Microplastics have been identified as an emerging pollutant due to their irrefutable prevalence in air, soil, and particularly, the aquatic ecosystem. Wastewater treatment plants (WWTPs) are seen as ...the last line of defense which creates a barrier between microplastics and the environment. These microplastics are discharged in large quantities into aquatic bodies due to their insufficient containment during water treatment. As a result, WWTPs are regarded as point sources of microplastics release into the environment. Assessing the prevalence and behavior of microplastics in WWTPs is therefore critical for their control. The removal efficiency of microplastics was 65 %, 0.2–14 %, and 0.2–2 % after the successful primary, secondary and tertiary treatment phases in WWTPs. In this review, other than conventional treatment methods, advanced treatment methods have also been discussed. For the removal of microplastics in the size range 20–190 μm, advanced treatment methods like membrane bioreactors, rapid sand filtration, electrocoagulation and photocatalytic degradation was found to be effective and these methods helps in increasing the removal efficiency to >99 %. Bioremediation based approaches has found that sea grasses, lugworm and blue mussels has the ability to mitigate microplastics by acting as a natural trap to the microplastics pollutants and could act as candidate species for possible incorporation in WWTPs. Also, there is a need for controlling the use and unchecked release of microplastics into the environment through laws and regulations.
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•Smaller microplastics (MPs) <100 μm are not effectively separated by conventional WWTPs.•Granules and fragments were easier to separate than microfibers and pellet shaped MPs.•Blue mussels, lugworms and sea grasses are candidate species for MPs' bioremediation.•Rapid sand filters and membrane bioreactors can remove 97 % and 99 % MPs respectively.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Microplastics (MPs) have been widely detected in wastewater treatment plants (WWTPs) due to their small particle size, wide distribution, and difficulty in removal. Previous studies, however, mostly ...focused on MPs in wastewater, thereby neglecting sludge. To comprehensively understand the changes of MPs in WWTPs, we investigated the quantity and characteristics of MPs in wastewater and sludge of a WWTP in Harbin, a typical inland city in China, and calculated the MPs removal rate. The results showed that there were 126.0 ± 14.0 particles/L MPs in the influent and 30.6 ± 7.8 particles/L in the effluent, about 75.7% MPs were removed and transferred to the sludge during this WWTP. The abundance of MPs in dewatered sludge and sludge filter cake was 36.3 ± 5.7 and 46.3 ± 6.2 particles/g (dry sludge), the sludge disposal scale of this WWTP can reach 1300 tons/day, which was equivalent to about 7.74 × 1012 microplastic particles accumulated in sludge per year. These sludges were used as fertilizers in the soil, which will cause secondary pollution of MPs. Raman spectroscopic analysis showed that about 89.5% of particles were plastic polymers, such as polyesters, polyamide (PA), polyethylene terephthalate (PET) and polyethylene (PE), which suggested that MPs may be derived from laundry and personal care products. Therefore, we recommend that more work should be devoted to how to control the release of MPs at the source and the reuse of sludge after treatment by WWTPs.
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•Microplastics (MPs) were analyzed for first time in WWTP in north region of China.•MPs were detected in the grille, grit chamber, returned sludge and filter cake.•About 75.7% MPs removed from the water phase and accumulated in sludge phase.•The main synthetic polymers tested by Raman were polyesters, PA and PET.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
This work studied the occurrence of microplastics in primary and secondary effluents and mixed sludge of a WWTP as well as in processed heat-dried sludge marketed as soil amendment. Sampled ...microparticles were divided into fragments and fibres, the latter defined as those with cylindrical shape and length to diameter ratio >3. We showed the presence of 12 different anthropogenic polymers or groups of polymers with a predominance of polyethylene, polypropylene, polyester and acrylic fibres together with an important amount of manufactured natural fibres. The smaller sampled fraction, in the 25–104 μm range, was the largest in both primary and secondary effluents. Fibres displayed lower sizes than fragments and represented less than one third of the anthropogenic particles sampled in effluents but up to 84% of heat-dried sludge. The plant showed a high efficiency (>90%) in removing microplastics from wastewater. However, the amount of anthropogenic plastics debris in the 25 μm - 50 mm range still released with the effluent amounted to 12.8 ± 6.3 particles/L, representing 300 million plastic debris per day and an approximate load of microplastics of 350 particles/m3 in the receiving Henares River. WWTP mixed sludge contained 183 ± 84 particles/g while heat-dried sludge bore 165 ± 37 particles/g. The sludge of the WWTP sampled in this work, would disseminate 8 × 1011 plastic particles per year if improperly managed. The agricultural use of sludge as soil amendment in the area of Madrid could spread up to 1013 microplastic particles in agricultural soils per year.
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•We identified 12 different polymers in microplastics form wastewater and sludge.•High efficiency of secondary A2O treatments in removing microplastics.•Fibres displayed lower sizes than fragments and predominated in samples from sludge.•The plant releases 300 million plastic debris per day to its receiving river.•Sludge agricultural use is a major contributor in disseminating microplastic particles.
Wastewater treatment plants release a huge number of particles through effluent and sludge contaminating effluents and agricultural soils.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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•Recent updates on the occurrence and removal of micro- and nanoplastics in WWTPs were critically discussed.•Sorption behavior and impacts of MPs and NPs on the performance of WWTP ...units have been critically elucidated.•Recent research progresses on developments of MPs and NPs-targeted treatments technologies were elaborated.•Knowledge gaps and future perspectives of MPs and NPs have been concluded.
The manifestation of microplastics (MPs) and nanoplastics (NPs) in wastewater treatment plants (WWTPs) has become a major challenge owing to their unique characteristics such as hydrophobicity, surface charges, longer molecular chain arrangement, higher specific surface area, variety of size, shape, color and functional groups. They can also act as a vector in spreading other toxic pollutants in the environment by making convoluted complexes. Therefore, in this review, the up-to-date status on occurrence and removal of MPs and NPs in WWTPs are comprehensively evaluated. The stimuli of pertinent factors on the removal of MPs and NPs in WWTPs are also elucidated. Furthermore, the sorption behavior and mechanism of MPs and NPs towards toxic pollutants are critically debated in order to inspect the genuine menaces of MPs and NPs to WWTPs performance and environment. Particularly, the impacts of MPs and NPs on the performance of different wastewater treatment processes have been critically discussed. So far, no specific treatment technology has been developed specifically to remove MPs and NPs from sewage effluents and sludge excluding the subsisting conventional treatment techniques. Hence, to fill this gap, the recent research innovations on the development of MPs- and NPs-targeted treatment technologies are critically reviewed. Regarding this, the performances, pros and cons of the proposed technologies are critically evaluated that will be helpful in developing more reliable and cutting-edge technologies to eradicate MPs and NPs from the environment. Moreover, this critical review also provides knowledge gaps/key challenges and future perspectives for scientific community to combat against MPs and NPs pollution.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
This paper presents a method for microplastic (MP) mass quantification using a Focal Plane Array-based Fourier Transform Infrared imaging technique. It discusses the issue that particle number is not ...a conserved base quantity and hence less suited than mass to compare independent studies on MP in the environment. It concludes that MP mass should be included when quantifying MP pollution in the environment, supplementing the conventional approach of reporting particle numbers. Applying mass as the unit of MP measurement, the paper presents data showing that Danish wastewater treatment plants discharge around 3 t/year of MP in the size range 10–500 μm. This value corresponds to an annual per capita emission from these plants of 0.56 g MP/(capita year). The distribution of polymer types by mass and particle number differed because the size of MP particles of the different material types varied.
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•98% of MPs are removed from influent wastewater in WWTPs.•The annual MP discharge from WWTPs in Denmark is approx. 0.56 g/(capita year).•MPs are quantified by mass in addition to particle number.•Mass can be estimated using FT-IR imaging.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
The presence of contaminants of emerging concern (CECs) such as pharmaceuticals and personal care products (PPCPs), endocrine-disrupting compounds (EDCs), flame retardants (FRs), pesticides, and ...artificial sweeteners (ASWs) in the aquatic environments remains a major challenge to the environment and human health. In this review, the classification and occurrence of emerging contaminants in aquatic environments were discussed in detail. It is well documented that CECs are susceptible to poor removal during the conventional wastewater treatment plants, which introduce them back to the environment ranging from nanogram per liter (e.g., carbamazepine) up to milligram per liter (e.g., acesulfame) concentration level. Meanwhile, a deep insight into the application of advanced oxidation processes (AOPs) on mitigation of the CECs from aquatic environment was presented. In this regard, the utilization of various treatment technologies based on AOPs including ozonation, Fenton processes, sonochemical, and TiO
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heterogeneous photocatalysis was reviewed. Additionally, some innovations (e.g., visible light heterogeneous photocatalysis, electro-Fenton) concerning the AOPs and the combined utilization of AOPs (e.g., sono-Fenton) were documented.
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•Microplastics reduce the efficiency of wastewater treatment processes.•Microplastics affect the effluent quality of wastewater treatment plants.•Microplastics inhibit sludge ...hydrolysis, acidification, and methanogenesis.•Negative impacts of microplastics come from the leaching of toxic additives and ROS production.
Microplastics are widely used and inevitably released into the environment, which can be easily enriched in wastewater treatment plants. This review assesses their potential effects on wastewater and sludge treatment and the methods for removing microplastics from wastewater and sludge. Firstly, recent advances of the methods for purification and detection of microplastics in wastewater and sewage sludge environment were reviewed. Then, the effects of microplastics on wastewater and sludge treatment and the mechanisms were discussed. It can be seen that when the size of microplastics reached the nanometer level, they infiltrated into the biofilm and produce ROS, which showed acute inhibitory effect on microbial community, key enzymes, metabolic intermediates and final products. Due to their large specific surface area and hydrophobic surface, persistent organic pollutants, metals and pathogens could be easily adsorbed on the surface of microplastics. As various additives were added in the production of plastics, the adsorption of environmental micropollutants and the exudation of additives made the mechanism of microplastics affecting sewage and sludge treatment more complicated. Also, the methods for removing microplastics from wastewater and sludge were reviewed and their removal efficiencies were compared. Finally, the problems that need to be addressed in the future were pointed out, and the key points for future investigation were proposed.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
This review presents the state-of-the-art sludge reduction technologies applied in both wastewater and sludge treatment lines. They include chemical, mechanical, thermal, electrical treatment, ...addition of chemical un-coupler, and predation of protozoa/metazoa in wastewater treatment line, and physical, chemical and biological pretreatment in sludge treatment line. Emphasis was put on their effect on sludge reduction performance, with 10% sludge reduction to zero sludge production in wastewater treatment line and enhanced TS (total solids) or volatile solids removal of 5–40% in sludge treatment line. Free nitrous acid (FNA) technology seems good in wastewater treatment line but it is only under the lab-scale trial. In sludge treatment line, thermal, ultrasonic (<4400kJ/kg TS), FNA pretreatment and temperature-phased anaerobic digestion (TPAD) are promising if pathogen inactivation is not a concern. However, thermal pretreatment and TPAD are superior to other pretreatment technologies when pathogen inactivation is required. The new wastewater treatment processes including SANI®, high-rate activated sludge coupled autotrophic nitrogen removal and anaerobic membrane bioreactor coupled autotrophic nitrogen removal also have a great potential to reduce sludge production. In the future, an effort should be put on the effect of sludge reduction technologies on the removal of organic micropollutants and heavy metals.
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•State-of-the-art sludge reduction technologies were reviewed.•Advantages and disadvantages of sludge reduction technologies were discussed.•Free nitrous acid technology seems good in wastewater treatment line.•Thermal pretreatment and TPAD are superior in sludge treatment line.•Future perspectives of sludge reduction technologies were elucidated.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
WWTPs may be one of the important ways for MPs to enter surface water. In the present study, the influent and effluent from eleven WWTPs in Changzhou were collected and analyzed. At the same time, ...the abundance, size, color, and shape of MPs in influent and effluent were investigated. The average abundance of MPs in the influent and effluent were 196.00 ± 11.89 n/L and 9.04 ± 1.12 n/L respectively, and the MPs removal efficiency of eleven WWTPs was almost over 90% in which it could be up to 97.15%. MPs were divided into four particle size based on abundance changes, and the size of MPs with the highest abundant was mainly concentrated at 0.1–0.5 mm. Among these MPs, fibers were the main shape in wastewater, followed by fragments, flakes, spheres and films. The colors of MPs in wastewater were various and 14 types of plastics were detected from wastewater using attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR). Moreover, Rayon and PET were the dominant polymer types in eleven WWTPs. The research results provided basic data for the research and supervision of MPs pollution in WWTPs.
•First comparison of MPs in eleven WWTPs from Changzhou, China.•Fiber MPs were the main shape and the proportion of MPs with the size of 0.1–0.5 mm was the largest in eleven WWTPs.•MPs removal efficiency of eleven WWTPs was almost over 90%.•Rayon and PET were the dominant polymer types in eleven WWTPs.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
In the last few decades, pharmaceuticals, credited with saving millions of lives, have emerged as a new class of environmental contaminant. These compounds can have both chronic and acute harmful ...effects on natural flora and fauna. The presence of pharmaceutical contaminants in ground waters, surface waters (lakes, rivers, and streams), sea water, wastewater treatment plants (influents and effluents), soils, and sludges has been well doccumented. A range of methods including oxidation, photolysis, UV-degradation, nanofiltration, reverse osmosis, and adsorption has been used for their remediation from aqueous systems. Many methods have been commercially limited by toxic sludge generation, incomplete removal, high capital and operating costs, and the need for skilled operating and maintenance personnel. Adsorption technologies are a low-cost alternative, easily used in developing countries where there is a dearth of advanced technologies, skilled personnel, and available capital, and adsorption appears to be the most broadly feasible pharmaceutical removal method. Adsorption remediation methods are easily integrated with wastewater treatment plants (WWTPs). Herein, we have reviewed the literature (1990–2018) illustrating the rising environmental pharmaceutical contamination concerns as well as remediation efforts emphasizing adsorption.
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IJS, KILJ, NUK, PNG, UL, UM
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