Recently the United States Environmental Protection Agency qualified biogas from landfills and anaerobic digesters as a cellulosic transportation biofuel under the expanded Renewable Fuel Standard ...(RFS2). Biogas is a renewable fuel that can generate Renewable Identification Number credits for the producer. The wastewater industry may not be able to keep pace with this opportunity. Less than 10% of WWTPs in the US have currently produced biogas for beneficial use. Supporting growth of the biogas industry requires implementation of new practices and policies. In this review, the barriers, gaps, and challenges in deploying biogas production technology are identified. Issues are classified as economic, technical, social or regulatory issues. Some of the critical challenges to the economics of digester operations are the slow rate of biogas generation, the low energy content of the biogas, and the costs to upgrade the biogas.
Currently there is little biogas utilization at US WWTPs. Most biogas is flared while some is used for onsite process heat and power production. Case studies of co-digestion of biosolids with organic wastes at field-scale show the use of co-digestion could overcome significant economic challenges including higher methane yield, more efficient digester volume utilization and reduced biosolids production. These findings could provide guidance in retrofitting existing facilities or in designing new biogas production and utilization systems. The RFS2 ruling increases market certainty, hence reduces risk. The evaluation of applications of co-digestion at WWTP scales ranging from 1 million gallons per day (MGD) to 375 MGD determined its potential feasibility for different types of digester operation, organic waste and loading rate as well as effectiveness of providing energy self-sufficiency at the WWTPs. This work could improve economics of anaerobic digestion at WWTPs, enabling viable and sustainable biogas industry and offsetting costs for wastewater management.
This study investigated the removal of microplastics from different treatment stages in three WWTPs and examined the performance of tertiary treatment that was done by coagulation and different ...technologies such as ozone (WWTP-A), membrane disc-filter (WWTP-B), and rapid sand filtration (WWTP-C). The results showed that the primary and secondary treatment processes effectively remove microplastics from wastewater with efficiencies ranging between 75% and 91.9%. The removal efficiency increased further to >98% after tertiary treatment. Microbeads and fragments were the major types of microplastics found in all wastewater sampling points. Microbeads found in the wastewater samples were classified as primary microplastics, that mainly came from personal care products, whereas secondary microplastics consisted of fragments, fibers, and sheets that were generated mainly due to fragmentation of larger plastics. Microplastics were still found in a high concentration in the final effluent, especially from WWTP-B, which is discharged into the Geumho river.
•The number of microplastics entering into WWTP is very high.•The number of microplastics drop very much after going through each treatment stages.•Microbead contribute to the most abundant type of microplastic were found in effluent.•Ozone is the promising technology to remove microplastic in wastewater.
This paper discusses about the role of two different wastewater treatment technologies in the abatement of microplastics (MPs) from the final effluent of an urban wastewater treatment plant (WWTP); ...i.e., membrane bioreactor technology (MBR) and rapid sand filtration (RSF). For this purpose, a WWTP with these two technologies was monitored for 18 months. The average microplastic concentration was 4.40 ± 1.01 MP L−1 for the influent, 0.92 ± 0.21 MP L−1 for MBR, and 1.08 ± 0.28 MP L−1 for RSF, without statistically significant differences for MPs removal between both technologies (F-test = 0.195, p = 0.661). The main MP forms isolated in our study were fibers (1.34 ± 0.23 items L−1), followed by films (0.59 ± 0.24 items L−1), fragments (0.20 ± 0.09 items L−1), and beads (0.02 ± 0.01 items L−1). All of them probed to be statistically significant reduced after both technologies, but without statistically significant differences between them. The MP removal efficiency was 79.01% and 75.49% for MBR and RSF, respectively, although higher for microplastic particulate forms (MPPs), 98.83% and 95.53%, than for fibers, 57.65% and 53.83% for MBR and RSF, respectively, displaying a selective removal of particulate forms against microfibers. Fourteen different plastic polymers were identified in the influent, only persisting low-density polyethylene (LDPE), nylon (NYL), and polyvinyl (PV) in RSF effluent, and melamine (MUF) after MBR treatment. The MP size ranged from 210 μm, corresponding to NYL fragment form in the influent, to 6.3 mm, corresponding to a red microfiber also from the influent. The maximum MP average size significantly decreased from MBR (1.39 ± 0.15 mm), to RSF (1.15 ± 0.08 mm) and influent (1.05 ± 0.05 mm) (F-test = 4.014, p = 0.019), exhibiting the fiber selection carried out by these advanced technologies for wastewater treatment.
•A 76.68% of microparticles isolated proved to be microplastics.•The removal percentage for MBR (79.01%) was higher than for RSF (75.49%).•Microfibers could bypass and escape through MBR and RSF.•No enhancement over a conventional sewage treatment could be observed.
This study investigated the role of a municipal wastewater treatment plant (WWTP) effluent and an abandoned coastal landfill as pathways for microplastics (MPs) input into the marine environment. MPs ...were first analyzed in raw sewage influent, sludge and effluent samples, and their fate was studied along a distance gradient from the WWTP in three matrices: surface water, sediments and wild mussels. All suspected MPs were characterized according to their polymer nature using micro-Raman spectroscopy. The investigated WWTP had an estimated daily discharge of 227 million MPs. MPs were found in all matrices with a decreasing abundance from the effluent. Strong MPs abundances (higher than those found near the WWTP effluent) were observed in the vicinity of the coastal landfill suggesting its importance as a MPs entry route into the marine coastal environment. Our study supports the idea that blue mussels are a promising sentinel species for MPs (<200 μm).
•Fate of microplastics discharged by Wastewater treatment plant (WWTP) is evaluated.•96% of microplastics decrease with increasing distance from the WWTP effluent.•Coastal landfills should be regarded as an important microplastics entry source.•Mussels are a promising sentinel species for microplastics (<200 μm).
This review highlights the methodologies for sampling, sample preparation, and identification of microplastics found in wastewater treatment plants. The presence and deposition of microplastics in ...the environment lead to serious environmental and ecological concerns. The role of wastewater treatment plants in spreading microplastics to the environment poses additional threats that need to be treated. Thus, the key challenges remain in understanding the fate and occurrence of microplastics in the wastewater treatment plant and the ability to detect them at each stage of the treatment. This review, therefore, helps to understand the fate and occurence of microplastics in the wastewater treatment plant. Besides, it is organized to present an overall discussion of the available microplastics detection techniques from sampling to identification.
In this study, two pyridine-degrading strains namely Enterobacter cloacae complex sp. BD17 and Enterobacter sp.BD19 were isolated from the aerobic tank of a pesticide wastewater treatment plant. The ...mixed bacteria H4 composed of BD17 and BD19 at a ratio of 1:1 was immobilized by Solidago canadensis L. stem biochar with a dosage of 2 g·L−1. The highest pyridine removal rate of 91.70% was achieved by the immobilized H4 at an initial pyridine concentration of 200 mg·L−1, pH of 7.0, temperature of 28 °C and salinity of 3.0% within 36 h. The main intermediates of pyridine degradation by BD17 were pyridine-2-carboxamide, 2-aminopropanediamide, and 2-aminoacetamide, while 2-picolinic acid, isopropyl acetate, isopropyl alcohol, and acetaldehyde were identified with BD19 by adopting GC-MS technique. Interestingly, there was a possibility of totally mineralization of pyridine and the corresponding degradation pathways of BD17 and BD19 were revealed for the first time.
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•Two Enterobacter sp. strains were first isolated for efficient pyridine degradation.•Degradation mechanisms of pyridine by two Enterobacter sp. strains were revealed.•The mixed bacteria H4 was constructed with two Enterobacter sp. strains at ratio 1:1.•Highest pyridine removal rate of 91.70% was reached by immobilized H4.
Wastewater treatment plants are one of the primary pathways through which microplastics enter aquatic environments. In this study, we have determined the microplastic concentrations of the influent ...and secondary effluent water of two wastewater treatment plants in Turkey. For this purpose, we have taken samples of the influent and effluent water of Seyhan and Yüreğir wastewater treatment facilities for 6 days in August 2017 and determined their microplastics’ content both visually and using μ-Raman spectroscopy. The results showed that the influent of the wastewater treatment contained 1 million–6.5 million particles per day, while the effluent contained 220,000–1.5 million particles per day. The removal rate of microplastics was found to be between 73 and 79%. In total, seven different types of polymers were detected. The most frequently observed polymer type was polyester.
Microplastics have aroused increasing concern as they pose threats to aquatic species as well as human beings. They do not only contribute to accumulation of plastics in the environment, but due to ...absorption they can also contribute to spreading of micropollutants in the environment. Studies indicated that wastewater treatment plants (WWTPs) play an important role in releasing microplastics to the environment. Therefore, effective detection of the microplastics and understanding their occurrence and fate in WWTPs are of great importance towards microplastics control. In this review, the up-to-date status on the detection, occurrence and removal of microplastics in WWTPs are comprehensively reviewed. Specifically, the different techniques used for collecting microplastics from both wastewater and sewage sludge, and their pretreatment and characterization methods are reviewed and analyzed. The key aspects regarding microplastics occurrence in WWTPs, such as concentrations, total discharges, materials, shapes and sizes are summarized and compared. Microplastics removal in different treatment stages and their retention in sewage sludge are explored. The development of potential microplastics-targeted treatment technologies is also presented. Although previous researches in microplastics have undoubtedly improved our level of understanding, it is clear that much remains to be learned about microplastics in WWTPs, as many unanswered questions and thereby concerns still remain; some of these important future research areas are outlined. The key challenges appear to be to harmonize detection methods as well as microplastics mitigation from wastewater and sewage sludge.
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•The detection, occurrence and behavior of microplastics in WWTPs are reviewed.•The collection, pretreatment and characterization of microplastics are analyzed.•The concentrations, materials and properties of microplastics are summarized.•The microplastics removal in WWTPs and retention in sewage sludge are explored.
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•A procedure for MP analysis was developed for different types of samples in WWTPs.•>90% removal of suspended solid was achieved with chemical digestion using H2O2.•Identification of ...MP by ATR-FTIR was not compromised by the use of H2O2.•More than 90% of the identified microparticles corresponded to microfibers.•Mainly fragments of PE and PP, and polyester and cotton fibres were identified.
Although wastewater treatment plants can retain a high percentage of microplastics (MP) arriving at the facilities, no method for extracting and characterizing these microparticles has been still standardized in these units. This study investigated three protocols of chemical digestion, prior to analysis of microplastics, one directed to the effluents, using peroxidation, and two for activated sludge (peroxidation and Fenton). The samples (primary effluent, secondary effluent and activated sludge) were collected from a wastewater treatment plant (WWTP) located in Valencia (Spain). In addition, four common types of polymers (Low density polyethylene-LDPE, Polypropylene-PP, Polystyrene-PS and Polyethylene terephthalate-PET) were used to assess the influence of reagent exposure on microparticle integrity. Peroxidation was effective in treating the studied effluents (primary and secondary) and was also identified as the ideal protocol for activated sludge. The analysis showed that the use of H2O2 does not compromise the identification of the polymers evaluated by FTIR and also significantly reduced the concentration of suspended solids, resulting in an efficient visual separation of the microparticles. After been properly separated, the microparticles were characterized according to their size, colour and shape, and a fraction submitted to identification by µ-ATR-FTIR/ATR-FTIR. In all samples, a high presence of microfibers (MF) was observed, corresponding to more than 90% of the microparticles. However, in relation to secondary effluents, only 9% of these MF were identified as plastics, the remaining ones corresponded to cotton. The fragments found in the samples were classified as secondary in origin, and were mainly PE and PP, lower than 1 mm size.
Pharmaceutical compounds, such as antibiotics, nonsteroidal anti-inflammatory drugs (NSAIDs), anticonvulsants, β-blocker, etc. have emerged as new classes of water pollutants due to their potential ...or proven adverse effects on human health and the aquatic environment. This paper aims to systematically review the current data available on the global occurrence and removal of 43 pharmaceutical compounds in municipal wastewater treatment plants (M-WWTPs) in the period from 2010 to 2020. Moreover, this work intends to assess the global daily mass load and emissions of pharmaceuticals in different regions. Nevertheless, the environmental risk of pharmaceuticals in the final effluents of M-WWTPs was also evaluated. Lastly, the guidelines and regulations concerning the occurrence of pharmaceuticals in the aquatic environment were summarized and discussed. The findings highlighted that there is significant variation in the concentrations of pharmaceuticals between different regions. Meanwhile, the concentrations of pharmaceuticals in the influents of Asian region tend to be higher than those in other monitored regions. In this respect, the highest average daily mass loads were observed for acetaminophen (473 g/1000 in./day) and atenolol (592 g/1000 in./day), while amoxicillin (944 g/day), sulfamethoxazole (688.38 g/day) recorded the highest daily emissions. The environmental risk assessment based on the risk quotient (RQ) showed that twelve of the monitored pharmaceuticals pose a high potential risk to the aquatic ecosystems. The emphasized guidelines and regulations laid focus on the measures that can be used to mitigate the occurrence of pharmaceuticals in the environment. Research needs and future recommendations are also identified and proposed.
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