure is drinking water.
Objective
To undertake a systematic review of MP contamination of drinking water and estimate quantitative exposures.
Methods
The protocol for the systematic review employed has been published in PROSPERO (PROSPERO 2019, Registration number: CRD42019145290). MEDLINE, EMBASE and Web of Science were searched from launch to the 3rd of June 2020, selecting studies that used procedural blank samples and a validated method for particle composition analysis. Studies were reviewed within a narrative analysis. A bespoke risk of bias (RoB) assessment tool was used.
Results
12 studies were included in the review: six of tap water (TW) and six of bottled water (BW). Meta-analysis was not appropriate due to high statistical heterogeneity (I²>95%). Seven studies were rated low RoB and all confirmed MP contamination of drinking water. The most common polymers identified in samples were polyethylene terephthalate (PET) and polypropylene (PP), Methodological variability was observed throughout the experimental protocols. For example, the minimum size of particles extracted and analysed, which varied from 1 to 100 μm, was seen to be critical in the data reported. The maximum reported MP contamination was 628 MPs/L for TW and 4889 MPs/L for BW, detected in European samples. Based on typical consumption data, this may be extrapolated to a maximum yearly human adult uptake of 458,000 MPs for TW and 3,569,000 MPs for BW.
Conclusions
This is the first systematic review that appraises the quality of existing evidence on MP contamination of drinking water and estimates human exposures. The precautionary principle should be adopted to address concerns on possible human health effects from consumption of MPs. Future research should aim to standardise experimental protocols to aid comparison and elevate quality.
People in remote areas are still drinking surface water that may contain certain pollutants include harmful microorganisms and chemical compounds directly without any pretreatment. In this study, we have designed and operated a pilot-scale drinking water treatment unit as part of our aim to find an economic and easily operable technology for providing drinking water to people in those areas. Our small-scale treatment unit contains filtration and disinfection (UV–C irradiation) stages to remove pollutants from source water. The water quality index was determined based on various parameters such as pH, temperature, dissolved oxygen, nitrate, nitrite, ammonium, phosphorus, dissolved organic carbon and bacteria. Water and media samples after DNA extraction were sequenced using Illumina Miseq throughput sequencing for the determination of bacterial community composition. After the raw water treatment, the reduction of bacteria concentration ranged from 1 to 2 log10. The average removal of the turbidity, ammonium, nitrite, phosphorus and dissolved organic carbon reached up to 95.33%, 85.71%, 100%, 28.57%, and 45%, respectively. In conclusion, multiple biological stages in our designed unit showed an improvement of the drinking water quality. The designed drinking treatment unit produces potable water meet standards at a lower cost operation and it can be used in remote areas.
In the present research diamond-like carbon (DLC) films containing 4–29 at.% of silicon were deposited by reactive magnetron sputtering of carbon target. Study by X-ray photoelectron spectroscopy revealed the presence of Si–C bonds in the films. Nevertheless, a significant amount of Si–O–C and Si–Ox bonds was present too. The shape of the Raman scattering spectra of all studied diamond-like carbon containing silicon (DLC:Si) films was typical for diamond-like carbon. However, some peculiarities related to silicon doping were found. Studies on the dependence of DLC:Si of the optical transmittance spectra on the Si atomic concentration have shown that doping by silicon affects linear, as well as nonlinear, optical properties of the films. It is shown that the normalized reflectance of DLC:Si films decreased with the increased exciting light fluence. No clear relation between the normalized reflectance and photoexcited charge carrier relaxation time was found. It was suggested that that the normalized reflectance decrease with fluence can be related to nonlinear optical properties of the hydrogenated diamond-like carbon phase in DLC:Si film.
Separating microplastics from marine and freshwater sediments is challenging, but necessary to determine their distribution, mass, and ecological impacts in benthic environments. Density separation is commonly used to extract microplastics from sediments by using heavy salt solutions, such as zinc chloride and sodium iodide. However, current devices/apparatus used for density separation, including glass beakers, funnels, upside-down funnel-shaped separators with a shut-off valve, etc., possess various shortcomings in terms of recovery rate, time consumption, and/or usability. In evaluating existing microplastic extraction methods using density separation, we identified the need for a device that allows rapid, simple, and efficient extraction of microplastics from a range of sediment types. We have developed a small glass separator, without a valve, taking a hint from an Utermöhl chamber. This new device is easy to clean and portable, yet enables rapid separation of microplastics from sediments. With this simple device, we recovered 94–98% of <1,000 µm microplastics (polyethylene, polypropylene, polyvinyl chloride, polyethylene terephthalate, and polystyrene). Overall, the device is efficient for various sizes, polymer types, and sediment types. Also, microplastics collected with this glass-made device remain chemically uncontaminated, and can, therefore, be used for further analysis of adsorbing contaminants and additives on/to microplastics.
Current problem facing researchers globally is microplastics as well as toxic chemical pollution of the ecosystem. Micro-plastics carry toxic chemicals in the ecosystem serving as a vector for transport. In this study, a review of the literature has been conducted with the following objectives: (1) to summarize the concentrations of toxic chemicals such heavy metals and hydrophobic organic contaminants sorped on microplastics; (2) to evaluate their spatial distribution regarding adsorbed contaminant; (3) to discuss plausible mechanism by which microplastics adsorp or desorp toxic chemicals in the environment; (4) to discuss implications of their occurrence in air, water and soil media; and (5) to discuss the impact of ingested microplastics to human health. Microplastics are ubiquitous environmental contaminant. Concentrations of sorped toxic chemical varied by location which represents a local problem; industrialized areas (especially areas experiencing crude oil-related activities or have history of crude oil pollution) have higher concentrations than less industrialized areas. Ingestion of microplastics has been demonstrated in a range of marine and soil organisms as well as edible plants, thus possibly contaminating the base of the food web. Potential health effect to human is by particle localization, chemical toxicity and microbial toxins. We conclude by highlighting the gap in knowledge and suggesting key future areas of research for scientists and policymakers.
Microplastics (MPs) pose a potential risk to aquatic ecosystems, and there is a growing demand to alleviate the contamination of MPs. Here, we introduce cationic-modified starch (CS) as an eco-friendly bio-coagulant for removing MPs from water. CS with varying degrees of substitution was synthesized and characterized, and its performance in removing MPs was evaluated under different MP sizes, types, and aging, as well as various water conditions. The results indicated that CS efficiently removed MPs, achieving an average removal rate of 65.33 % for polystyrene particles, with higher removal rates for larger, high-density, and aged MPs. The efficiency of CS remained consistent across a wide range of water pH values, but was significantly reduced in the presence of kaolin clay or/and humic acid. The removal efficiency of CS for MPs was enhanced by the non-ionic surfactant, Tween 20, but inhibited by the anionic surfactant, cetyltrimethylammonium bromide. In addition, CS could concurrently remove both MPs and phenanthrene, as a typical water contaminant. Moreover, the applicability of CS was demonstrated in natural water samples from the Ecological Demonstration Zone of the Yangtze River Delta, China, with an average removal rate of 60.13 ± 3.15 %. Taken together, this study offers an environmentally friendly and cost-effective approach for the removal of MPs from water, demonstrating CS has significant application potential as a sustainable solution to mitigate microplastic pollution.
Microplastics (MPs) are pervasive contaminants with unclear toxicological impacts. Current research on MP pollution relies on low-throughput methodologies, which are time-consuming and cannot directly measure MP concentration in suspensions. This study presents a qualitative and quantitative flow cytometry-based method for analyzing MPs in water, offering a faster and more sustainable alternative. The method involves density separation to remove interfering particles, UV irradiation to eliminate microorganisms, and filtration to remove particles above 100 µm. The sensitivity of the method for different types of MPs, such as polystyrene (PS), polypropylene (PP), polyvinyl chloride (PVC), polyethylene terephthalate (PET), and polyamide (PA) microbeads, ranges from 2 µg/L to 1 mg/L. For these MPs, good linearity was found in matrix-matched calibration where the most concentrated standard was 5 mg/L (R2 0.9820-0.9989) although the linear range can be larger (e.g. 42 mg MP/L for PP microbeads). The repeatability and reproducibility of the method for the model PS MP were <17 % and 8.5 %, respectively. The sample treatment method consisting of density separation and UV pretreatment, when carried out independently, led to 95.0 % and 93.4 % recoveries. The overall trueness of the optimized method for various sizes and compositions of microbeads is about 97 %, according to validation supported by microscopy analysis. This method can substitute the traditional quantitative analytical approach based on counting microbeads with microscopy.
Adsorption is a widely used unit process in various fields, such as chemical, environmental and pharmaceutical, etc. The intraparticle diffusion adsorption kinetics model is one of the most widely used adsorption kinetics models. However, the application and solving method of this model have yet to be discussed. This model has two forms (qt = kt1/2 and qt = kt1/2 + constant, where qt is the adsorption capacity at time t, k and constant are the model parameters), which have not been unified yet. Moreover, the interpretation of this kinetics model lacks a theoretical basis (if the line passes through the origin point (0, 0), the adsorption is dominated by the intraparticle diffusion; if not, it is a multiple adsorption process). In this study, we analyzed the proper equations of the intraparticle diffusion model and their applications, discussed the interpretation of the mass transfer steps revealed by this model, and provided the solving methods. The result indicated that the piecewise function qt = k1t1/2 (0 ≤ t ≤ t1); qt - qt = t1 = k2(t – t1)1/2 (t1 < t ≤ t2) is the proper form of this model. The adsorbate diffusion in the pores inside the adsorbent is the mass transfer step revealed by this model. The statistical parameters should be used to evaluate the fitting results instead of judging whether the model lines pass through the origin point (0, 0). We provide the solving methods to use the Origin and Microsoft EXCEL software to solve the model. Our study established the method for application of the intraparticle diffusion model.
Back washing is putting it simply; backwashing is cleaning the filter by reversing the flow of water to remove any debris, build up, and contaminants. For the backwashing of rapid sand filter about 5 % of clean water requires and frequent backwashing (24 – 72 hr) will consume more amount of water for the back washing purpose. To minimize the amount of water require for the backwashing system, to improve the structure of rapid sand filter for the high efficient back washing purpose, to improve backwashing technique to consume less time and efficient backwashing system. This project deals with the modified structure and modified technique of backwashing. Here I am going to use the combine water and air filtration technique for backwashing system, this will results to minimize the required water for backwashing. In this project comparative analysis has been conducted by performing the experimental setup for the conventional and modified rapid sand filter system.
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.
Plastics have been produced for over a century, but definitive evidence of complete plastic biodegradation in different habitats, particularly freshwater ecosystems, is still missing. Using 13 C-labelled polyethylene microplastics (PE-MP) and stable isotope analysis of produced gas and microbial membrane lipids, we determined the biodegradation rate and fate of carbon in PE-MP in different freshwater types. The biodegradation rate in the humic-lake waters was much higher (0.45% ± 0.21% per year) than in the clear-lake waters (0.07% ± 0.06% per year) or the artificial freshwater medium (0.02% ± 0.02% per year). Complete biodegradation of PE-MP was calculated to last 100-200 years in humic-lake waters, 300-4000 years in clear-lake waters, and 2000-20,000 years in the artificial freshwater medium. The concentration of 18:1ω7, characteristic phospholipid fatty acid in Alpha- and Gammaproteobacteria, was a predictor of faster biodegradation of PE. Uncultured Acetobacteraceae and Comamonadaceae among Alpha- and Gammaproteobacteria, respectively, were major bacteria related to the biodegradation of PE-MP. Overall, it appears that microorganisms in humic lakes with naturally occurring refractory polymers are more adept at decomposing PE than those in other waters.
Concerns have been raised about the risks that pharmaceuticals and personal care products (PPCPs) in aquatic environments posed to humans and the environment. In recent years, sand filtration has been used to potentially remove these emerging contaminants from water. However, there has been no review of the effectiveness of this technology to date. This paper presents a brief introduction of sand filtration types, reviews the current progress in PPCPs removal through sand filtration, and discusses the mechanisms behind this process and the combination of granular activated carbon (GAC) and sand as an enhanced sand-GAC filtration technology. Sand filtration achieves a reasonable but highly variable degree of PPCPs removal. Biodegradation and adsorption are the two main mechanisms of PPCPs removal, in particular the biodegradation since adsorption capacity of sand is relatively low. Other processes, such as bio-sorption and indirect adsorption, may also contribute to PPCPs removal. To compensate for the inadequate PPCPs removal through sand filtration, porous GAC has been combined with sand to develop sand-GAC filtration technologies. Serial, dual, and sandwich filters have been investigated, and significant removal enhancement has been observed, due to the strengthened adsorption capacity, suggesting the applicability of these variants. Future research focus, such as investigating the influence of different operational conditions on sand filter performance, obtaining a deeper understanding of the various removal mechanisms, and investigating of long-term performance of the filter used for PPCPs removal, are suggested.
The prevalence of micro and nanoplastics (MNPs) across the various environments and their negative impact on ecosystems have become a serious global threat and are currently a subject of many environmental concerns. Studies have provided evidence that MNPs have the potential to leach toxic plastic chemical additives and can adsorb a variety of persistent organic environmental pollutants, thereby enhancing their bioavailability, toxicity, and dispersion. Moreover, these MNPs easily penetrate the food chain and might cause health problems when ingested by humans and other organisms. Currently, there is complexity in understanding the mechanisms by which these toxic chemicals adsorb/desorb onto/from MNPs, and the physical and biological impacts of these chemical additives. To date, there is a considerable lack of knowledge on the major chemical additives of concern used in the plastic industry, their fate once MNPs dispose into the environment, the factors that affect their degradation, and their consequent impacts on human health. This review critically analyzes the current knowledge concerning the physical, chemical, and biological impacts of MNPs, and the various chemical and organic pollutants associated with MNPs. Emphasis was laid on their types, occurrence, fate, and distribution in the environment. The different techniques used in their identification, characterization, and removal were also elucidated. Furthermore, the consequent harmful effects of MNPs on human health were discussed to spur more future studies and fill knowledge gaps in this area.
The highly effective removal of multiple kinds of microplastics (MP) by microalgae Scenedesmus abundans was accomplished and the main mechanism of the MP removal was identified as hetero-aggregation. The accurate quantification of removal efficiency was achieved by quantifying free suspended microparticles before and after microalgae treatment. Scenedesmus abundans was tested against three kinds of plastics, including polystyrene (PS), poly(methyl methacrylate) (PMMA), and polylactide (PLA), and total removal efficiency (η) higher than 84% was achieved for all MP. Among these MP, S. abundans were highly effective for removing PMMA microparticles (η=98%). For the other two kinds of MP, pre-exposure was required to achieve a total removal efficiency higher than 70%. As validated by SEM, a long-term exposure to MP (>2 days) promoted the formation of bound extracellular polymeric substances (EPS) and hetero-aggregation, leading to a much higher fraction of MP removed by aggregations (ηa>70%). On the contrary, if MP exposure is short, enhanced adsorption onto solid surfaces can play an important role in MP removal, especially in the case of PLA. In this respect, the abundance of soluble EPS was proportional to the amount of MP adsorbed onto the container wall. These results suggest that the removal efficiency of microplastics, as well as the underlying mechanism, was affected by plastic kinds and exposure duration. Pre-exposure to MP greatly increased the removal efficiency and can be a promising strategy for real-life practices.
Microplastics are an emerging threat and a big challenge for the environment. The presence of microplastics (MPs) in water is life-threatening to diverse organisms of aquatic ecosystems. Hence, the scientific community is exploring deeper to find treatment and removal options of MPs. Various physical, chemical and biological methods are researched for MPs removal, among which few have shown good efficiency in the laboratory. These methods also have a few limitations in environmental conditions. Other than finding a suitable method, the creation of legal restrictions at a governmental level by imposing policies against MPs is still a daunting task in many countries. This review is an effort to place all effectual MP removal methods in one document to compare the mechanisms, efficiency, advantages, and disadvantages and find the best solution. Further, it also discusses the policies and regulations available in different countries to design an effective global policy. Efforts are also made to discuss the research gaps, recent advancements, and insights in the field.
Microplastics (MPs) have been widely detected in aquatic environments, and become emerging contaminants of growing concern. It is urgently needed to explore how to effectively remove MPs from water. This study first established an alternative method of removing MPs by magnetic nano-Fe3O4. Results showed that 1.3 g·L⁻¹ nano-Fe3O4 and 150 min treatments caused optimal magnetization of MPs via surface absorption. Then, magnetized MPs in water can be conveniently removed by suction of the magnet. The average removal rate of four common types of MPs including polyethylene, polypropylene, polystyrene and polyethylene terephthalate in size of approximately 200–900 μm was 86.87 ± 6.92%, 85.05 ± 4.70%, 86.11 ± 6.21%, and 62.83 ± 8.34%, respectively. The removal rate varied among polymer- and size-different MPs, and was positively related to the density of nano-Fe3O4 absorbed on MP surfaces. In addition, the removal rate of MPs in artificial seawater was relatively high in comparison to pure water. Furthermore, the established approach was effectively applied to remove MPs in environmental water bodies including river water, domestic sewage, and natural seawater, with the removal rate of higher than 80%. Altogether, this study provided a novel and simple removal approach to remove MPs in water, which has a certain application prospect.
The pollution of perfluorooctanoate (PFOA) in water bodies has been a serious threat to environment and human health. Ordered mesoporous carbons (OMCs) with different oxygen contents were prepared and first used for adsorbing perfluorooctanoate (PFOA) from aqueous solutions. The OMC-900 with a lower oxygen content has a higher PFOA adsorption capacity than the oxygen-rich OMC-700. OMCs require a much shorter time to reach the adsorption equilibrium comparing with other adsorbents reported in the literature. The mesopores play an important role in this rapid adsorption kinetics. The pseudo-second-order model better fitted the kinetic data. The multilayers adsorption was proposed for the adsorption of PFOA onto OMCs since the Freundlich isotherm model fits the experimental data well. The micelle or hemi-micelle structures may be formed during the adsorption. Various background salts showed a positive effect on PFOA adsorption due to the salting-out and divalent bridge effects. The humic acid can lead to a discernible reduction in PFOA adsorption by competing for adsorption sites on OMCs. The hydrophobic interaction and electrostatic interaction adsorption mechanisms were proposed and verified by the adsorption data. The high adsorption capacity and fast adsorption kinetics of the OMC make it a potential adsorbent for PFOA removal in engineering applications.
Effluent discharge from wastewater treatment plants (WWTPs) is an important source of microplastics, which has attracted worldwide attention. Tertiary sewage treatment of microplastics in WWTPs has also been implemented. In this paper, microplastic removal by aluminosilicate filter media and their cationic surfactant modified products as the potential low-cost integrated material was studied. The role of modified aluminosilicate filter media in the removal of microplastics from WWTPs has not been focused on in the previous studies. The concentration of microplastics with particle size<10 μm in wastewater was not clear due to the exclusion in many studies and the difficulty in quantification. The granular polyethylene microplastic (PE, 10 μm) and fibrous polyamide microplastic (PA, 100 μm) were selected based on their frequent detection in sewage samples. According to a series of column test and further analysis, the immobilization and removal mechanisms of microplastics by filter were explored. Current results demonstrated that aluminosilicate filter media modified by cationic surfactant had a significant removal (>96%) and fixation capacity for PE and PA, which is much greater than that of rapid sand filter (63%). The obtained scanning electron microscopy (SEM) images showed three morphological retention mechanisms: captured, trapped and entangled. The negatively charged microplastics can also be directly electrostatically bonded with the positively charged HDPB head base. The entangled fixation mechanisms provided a higher removal efficiency of microplastics in wastewater for the modified aluminosilicate filter media than the rapid sand filter. The modified materials provided a wide range of potential for the immobilization of microplastic in wastewater treatment process. In principle, this performance can be further studied and utilized to improve the removal efficiency of microplastics in WWTPs.
Research studies published so far on microplastics in drinking water prove that both, bottled and tap water, may contain microscopic plastic pieces. Their possible origin ranges from raw water over treatment processes to packaging material and distribution systems. Various analytical techniques were used, which provide more or less reliable results. Consequently, reported amounts of microplastics in drinking water are difficult to compare, if not incomparable, with each other and with studies on microplastics in other food. Projections on the total intake of microplastics by humans via foodstuff should be made with care. Conclusions on the major intake pathways are not justified, yet. Instead, harmonized, valid methods and more research are needed to reliably determine microplastics in drinking water and more complex foodstuff.
Microplastics are recognized as ubiquitous pollutants in aquatic environments; however, very little study is done on their occurrence and fate at drinking water treatment plants (DWTPs). Though, the toxic effect of microplastics on human health is not yet well established; there is global concern about their possible ill effect on the human. Hence, the present study evaluates the occurrence of microplastics at different treatment stages of a typical DWTP with pulse clarification and its removal efficiency. In the test DWTP, raw water, sourced from river Ganga, was found to contain microplastics 17.88 items/L. Cumulative microplastic removal at key treatment stages viz. pulse clarification and sand filtration was found to be 63% and 85%, respectively. The study also revealed higher microplastic abundance on the sand filter bed due to the screening effect. The most frequently occurring microplastics were fibers and films/fragments with polyethylene terephthalate and polyethylene as a major chemical type. The t-distributed stochastic neighbor embedding machine learning algorithm revealed a strong association between microplastic abundance with turbidity, phosphate and nitrate. The test DWTP with a pulse clarification system was having comparable microplastics removal efficiency with previously reported advanced DWTPs.
Understanding the sources, impacts, and fate of microplastics in the environment is critical for assessing the potential risks of these anthropogenic particles. However, our ability to quantify and identify microplastics in aquatic ecosystems is limited by the lack of rapid techniques that do not require visual sorting or preprocessing. Here, we demonstrate the use of impedance spectroscopy for high-throughput flow-through microplastic quantification, with the goal of rapid measurement of microplastic concentration and size. Impedance spectroscopy characterizes the electrical properties of individual particles directly in the flow of water, allowing for simultaneous sizing and material identification. To demonstrate the technique, spike and recovery experiments were conducted in tap water with 212–1000 μm polyethylene beads in six size ranges and a variety of similarly sized biological materials. Microplastics were reliably detected, sized, and differentiated from biological materials via their electrical properties at an average flow rate of 103 ± 8 mL/min. The recovery rate was ≥90% for microplastics in the 300–1000 μm size range, and the false positive rate for the misidentification of the biological material as plastic was 1%. Impedance spectroscopy allowed for the identification of microplastics directly in water without visual sorting or filtration, demonstrating its use for flow-through sensing.
Extensive presence of microplastic pollution in the aquatic environment has recently been identified as a critical global challenge. A large proportion of the microplastic in aquatic environments originates from the effluent discharges from wastewater treatment plants and urban runoff. We present an experimental study on the removal of microplastic spheres using biochar as potential low-cost material for integration in sand filter systems to improve their efficiency for removing microbeads in wastewater treatment plants. Based on the results of a series of filtration tests and microscopic characterisation, the major mechanisms of interactions between the microplastic spheres and biochar and immobilisation processes are presented.
The results of leaching column tests on three biochar samples produced at three different temperatures from corn straw and a hardwood biochar are compared. The results show that the biochar filters provide significant capacity for the removal and immobilisation of 10 µm diameter microplastic spheres (above 95%) which is much larger than that of similar grain-sized sand filter studied. The extensive ESEM microscopic examination on the samples retrieved after the leaching tests show that the microplastic spheres were immobilised through three morphologically controlled mechanisms which are conceptualised to be ‘Stuck’, ‘Trapped’ and ‘Entangled’ whilst the microplastic spheres only ‘Stuck’ in sand filter. The presence of abundant honeycomb structures and thin chips to the high removal and immobilisation capacity of corn straw biochar produced at 500 °C and the hardwood biochar. In this study, we demonstrate that biochar can offer extensive potential for immobilisation of microplastic spheres (microbeads). This capacity can in principle be investigated and utilised to improve the efficiency of sand filters to remove microplastic in wastewater treatment plants.
Microplastics (MPs) are one of the emerging pollutants that have gained the most attention recently. The widespread distribution and potential for its adverse impact on human health and the ecosystem have been warned. MPs have been introduced into the environment by various routes such as direct disposal through human activities, textile industry and wastewater treatment systems. Recently, the reduction of MPs from wastewater treatment systems has been attracted much attention from the scientific community. There have been many reviews on the emission sources, distribution and impacts of MP in environment. However, the better understanding of MPs removal efficiencies by different wastewater treatment technologies has not been reviewed and discussed. Therefore, the objective of this review is to provide technologies to be applied in MPs removal. In addition, basic knowledge about MPs in water body such as characteristics, emission sources, transport path and its impact on human health and the ecosystem was also presented and discussed. This review is expected to provide useful information to scientists as well as decision makers to continue researching, developing and proposing an effective strategy to control and prevent water pollution from MPs.
Microplastics (MPs) are emerging globally distributed pollutants of aquatic environments, and little is known about their fate at drinking water treatment plants (DWTPs), which provide a barrier preventing MPs from entering water for human consumption. This study investigated MPs ≥ 1 μm in raw and treated water of two DWTPs that both lie on the same river, but the local quality of water and the treatment technology applied differ. In the case of the more complex DWTP, MPs were analysed at 4 additional sampling sites along the treatment chain. The content of MPs varied greatly between the DWTPs. There were 23 ± 2 and 14 ± 1 MPs L⁻¹ in raw and treated water, respectively, at one DWTP, and 1296 ± 35 and 151 ± 4 MPs L⁻¹ at the other. Nevertheless, MPs comprised only a minor proportion (<0.02%) of all detected particles at both DWTPs. With regard to size and shape of MPs, the majority (>70%) were smaller than 10 μm, and only fragments and fibres were found, while fragments clearly prevailed. The most frequently occurring materials were cellulose acetate, polyethylene terephthalate, polyvinyl chloride, polyethylene, and polypropylene. Much higher total removal of MPs was achieved at the DWTP with a higher initial MP load and more complicated treatment (removal of 88% versus 40%); coagulation-flocculation-sedimentation, deep-bed filtration through clay-based material, and granular activated carbon filtration contributed to MP elimination by 62%, 20%, and 6%, respectively. Additionally, results from this more complex DWTP enabled to observe relationships between the removal efficiency and size and shape of MPs, particularly in the case of the filtration steps.
In this paper, study on the removal of imitated polystyrene (ps) microplastics in water was carried out based on the adsorption capacity of three-dimensional reduced graphene oxide (3D RGO). Scanning electron microscopy and X-ray diffractometry characterization showed that the freeze-dried 3D RGO formed a distinct porous spatial structure. Different experimental parameters, such as pH, ion concentrations, contact time, and temperature, were studied to investigate the ps microplastic adsorption performance of 3D RGO. The adsorption mechanism was mainly attributed to the strong πÿπ interaction between the carbon ring of 3D RGO and the benzene ring of ps microplastics. Sorption kinetic and isothermal data were obtained by the well-fitted Langmuir adsorption isotherm model and pseudo-second-order kinetic model. Meanwhile, the result of thermodynamic analysis showed that the adsorption of ps microplastics was a spontaneous endothermic process. Under the optimal conditions of pH = 6, C0 = 600 mg/L, t = 120 min, and T = 26 °C, the maximum adsorption capacity of the prepared 3D RGO on ps microplastics was 617.28 mg/g. Furthermore, this method exhibits good feasibility in tap water and lake water.
The emerging threat microplastic pollution poses to soil and its biota necessitates development of methods to detect microplastic ingestion by soil animals. Fluorescent staining with Nile red dye has proven effective at distinguishing microplastics from inorganic and some biological material, but is not suitable for separating them from invertebrate remains. Here we report on the development and validation of a novel fluorescent counterstaining technique for detection of microplastics within terrestrial invertebrate biomass and fecal material. After staining with a blend of Calcofluor white and Evans blue dyes in addition to Nile red, ground arthropod biomass appeared blueish-purple, whereas different plastic polymers appeared red, green, and yellow when viewed under laser scanning confocal microscopy. Non-arthropod invertebrate biomass and fecal material were also distinguishable from plastic, though to a lesser extent. Our results highlight the value of this method for detecting microplastic ingestion by terrestrial invertebrates.
Investigating wide range of food products of direct human consumption for microplastics is critical to understand the routes of contamination and assess the risks in microplastics uptake by humans. However, microplastics knowledge for many beverage products excluding beers is still lacking. Here, common beverages (n = 57; 27 brands) such as soft drinks (n = 19), energy drinks (n = 8), cold tea (n = 4) and beer (n = 26) were targeted for microplastics occurrences in Mexico and their shape, size, surface morphology and polymer composition were analyzed. Microplastics were detected in 48 out of 57 samples tested. The results identified microplastics of various forms (fibers and fragments) and sizes (0.1–3 mm) of colors (blue, red, brown, black and green), in amounts ranging from not detected to 28 ± 5.29 particles/L. Micro-Raman spectroscopy identified particles as polyamide, poly(ester-amide), acrylonitrile-butadiene-styrene and poly(ethylene-terephthalate) indicating microplastics contamination of synthetic textiles and packaging origin in the beverage products. Finally, this paper discusses that human excreta could act as a vehicle for the dispersion and accumulation of microplastics into terrestrial and aquatic environments. Combined, it is the first study to investigate microplastics contamination on soft drinks, energy drinks and cold tea and to document the material composition of microplastics from beverage products.
This study investigated the removal efficiency of micro- and nanoplastics (180 nm–125 μm) during drinking water treatment, particularly coagulation/flocculation combined with sedimentation (CFS) and granular filtration under ordinary working conditions at water treatment plants (WTPs). It also studied the interactions between biofilms and microplastics and the consequential impact on treatment efficiency. Generally, CFS was not sufficient to remove micro- and nanoplastics. The sedimentation rate of clean plastics was lower than 2.0% for all different sizes of plastic particles with coagulant Al2(SO4)3. Even with the addition of coagulant aid (PolyDADMAC), the highest removal was only 13.6% for 45–53 μm of particles. In contrast, granular filtration was much more effective at filtering out micro- and nanoplastics, from 86.9% to nearly complete removal (99.9% for particles larger than 100 μm). However, there existed a critical size (10–20 μm) where a significant lower removal (86.9%) was observed. Biofilms were easily formed on microplastics. In addition, biofilm formation significantly increased the removal efficiency of CFS treatment from <2.0% to 16.5%. This work provides new knowledge to better understand the fate and transport of emerging micro- and nanoplastic pollutants during drinking water treatment, which is of increasing concern due to the potential human exposure to micro- and nanoplastics in drinking water.
Micro-plastic (MP) contamination of drinking water is an emerging global concern. Findings on the cytotoxic effects of MPs in human cells are an incentive to investigate the MP concentration in drinking water. The present study quantitatively and qualitatively analyzes the MPs in 10 brands of single-use PET-bottled water, sourced from Thailand. A set of glass-bottled water was similarly analyzed to compare the MP concentrations between the two packaging. Two sorting techniques were used: 1) fluorescent tagging with Nile Red (≥6.5 μm) and 2) optical microscopy (≥50 μm). ATR-FT-IR (≥50 μm) and confocal Raman spectroscopy (1-50 μm) were also used. The MP concentration was found to be 140 ± 19 p/L in single-use plastic-bottled water and 52 ± 4 p/L in glass-bottled water. Plastic bottles had a significantly higher MP quantity than the latter. Both 6.5-20 μm and 20-50 μm MPs showed significant dominance over the ≥50 μm fraction. Fibers accounted for 62.8% of the total particle content, followed by fragments. Under optical microscopy, ≥50 μm particles were 10 ± 1 p/L (on average), which did not differ largely from that of fluorescent-tagged particles in the same size range (12 ± 1 p/L), implying the suitability of both techniques to sort ≥50 μm MPs. However, fluorescent-tagging was more reliable for MP identification in drinking water, particularly in the 6.5-50 μm range. Among the particles that were confirmed to be polymeric, PET, PE, PP, and PA were dominant. Accordingly, the contamination mainly emanates from the packaging, but could also occur during the manufacturing process. Given the direct human exposure to MPs through bottled water and their cellular toxicity, further studies are encouraged on smaller-sized MPs in drinking water.
Microplastics (MPs) have attracted worldwide attention as the emerging persistent pollutants. Since they have been detected in raw water and the treated water of drinking water treatment plants (DWTPs), there was an urgent need to explore the properties and fates of microplastics in DWTPs. The characteristics of the effluent MPs from each treatment unit in an advanced drinking water treatment plant (ADWTP) were studied, and the relationship between the variations of MPs and the removal performances of treatment processes was also explored. Overall, both the coagulation combined with sedimentation and the granular activated carbon (GAC) filtration performed well in removing microplastics. The former had a removal efficiency of about 40.5-54.5%, mainly for fibres' removal, and the presence of GAC filtration reduced the microplastic abundance by about 56.8-60.9%, mainly for small-sized MPs. It was worthy of attention that a larger amount of polyacrylamide (PAM) was detected in the effluent of the sedimentation compared to raw water, which was caused by the usage of coagulant containing PAM. Specially, the number of 1-5 μm MPs in the effluent of ozonation tank was increased by 2.8-16.0%, resulting in a negative removal efficiency in ozonation. The removals of microplastics were depended primarily on their physical properties (size and shape).