Fate of phthalic acid esters during composting of both lagooning and activated sludges

Phthalates contamination in sediments: A review of sources, influencing factors, benthic toxicity, and removal strategies

Sediments provide habitat and food for benthos, and phthalates (PAEs) have been detected in numerous river and marine sediments as a widely used plastic additive. PAEs in sediments is not only toxic to benthos, but also poses a threat to pelagic fish and human health through the food chain, so it is essential to comprehensively assess the contamination of sediments with PAEs. This paper presents a critical evaluation of PAEs in sediments, which is embodied in the analysis of the sources of PAEs in sediments from multiple perspectives. Biological production is indispensable, while artificial synthesis is the most dominant, thus the focus was on analyzing the industrial and commercial sources of synthetic PAEs. In addition, since the content of PAEs in sediments varies, some factors affecting the content of PAEs in sediments are summarized, such as the properties of PAEs, the properties of plastics, and environmental factors (sediments properties and hydrodynamic conditions). As endocrine disruptors, PAEs can produce toxicity to its direct contacts. Therefore, the effects of PAEs on benthos immunity, endocrinology, reproduction, development, and metabolism were comprehensively analyzed. In addition, we found that reciprocal inhibition and activation of the systems lead to genotoxicity and apoptosis. Finally, the paper discusses the feasible measures to control PAEs in wastewater and leachate from the perspective of source control, and summarizes the in-situ treatment measures for PAEs contamination in sediments. This paper provides a comprehensive review of PAEs contamination in sediments, toxic effects and removal strategies, and provides an important reference for reducing the contamination and toxicity of PAEs to benthos.

Exploring the potential of a new marine bacterium associated with plastisphere to metabolize dibutyl phthalate and bis(2-ethylhexyl) phthalate by enrichment cultures combined with multi-omics analysis

Phthalic acid esters (PAEs) plasticizers are virulent endocrine disruptors that are mixed into plastics while fabricating and can filter out once they release into the surrounding environments. Plastic surfaces serve as new habitats for microorganisms, referred to as 'plastisphere'. Previous metagenomic investigations of the 'plastisphere' indicated that marine plastic surfaces may harbor microbes that degrade PAEs plasticizers. To our knowledge, the potential of microorganisms in the marine 'plastisphere' to metabolize PAEs is poorly understood. In this study, by screening the natural microbial community on plastic debris that had been deployed in situ for up to 20 months, a novel marine bacterium, Microbacterium esteraromaticum DEHP-1, was successfully isolated, which could degrade and mineralize 10-200 mg/L dibutyl phthalate (DBP) and bis(2-ethylhexyl) phthalate (DEHP). According to the results of gas chromatography-mass spectrometry (GC-MS) and whole genome mining of strain DEHP-1, we found that strain DEHP-1 may metabolize DBP by successive removal of the ester side chain by esterase 2518 to produce mono-butyl phthalate (MBP) and phthalic acid (PA), whereas the degradation of DEHP may take place by the direct action of monooxygenase 0132 on the fatty acid side chain of the DEHP molecule to produce di-n-hexyl phthalate (DnHP) and DBP, and then the subsequent hydrolysis of DBP by de-esterification to PA and finally into the tricarboxylic acid (TCA) cycle. Non-targeted metabolomics results showed that intracellular degradation of PAEs did not happen. However, exposure to PAEs was found to significantly affect pathways such as arginine and proline, riboflavin, glutathione and lysine degradation. Therefore, the intracellular metabolic behavior of strain DEHP-1 exposed to PAEs was proposed for the first time. This study sheds light on the metabolic capacity and strategies of bacteria in the marine 'plastisphere' to effectively degrade PAEs and highlights the importance of marine microbes in mitigating plastic poisonousness.

Effect of hydraulic parameters of leachate treatment process on di(2-ethylhexyl) phthalate removal from aged leachate

The effect of hydraulic parameters of an anaerobic/anoxic/oxic leachate treatment reactor on the removal of di(2-ethylhexyl) phthalate (DEHP) from aged landfill leachate was studied. The mean DEHP removal efficiencies were 79.5%, 87.1%, 89.7% and 87.8% at hydraulic retention times of 6, 4.5, 3 and 2 d, respectively. The removal efficiency of DEHP was significantly higher when the internal reflux ratio was 200% than others. There was no significant difference among the DEHP removal efficiencies at different external reflux ratios of the reactor. Due to the overall efficiency of the reactor, hydraulic retention time 3 d, internal reflux ratio 200% and external reflux ratio 60%, were considered the optimal hydraulic parameters for DEHP removal from aged leachate. The removal efficiency of DEHP was significantly improved (from 75.7% to 89.1%) after the optimization of hydraulic parameters of the reactor. The removal percentages of DEHP in the anaerobic, anoxic, and oxic units of the reactor were 42.8%, 17.6%, and 15.3%, respectively. The oxic microcosms in the reactor had little effect on DEHP removal. The correlation between DEHP and leachate pollutants indicated that DEHP removal was strongly correlated with leachate COD and NH₄⁺-N.

Major biotransformation of phthalic acid esters in Eisenia fetida: Mechanistic insights and association with catalytic enzymes and intestinal symbionts

Phthalic acid esters (PAEs) are an important group of organic pollutants that are widely used as plasticizers in the environment. The PAEs in soil organisms are likely to be biotransformed into a variety of metabolites, and the combined toxicity of PAEs and their metabolites might be more serious than PAEs alone. However, there are only a few studies on PAE biotransformation by terrestrial animals, e.g. earthworms. Herein, the key biotransformation pathways of PAEs and their association with catalytic enzymes and intestinal symbionts in earthworms were studied using in vivo and in vitro incubation approaches. The widely distributed PAE in soil, dibutyl phthalate (DBP), was proven to be biotransformed rapidly together with apparent bioaccumulation in earthworms. The biotransformation of PAE congeners with medium or long side chains appeared to be faster compared with those with short side chains. DBP was biotransformed into butyl methyl phthalate (BMP), monobutyl phthalate (MBP), and phthalic acid (PA) through esterolysis and transesterification. Besides, the generation of small quantities of low-molecular weight metabolites via β-oxidation, decarboxylation or ring-cleavage, was also observed, especially when the appropriate proportion of NADPH coenzyme was applied to transfer electrons for oxidases. Interestingly, the esterolysis of PAEs was mainly regulated by the cytoplasmic carboxylesterase (CarE) in earthworms, with a Michaelis constant (K_m) of 0.416 mM in the catalysis of DBP. The stronger esterolysis in non-intestinal tissues indicated that the CarE was primarily secreted by non-intestinal tissues of earthworms. Additionally, the intestinal symbiotic bacteria of earthworms could respond to PAE stress, leading to the changes in their diversity and composition. The enrichment of some genera e.g. Bacillus and Paracoccus, and the enhancement of metabolism function, e.g. amino acids, energy, lipids biosynthesis and oxidase secretion, indicated their important role in the degradation of PAEs.

Biodegradation of high di-(2-Ethylhexyl) phthalate (DEHP) concentration by food waste composting and its toxicity assessment using seed germination test

Di-(2-ethylhexyl) phthalate (DEHP), a plasticizer derived from phthalate ester, is used as an additive in industrial products such as plastics, paints, and medical devices. However, DEHP is known as an endocrine-disrupting chemical, causing cancers and adverse effects on human health. This study evaluated DEHP biodegradation efficiency via food waste composting during 35 days of incubation. At high DEHP concentrations (2167 mg kg^-1) in food waste compost mixture, the DEHP biodegradation efficiency was 99% after 35 days. The highest degradation efficiency was recorded at the thermophilic phase (day 3 - day 11) with the biodegradation rate reached 187 mg kg^-1 day^-1. DEHP was metabolized to dibutyl phthalate (DBP) and dimethyl phthalate (DMP) and would be oxidized to benzyl alcohol (BA) and mineralized into CO₂ and water via various metabolisms. Finally, the compost's quality with residual DEHP was evaluated using Brassica chinensis L. seeds via 96 h of germination tests. The compost (at day 35) with a trace amount of DEHP as the end product showed no significant effect on the germination rate of Brassica chinensis L. seeds (88%) compared to that without DEHP (94%), indicating that the compost can be reused as fertilizer in agricultural applications. These results provide an improved understanding of the DEHP biodegradation via food waste composting without bioaugmentation and hence facilitating its green remediation and conversion into value-added products. Nevertheless, further studies are needed on DEHP biodegradation in large-scale food waste composting or industrial applications.

Impacts of dibutyl phthalate on biological municipal wastewater treatment in a pilot-scale A2/O-MBR system

Dibutyl phthalate (DBP) is a typical contaminant in pharmaceutical wastewater with strong bio-depressive properties which potentially affects the operation of municipal wastewater treatment systems. Based on a year-round monitoring of the quality of influent and effluent of a full-scale pharmaceutical wastewater treatment plant in Northeast China, the DBP was found to be the representative pollutant and its concentration in the effluent ranged 4.28 ± 0.93 mg/L. In this study, the negative effects of DBP on a pilot-scale A²/O-MBR system was investigated. When the influent DBP concentration reached 8.0 mg/L, the removals of chemical oxygen demand (COD) and total nitrogen (TN) were significantly inhabited (P < 0.01), with the effluent concentration of 54.7 ± 2.6 mg/L and 22.8 ± 3.7 mg/L, respectively. The analysis of pollutant removal characteristics of each process unit showed that DBP had the most significant effects on the removals of COD and TN in the anoxic tank. The α- and β-diversity in the system decreased significantly when the influent DBP concentration reached 8.0 mg/L. The impacts of DBP on known nitrifying bacteria, such as Nitrospira, and phosphorus accumulating organisms (PAOs), such as Cadidatus Accumulibacter, were not remarkable. Whereas, DBP negatively affected the proliferation of key denitrifying bacteria, represented by Simplicispira, Dechloromonas and Acinetobacter. This study systematically revealed the impacts of DBP on the pollutants removal performance and the bacterial community structure of the biological municipal wastewater treatment process, which would provide insights for understanding the potential impacts of residues in treated pharmaceutical wastewater on biological municipal wastewater treatment.

Composting and green technologies for remediation of phthalate (PAE)-contaminated soil: Current status and future perspectives

Phthalate esters (PAEs) are hazardous organic compounds that are widely added to plastics to enhance their flexibility, temperature, and acidic tolerance. The increase in global consumption and the corresponding environmental pollution of PAEs has caused broad public concerns. As most PAEs accumulate in soil due to their high hydrophobicity, composting is a robust remediation technology for PAE-contaminated soil (efficiency 25%-100%), where microbial activity plays an important role. This review summarized the roles of the microbial community, biodegradation pathways, and specific enzymes involved in the PAE degradation. Also, other green technologies, including biochar adsorption, bioaugmentation, and phytoremediation, for PAE degradation were also presented, compared, and discussed. Composting combined with these technologies significantly enhanced removal efficiency; yet, the properties and roles of each bacterial strain in the degradation, upscaling, and economic feasibility should be clarified in future research.

Biochemical pathways and associated microbial process of di-2-ethyl hexyl phthalate (DEHP) enhanced degradation by the immobilization technique in sequencing batch reactor

A bacterial strain ASLT-13 was successfully isolated from activated sludge and identified as Pseudomonas amygdali. Gas chromatograph-mass spectrometer (GC-MS) analysis indicated that strain ASLT-13 could completely mineralize di 2-ethyl hexyl phthalate (DEHP). DEHP was first metabolized from the longer side chain of the benzene ring into shorter branches (Phatlalic mono-esters) like Dibutyl phthalate (DBP) under the action of degrading genes. DBP was then converted into di-methyl phthalate (DMP), and then hydrolysed to phthalic acid (PA). PA was eventually converted to CO₂ and H₂O through the TCA cycle. The optimal conditions for immobilization were the sodium alginate (SA) concentration of 6%, CaCl₂ concentration of 5%, ratio of bacteria and SA of 1:1, crosslinking time of 6 h. Bacterial quantity and community structure in sequencing batch reactors (SBRs) was investigated by q-PCR and high-throughput sequencing. The results indicated that DEHP removal efficiency was significantly enhanced by immobilization. Arthrobacter, Acinetobacter, Bacillus and Rhodococcus were the predominant genera for DEHP degradation. This study suggested that the cell immobilization technology had a potential application in DEHP wastewater treatment.

Biodeterioration of Compost-Pretreated Polyvinyl Chloride Films by Microorganisms Isolated From Weathered Plastics

Polyvinyl chloride (PVC) is a petroleum-based plastic used in various applications, polluting the environment because of its recalcitrance, large content of additives, and the presence of halogen. In our case study, a new, two-stage biodegradation technology that combined composting process used for PVC pretreatment with a subsequent PVC attack by newly-isolated fungal and bacterial strains under SSF conditions was used for biodegradation of commercial PVC films. The novelty consisted in a combined effect of the two biodegradation processes and the use for augmentation of microbial strains isolated from plastic-polluted environments. First, the ability of the newly-isolated strains to deteriorate PVC was tested in individual, liquid-medium- and SSF cultures. Higher mass-reductions of PVC films were obtained in the former cultures, probably due to a better mass transfer in liquid phase. Using the two-stage biodegradation technology the highest cumulative mass-reductions of 29.3 and 33.2% of PVC films were obtained after 110 days with Trichoderma hamatum and Bacillus amyloliquefaciens applied in the second stage in the SSF culture, respectively. However, FTIR analysis showed that the mass-reductions obtained represented removal of significant amounts of additives but the PVC polymer chain was not degraded.

Occurrence and cross-interface transfer of phthalate esters in the mangrove wetland in Dongzhai Harbor, China

Phthalate esters (PAEs), the most widely used plasticizers, are extensively present in various environmental media, and are continuously transported from land to sea. However, PAEs have not been well characterized in multiple media in mangrove wetlands, an important land-sea interface. This study investigated the distribution and transfer of six PAEs in water, sediment, mangroves, and fish in Dongzhai Harbor. The mangrove forest in Dongzhai Harbor is the largest in China and is surrounded by shrimp ponds and villages. PAEs are ubiquitous in the study area. The mean concentration range of ∑₆PAEs was 0.31-1.52 μg/L in water, 450-2096 μg/kg dry weight (dw) in sediment, 210-937 μg/kg dw in mangrove plants, and not detected (n.d.) -205 μg/kg in fish. Among the six PAEs, di-n-butyl phthalate (DBP) and di-ethylhexyl phthalate (DEHP) were predominant. The concentrations of the PAEs in mangrove plants tended to decrease from the river and coast to tidal gullies, which might be related to the periodic inundation of tides. A study of PAEs bioaccumulation showed that the concentration of PAEs in herbivorous fish was higher than that in carnivorous fish. In the same species, larger individuals had a lower concentration of ∑₆PAEs. Di-n-octyl phthalate (DnOP) and DEHP tended to transfer from water to sediments, while the four less-hydrophobic PAEs, such as DBP, were more likely to be released from sediments to water. Our results can provide important information of the distribution and fate of PAEs in mangrove wetlands.

Composting and its application in bioremediation of organic contaminants

This review investigates the findings of the most up-to-date literature on bioremediation via composting technology. Studies on bioremediation via composting began during the 1990s and have exponentially increased over the years. A total of 655 articles have been published since then, with 40% published in the last six years. The robustness, low cost, and easy operation of composting technology make it an attractive bioremediation strategy for organic contaminants prevalent in soils and sediment. Successful pilot-and large-scale bioremediation of organic contaminants, e.g., total petroleum hydrocarbons, plasticizers, and persistent organic pollutants (POPs) by composting, has been documented in the literature. For example, composting could remediate >90% diesel with concentrations as high as 26,315 mg kg^−a of initial composting material after 24 days. Composting has unique advantages over traditional single- and multi-strain bioaugmentation approaches, including a diverse microbial community, ease of operation, and the ability to handle higher concentrations. Bioremediation via composting depends on the diverse microbial community; thus, key parameters, including nutrients (C/N ratio = 25–30), moisture (55–65%), and oxygen content (O₂ > 10%) should be optimized for successful bioremediation. This review will provide bioremediation and composting researchers with the most recent finding in the field and stimulate new research ideas.

Mass balance and kinetics of biodegradation of endocrine disrupting phthalates by Cellulosimicrobium funkei in a continuous stirred tank reactor system

This study investigated the potential ofCellulosimicrobium funkeifor degrading dimethyl phthalate (DMP) and diethyl phthalate (DEP). Effect of different initial concentrations of phthalates on their biodegradation and growth ofC. funkeiwas examined using shake flasks and a continuous stirred tank reactor (CSTR). Complete degradation of both DMP and DEP was achieved in CSTR, even up to 3000 and 2000 mg/L initial concentrations, respectively. Simultaneous degradation of the phthalates in mixture, i.e. more than 80% and 55% biodegradation efficiency were achieved at 1000 and 2000 mg/L initial concentrations of DMP and DEP, respectively, using the CSTR. Mass balance analysis of the degradation results suggested proficient degradation of DMP and DEP with biomass yield values of 0.64 and 0.712, respectively. The high values of inhibition constant Kiestimated using the Tessier and Edward substrate inhibition models indicated very good tolerance ofC. funkeitoward biodegradation of DMP and DEP.

Organic additive release from plastic to seawater is lower under deep-sea conditions

Plastic garbage patches at the ocean surface are symptomatic of a wider pollution affecting the whole marine environment. Sinking of plastic debris increasingly appears to be an important process in the global fate of plastic in the ocean. However, there is insufficient knowledge about the processes affecting plastic distributions and degradation and how this influences the release of additives under varying environmental conditions, especially in deep-sea environments. Here we show that in abiotic conditions increasing hydrostatic pressure inhibits the leaching of the heaviest organic additives such as tris(2-ethylhexyl) phosphate and diisononyl phthalate from polyethylene and polyvinylchloride materials, whereas deep-sea and surface marine prokaryotes promote the release of all targeted additives (phthalates, bisphenols, organophosphate esters). This study provides empirical evidences for more efficient additive release at the ocean surface than in deep seawater, where the major plastic burden is supposed to transit through before reaching the sediment compartment.

Reduction effects of solar radiation, mechanical tension, and soil burial on phthalate esters concentrations in plastic film and soils

Phthalate esters (PAEs) are potentially dangerous chemicals in plastic film mulched fields; however, few studies have investigated how to reduce their concentrations in plastic film and soil. In this study, the effects of solar radiation, mechanical tension, and soil burial on PAEs concentrations in polyethylene (PE) film and degradable film were investigated, and the half-lives of di-n-butyl phthalate (DBP) and di(2-ethylhexyl) phthalate (DEHP) in soil also studied. PAEs concentrations in polyethylene films were about twice those in the degradable films; however, PAEs concentrations in all experimental films were similar after 1-year of field exposure. Mechanical tension had no effect on the PAEs concentrations of polyethylene films, but increased the detected concentrations of PAEs in degradable films by 34%-120%. After 4-years of burial, the PAEs concentrations in films decreased by 79.2%-98.0%, and mechanical tension promoted the reductions. However, there was little difference in PAEs concentrations between the buried soils with and without films, indicating the released PAEs reduced quickly in soil. Also, the half-lives of DBP and DEHP were 2.4-4.6 days and 18.5-41.4 days, respectively. Overall, the results presented herein provide reasonable approaches to reduce the concentrations of PAEs in plastic films and soils.

Occurrence and dissipation mechanism of organic pollutants during the composting of sewage sludge: A critical review

Sewage sludge contains various classes of organic pollutants, limiting its land application. Sludge composting can effectively remove some organic pollutants. This review summarizesrecent researches on concentration changes and dissipation of different organic pollutants including persistent organic pollutants during sludge composting, and discusses their dissipation pathways and the current understanding on dissipation mechanism. Some organic pollutants like PAHs and phthalates were removed mainly through biodegradation or mineralization, and their dissipation percentages were higher than those of PCDD/Fs and PCBs. Nevertheless, some recalcitrant organic pollutants could be sequestrated in organic fractions of sludge mixtures, and their levels and ARG abundance even increased after sludge composting in some studies, posing potential risks for land application. This review demonstrated that microbial community and their corresponding degradation for organic pollutants were influenced by different pollutants, bulking agents, composting methods and processes. Further research perspectives on removing organic pollutants during sludge composting were highlighted.

Bacterial community progression during food waste composting containing high dioctyl terephthalate (DOTP) concentration

The overall dioctyl terephthalate (DOTP) degradation efficiency during food waste composting was 98%. The thermophilic phases contributed to 76% of the overall degradation efficiency, followed by the maturation phase (22%), then the mesophilic phase (0.7%). The thermophilic phase had the highest specific degradation rate of 0.149 d^-1. The progression of the bacterial community during the composting process was investigated to understand DOTP biodegradation. The results showed that the bacterial richness and the alpha diversity of the DOTP composting were similar to a typical composting process, indicating that the high concentration of DOTP did not hinder the thriving and evolution of the bacterial community. Additionally, Firmicutes was the most dominant at the phylum level, followed by Proteobacteria and Bacteroidetes. Bacilli was the most dominant class (70%) in the mesophilic phase, with the abundance decreasing thereafter in the thermophilic and maturation phase. Moreover, Lactobacillus sp. was the dominant species at the beginning of the experiment, which was probably responsible for DOTP biodegradation. The high removal efficiency observed in the maturation phase indicates that degradation occurs in all the composting phases, and that compost can be used to enhance natural attenuation. These findings provide a better understanding of the bacterial communities during biodegradation of DOTP and plasticizers via food waste composting and should facilitate the development of appropriate green bioremediation technologies.

Sorption behavior of dimethyl phthalate in biochar-soil composites: Implications for the transport of phthalate esters in long-term biochar amended soils

The characteristics and content of organo-mineral complex were confirmed to be changed in agriculture soils under the biochar application with long-term, but the resulting environmental effects in the retention and lasting of agrochemicals and xenobiotic pollutants is far from clear. In this study, biochar-soil composites were prepared by one-step dry ball-milling method, and a sorption case study was proceed to investigate the biochar incorporated affection in soils on the transport of dimethyl phthalate (DMP). More surface oxygen-containing functional groups on ball-milled biochar enhanced its complexation with soil minerals. Sorption isotherms of DMP onto the biochar-soil composites were well described by the Freundlich model, both heterogeneous surface and multilayer interactions occurred simultaneously. The kinetics of sorption could be simulated with the pseudo-second-order model (R² > 0.98), while the average sorption energy (E_a) calculated from Dubinin-Radushkevich isotherms were found in the range of 3.83-5.60 kJ mol^-1, which revealed that the sorption processes coexist of chemisorption and physisorption, and π-π electron donor-acceptor interaction, pore-filling and hydrophobic interactions could be identified as the main sorption mechanisms. Desorption of absorbed DMP appeared obvious nonlinear characteristics and lag effect, the calculated hysteresis index (HI) increased with the application of biochar into soil. Considering the phenomenon of biochar aging and soil complexation, it is important to verify how the transport and natural attenuation of contaminant will be influenced by biochar addition, especially the long-term effect in soil ecosystem.

Biodegradation of Di (2-Ethylhexyl) Phthalate by a novel Enterobacter spp. Strain YC-IL1 Isolated from Polluted Soil, Mila, Algeria

Di-(2-ethylhexyl) phthalate (DEHP) is one of the phthalic acid ester representatives and is mainly used as a plasticizer to endow polyvinyl chloride plastics with desirable physical properties. It is synthesized in massive amounts worldwide. Many studies have proved the adverse effects of DEHP on human health and wildlife. DEHP is labeled as an endocrine disruptor which causes human reproductive problems. Enterobacter spp. YC-IL1, a novel isolated strain from contaminated soil, was identified by 16S rRNA gene analysis and electronic microscope. It is capable of efficiently degrading DEHP (100%) and a wide range of phthalic acid ester PAEs, particularly those containing side chains with branches, or ring structures such as dutylbenzyl phthalate and dicyclohexyl phthalate, which are hard to degrade, with, respectively, 81.15% and 50.69% degradation after 7 days incubation. YC-IL1 is an acido-tolerant strain which remained in pH values lower than pH 5.0 with the optimum pH 7.0 and temperature 30 °C. The DEHP metabolites were detected using HPLC-QQQ and then the degradation pathway was tentatively proposed. Strain YC-IL1 showed high DEHP degradation rate in artificially contaminated soil with 86% removed in 6 days. These results indicate the application potential of YC-IL1 in bioremediation of PAE-polluted sites, even the acidic ones.

Uptake, translocation and metabolism of di-n-butyl phthalate in alfalfa (Medicago sativa)

Uptake and metabolism by plants are important biotransformation processes of organic pollutants in ecosystems. However, very limited information is currently available on the metabolism of phthalic acid esters (PAEs) in plants. In this study, alfalfa, highly efficient in phytoremediation of PAE contaminated soil, was chosen as the model to understand the fate of di-n-butyl phthalate (DnBP) in remediation plant. The results of hydroponic experiments indicated that DnBP accumulated mainly in alfalfa roots and adsorption to root epidermis might be the primary uptake mechanism. A large proportion of DnBP was subjected to apparent metabolism. De-esterification could be specified to be the predominant metabolism pathway. Mono-n-butyl phthalate (MnBP) and phthalic acid (PA) were detected as DnBP metabolites in all alfalfa roots and shoots throughout the entire exposure period. Around >90% of MnBP were distributed in cell soluble components and organelles, and MnBP gradually transferred from organelles and cell walls to soluble components as the exposure time extended. Similar to MnBP, PA located mainly in soluble components and organelles as well, while no PA existed in alfalfa cell walls. Exposure to DnBP ultimately resulted in the coexistence of DnBP and MnBP for a long term in interior plants, raising concerns on their combined potential toxicity on plant health or even ecosystem.

High-effectively degrade the di-(2-ethylhexyl) phthalate via biochemical system: Resistant bacterial flora and persulfate oxidation activated by BC@Fe3O4

Di-(2-ethylhexyl) phthalate (DEHP) has been classified as a priority pollutant which increased the healthy risk to human and animals dramatically. Hence, a novel biochemical system combined by DEHP-resistant bacterial flora (B) and a green oxidant of persulfate (PS) activated by Nano-Fe₃O₄ was applied to degrade DEHP in contaminated soil. In this study, the resistant bacterial flora was screened from activated sludge and immobilized by sodium alginate (SAB). Nano-Fe₃O₄ was coated on biochar (BC@Fe₃O₄) to prevent agglomerating in soil. X-ray diffraction (XRD) and scanning electron microscope (SEM) were utilized to characterize BC@Fe₃O₄. Results demonstrated that the treatment of biochemical system (SAB + BC@Fe₃O₄ + PS) presented the maximum degradation rate about 92.56% within 24 days of incubation and improved soil microecology. The 16S rDNA sequences analysis of soil microorganisms showed a significantly different abundance and a similar diversity among different treatments. Kyoto Encyclopedia of Genes and Genomes (KEGG) functional genes difference analysis showed that some metabolic pathways, such as metabolism of cofactors and vitamins, energy metabolism, cell growth and death, replication and repair, were associated with the biodegradation of DEHP. Besides, DEHP was converted to MEHP and PA by biodegradation, while DEHP was converted to DBP and PA by persulfate and BC@Fe₃O₄, and then ultimately degraded to CO₂ and H₂O.

The occurrence and spatial distribution of phthalate esters (PAEs) in the Lanzhou section of the Yellow River

The occurrence and spatial distribution of 22 congener phthalate esters (PAEs) in the Lanzhou section of the Yellow River were investigated using water and sediment samples collected from 12 stations along the river in August 2016 to March 2017. PAEs were determined by liquid-liquid extraction and gas chromatography-mass spectrometry. The average concentrations of PAE in the water samples during the dry and wet periods were 3236.0 ng/L and 2300.0 ng/L, and the average dry and wet periods of the PAEs in the sediments were 4238.9 ng/g and 3959.9 ng/g, respectively. PAEs were detected in all sampling sites. The six PAEs controlled by the United States Environmental Protection Agency (U.S. EPA), namely dimethyl phthalate (DMP), diethyl phthalate (DEP), dibutyl phthalate (DBP), di-2-ethylhexyl phthalate (DEHP), di-n-octyl phthalate (DNOP), and butyl benzyl phthalate(BBP), were detected. DMP, DEP, DBP, and DEHP accounted for more than 70% of all PAEs. In view of time distribution, PAEs concentration in the water samples of the dry season were greater than those of the wet season, but the sediments did not differ remarkably across the different periods. As for spatial distribution, the PAEs initially exhibited low concentrations in the upper reaches, high concentrations in the middle part, and low concentrations in the downstream; a health risk assessment of the six PAEs controlled by the U.S. EPA was carried out according to priority. Results showed that the carcinogenic risk value was less than 10^-6, and the values of the non-carcinogenic compound risk index were less than 1, indicating the absence of carcinogenic damage to organisms or humans.

Biodegradation of recalcitrant compounds and phthalates by culturable bacteria isolated from Liometopum apiculatum microbiota

Liometopum apiculatum is a species of ants widely distributed in arid and semi-arid ecosystems where there is a relative food shortage compared with tropical ecosystems. L. apiculatum has established an ecological balance involving symbiotic interactions, which have allowed them to survive through mechanisms that are still unknown. Therefore, the aim of this study was to explore the metabolic potential of isolated bacteria from L. apiculatum using enzymatic activity assay and substrate assimilation. Results revealed a complex bacteria consortium belonging to Proteobacteria, Firmicutes, and Actinobacteria phylum. Most of the isolated bacteria showed activities associated with biopolymers degradation, from them Exiguobacterium and B. simplex showed the highest amylolytic activity (27 U/mg protein), while A. johnsonii and B. pumulis showed the highest cellulolytic and xylanolytic activities (1 and 2.9 U/mg protein, respectively). By other hand, some microorganisms such as S. ficaria, E. asburiae, P. agglomerans, A. johnsonii, S. rubidaea, S. marcescens, S. warneri, and M. hydrocarbonoxydans were able to grow up to 1000 mg/L of phthalates esters. These results not only revealed the important contribution of the symbionts in L apiculatum ants feeding habits, but also have shown a promising source of enzymes with potential biotechnological applications such as lignocellulosic biomass hydrolysis and bioremediation processes.

Biotransformation of Phthalate Plasticizers and Bisphenol A by Marine-Derived, Freshwater, and Terrestrial Fungi

Phthalate esters (PEs, Phthalates) are environmentally ubiquitous as a result of their extensive use as plasticizers and additives in diverse consumer products. Considerable concern relates to their reported xenoestrogenicity and consequently, microbial-based attenuation of environmental PE concentrations is of interest to combat harmful downstream effects. Fungal PE catabolism has received less attention than that by bacteria, and particularly fungi dwelling within aquatic environments remain largely overlooked in this respect. We have compared the biocatalytic and biosorptive removal rates of di-n-butyl phthalate (DBP) and diethyl phthalate (DEP), chosen to represent two environmentally prominent PEs of differing structure and hydrophobicity, by marine-, freshwater-, and terrestrial-derived fungal strains. Bisphenol A, both an extensively used plastic additive and prominent environmental xenoestrogen, was included as a reference compound due to its well-documented fungal degradation. Partial pathways of DBP metabolization by the ecophysiologically diverse asco- and basidiomycete strains tested were proposed with the help of UPLC-QTOF-MS analysis. Species specific biochemical reaction steps contributing to DBP metabolism were also observed. The involved reactions include initial cytochrome P450-dependent monohydroxylations of DBP with subsequent further oxidation of related metabolites, de-esterification via either hydrolytic cleavage or cytochrome P450-dependent oxidative O-dealkylation, transesterification, and demethylation steps - finally yielding phthalic acid as a central intermediate in all pathways. Due to the involvement of ecophysiologically and phylogenetically diverse filamentous and yeast-like fungi native to marine, freshwater, and terrestrial habitats the results of this study outline an environmentally ubiquitous pathway for the biocatalytic breakdown of plastic additives. Beyond previous research into fungal PE metabolism which emphasizes hydrolytic de-esterification as the primary catabolic step, a prominent role of cytochrome P450 monooxygenase-catalyzed reactions is established.

Plasticizer Degradation by Marine Bacterial Isolates: A Proteogenomic and Metabolomic Characterization

Many commercial plasticizers are toxic endocrine-disrupting chemicals that are added to plastics during manufacturing and may leach out once they reach the environment. Traditional phthalic acid ester plasticizers (PAEs), such as dibutyl phthalate (DBP) and bis(2-ethyl hexyl) phthalate (DEHP), are now increasingly being replaced with more environmentally friendly alternatives, such as acetyl tributyl citrate (ATBC). While the metabolic pathways for PAE degradation have been established in the terrestrial environment, to our knowledge, the mechanisms for ATBC biodegradation have not been identified previously and plasticizer degradation in the marine environment remains underexplored. From marine plastic debris, we enriched and isolated microbes able to grow using a range of plasticizers and, for the first time, identified the pathways used by two phylogenetically distinct bacteria to degrade three different plasticizers (i.e., DBP, DEHP, and ATBC) via a comprehensive proteogenomic and metabolomic approach. This integrated multi-OMIC study also revealed the different mechanisms used for ester side-chain removal from the different plasticizers (esterases and enzymes involved in the β-oxidation pathway) as well as the molecular response to deal with toxic intermediates, that is, phthalate, and the lower biodegrading potential detected for ATBC than for PAE plasticizers. This study highlights the metabolic potential that exists in the biofilms that colonize plastics-the Plastisphere-to effectively biodegrade plastic additives and flags the inherent importance of microbes in reducing plastic toxicity in the environment.

Metabolic process of di-n-butyl phthalate (DBP) by Enterobacter sp. DNB-S2, isolated from Mollisol region in China

The accumulation of phthalate acid esters (PAEs) in the environment has aroused a global concern. Microbial degradation is the most promising method for removing PAEs from polluted environment. Di-n-butyl phthalate (DBP) is one of the most widely used PAEs. In this study, a highly efficient DBP-degrading strain, Enterobacter sp. DNB-S2 was isolated from Mollisol in northeast China, and the degradation rate of 500 mg L^-1 DBP reached 44.10% at 5 °C and 91.08% at 50 °C within 7 days. A new intermediate, n-butyl benzoate BP, was detected, implying a new degradation pathway. The complete genome of the strain DNB-S2 was successfully sequenced to comprehensively understand of the entire DBP catabolic process. Key genes were proposed to be involved in DBP degradation, such as esterases, 3,4-dihydroxybenzoate decarboxylase and catechol 2,3-dioxygenase genes. Intermediate-utilization tests and real-time quantitative polymerase chain reaction (RT-qPCR) validated the proposed DBP catabolic pathway. The aboriginal bacterium DNB-S2 is a promising germplasm for restoring PAE-contaminated Mollisol regions at low temperature. This study provides novel insight into the catabolic mechanisms and abundant gene resources of PAE biodegradation.

Degradation of phthalate esters in floor dust at elevated relative humidity

Emerging investigator series: Phthalate esters are present at elevated concentrations in floor dust, and resuspension of dust represents a major source for human exposure to chemicals. Biodegradation of phthalates occurs in aquatic systems and soils but has not been demonstrated in house dust. The goal of this study was to quantify indoor phthalate ester degradation through both biotic and abiotic mechanisms. Worn carpet squares were embedded with dust and incubated for one to six weeks at equilibrium relative humidity (ERH) levels of 50, 80, 85, 90, 95, and 100%, and nine phthalates were measured. Removal was observed for DEHP, BBzP, DINP, DiDP, and DMP (p < 0.05) when incubated under elevated relative humidity conditions. Abiotic and biotic losses were examined separately using dust spiked with deuterated di(2-ethylhexyl)phthalate (d-DEHP) that was embedded in carpet and incubated at 100% ERH. Abiotic processes resulted in a 10.1% (±1.1%, standard error) to 69.6% (±4.8%) decrease in total d-DEHP after one week (p = 0.03) and a 27.2% (±1.4%) to 52.0% (±2.1%) decrease after three weeks (p = 0.008). Biodegradation resulted in a decrease in total d-DEHP after one week, ranging from 5.9% (±8.9%) to 8.5% (±1.7%) (p = 0.07) and a 1.7% (±3.9%) to 10.3% (±4.5%) decrease after three weeks (p = 0.044). Metatranscriptomic-based analysis indicates that fungi found in carpet dust express genes capable of degrading phthalate esters via various biochemical processes (including β-oxidation and hydrolysis). Overall, these results support the hypothesis that phthalate losses in floor dust are due to a combination of abiotic and microbial degradation at ≥80% ERH.

Fate of di (2-ethylhexyl) phthalate and its impact on soil bacterial community under aerobic and anaerobic conditions

In this study, we examined the influence of oxygen on the degradation of di (2-ethylhexyl) phthalate (DEHP), the accumulation of its monoester metabolite mono (2-ethylhexyl) phthalate (MEHP) and their impact on soil bacterial communities. Soil microcosms artificially contaminated with DEHP (0, 100 and 1000 mg kg^-1) were incubated under aerobic and anaerobic flooded conditions, and sacrificed after 0, 21 and 42 days. The results indicated that DEHP degradation proceeded at similar rates in aerobic and anaerobic flooded soils, but accumulation of metabolite MEHP was more likely to occur in anaerobic soils. Moreover, MEHP generated from DEHP degradation seemed to be readily released into the water phase, which may arouse health concerns. Illumina Miseq sequencing showed that MEHP had a greater impact on soil bacterial community than DEHP at the same dosage, and a wide range of bacterial phylotypes were inhibited by MEHP under anaerobic conditions. High DEHP contamination (1000 mg kg^-1) significantly reduced bacterial diversity and altered bacterial community structure under anaerobic conditions, but not under aerobic conditions. Firmicutes was constantly inhibited by DEHP under both aerobic (Bacillus) and anaerobic (unclassified Clostridiales Family_XVIII) conditions. On the other hand, bacterial phylotypes belonging to Actinobacteria, β-Proteobacteria and Gemmatimonadaceae were constantly enriched by DEHP in anaerobic soils, however no such a clear pattern existed in aerobic soils. This work greatly expanded our understanding of the fate of DEHP and its modifying effect on bacterial communities under different environmental conditions.

Phthalate Release from Plastic Fragments and Degradation in Seawater

Plastic debris in the environment contains plasticizers, such as phthalates (PAEs), that can be released during plastic aging. Here, two common plastic materials, an insulation layer of electric cables (polyvinyl chloride, PVC-cables) and plastic garbage bag (polyethylene, PE-bags), were incubated in natural seawater under laboratory conditions, and the PAE migration to the seawater phase was studied with varying light and bacterial conditions over a 90-day time course. Free PAEs diluted in seawater were also studied for bacterial degradation. Our results showed that, within the first month of incubation, both plastic materials significantly leached out PAEs into the surrounding water. We found that di-isobutyl phthalate (DiBP) and di- n-butyl phthalate (DnBP) were the main PAEs released from the PE-bags, with the highest values of 83.4 ± 12.5 and 120.1 ± 18.0 ng g^-1 of plastic, respectively. Furthermore, dimethyl phthalate (DMP) and diethyl phthalate (DEP) were the main PAEs released from PVC-cables, with mass fractions as high as 9.5 ± 1.4 and 68.9 ± 10.3 ng g^-1, respectively. Additionally, we found that light and bacterial exposure increased the total amount of PAEs released from PVC-cables by a factor of up to 5, whereas they had no influence in the case of PE-bags.

Factors impacting the interactions of engineered nanoparticles with bacterial cells and biofilms: Mechanistic insights and state of knowledge

Since their advent a few decades ago, engineered nanoparticles (ENPs) have been extensively used in consumer products and industrial applications and their use is expected to continue at the rate of thousands of tons per year in the next decade. The widespread use of ENPs poses a potential risk of large scale environmental proliferation of ENPs which can impact and endanger environmental health and safety. Recent studies have shown that microbial biofilms can serve as an important biotic component for partitioning and perhaps storage of ENPs released into aqueous systems. Considering that biofilms can be one of the major sinks for ENPs in the environment, and that the field of biofilms itself is only three to four decades old, there is a recent and growing body of literature investigating the ENP-biofilm interactions. While looking at biofilms, it is imperative to consider the interactions of ENPs with the planktonic microbial cells inhabiting the bulk systems in the vicinity of surface-attached biofilms. In this review article, we attempt to establish the state of current knowledge regarding the interactions of ENPs with bacterial cells and biofilms, identifying key governing factors and interaction mechanisms, as well as prominent knowledge gaps. Since the context of ENP-biofilm interactions can be multifarious-ranging from ecological systems to water and wastewater treatment to dental/medically relevant biofilms- and includes devising novel strategies for biofilm control, we believe this review will serve an interdisciplinary audience. Finally, the article also touches upon the future directions that the research in the ENP-microbial cells/biofilm interactions could take. Continued research in this area is important to not only enhance our scientific knowledge and arsenal for biofilm control, but to also support environmental health while reaping the benefits of the 'nanomaterial revolution'.

Biodegradation pathway of di-(2-ethylhexyl) phthalate by a novel Rhodococcus pyridinivorans XB and its bioaugmentation for remediation of DEHP contaminated soil

A novel bacterial strain designated as Rhodococcus pyridinivorans XB, capable of utilizing various endocrine disruptor phthalates or phthalic acid (PA) as sole source of carbon and energy, was isolated from activated sludge. Under the optimal culture conditions (pH 7.08, 30.4 °C, inoculum size (OD_{600 nm}) of 0.6) obtained by response surface methodology, di-(2-ethylhexyl) phthalate (DEHP, 200 mg/L) could be degraded by strain XB with a removal rate of 98% within 48 h. Under the observation of an atomic force microscope, it was confirmed that DEHP did not inhibit the growth of strain XB which might produce some extracellular polymeric substances as a response to DEHP stress, resulting in rapid degradation of DEHP. At initial concentrations of 50-800 mg/L DEHP, its degradation curves were well fitted with the first-order kinetic model, and the half-life of DEHP degradation varied from 5.44 to 23.5 h. The degradation intermediates of DEHP were identified by both GC-MS and high performance liquid chromatography-time of flight-mass spectrometry (HPLC-TOF-MS). Significant up-regulation was observed for the relative expression levels of genes (i.e., phthalate hydrolase, PA 3,4-dioxygenase, protocatechuate 3,4-α and 3,4-β dioxygenase) involved in DEHP degradation determined by real-time quantitative PCR (RT-qPCR). A DEHP biodegradation pathway by strain XB was proposed based on the identified intermediates and the degrading genes. Bioaugmentation of DEHP-contaminated soils with strain XB could efficiently promote DEHP removal, offering great potential in bioremediation of DEHP-contaminated environment.

A comparative study of anaerobic fixed film baffled reactor and up-flow anaerobic fixed film fixed bed reactor for biological removal of diethyl phthalate from wastewater: a performance, kinetic, biogas, and metabolic pathway study

BACKGROUND

Phthalic acid esters, including diethyl phthalate (DEP), which are considered as top-priority and hazardous pollutants, have received significant attention over the last decades. It is vital for industries to select the best treatment technology, especially when the DEP concentration in wastewater is high. Meanwhile, anaerobic biofilm-based reactors are considered as a promising option. Therefore, in the present study, for the biological removal of DEP from synthetic wastewater, two different anaerobic biofilm-based reactors, including anaerobic fixed film baffled reactor (AnFFBR) and up-flow anaerobic fixed film fixed bed reactor (UAnFFFBR), were compared from kinetic and performance standpoints. As in the previous studies, only the kinetic coefficients have been calculated and the relationship between kinetic coefficients and their interpretation has not been evaluated, the other aim of the present study was to fill this research gap.

RESULTS

In optimum conditions, 90.31 and 86.91% of COD as well as 91.11 and 88.72% of DEP removal were achieved for the AnFFBR and UAnFFFBR, respectively. According to kinetic coefficients (except biomass yield), the AnFFBR had better performance as it provided a more favorable condition for microbial growth. The Grau model was selected as the best mathematical model for designing and predicting the bioreactors' performance due to its high coefficients of determination (0.97 < R²). With regard to the insignificant variations of the calculated Grau kinetic coefficients (K_G) when the organic loading rate (with constant HRT) increased, it can be concluded that both of the bioreactors can tolerate high organic loading rate and their performance is not affected by the applied DEP concentrations.

CONCLUSIONS

Both the bioreactors were capable of treating low-to-high strength DEP wastewater; however, according to the experimental results and obtained kinetic coefficients, the AnFFBR indicated higher performance. Although the AnFFBR can be considered as a safer treatment option than the UAnFFFBR due to its lower DEP concentrations in sludge, the UAnFFFBR had lower VSS/TSS ratio and sludge yield, which could make it more practical for digestion. Finally, both the bioreactors showed considerable methane yield; however, compared to the UAnFFFBR, the AnFFBR had more potential for bioenergy production. Although both the selected bioreactors achieved nearly 90% of DEP removal, they can only be considered as pre-treatment methods according to the standard regulations and should be coupled with further technology.

Biodegradation of di-n-butyl phthalate by bacterial consortium LV-1 enriched from river sludge

A stable bacterial consortium (LV-1) capable of degrading di-n-butyl phthalate (DBP) was enriched from river sludge. Community analysis revealed that the main families of LV-1 are Brucellaceae (62.78%) and Sinobacteraceae (14.83%), and the main genera of LV-1 are Brucella spp. (62.78%) and Sinobacter spp. (14.83%). The optimal pH and temperature for LV-1 to degrade DBP were pH 6.0 and 30°C, respectively. Inoculum size influenced the degradation ratio when the incubation time was < 24 h. The initial concentration of DBP also influenced the degradation rates of DBP by LV-1, and the degradation rates ranged from 69.0–775.0 mg/l/d in the first 24 h. Degradation of DBP was best fitted by first-order kinetics when the initial concentration was < 300 mg/l. In addition, Cd²⁺, Cr⁶⁺, and Zn²⁺ inhibited DBP degradation by LV-1 at all considered concentrations, but low concentrations of Pb²⁺, Cu²⁺, and Mn²⁺ enhanced DBP degradation. The main intermediates (mono-ethyl phthalate [MEP], mono-butyl phthalate [MBP], and phthalic acid [PA]) were identified in the DBP degradation process, thus a new biochemical pathway of DBP degradation is proposed. Furthermore, LV-1 also degraded other phthalates with shorter ester chains (DMP, DEP, and PA).

Modeling the adsorption of hydrogen, sodium, chloride and phthalate on goethite using a strict charge-neutral ion-exchange theory

Simultaneous adsorption modeling of four ions was predicted with a strict net charge-neutral ion-exchange theory and its corresponding equilibrium and mass balance equations. An important key to the success of this approach was the proper collection of all the data, particularly the proton adsorption data, and the inclusion of variable concentrations of conjugate ions from the experimental pH adjustments. Using IExFit software, the ion-exchange model used here predicted the competitive retention of several ions on goethite by assuming that the co-adsorption or desorption of all ions occurred in the correct stoichiometries needed to maintain electroneutrality. This approach also revealed that the retention strength of Cl⁻ ions on goethite increases in the presence of phthalate ions. That is, an anion-anion enhancement effect was observed. The retention of Cl⁻ ions was much weaker than phthalate ions, and this also resulted in a higher sensitivity of the Cl⁻ ions toward minor variations in the surface reactivity. The proposed model uses four goethite surface sites. The drop in retention of phthalate ions at low pH was fully described here as resulting from competitive Cl⁻ reactions, which were introduced in increasing concentrations into the matrix as the conjugate base to the acid added to lower the pH.

Performance, kinetic, and biodegradation pathway evaluation of anaerobic fixed film fixed bed reactor in removing phthalic acid esters from wastewater

Emerging and hazardous environmental pollutants like phthalic acid esters (PAEs) are one of the recent concerns worldwide. PAEs are considered to have diverse endocrine disrupting effects on human health. Industrial wastewater has been reported as an important environment with high concentrations of PAEs. In the present study, four short-chain PAEs including diallyl phthalate (DAP), diethyl phthalate (DEP), dimethyl phthalate (DMP), and phthalic acid (PA) were selected as a substrate for anaerobic fixed film fixed bed reactor (AnFFFBR). The process performances of AnFFFBR, and also its kinetic behavior, were evaluated to find the best eco-friendly phthalate from the biodegradability point of view. According to the results and kinetic coefficients, removing and mineralizing of DMP occurred at a higher rate than other phthalates. In optimum conditions 92.5, 84.41, and 80.39% of DMP, COD, and TOC were removed. DAP was found as the most bio-refractory phthalate. The second-order (Grau) model was selected as the best model for describing phthalates removal.

Environmental dynamics of metal oxide nanoparticles in heterogeneous systems: A review

Metal oxide nanoparticles (MNPs) have been used for many purposes including water treatment, health, cosmetics, electronics, food packaging, and even food products. As their applications continue to expand, concerns have been mounting about the environmental fate and potential health risks of the nanoparticles in the environment. Based on the latest information, this review provides an overview of the factors that affect the fate, transformation and toxicity of MNPs. Emphasis is placed on the effects of various aquatic contaminants under various environmental conditions on the transformation of metal oxides and their transport kinetics - both in homogeneous and heterogeneous systems - and the effects of contaminants on the toxicity of MNPs. The presence of existing contaminants decreases bioavailability through hetero-aggregation, sorption, and/or complexation upon an interaction with MNPs. Contaminants also influence the fate and transport of MNPs and exhibit their synergistic toxic effects that contribute to the extent of the toxicity. This review will help regulators, engineers, and scientists in this field to understand the latest development on MNPs, their interactions with aquatic contaminants as well as the environmental dynamics of their fate and transformation. The knowledge gap and future research needs are also identified, and the challenges in assessing the environmental fate and transport of nanoparticles in heterogeneous systems are discussed.

Adsorption of Phthalates on Municipal Activated Sludge

Phthalates (PAEs) are commonly detected in discharge of municipal wastewater treatment plants. This study investigated the removal of six typical PAEs with activated sludge and the results revealed that concentrations of aqueous PAEs decreased rapidly during the beginning 15 min and reached equilibrium within 2 hours due to the adsorption of activated sludge. The process followed first-order kinetic equation, except for dioctyl phthalate (DOP). The factors influencing the adsorption were also evaluated and it was found that higher initial concentrations of PAEs enhanced the removal but affected little the adsorption equilibrium time. The adsorption of PAEs favored lower operating temperature (the optimum temperature was approximately 25°C in this research), which could be an exothermic process. Additionally, lower aqueous pH could also benefit the adsorption.

Effects of clay minerals on diethyl phthalate degradation in Fenton reactions

Phthalate esters are a group of plasticizers, which are commonly detected in China's soils and surface water. Fenton reactions are naturally occurring and widely applied in the degradation of contaminants. However, limited research was considered the effects of clay minerals on contaminants degradation with OH oxidation. In this study, batch experiments were conducted to investigate the degradation of diethyl phthalate (DEP) in Fenton reactions in the presence of clay minerals, and the effects of clay type, Fe content in clay structure. The results showed the clay adsorption inhibited total degradation of DEP, and Fe content in clay structure played an important role in DEP degradation, including in solution and adsorbed in clay minerals. Clay minerals with less Fe content (<3%) quenched OH radical, while nontronite with Fe content 19.2% improved OH radical generation and accelerated DEP degradation in solution. The degradation of clay-adsorbed DEP was much slower than DEP in solution. Six main products of DEP degradation were identified, including monoethyl phthalate, phthalate acid, hydroxyl diethyl phthalate, etc. This study implied that phthalate ester's degradation would be much slower in natural water than expected in the presence of clay minerals.

Distribution of phthalate esters in agricultural soil with plastic film mulching in Shandong Peninsula, East China

The content of phthalate esters (PAEs) was investigated in 36 vegetable fields with plastic film mulching in Shandong Peninsula, East China. Soils at depths of 0-10 cm, 10-20 cm, and 20-40 cm were collected, and 16 PAEs were analyzed by gas chromatography-mass spectrometry. PAEs were detected in all the analyzed samples. The total contents of the 16 PAEs (Σ₁₆PAEs) ranged from 1.374 to 18.810 mg/kg, with an average of 6.470 mg/kg. Among the four areas of Shandong Peninsula, including Qingdao, Weihai, Weifang, and Yantai, the highest Σ₁₆PAE in the soil was observed in Weifang district (9.786 mg/kg), which is famous for large-scale vegetable production. Despite the significant differences among the Σ₁₆PAEs, the PAE compositions in soils with plastic film mulching in Shandong Peninsula were comparable. Diethyl phthalate (DEP), diisobutyl phthalate, and di(4-methyl-2-pentyl) phthalate were present in all the samples, whereas di-n-hexyl phthalate was detected only in Qingdao (∼1%) and dicyclohexyl phthalate was observed only in Weifang (5.7-8.2%) in low proportions. The ratios of dimethyl phthalate, DEP, and di-n-butyl phthalate, which exceeded allowable concentrations, were 63.9-100% at different soil depths, indicating high PAE pollution. The concentration of butyl benzyl phthalate detected only in Weifang exceeded the recommended allowable soil concentration. Overall, the high PAE content in the soil with plastic film mulching in Shandong Peninsula is an issue of concern because of the large amounts of plastic film used.

Degradation of di(2-ethyl hexyl) phthalate by Fusarium culmorum: Kinetics, enzymatic activities and biodegradation pathway based on quantum chemical modelingpathway based on quantum chemical modeling

Di(2-ethylhexyl) phthalate (DEHP) is a plasticizer widely used in the manufacture of plastics, and it is an environmental contaminant. The specific growth rate (μ), maximum biomass (Xmax), biodegradation constant of DEHP (k), half-life (t1/2) of DEHP biodegradation and removal efficiency of DEHP, esterase and laccase specific activities, and enzymatic yield parameters were evaluated for Fusarium culmorum grown on media containing glucose and different concentrations of DEHP (0, 500 and 1000mg/L). The greatest μ and the largest Xmax occurred in media supplemented with 1000mg of DEHP/L. F. culmorum degraded 95% of the highest amount of DEHP tested (1000mg/L) within 60h of growth. The k and t1/2 were 0.024h(-1) and 28h, respectively, for both DEHP concentrations. The removal efficiency of DEHP was 99.8% and 99.9% for 1000 and 500mg/L, respectively. Much higher specific esterase activity than specific laccase activity was observed in all media tested. The compounds of biodegradation of DEHP were identified by GC-MS. A DEHP biodegradation pathway by F. culmorum was proposed on the basis of the intermolecular flow of electrons of the identified intermediate compounds using quantum chemical modeling. DEHP was fully metabolized by F. culmorum with butanediol as the final product. This fungus offers great potential in bioremediation of environments polluted with DEHP.

Study on the mechanism of action between dimethyl phthalate and herring sperm DNA at molecular level

Dimethyl phthalate (DMP), a typical phthalic acid ester, is widespread in the environment and causes extensive concern due to its adverse effects on human health. To understand the genotoxicity of DMP at molecular level, the toxic interaction of DMP with herring sperm (hs) deoxyribonucleic acid (DNA; hs-DNA) was investigated in vitro under simulated physiological conditions using multi-spectroscopic techniques and a molecular modeling method. The results of Ultraviolet-Visible absorption spectroscopy, fluorescence emission spectroscopy, and circular dichroism spectra indicated that DMP interacts with hs-DNA in a groove-binding mode that changes the double helical structure of DNA. The binding constant and the number of binding sites calculated from the fluorescence quenching data were 565.718 L mol(-1) and 0.7872, respectively. A molecular modeling study revealed that DMP tends to bind with DNA in the A-T-rich regions of minor groove and that hydrogen bonding and van der Waals forces play main roles in the interaction. This research can help to elucidate the mechanism of DMP toxicity in vivo.

Nutrients, heavy metals and phthalate acid esters in solar greenhouse soils in Round-Bohai Bay-Region, China: impacts of cultivation year and biogeography

Solar greenhouse is a common facility type used for horticultural crop production in China. However, most solar greenhouse fields have been degraded due to continuous cropping and excessive fertilizer use. Therefore, we investigated solar greenhouse soils covering a wide range of cultivation years and environmental conditions in Round-Bohai Bay-Region to test the effects of cultivation year and biogeography on nutrients, heavy metals, and phthalate acid esters (PAEs). In general, soil pH decreased while soil electrical conductivity (EC), organic matter (OM), total nitrogen (TN), NO3 (-)-N, NH4 (+)-N, mineral nitrogen (MN), Olsen-P, and NH4OAc-K contents increased as time of cultivation increased. However, this trend was influenced by sampling sites. Among sampling sites, Jiangsu showed a relatively low soil pH and high Olsen-P content, while Hebei showed a relatively high soil EC value, NO3 (-)-N, NH4 (+)-N, MN, and NH4OAc-K contents. Liaoning was characterized by relatively high soil OM and TN contents. The nutrient level indexes in evaluation of soil quality on Olsen-P and NH4OAc-K exceeded the standard seriously. The maximum values of the heavy metals Cd, Cu, and Zn were 4.87, 2.78, and 1.15 times higher than the threshold values, respectively. There was a rising trend on the heavy metal contents with the increasing cultivation years, and this trend was significantly influenced by sampling sites. Both Cu and Zn had relative high heavy metal indexes in evaluation of soil pollution. The PAEs were not detected in almost all sampling soils. Overall, the excessive fertilizer application was an important cause of nutrient accumulation and heavy metal pollution, resulting in soil degradation in solar greenhouses.

Synergistic effect using vermiculite as media with a bacterial biofilm of Arthrobacter sp. for biodegradation of di-(2-ethylhexyl) phthalate

Vermiculite is one of matrix material used for constructed wetland (CW) for the treatment of municipal wastewater. Arthrobacter sp. strain C21 (CGMCC No. 7671), isolated from a constructed wetland receiving municipal wastewater, forms biofilm on the surface of vermiculite. Di-(2-ethylhexyl) phthalate (DEHP), a typical phthalate pollutant in environment, can be degraded by the biofilm of strain C21 formed on vermiculite. Results of laboratory studies indicated that DEHP was removed from aqueous phase via biodegradation, adsorption by vermiculite, and adsorption by biofilm biomass. Synergistic effect of these three reactions enhanced the overall DEHP removal efficiency. During a batch incubation test with vermiculite and the cell suspension, bacterial adhesion to the media surface occurred within 5h and the phthalate esters (PEs) removal was due to both biodegradation and vermiculite adsorption. As the biofilm developed on surface of vermiculite (5-36 h), biodegradation became the predominance for PEs removal. As mature biofilm was formed (36-54 h), the adsorption of PEs by biofilm biomass became a main driving force for the removal of PEs from aqueous phase. The content of extracellular polymers (EPS) of the biofilm and DEHP removal performance showed a significant positive correlation (rp>0.86).

Composting of wastewater treatment sludge with different bulking agents

The main objectives of this study were to investigate the compostability of wastewater treatment sludge (WTS) containing different bulking agents (BAs) and to determine the most efficient BA. Four different compost trials consisting of mixtures of wheat straw (WS), plane leaf (PL), corncob (CC) and sunflower stalk (SS) with WTS were performed in laboratory reactors. In all experiments, a mixture of 60% WTS and 40% BA (wet basis) was used. The temperature, dry matter (DM), organic matter (OM), pH, electrical conductivity (EC) and C/N ratio were monitored during the composting process. Evaluation of the operational parameters showed that the highest organic matter degradation (i.e. 37.6%), loss of dry matter (i.e. 29.6%) and temperature (i.e. 64 °C) were achieved for the WTS-CC mixtures. Results also showed that the WTS-SS mixture was also successful in terms of these operational parameters. Use of bulking agents for the treatment of wastewater treatment sludge in composting process is an important issue with regards to process efficiency, economy and disposal of agricultural waste. Corncob and sunflower stalk that were previously not used for the composting of WTS from food industry were shown to be highly successful BA materials in this study.

IMPLICATIONS

The compostability of wastewater treatment sludge from the food industry with different bulking agents was studied. Wheat straw, plane leaf, corncob, and sunflower stalk were used as bulking agents. The required microbial stabilization and degree of mineralization were achieved with corncobs and sunflower stalks.

Phthalate esters in the environment: A critical review of their occurrence, biodegradation, and removal during wastewater treatment processes

Phthalate esters are one of the most frequently detected persistent organic pollutants in the environment. A better understanding of their occurrence and degradation in the environment and during wastewater treatment processes will facilitate the development of strategies to reduce these pollutants and to bioremediate contaminated freshwater and soil. Phthalate esters occur at measurable levels in different environments worldwide. For example, the concentrations of dimethyl phthalate (DMP) in atmospheric particulate matter, fresh water and sediments, soil, and landfills are N.D.-10.4 ng/m(3), N.D.-31.7 μg/L, N.D.-316 μg/kg dry weight, and N.D.-200 μg/kg dry weight, N.D.-43.27 μg/L, respectively. Bis(2-ethylhexyl) phthalate (DEHP) and di-n-butyl phthalate (DBP) are primary phthalate ester pollutants. Urbanization has increased the discharge of phthalate esters to atmospheric and aquatic environments, and the use of agricultural plastics has exacerbated soil contamination by phthalate esters in rural areas. Aerobic biodegradation is the primary manner of phthalate ester mineralization in the environment, and this process has been widely studied. Phthalate esters can be removed during wastewater treatment processes. The combination of different wastewater treatment technologies showed greater efficiency in the removal of phthalate esters than individual treatment steps, such as the combination of anaerobic wastewater treatment with a membrane bioreactor would increase the efficiency of phthalate ester removal from 65%-71% to 95%-97%. This review provides a useful framework to identify future research objectives to achieve the mineralization and elimination of phthalate esters in the environment.

A monograph on the remediation of hazardous phthalates

Phthalates or phthalic acid esters are a group of xenobiotic and hazardous compounds blended in plastics to enhance their plasticity and versatility. Enormous quantities of phthalates are produced globally for the production of plastic goods, whose disposal and leaching out into the surroundings cause serious concerns to the environment, biota and human health. Though in silico computational, in vitro mechanistic, pre-clinical animal and clinical human studies showed endocrine disruption, hepatotoxic, teratogenic and carcinogenic properties, usage of phthalates continues due to their cuteness, attractive chemical properties, low production cost and lack of suitable alternatives. Studies revealed that microbes isolated from phthalate-contaminated environmental niches efficiently bioremediate various phthalates. Based upon this background, this review addresses the enumeration of major phthalates used in industry, routes of environmental contamination, evidences for health hazards, routes for in situ and ex situ microbial degradation, bacterial pathways involved in the degradation, major enzymes involved in the degradation process, half-lives of phthalates in environments, etc. Briefly, this handy module would enable the readers, environmentalists and policy makers to understand the impact of phthalates on the environment and the biota, coupled with the concerted microbial efforts to alleviate the burden of ever increasing load posed by phthalates.

Occurrence, fate, behavior and ecotoxicological state of phthalates in different environmental matrices

Because of their large and widespread application, phthalates or phthalic acid esters (PAEs) are ubiquitous in all the environmental compartements. They have been widely detected throughout the worldwide environment. Indoor air where people spend 65-90% of their time is also highly contaminated by various PAEs released from plastics, consumer products as well as ambient suspended particulate matter. Because of their widespread application, PAEs are the most common chemicals that humans are in contact with daily. Based on various exposure mechanisms, including the ingestion of food, drinking water, dust/soil, air inhalation and dermal exposure the daily intake of PAEs may reach values as high as 70 μg/kg/day. PAEs are involved in endocrine disrupting effects, namely, upon reproductive physiology in different species of fish and mammals. They also present a variety of additional toxic effects for many other species including terrestrial and aquatic fauna and flora. Therefore, their presence in the environment has attracted considerable attention due to their potential impacts on ecosystem functioning and on public health. This paper is a synthesis of the extensive literature data on behavior, transport, fate and ecotoxicological state of PAEs in environmental matrices: air, water, sediment, sludge, wastewater, soil, and biota. First, the origins and physicochemical properties of PAEs that control the behavior, transport and fate in the environment are reviewed. Second, the compilation of data on transport and fate, adverse environmental and human health effects, legislation, restrictions, and ecotoxicological state of the environment based on PAEs is presented.

Adsorption of diethyl phthalate ester to clay minerals

Phthalate esters are a group of plasticizers, which have been widely detected in China's agricultural and industrial soils. In this study, batch adsorption experiments were conducted to investigate the environmental effects on the adsorption of diethyl phthalate ester (DEP) to clay minerals. The results showed that DEP adsorption isotherms were well fitted with the Freundlich model; the interlayer spacing of K(+) saturated montmorillonite (K-mont) was the most important adsorption area for DEP, and di-n-butyl ester (DnBP) was limited to intercalate into the interlayer of K-mont due to the bigger molecular size; there was no significant effect of pH and ionic strength on DEP adsorption to K-mont/Ca-mont, but to Na-mont clay. The adsorption to kaolinite was very limited. Data of X-ray diffraction and FTIR spectra further proved that DEP molecules could intercalate into K-/Ca-mont interlayer, and might interact with clay through H-bonding between carbonyl groups and clay adsorbed water. Coated humic acid on clay surface would enhance DEP adsorption at low concentration, but not at high concentration (eg. Ce>0.26 mM). The calculated adsorption enthalpy (ΔHobs) and adsorption isotherms at varied temperatures showed that DEP could be adsorbed easier as more adsorbed. This study implied that clay type, compound structure, exchangeable cation, soil organic matter and temperature played important roles in phthalate ester's transport in soil.

Leaching of the plasticizer di(2-ethylhexyl)phthalate (DEHP) from plastic containers and the question of human exposure

Di(2-ethylhexyl)phthalate (DEHP) is a widely used plasticizer to render poly(vinyl chloride) (PVC) soft and malleable. Plasticized PVC is used in hospital equipment, food wrapping, and numerous other commercial and industrial products. Unfortunately, plasticizers can migrate within the material and leach out of it over time, ending up in the environment and, frequently, the human body. DEHP has come under increased scrutiny as its breakdown products are believed to be endocrine disruptors and more toxic than DEHP itself. DEHP and its breakdown products have been identified as ubiquitous environmental contaminants, and daily human exposure is estimated to be in the microgram per kilogram level. The objective of this review is to summarize and comment on published sources of DEHP exposure and to give an overview of its environmental fate. Exposure through bottled water was examined specifically, as this concern is raised frequently, yet only little exposure to DEHP occurs through bottled water, and DEHP exposure is unlikely to stem from the packaging material itself. Packaged food was also examined and showed higher levels of DEHP contamination compared to bottled water. Exposure to DEHP also occurs in hospital environments, where DEHP leaches directly into liquids that passed through PVC/DEHP tubing and equipment. The latter exposure is at considerably higher levels compared to food and bottled water, specifically putting patients with chronic illnesses at risk. Overall, levels of DEHP in food and bottled water were below current tolerable daily intake (TDI) values. However, our understanding of the risks of DEHP exposure is still evolving. Given the prevalence of DEHP in our atmosphere and environment, and the uncertainty revolving around it, the precautionary principle would suggest its phaseout and replacement. Increased efforts to develop viable replacement compounds, which necessarily includes rigorous leaching, toxicity, and impact assessment studies, are needed before alternative plasticizers can be adopted as viable replacements.