Parameters affecting the occurrence and removal of polybrominated diphenyl ethers in twenty Canadian wastewater treatment plants

Quantifying the removal of polybrominated diphenyl ethers (PBDEs) in physical, chemical, and biological sludge treatment systems

Polybrominated diphenyl ethers (PBDE) are priority contaminants historically used as flame retardants. PBDEs are known to occur in wastewater biosolids posing potential concerns with the beneficial land application of the biosolids. This study evaluated the removal of 21 congeners in nine full-scale sludge treatment systems including pelletization (P), alkaline stabilization (AS), and aerobic (AE) and anaerobic (AN) digestion. It is the first study to conduct a mass balance analysis of a broad spectrum of PBDEs during physical, chemical, and biological sludge treatment. The PBDE congener pattern in raw sludge and biosolids samples was consistent with commercial formulations. The fully brominated congener BDE-209 dominated biosolids from all sites with an average concentration of 620 ng/g dry weight (dw), followed by BDE-99 (173 ng/g dw) and BDE-47 (162 ng/g dw). Mass balance analysis on the P and AS processes showed no change in PBDE mass flows with treatment. However, aerobic and anaerobic digestion processes reported significant levels of removal and formation of individual congeners, though the results were not consistent between facilities. One aerobic digestion process (AE2) reported an overall average removal of 48%, whereas the other (AE1) reported very high levels of accumulation of tri- and tetraBDE congeners. Similarly, there were significant variations in PBDE behavior across the five anaerobic digestion plants studied. The plant with the longest solids retention time (SRT) (AN1) reported a moderate removal (50%) of overall PBDE loading and lower congeners, whereas other plants (AN2-AN5) showed significant low (-19%) to high (-166%) levels of formation of lower congeners. The results suggest that reduced SRTs result in formation of lower congeners while extended SRTs can lead to moderate removal of some PBDEs. Conventional sludge treatment result in low to moderate PBDE removal and advanced thermal conversion technologies may be needed to improve the contaminant removal during sludge treatment.

ECHIDNA (Emerging CHemIcals Database for National Awareness): a framework to prioritise contaminants of emerging concern in water

The widespread presence of contaminants of emerging concern (CEC) in surface waters, treated wastewater and drinking water is an ongoing issue for the water industry. The absence of regulatory guidance and limited occurrence, toxicity and removal data are defining criteria of CEC and make it difficult to prioritise which CEC pose the greatest risk. The online Emerging CHemIcals Database for National Awareness (ECHIDNA) aims to classify and prioritise CEC based on their potential risk, with the information presented in an easily accessible and intuitive manner. A candidate list of almost 1,800 potential CEC, including pesticides, pharmaceuticals and industrial compounds, was compiled using both Australian and international resources. These were ranked based on in silico assessment of their persistent, bioaccumulative and toxic (PBT) properties, as well as potential chronic toxicity hazard, yielding 247 CEC for further prioritisation. Risk Quotients (RQ) identified between 5 and 87 CEC posing a risk to human and ecosystem health, respectively, across drinking water, surface water, treated wastewater and raw wastewater. While the ability of the water industry to effectively prioritise CEC is limited by candidate identification and data availability, ECHIDNA can provide valuable information for better decision-making surrounding CEC management.

Photo-induced degradation and toxicity change of decabromobiphenyl ethers (BDE-209) in water: Effects of dissolved organic matter and halide ions

BDE-209 is a widely used brominated flame retardant that is ubiquitous in the aquatic environment, especially in marine water. However, photodegradation of BDE-209 in seawater is still not fully understood. In this work, the photodegradation kinetics of BDE-209 in water was studied and the effects of seawater dissolved organic matter (S-DOM) and halide ions (Cl^-, Br^-) were evaluated. S-DOM inhibited the degradation of BDE-209 through dynamic quenching and light shielding effect. However, with the coexistence of S-DOM, Cl^- and Br^-, the photodegradation of BDE-209 was significantly promoted. The promotional effect is attributed to the generation of excited triplet state S-DOM, singlet oxygen, and reactive halogen radicals. The results of density functional theory calculation showed that •Cl addition reaction on C-Br sites of BDE-209 is the main reaction pathway of BDE-209 with chlorine radical, which leads to the generation of mixed Cl/Br substituted intermediates. The acute toxicity and estrogenic effects of BDE-209 solution were enhanced during simulated sunlight irradiation. These results indicate that the environmental factors in seawater play important roles in the photodegradation of BDE-209, and contribute to the potential ecological risks of PBDEs in the marine environment.

New iodine-based electrochemical advanced oxidation system for water disinfection: Are disinfection by-products a concern?

A novel electrochemical Advanced Oxidation System (AOS) has been recently developed for water disinfection where iodide is used to generate active iodine species in-situ. However, the presence of iodide during water disinfection can lead to the formation of iodinated disinfection byproducts (I-DBPs), which have been shown to be more cyto- and genotoxic than their chlorinated and brominated analogs. In this study, the formation of DBPs was assessed in ultrapure water, river water and secondary wastewater effluents treated by the AOS. A comprehensive total organic halogen and target DBP analysis was used that included 25 unregulated DBPs, and the total organic halogen (TOX) quantified as total organic chlorine (TOCl), total organic bromine (TOBr), and total organic iodine (TOI). Ultrapure water disinfection only quantified iodoform (TIM) at a maximum concentration of 0.90 ± 0.05 µg/L. River water results show that TOI increase from 1.3 ± 0.3 µg/L before disinfection (t = 0) to a maximum of 3.5 ± 1.1 µg/L. TIM and bromodiiodomethane (BDIM) were the only targeted iodo-trihalomethanes (I-THMs) that were quantified with a maximum total I-THM concentration of 0.44 µg/L. Secondary wastewater effluent disinfection results show that TOI increased from 1.8 ± 0.3 µg/L (t = 0) to a maximum concentration of 35.3 ± 0.3 µg/L. Iodide and iodate were the main iodinated species exiting the AOS system with a iodine recovery of 94-101%. The results from this study show that the AOS formed low levels of iodinated DBPs in treated water sources that are comparable to the levels found in disinfected drinking water and wastewater.

Occurrence, removal and mass balance of substituted diphenylamine antioxidants in wastewater treatment plants in Northeast China

Substituted diphenylamine antioxidants (SDPAs) are additives used in various commodities and are commonly found in environmental samples. However, limited information was available on their fate and removal in wastewater treatment plants (WWTPs). This paper reports the results on the occurrence and removal efficiency of ten selected SDPAs in six WWTPs equipped with different treatment processes in Northeast China. Quite similar distributions of different SDPA congeners were shown in the studied WWTPs, with ditertoctyl-diphenylamine (C8/C8-DPA), tertbutyl-tertoctyl-diphenylamine (C4/C8-DPA), and tertoctyl-diphenylamine (C8-DPA) being always dominant in the influent, effluent, and sludge (total > 80%). A cyclic activated sludge system combined with a V-shape filter achieved the highest removal efficiencies of SDPAs among various treatment processes. Styrenated-diphenylamine1 (S-DPA1) (96 ± 10%), C8-DPA (95 ± 5.5%), and distyrenated-diphenylamine1 (DS-DPA1) (94 ± 9.3%) showed high and stable removal efficiencies, whereas C4/C8-DPA (85 ± 31%) and C8/C8-DPA (84 ± 62%) showed considerably varied removal efficiencies. Per-day discharges of SDPAs to the receiving environment through effluent and sludge were estimated as 828 ± 350 and 5578 ± 5196 mg, respectively. A median of 85% of the initial mass loadings of SDPAs was found in the sludge samples, suggesting that the observed removal of SDPAs in the WWTPs was caused by their sorption to the sludge, rather than biodegradation/transformation. This work provides an overall description of the occurrence, fate, and mass balance of SDPAs in WWTPs in Northeast China and highlights a new emission route to the environment via WWTPs.

Feasibility of iron scraps for enhancing nitrification of domestic wastewater at low temperatures

The development of an effective approach to improve low-temperature nitrification of domestic wastewater remains an important issue that needs to be urgently addressed. This study was intended to verify the feasibility of using iron scraps as an effective immobilization material to enhance nitrification activity in domestic wastewater-treatment systems at low temperatures. Iron scraps were tried and compared with one common immobilization material (PVA-SA embedded balls) in terms of low-temperature nitrification performances, anti-shock capacity, dynamics of microbial community, and economic costs. The results showed that compared with control, the average nitrification efficiency of iron scraps and PVA-SA embedded balls increased separately by 15.7% and 27.6% at low temperatures. Among these groups, the iron scrap-based group demonstrated the best anti-shock capacity and the smallest fluctuation (lower than 10%) with the shortening of HRT (hydraulic retention time) or the increase of inlet ammonium level. Nitrosomonas was found to be the dominant bacterial genera for these two immobilization materials. The increased costs of iron scraps and PVA-SA embedded balls were about ¥0.03 and ¥0.78 per ton of treated domestic wastewater. Taken together, iron scraps have some significant advantages including low costs, easy availability, and good anti-shock capacity, which make them a promising candidate for enhanced nitrification of domestic wastewater at low temperatures.

Occurrence and removal of micropollutants in full-scale aerobic, anaerobic and facultative wastewater treatment plants in Brazil

This study aims to evaluate micropollutant occurrence and removal in a low-middle income country (LMIC) by investigating the occurrence of 28 chemicals from different classes (triclosan, 15 polycyclic aromatic hydrocarbons (PAHs), 4 estrogens and 8 polybrominated diphenyl ether (PBDE) congeners) in three technologically diverse full-scale Brazilian wastewater treatment plants (WWTPs). These chemicals were detected at concentrations similar to those reported in other low-middle income countries (LMICs) and high-income countries (HICs) (0.1-49 μg/L) indicating their widespread use globally and the need for more studies in LMICs that are typically characterized by relatively inadequate wastewater treatment barriers. Among the three different WWTPs investigated for removal of these chemicals, the least energy intensive system, waste stabilization ponds (WSPs), was the most effective (95-99%) compared to the activated sludge (79-94%), and Up-flow sludge blanket reactor (UASB) with trickling filters system (89-95%). These results highlight the potential of WSPs for micropollutant removal-especially in warm climates. However, the effluent from all three WWTP could pose a risk to aquatic organisms when discharged into the receiving waters as the effluent concentrations of triclosan, some estrogens, PAHs and BDE 209 were above European environmental quality standards (EQS) or predicted no effect concentration (PNEC values), indicating that receiving water bodies could benefit from further treatment. In combination, these results help to further understand prevailing concentrations of micropollutants globally and fate in current wastewater treatment systems.

Insights into the Occurrence, Fate, and Impacts of Halogenated Flame Retardants in Municipal Wastewater Treatment Plants

Halogenated flame retardants (HFRs) have been extensively used in various consumer products and many are classified as persistent organic pollutants due to their resistance to degradation, bioaccumulation potential and toxicity. HFRs have been widely detected in the municipal wastewater and wastewater treatment solids in wastewater treatment plants (WWTPs), the discharge and agricultural application of which represent a primary source of environmental HFRs contamination. This review seeks to provide a current overview on the occurrence, fate, and impacts of HFRs in WWTPs around the globe. We first summarize studies recording the occurrence of representative HFRs in wastewater and wastewater treatment solids, revealing temporal and geographical trends in HFRs distribution. Then, the efficiency and mechanism of HFRs removal by biosorption, which is known to be the primary process for HFRs removal from wastewater, during biological wastewater treatment processes, are discussed. Transformation of HFRs via abiotic and biotic processes in laboratory tests and full-scale WWTPs is reviewed with particular emphasis on the transformation pathways and functional microorganisms responsible for HFRs biotransformation. Finally, the potential impacts of HFRs on reactor performance (i.e., nitrogen removal and methanogenesis) and microbiome in bioreactors are discussed. This review aims to advance our understanding of the fate and impacts of HFRs in WWTPs and shed light on important questions warranting further investigation.

Diphenylamine Antioxidants in wastewater influent, effluent, biosolids and landfill leachate: Contribution to environmental releases

Diphenylamine antioxidants (DPAs) are widely used industrial chemicals. Wastewater effluents and biosolids are important pathways for DPAs to enter the environment. Information on the fate of DPAs in wastewater treatment plants (WWTPs) and their environmental releases is limited. In this study, we characterized the occurrence, removal efficiencies, distribution, mass balance, and environmental releases of 17 DPAs in ten Canadian WWTPs and four landfill sites from 2013 to 2015. These WWTPs are different in sizes, and treatment technologies. Median concentrations of ΣDPAs were 78 ng/L in influent, 6.9 ng/L in effluent, 326 ng/L in leachate, and 445 ng/g in biosolids (dry weight), respectively. Diphenylamine (DPA) and ditertoctyl-diphenylamine (DTO-DPA) were the predominant congeners of DPAs in all the matrices. Residues of DPAs were not completely removed during wastewater treatment processes: most DPAs were detected in at least one sample of WWTP effluent with the highest concentration of 117 ng/L (DPA). Overall, high removal efficiencies (median > 90%) of most of the DPAs were observed in the secondary and advanced treatment, as well as in the facultative and aerated lagoons. In contrast, primary treatment exhibited a lower removal efficiency of the DPAs. Mass balance analysis shows that sorption to biosolids is the major removal pathway of DPAs in WWTPs. The results also highlight that environmental releases of DPAs via biosolid applications (70 mg/d/1000 people) can be over several times higher than that via wastewater effluent (2.5-36 mg/d/1000 people).

Sediment Bacterial Community Structure Under the Influence of Different Domestic Sewage Types

Sediment bacterial communities are critical to the biogeochemical cycle in river ecosystems, but our understanding of the relationship between sediment bacterial communities and their specific input streams in rivers remains insufficient. In this study, we analyzed the sediment bacterial community structure in a local river receiving discharge of urban domestic sewage by applying Illumina MiSeq high-throughput sequencing. The results showed that the bacterial communities of sediments samples of different pollution types had similar dominant phyla, mainly Proteobacteria, Actinobacteria, Chloroflexi and Firmicutes, but their relative abundances were different. Moreover, there were great differences at the genus level. For example, the genus Bacillus showed statistically significant differences in the hotel site. The clustering of bacterial communities at various sites and the dominant families (i.e., Nocardioidaceae, and Sphingomonadaceae) observed in the residential quarter differed from other sites. This result suggested that environmentally induced species sorting greatly influenced the sediment bacterial community composition. The bacterial cooccurrence patterns showed that the river bacteria had a nonrandom modular structure. Microbial taxonomy from the same module had strong ecological links (such as the nitrogenium cycle and degradation of organic pollutants). Additionally, PICRUSt metabolic inference analysis showed the most important function of river bacterial communities under the influence of different types of domestic sewage was metabolism (e.g., genes related to xenobiotic degradation predominated in residential quarter samples). In general, our results emphasize that the adaptive changes and interactions in the bacterial community structure of river sediment represent responses to different exogenous pollution sources.

Wastewater Treatment Lagoons: Local Pathways of Perfluoroalkyl Acids and Brominated Flame Retardants to the Arctic Environment

Concentrations of perfluoroalkyl acids (PFAAs), polybrominated diphenyl ethers (PBDEs), and "novel" brominated flame retardants (NBFRs) were determined in lagoons processing wastewater from two high-Arctic and two sub-Arctic of Canada communities to assess the importance of local anthropogenic sources. ∑PFAAs in influent and effluent of the Arctic lagoons were within the lower end of the range of concentrations previously observed in Canadian temperate wastewater treatment plants (WWTPs). In comparison, influent and effluent concentrations of ∑PBDEs and NBFRs were significantly greater (p < 0.05) in high-Arctic lagoons compared to sub-Arctic and temperate plants. The surprisingly elevated concentrations of PBDEs and NBFRs in high-Arctic lagoons were probably related to high organic matter found in Arctic wastewater due to lower consumption of potable water leading to less dilution compared to temperate regions. Although PFAAs also sorb to solids, the wastewater samples were filtered prior to analysis of PFAAs (but not PBDEs and NBFRs), which likely reduced the impacts of solids on the results for PFAAs. Based on an extrapolation of per capita mass effluent loadings of the four Arctic lagoons, mass loadings to the Arctic of Canada via WWTP effluent were estimated as 1405 g/year and 549 g/year for ∑PFAAs and ∑PBDEs, respectively.

Diethylhexyl phthalate removal in full scale activated sludge plants: Effect of operational parameters

Removal of emerging contaminants (ECs) is a serious concern in wastewater industry especially for public acceptance of reclaimed water. Diethylhexyl phthalate (DEHP) is one of the ubiquitous and detectable plasticizers in municipal wastewater across the globe. Water Framework Directive (2000/60/EC) has prioritized it for the establishment of discharge regulations. A cost-effective strategy, especially for developing nations, may be the re-engineering of the existing biological process for the simultaneous removal of ECs and conventional pollutants. Wastewater treatment plants are one of the main sources for DEHP occurrence in surface water. In this study, possible role of activated sludge process operational parameters in effective removal of DEHP was assessed. Principal component analysis of occurrence data showed dissimilarity with the organic and nutrient characteristics of sewage. DEHP concentration in more than half (55%) of treated wastewater samples was more than environmental quality standard value for inland and surface water bodies (1.3 μg/L). At a mixed liquor suspended solid (MLSS) concentration range of 3461-4972 mg/L, overall removal was 23.9 μg/gMLSS.d (92 ± 6%) with biodegraded portion as 22.4 μg/gMLSS.d (85 ± 4%) and sorbed portion of 1.5 μg/gMLSS.d (7 ± 4%). DEHP removal showed an increasing trend at higher oxygen uptake rates (OUR) of sludge with DEHP removal of 8.1  μg DEHP/gMLSS.d (70 ± 6%), in the OUR range of 20-28mgO₂/L/h. Increase in overall removal of DEHP showed a positive correlation (r² = 0.7) with increasing sludge retention time (SRT) and so does the decreasing food to microorganism (F/M) ratio with increasing removal of DEHP (r² = 0.8). A temperature decrease of 13 °C caused a decrease of 30% in overall removal of DEHP.

Occurrence and removal of triclosan in Canadian wastewater systems

Triclosan (TCS) is an antimicrobial agent used in many personal care and cleaning products. It has been detected in most environmental compartments and the main entry pathway is wastewater effluents and biosolids. TCS was analyzed in 300 samples of raw influent, final effluent, and biosolids from 13 wastewater treatment plants (WWTPs) across Canada representing five types of typical wastewater treatment systems. TCS was almost always detected in influent (median 1480 ng/L), effluent (median 107 ng/L), and biosolids (median 8000 ng/g dry weight) samples. Removals of TCS from lagoons as well as secondary and advanced treatment facilities were significantly higher than primary treatment facilities (p < 0.001). TCS removal was strongly correlated with organic nitrogen removal. TCS removals at most lagoons and plants that use biological treatment were higher during summer compared with winter. However, no seasonal or temperature effects were observed at the two primary facilities, likely due to the absence of biological activity. Aerobically digested solids contained the lowest levels (median 555 ng/g) while anaerobically digested primary solids contained the highest levels of TCS (median 22,700 ng/g). The results of this large comprehensive study demonstrate that TCS is consistently present in wastewater and biosolids at relatively high concentrations and that removal from wastewater and levels in biosolids are strongly influenced by the wastewater and solids treatment types.

Associations between organohalogen exposure and thyroid- and steroid-related gene responses in St. Lawrence Estuary belugas and minke whales

Elevated concentrations of persistent organic pollutants (POPs) and emerging halogenated flame retardants (HFRs) have been reported in tissues of the endangered St. Lawrence Estuary (Canada) beluga population as well as in minke whales visiting that same feeding area. This study examined the linkages between blubber concentrations of POPs and emerging HFRs, and transcription in skin of genes involved in the regulation of thyroid and steroid axes in belugas and minke whales from the St. Lawrence Estuary. In belugas, concentrations of PCBs, OCs and hexabromobenzene (HBB) were positively correlated with the transcription of thyroid- and/or steroid-related genes, while Dec-604 CB concentrations were negatively associated with the transcription of glucocorticoid and thyroid genes. In minke whales, PBDE concentrations changed positively with Esrβ transcript levels and HBB concentrations negatively with Nr3c1 transcripts. Present results suggest that several biological functions including reproduction and energetic metabolism may represent potential targets for organohalogens in these whales.

Distribution and fate of synthetic phenolic antioxidants in various wastewater treatment processes in Canada

Synthetic phenolic antioxidants (SPAs) are of emerging concern due to their potential environmental risks. However, the environmental occurrence and fate of SPAs are poorly understood. In this study, 13 SPAs were analyzed in 70 liquid and 21 solid samples from 12 wastewater treatment plants (WWTPs) in 2016 to investigate the distribution and composition of SPAs in different wastewater treatment processes in Canada. Wastewater samples were liquid-liquid extracted and biosolids were treated using ultrasonic assisted solvent extraction. SPAs were analyzed by ultra-performance liquid chromatography-tandem mass spectrometry. The concentrations of total SPAs were in the ranges of 71-3193 ng L^-1 in influent, less than method quantification limits (MQLs)-520 ng L^-1 in effluent, and 479-4794 ng g^-1 in biosolids (dry weight (dw)). SPAs were effectively removed (median >75%) from the liquid stream in most WWTPs. In one aerated lagoon and two primary treatment sites, low removal efficiency (median -26%-43%) was observed for 4-tert-octylphenol (4-tOP). These results indicate that wastewater effluent is a vector for SPAs, including the endocrine disruptor 4-tOP, to aquatic environments. The mass balance approximation found major removal mechanisms are sludge sorption/separation and degradation. A preliminary risk assessment suggested that most SPAs in WWTP effluent were unlikely to pose ecotoxicological risks to aquatic organisms in the receiving waters. Future research should evaluate the environmental risks of SPAs associated with land application of biosolids and investigate the occurrence and fate of the degradation products of these contaminants.

Characterization of polybrominated diphenyl ethers (PBDEs) in various aqueous samples in Taiwan

In this study, 20 groundwater samples and 7 surface water samples were collected and analyzed by HRGC-HRMS to evaluate the levels, congener distributions, and dissolved/solid partitioning of polybrominated diphenyl ethers (PBDEs) in water matrix as well as the removal efficiency of a typical water treatment plant (WTP). The results indicated that the level of PBDEs concentrations ranging from 18.51 to 4212 pg/L and 30.24 to 1021 pg/L were found in groundwater and surface water, respectively. BDE-209 predominated and contributed over 90% of total PBDEs concentrations for all samples analyzed. In addition, the dissolved/solid distribution indicated that 60-80% of PBDEs were measured in solid phase. 97% of total PBDEs was removed in a WTP. Positive matrix factorization (PMF) analysis was conducted for groundwater samples and the results indicated that 3% and 41% of PBDEs were attributed to octa and deca-BDEs commercial mixtures, respectively, while 56% resulted from anaerobic microorganism debromination process. Understanding the PBDEs occurrences, distribution and debromination process as well as their removal efficiency of water treatment plant could provide valuable information on the fate of those compounds in environment.

Variability of release rate of flame retardants in wastewater treatment plants

Information on variability is important in the assessment of the releases and potential risks of brominated flame retardants (BRFs) in the environment, but related data are limited. In this study, two release-characterizing parameters, release fraction to final effluent and influent-biosolids transfer coefficient, were used to quantify releases of five BFRs from eight secondary wastewater treatment plants (WWTPs). The five BFRs are recalcitrant, hydrophobic, and low in volatility. The two parameters for these BFRs were found to vary from day to day and season to season within individual WWTPs as well as from one WWTP to another. These temporal and spatial variations were, however, comparable to each other and both within a factor of 3 above or below the parameter averages. Averages for release fraction were in the range of 0.02-0.29 and those for influent-biosolids transfer coefficient in the range of 3-26 L/g, depending upon a given BFR at a given WWTP. These ranges and the observed factor-3 variability are not only useful for estimating releases of the five BFRs, but more importantly provide read-across data for the assessment of substances with similar physical-chemical properties.

Is it photosensitization or photodegradation when UV-B irradiation is combined with BDE-47? Evidence from the growth and reproduction changes of rotifer Brachionus plicatilis

Ecotoxicological methods were applied in the present study, and the marine rotifer Brachionus plicatilis was used as the toxic endpoint to depict what occurred when 2,2',4,4'-tetrabromodiphenyl ether (BDE-47) was combined with solar ultraviolet-B radiation (UV-B). B. plicatilis was exposed to three different combination methods of BDE-47 and UV-B at an equal toxicity ratio, including normal rotifer co-cultured with UV-B-irradiated BDE-47 (known as Method I), UV-B-irradiated rotifer co-cultured with BDE-47 exposure (known as Method II) and normal rotifer co-cultured with the simultaneous addition of BDE-47 and UV-B irradiation (known as Method III). Acute and chronic experiments were preformed to determine the toxicity differentiation according to the growth and reproduction changes in the rotifer. Twenty-four-hour acute experiments showed that the modes of three combined methods changed from antagonism to additive, to synergistic with the concentration/dose increment, and the contribution rates of Method I and Method II to Method III were calculated by approximately 40.4% and 59.6%, respectively. Chronic exposure to either the single stressor or the combination of stressors inhibited the growth and reproduction of the rotifer, demonstrating the inhibition of the population growth rate and the decrease in the larvae production. Three combined groups presented more serious damages compared to groups with single stress exposure, and the ascending sequence of toxicity was Method I<Method II<Method III. A higher bioaccumulation of BDE-47 was found in all combined groups than BDE-47 single stress group, and bioconcentration factor (BCF) general ranked Method II<Method I<Method III. Moreover, BDE-28, photodegradation production of BDE-47, were found in groups preformed Method I and III. We thus speculated that the toxicity enhancement when BDE-47 was combined with UV-B was mainly due to photosensitization and photodegradation, and the photosensitization might be more noxious to the growth and reproduction of the rotifer.

Deca-BDE and alternative halogenated flame retardants in a wastewater treatment plant in Harbin (2009-2016): Occurrence, temporal trends, seasonal variation, and fate

This study is the first attempt to comprehensively investigate deca-BDE and alternative flame retardants in a wastewater treatment plant in such a long term in China (2009-2016). Influent, effluent and sludge samples were collected. The mean concentration of deca-BDE, Σ₁₉NBFRs and ΣDPs in influent were 311.5, 76.0 and 1.4ng/L, respectively, which were at the low end of the global range. The levels of deca-BDE, Σ₁₉NBFRs and ΣDPs in effluent were range from 9.5-68.6, 4.1-38.5 and BLD-1.6ng/L, respectively. In sludge samples, the mean concentrations were 406.7, 510.5 and 6.9ng/g dw for deca-BDE, Σ₁₉NBFRs and ΣDPs. The concentration of temporal trends in this study may reflected the release of those compounds. Compared to the beginning year of this study, the usage of deca-BDE was decreased but the usage of total NBFRs and DPs presented sustained increase over the sampling period. There were no significant variation of deca-BDE, NBFRs and DPs in the wastewater treatment plant in Harbin was observed in the four seasons except for NBFRs in influents, which the Σ₁₉NBFRs mean concentration in influents in the summer was statistically significantly higher than that in winter indicating that NBFRs was easier impacted by temperature compared to deca-BDE and DPs. In addition, sorption and accumulation to sludge was the major removal mechanism for those compounds, accounting for 73.3% to 89.0%.

Vertical and horizontal assemblage patterns of bacterial communities in a eutrophic river receiving domestic wastewater in southeast China

Bacterial communities in rivers receiving untreated domestic wastewater may show specific spatial assemblage patterns due to a wide range of physicochemical conditions created by periodic algal bloom. However, there are significant gaps in understanding environmental forces that drive changes in microbial assemblages in polluted rivers. In this study, we applied high-throughput sequencing of 16S rRNA gene amplicons to perform comprehensive spatio-temporal profiling of bacterial community structure in a local river segment receiving domestic wastewater discharge in southeast China. Multivariate statistics were then used to analyse links between bacterial community structure and environmental factors. Non-metric multidimensional scaling (NMDS) plots showed that the bacterial community structure was different between upstream and downstream sections of the river. While the upstream water contained a high proportion of bacteria degrading xenobiotic aromatic compounds, the downstream water experiencing stronger algal bloom had a more diverse bacterial community which included the genus Aeromonas comprising 14 species, most of which are human pathogens. Least discriminant analysis (LDA) effect size revealed that the surface water was mainly inhabited by aerobic microorganisms capable of degrading aromatic compounds, and also contained bacterial genera including pathogenic species. In contrast, in the bottom water we found, along with aromatic compound-degrading species, anaerobic denitrifiers and Fe³⁺-reducing and fermentative bacteria. Variance partitioning canonical correspondence analysis (VPA) showed that nutrient ratios had a stronger contribution to bacterial dissimilarities than other major physicochemical factors (temperature, pH, dissolved oxygen, total organic carbon, and chlorophyll a). These results show that microbial communities in rivers continuously receiving domestic wastewater have specific longitudinal and vertical assemblage patterns and may contain pathogenic species presenting a high threat to public health. These factors should be taken into consideration while developing pollution management strategies.

Occurrence and fate of substituted diphenylamine antioxidants and benzotriazole UV stabilizers in various Canadian wastewater treatment processes

Substituted diphenylamine antioxidants (SDPAs) and benzotriazole UV stabilizers (BZT-UVs) are additives used in industrial and consumer products to prevent degradation or color change of materials, but their environmental fate and disposition are not well characterized. In this study, SDPAs and BZT-UVs were analyzed in 68 liquid and 39 solid samples collected from 9 wastewater treatment plants (WWTPs) in Canada to investigate the occurrence and fate of these contaminants. The median concentrations of ΣSDPAs and ΣBZT-UVs was 483 and 76.2 ng L^-1 in influent, 28.4 and 4.84 ng L^-1 in effluent, and 2750 and 457 ng g^-1 in biosolids (dry weight), respectively. Dinonyl-diphenylamine (C9C9) was the predominant congener of SDPAs in all matrices (>40%). For target BZT-UVs, the major components were 2-(2H-benzotriazol-2-yl)-4,6-bis(1-methyl-1-phenylethyl)phenol (UV234) and 2-(2H-benzotriazol-2-yl)-4,6-di-tert-pentylphenol (UV328). SDPAs and BZT-UVs were effectively removed (>90%) from the liquid stream in most WWTPs mainly through sludge sorption and separation, but biotransformation, UV treatment and filtration may also contribute to removal of some contaminants in advanced treatment plants. In contrast, the removal efficiency of target contaminants using chemically assisted primary treatment was low, likely due to the short hydraulic retention time of this site. Our results suggest that wastewater effluent is a vector of SDPAs and BZT-UVs to the aquatic environment. The results also highlight the high concentrations of SDPAs and BZT-UVs associated with the solid stream in WWTPs, which could affect the beneficial use of biosolids (e.g., compost or land applications).

Photodebromination behaviors of polybrominated diphenyl ethers in methanol/water systems: Mechanisms and predicting descriptors

This study investigated the photodebromination behaviors of polybrominated diphenyl ethers (PBDEs) in methanol or methanol/water systems. The kinetics of three sets of bromated diphenyl ether (BDE) isomers were compared in the same reactors, and the results showed that the PBDE isomers with lower energy of lowest unoccupied molecular orbital and higher energy of highest occupied molecular orbital will be degraded faster by ultraviolet (UV) light than other BDE isomers. The overall debromination pathways of 2,2',4,4'-tetrabromodiphenyl ether (BDE-47) were elucidated, and we found that the bromine substituents with higher Mulliken charges were preferentially removed. This demonstrated that Mulliken charges can be used to predict the photodebromination pathways of PBDEs. In methanol/water systems, when the ratio of methanol and water decreased, the degradation rate of BDE-47 decreased, whereas that of diphenyl ether increased. This phenomenon can be attributed to the mechanism of photodegradation of PBDEs gradually shifting from the reductive debromination to the undebromination process as the ratio of methanol and water decreases. The chromatogram of high-performance liquid chromatography and gas chromatography-mass spectrometry during this process also verified this explanation. The debromination pathways of BDE-47 are consistent in methanol/water systems with different methanol to water ratios and in different organic solvents.

Environmental exposure to a major urban wastewater effluent: Effects on the energy metabolism of northern pike

Municipal wastewater effluents (MWWEs) consist of dynamic and complex mixtures of chemical and biological compounds that can alter the health of exposed aquatic organisms. Disturbance of energy metabolism has been reported in fish exposed to MWWEs. However, there is a scarcity of knowledge on the physiological events leading to perturbation of energy balance and thyroid regulation, and associated lipid metabolism. The objective of the present study was to use a set of biomarkers, from gene transcription to body condition, to investigate the effects of a chronic environmental exposure to a major primary MWWE on fatty acid metabolism and thyroid hormone levels in northern pike (Esox lucius) collected from the St. Lawrence River near Montreal (QC, Canada). The exposure of pike to MWWE was examined through determination of a suite of persistent and bioaccumulative halogenated flame retardants in liver as this effluent is a known regional source for these chemicals. Greater hepatic concentrations of polybrominated diphenyl ethers (PBDEs, range: 29.6-465ng/g w.w. and 88.8-823ng/g w.w. in females and males, respectively) and other halogenated flame retardants (e.g., dechlorane-related compounds) were determined in fish collected downstream of the MWWE's point of discharge relative to the upstream site. This exposure in male pike was associated with decreased acyl-coA oxidase (acox1) and fatty acid synthase (fasn) mRNA levels as well as a decreased acyl-coA oxidase (ACOX) activity in liver. In female pike, MWWE exposure was associated with lower circulating free and total triiodothyronine (T₃) levels and a tendency for greater total lipid percentages in liver. Present findings provide evidence that chronic exposure of a top predator fish to MWWE can be related to gender-specific effects on fatty acid metabolism and thyroid hormone homeostasis, and highlight the need for further investigation.

Volatile Methylsiloxanes and Organophosphate Esters in the Eggs of European Starlings (Sturnus vulgaris) and Congeneric Gull Species from Locations across Canada

Volatile methylsiloxanes (VMSs) and organophosphate esters (OPEs) are two suites of chemicals that are of environmental concern as organic contaminants, but little is known about the exposure of wildlife to these contaminants, particularly in birds, in terrestrial and aquatic ecosystems. The present study investigates the spatial distributions of nine cyclic and linear VMSs and 17 OPEs in the eggs of European starlings (Sturnus vulgaris) and three congeneric gull species (i.e., herring gull (Larus argentatus), glaucous-winged gull (L. glaucescens), and California gull (L. californicus)) from nesting sites across Canada. ∑VMS concentrations for all bird eggs were dominated by decamethylcyclopentasiloxane (D5), dodecamethylcyclohexasiloxane (D6), and octamethylcyclotetrasiloxane (D4). With European starlings, birds breeding adjacent to landfill sites had eggs containing significantly greater ∑VMS concentrations (median: 178 ng g^-1 wet weight (ww)) compared with those from the urban industrial (20 ng g^-1 ww) and rural sites (1.3 ng g^-1 ww), indicating that the landfills are important sources of VMSs to Canadian terrestrial environments. In gull eggs, the median ∑VMS concentrations were up to 254 ng g^-1 ww and suggested greater detection frequencies and levels of VMSs in aquatic- versus terrestrial-feeding birds in Canada. In contrast, the detection frequency of OPEs in all European starling and gull eggs was lower than 16%. This suggested that low dietary exposure or rapid metabolism of accumulated OPEs occurs in aquatic feeding birds and may warrant further investigation for the elucidation of the reasons for these differences.

Pollution Status and Human Exposure of Decabromodiphenyl Ether (BDE-209) in China

Decabromodiphenyl ether (BDE-209/decaBDE) is a high-production-volume brominated flame retardant in China, where the decaBDE commercial mixture is manufactured in Laizhou Bay, Shandong Province, even after the prohibition of penta- and octaBDE mixtures. The demand for flame retardants produced in China has been increasing in recent years as China not only produces electronic devices but also has numerous electronic waste (e-waste) recycling regions, which receive e-wastes from both domestic and foreign sources. High concentrations of BDE-209 have been observed in biotic and abiotic media in each of the different areas, especially within the decaBDE manufacturers and e-waste recycling areas. BDE-209 has been viewed as toxic and bioaccumulative because it might debrominate to less brominated polybrominated diphenyl ethers (PBDEs) (lower molecular weight and hydrophobicity), which are more readily absorbed by organisms. The highest concentration of PBDEs in dust within urban areas reached 40 236 ng g^-1 in the Pearl River Delta, and BDE-209 contributed the greatest proportion to the total PBDEs (95.1%). Moreover, the maximum hazard quotient was found for toddlers (0.703) for BDE-209, which was close to 1. This suggests that exposure to BDE-209 might lead to increased potential for adverse effects and organ harm (e.g., the lungs) through inhalation, dust ingestion, and dermal absorption, especially for the group of toddlers compared to others. In daily food and human tissues, the amount of BDE-209 was also extensively detected. However, the toxicity and adverse effect of BDE-209 to humans are still not clear; thus, further studies are required to better assess the toxicological effects and exposure scenarios, a more enhanced environmental policy for ecological risks regarding BDE-209 and its debrominated byproducts in China.

Effect of anthraquinone-2,6-disulfonate on the photolysis of 2,4,4'-tribromophenylphenyl ether

In this study, we have investigated the photolysis of 2,4,4'-tribromophenylphenyl ether (BDE-28) in Triton X-100 (TX-100) solutions, and discussed the effect of anthraquinone-2,6-disulfonate (AQDS) on the photolysis of BDE-28. The effect of TX-100 on the photolysis of BDE-28 was mainly related to the concentration of TX-100. The fastest photolysis of BDE-28 was at 500 mg L^-1 of the TX-100 solution, and the corresponding photolysis rate constant was 0.12 min^-1. The direct photolysis rate of BDE-28 decreased from 0.17 min^-1 to 0.08 min^-1 and 0.12 min^-1 when NaN₃ and isopropanol were added, respectively. The effect of AQDS on the photolysis of BDE-28 was also mainly related to the concentration of AQDS. When the concentration of AQDS was 0.6 μM, it has a slight influence in promoting the photodegradation of BDE-28; as the AQDS concentrations increased, the suppressing effect was more obvious. AQDS can inhibit the photolysis of BDE-28. Photolysis kinetics and quenching reactions illustrated that BDE-28 can produce a photosensitization reaction in TX-100 solutions, and the effects of AQDS on the photolysis of BDE-28 were mainly dominated by inhibition. In addition to its light shielding effect, AQDS can also combine with BDE-28 and anti-oxidation to inhibit the photolysis of BDE-28. We found that the degradation pathway of BDE-28 was mainly based on de-bromination, and the ions at para positions were preferentially debrominated.

Tolerance of cyanobacteria to the toxicity of BDE-47 and their removal ability

Polybrominated diphenyl ethers are ubiquitous and toxic contaminants in aquatic environments. The effect of polybrominated diphenyl ether BDE-47 on five species of cyanobacteria, along with their removal ability was investigated. Four species, namely Synechocystis sp., Oscillatoria planctonica, Microcystis flos-aquae and Nostoc sp., were exposed to BDE-47 at concentrations ranging from 0.05 to 1.0 mg L^-1 for 14 days, while the exposure time for Pseudanabaena sp. was 30 days. The first four species were very tolerant to BDE-47 while growth and photosynthesis of Pseudanabaena were significantly inhibited by BDE-47 at concentrations over 0.1 mg L^-1. However, this species could recover from the toxicity of high concentrations of BDE-47 after 30 days of exposure, indicating the development of some "resistance" after pre-exposure to 1.0 mg L^-1 BDE-47. The "resistant" cells had a higher growth rate, photosynthesis and glutathione S-transferase activity than normal Pseudanabaena cells. The sensitivity of Pseudanabaena to BDE-47 toxicity was affected by its initial filament density, with cultures having a low filament density (2.3 × 10⁶ filaments mL^-1) being up to 14-15 times more sensitive than cultures with a high filament density (13 × 10⁶ filaments mL^-1). All cyanobacteria could remove 70-82% of BDE-47 in their media, with more than 60% of BDE-47 accumulated in cells. This is the first study showing the high tolerance of different cyanobacteria species to BDE-47 toxicity and their removal ability. The study also revealed that the sensitive Pseudanabaena could acquire a "resistance" to BDE-47, which was transferred to the next generation.

Comparative assessment of phthalate removal and risk in biological wastewater treatment systems of developing countries and small communities

Phthalates are widely used in plastic and personnel care products. Being non-steroid endocrine disrupting compounds, their exposure have toxic effects on aquatic life and human health. The aim of this study was a comparative assessment of their fate and risk in full scale wastewater treatment along with influence of seasonal variations. Four priority phthalates, Diethylphthalate (DEP), Dibutylphthalate (DBP), Benzylbutyl phthalate (BBP) and Diethylhexyl phthalate (DEHP) were chosen for this study and wastewater treatment plants investigated were designed as nutrient removal based sequencing batch reactor (SBR), conventional activated sludge process (ASP) and up flow anaerobic sludge blanket (UASB) with polishing pond. Results showed that the main removal mechanism of phthalates was biotransformation with removal contribution of 74% in SBR, 65% in conventional ASP and 37% in UASB. Overall removal of phthalates was maximum in the treatment combination of UASB and pond (83%) followed by SBR (80%) and conventional ASP (74%). Seasonal influences on occurrence, removal and risk of these phthalates were also studied. The concentration of DEP, DBP and DEHP in untreated wastewater increased by 2, 7 and 2μg/L, respectively in summer. However in sludge, only large molecular weight phthalates BBP and DEHP increased in winter by 3mg/kg and 12mg/kg, respectively. Seasonal variations in removal of phthalates were discrepant in each process with better removal during summer. Risk assessment of phthalates to aquatic life showed that there is no potential risk of DEP, DBP and BBP from effluents of treatment plants however risk quotient of DEHP was in the range of 27-73 in both seasons which indicate probable risk to aquatic organisms. Phthalate risk to human beings estimated by daily intake of phthalates was in the range of 0.3±0.1 to 20±0.7ng/kg/d and far below their respective reference dosages, demonstrating the potential of these treatment plants to reduce the risk of phthalates.

Occurrence and fate of PBDEs and novel brominated flame retardants in a wastewater treatment plant in Harbin, China

Wastewater treatment plant (WWTP) is considered to be an important medium for the transport and transformation of organic pollutants. This study attempted to comprehensively investigate polybrominated diphenyl ethers (PBDEs) and novel brominated flame retardants (NBFRs) in a WWTP in Harbin, one of the main "Old Industrial Base" in China. The mean concentrations of the total PBDEs in the influent, effluent, and sludge were 152 ng/L, 16.2 ng/L, and 503 g/g dw, respectively, which were at the low end of the global range. BDE-209 was the most abundant congener, with contributions to the total PBDE ranging from 90.5 to 98.5 %. The level of the total NBFRs ranged from 24.5 to 107 ng/L, 0.95 to 20.3 ng/L, and 305 to 1202 ng/g dw in the influent, effluent, and sludge, respectively. For NBFRs, DBDPE was the most abundant congener (38.8-50.5 %), followed by BEHTBP (11.0-35.0 %). The ratio for DBDPE/BDE-209 (0.62 ± 0.42) was found less than 1 in sludge, which indicated that Deca-BDE is still the major BFR product in this city. Source identification suggested that indoor dust should be an important source of BFRs in the WWTP. Approximately 20.8 and 7.79 kg of PBDEs and NBFRs on annual basis were removed with the sludge. Biodegradation could play an important role on the fate of BFRs in the WWTP, which is required for future research.

Adsorption-uptake-metabolism kinetic model on the removal of BDE-47 by a Chlorella isolate

Polybrominated diphenyl ethers (PBDEs) are persistent and toxic organic pollutants, causing hazardous to ecosystems and human health but are difficult to remove from contaminated environments. The mechanism and kinetics of a Chlorella isolate to remove BDE-47 were investigated. This species isolated from the influent of wastewater treatment plants in Hong Kong was PBDE tolerant. More than 80% of BDE-47 was removed in short- and long-term experiments lasting 1 h and 7 days, respectively. The dominant removal process was adsorption on cell surfaces, with 73% of the spiked BDE-47 removed within five minutes of exposure. As the exposure prolonged, the adsorption became saturated. BDE-47 on cell surfaces was then gradually taken up into cells. At the end of the 7-day exposure, 17% of the spiked BDE-47 was within cells, while 27% was metabolized. Four metabolites, including BDE-28, 6-OH- and 5-OH-BDE-47, and 6-MeO-BDE-47, were produced from the debromination, hydroxylation and methoxylation of BDE-47. The removal kinetics of BDE-47 by freshwater microalgae could be explained by the multi-compartmental adsorption-uptake-metabolism model developed in this study.

Environmental pollution of polybrominated diphenyl ethers from industrial plants in China: a preliminary investigation

Although numerous studies have shown the presence of polybrominated diphenyl ethers (PBDEs) in various environmental media, attention to their distribution in the environmental media surrounding industrial facilities is limited. In this study, eight PBDEs congeners (BDE-28, -47, -99, -100, -153, -154, -183, -209) were investigated in surface soils and water samples collected from commercial PBDE manufacturers, flame-retardant plastic modification plants and waste electrical and electronic equipment recycling facilities in China. Analysis of target compounds was performed using the model NCI GC-MS in SIM mode. The concentrations of ∑8PBDEs varied from 193.1 to 22,004.3 ng/L in water samples and from 1209.3 to 226,906 ng/g dry wt in surface soils, respectively. More severe PBDE contamination, when compared with previously reported data, was found in industrial areas in this study. This indicates that these industrial areas are highly polluted with PBDEs. BDE-209 was the predominant congener, accounting for more than 94% in this study, except for a 68.75% portion at one site. Our results show that PBDE manufacturing and flame-retardant plastic modification plants, easily overlooked by the public, are two primary PBDE pollution sources although they affect surrounding areas. Further research is needed, aimed at managing industrial PBDE emissions and eliminating environmental PBDE pollution, to investigate the material flows and environmental fates of PBDEs in all stages of the life cycle.

Chemical and photochemical degradation of polybrominated diphenyl ethers in liquid systems - A review

Polybrominated diphenyl ethers (PBDEs) are brominated flame retardants which have received a great deal of attention due to their persistence, potential to bioaccumulate and possible toxic effects. PBDEs have been globally detected in humans, wildlife and environment, highlighting the urgency of looking for effective removal technologies to mitigate their spread and accumulation in the environment. Among all environmental compartments, the water has raised particular attention. This paper aims to provide information about the suitability of the main degradation processes investigated to date (photolysis, zerovalent iron and TiO2 photocatalysis) for the degradation of PBDEs in water matrices. The most relevant criteria behind the design of a system for such purpose are discussed in detail for each individual process. The comparative analysis suggests that the oxidative degradation by TiO2 is the most appropriated technology to treat waters contaminated with PBDEs because higher debromination and mineralization degrees are achieved, preventing the formation/accumulation of lower brominated PBDE congeners and promoting the cracking of aromatic cores.

Tracking the sources of polybrominated diphenyl ethers in birds: foraging in waste management facilities results in higher DecaBDE exposure in males

Differences in feeding ecology are now recognized as major determinants of inter-individual variations in contaminant profiles of free-ranging animals, but exceedingly little attention has been devoted to the role of habitat use. Marked inter-individual variations and high levels of polybrominated diphenyl ethers (PBDEs) (e.g., DecaBDE) have previously been documented in ring-billed gulls (Larus delawarensis) breeding in a colony near Montreal (QC, Canada). However, the environmental sources of these compounds, and thus the reasons causing these large inter-individual variations remain unidentified. In the present study, we used GPS-based telemetry (±5 to 10m precision) to track ring-billed gulls from this colony to reconstruct their movements at the landscape level. We related habitat use of individual gulls (n=76) to plasma concentrations (ng/g ww) and relative contributions (percentages) to Σ38PBDEs of major congeners in the internationally restricted PentaBDE and current-use DecaBDE mixtures. Male gulls that visited waste management facilities (WMFs; i.e., landfills, wastewater treatment plants and related facilities; 25% of all GPS-tracked males) exhibited greater DecaBDE (concentrations and percentages) and lower PentaBDE (percentages) relative to those that did not. In contrast, no such relationships were found in females. Moreover, in males, DecaBDE (concentrations and percentages) increased with percentages of time spent in WMFs (i.e., ~5% of total foraging time), while PentaBDE (percentages) decreased. No relationships between percentages of time spent in other habitats (i.e., urban areas, agriculture fields, and St. Lawrence River) were found in either sex. These findings suggest that animals breeding in the vicinity of WMFs as well as mobile species that only use these sites for short stopovers to forage, could be at risk of enhanced DecaBDE exposure.

Bisphenol-A removal in various wastewater treatment processes: operational conditions, mass balance, and optimization

Bisphenol-A (BPA) was analyzed in 499 liquid and 347 solid samples collected from twenty-five wastewater treatment plants (WWTPs) to investigate parameters affecting BPA occurrence, removal, and fate. Lagoons, chemically-assisted primary treatment, secondary treatment, and advanced treatment processes were included. Median BPA concentrations in influent and final effluent were 400 ng/L and 150 ng/L, respectively. Median removal efficiencies ranged from 1 to 77%. Respective median BPA levels in primary sludge, secondary biological sludge, and biosolids were 230, 260, and 460 ng/g with digested biosolids having the highest concentrations. The biological aerated filter and membrane bioreactor processes showed the best performance, while chemically-assisted primary treatment achieved the lowest removal. Biodegradation and sorption contributing to BPA removal were influenced by operational conditions: hydraulic retention time (HRT), solids retention time (SRT), and mixed liquor suspended solids (MLSS). The influence of HRT, SRT, and MLSS in the bioreactor was stronger during cold temperatures. In order to achieve above 80% removal, the required conditions for HRT, SRT, and MLSS were 13 h, 7 days, and 1600 mg/L during summer (median temperature 19 °C) and 13 h, 17 days, and 5300 mg/L during winter (median temperature 10 °C); indicating that longer SRT and higher MLSS were needed during winter. BPA's sorption tendency to sludge was strongly influenced by the degree of nitrification and HRT.

Temporal and spatial contamination of polybrominated diphenyl ethers (PBDEs) in wastewater treatment plants in Hong Kong

Polybrominated diphenyl ethers (PBDEs) are widely used as flame retardants which cause adverse effects to human health and environments. Wastewater treatment plants (WWTPs) receive PBDEs from various discharges but also release them back to the environment via treated effluent and sludge, depending on the removal efficiency of WWTPs. This study investigated the contamination of PBDEs in primary influent, final effluent and dewatered sludge in four WWTPs in Hong Kong from October 2011 to January 2013. Results showed that the concentrations and composition profiles of eight PBDE congeners (BDE-28, －47, －99, －100, －153, －154,－183 and －209) differed among WWTPs and fluctuated during the study period. Higher concentrations of PBDEs were detected in the influent and dewatered sludge from the two WWTPs receiving both domestic and industrial wastewaters than the two serve mainly residential and commercial districts. However, the PBDE concentrations in the effluent were comparable among WWTPs. The concentrations of Σ8PBDEs (total of eight congeners) in the influent of all WWTPs ranged from 1 to 254 ng L(-1) but decreased to 12-27 ng L(-1) in effluent, with removal efficiency ranged from 20 to 53%. High concentrations of PBDEs, ranging from 9 to 307 ng g(-1) dry weights, were detected in dewatered sludge. The predominated congeners in influent were BDE-47 and -209 but shifted to BDE-47 and －99 in effluent and BDE-209 in dewatered sludge. Every day, it is estimated 0.66-73 g PBDEs entered the four WWTPs, while 0.38-38 g and 0.17-17 g PBDEs were discharged to the surrounding waters via effluent and disposed to landfill sites in sludge form, respectively. These results indicated that the four WWTPs in Hong Kong were not designed for effectively removal of PBDEs, 52-80% of the incoming PBDEs were still remained in effluent and 21-45% was precipitated in sludge, both outputs became significant contamination sources.

Occurrence and fate of four novel brominated flame retardants in wastewater treatment plants

Four novel brominated flame retardants (NBFRs), i.e., decabromodiphenylethane (DBDPE), 1,2-bis(2,4,6-tribromophenoxy) ethane (BTBPE), pentabromoethylbenzene (PBEB), and hexabromobenzene (HBB) were studied in 377 liquid samples and 288 solid samples collected from 20 wastewater treatment plants. Lagoon, primary, secondary, and advanced treatment processes were included, in order to investigate NBFR occurrence and the effects of WWTP operational conditions on NBFR removal. Median influent and effluent levels were 14 to 3,700 and 1.0 to 180 pg/L respectively, with DBDPE being the highest in both. Overall median removal efficiencies for DBDPE, BTBPE, HBB, and PBEB across all process types were 81 to 93, 76 to 98, 61 to 97, and 54 to 97 %, respectively with advanced treatment processes obtaining the best removals. NBFRs removal was related to retention time, surface loading rate, and biomass concentration. Median NBFR levels in treated biosolids were 80 to 32,000 pg/g, influenced by solids treatment processes.

Nonionic surfactant greatly enhances the reductive debromination of polybrominated diphenyl ethers by nanoscale zero-valent iron: mechanism and kinetics

Nanoscale zero-valent iron (nZVI) has been considered as an effective agent for reductive debromination of polybrominated diphenyl ethers (PBDEs). But the high lipophilicity of PBDEs will hinder their debromination owing to the inefficient contact of PBDEs with nZVI. In this study, different ionic forms of surfactants were investigated aiming to promote PBDE debromination, and the beneficial effects of surfactant were found to be: nonionic polyethylene glycol octylphenol ether (Triton X-100, TX)>cationic cetylpyridinium chloride (CPC)>anionic sodium dodecyl benzenesulfonate (SDDBS). Except for with SDDBS, the promotion effect for PBDE debromination was positively related to the surfactant concentrations until a critical micelle concentration (CMC). The debromination process of octa-BDE and its intermediates could be described as a consecutive reaction. The corresponding rate constants (k) for the debromination of parent octa-BDE (including nona- to hepta-BDEs), the intermediates hexa-, penta-, and tetra-BDEs are 1.24 × 10(-1) h(-1), 8.97 × 10(-2) h(-1), 6.50 × 10(-2) h(-1) and 2.37 × 10(-3) h(-1), respectively.

Polybrominated diphenyl ethers (PBDEs) and dechlorane plus (DP) in a conventional wastewater treatment plant (WWTP) in Shanghai: seasonal variations and potential sources

Wastewater treatment plants (WWTPs) are considered an important medium for the transport and transformation of organic pollutants, such as polybrominated diphenyl ethers (PBDEs) and dechlorane plus (DP). However, limited data on PBDEs and no data on DP were available regarding wastewater and sludge from China, especially in Shanghai, one of the most developed cities in China. This study examined the occurrence of PBDEs and DP in a conventional WWTP in Shanghai for one year. The levels of the total PBDEs in the influent and dewatered sludge ranged from 5.31 to 27.9 ng/L and 31.0 to 99.5 ng/g, respectively, which were at the low end of the global range. DP was reported in wastewater with a mean concentration of 0.46 ng/L (range: 0.05 to 1.40 ng/L) and sludge contained DP in the range of 1.1 to 2.0 ng/g. For both PBDEs and DP, there were no significant seasonal variations observed in the four seasons. Indoor dust and outdoor air could be two main sources of PBDEs and DP in the WWTP. In both the influent and sewage sludge, BDE-209 was the most abundant congener, with contributions to the total PBDE levels ranging from 52.9 to 82.6% and 82.7 to 84.0%, respectively. The fraction of anti-DP was consistently higher than that of syn-DP, and the average of fsyn ranged from 0.16 to 0.33, which fell in the range of two commercial DP mixtures. The annual releases of PBDEs and DP via sewage sludge from WWTPs in Shanghai were estimated to be 6,370 g and 164.8 g, respectively. The fate and risk of these compounds after being released into the environment require further research. To the best of our knowledge, this study is the first to report on the occurrence of DP in wastewater.

From the city to the Lake: loadings of PCBs, PBDEs, PAHs and PCMs from Toronto to Lake Ontario

Loadings from Toronto, Canada to Lake Ontario were quantified and major sources and pathways were identified, with the goal of informing opportunities for loading reductions. The contaminants were polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs), polycyclic aromatic hydrocarbons (PAHs) and polycyclic musks (PCMs). Loadings were calculated from measured concentrations for three major pathways: atmospheric processes, tributary runoff, and wastewater treatment plant (WWTP) effluents. Although atmospheric deposition to the Great Lakes has received the greatest attention, this was the dominant loading pathway for PCBs only (17 ± 5.3 kg/y or 66% of total loadings). PCB loadings reflected elevated urban PCB air concentrations due to, predominantly, primary emissions. These loadings contribute to consumption advisories for nearshore fish. PBDE loadings to the lake, again from mainly primary emissions, were 48% (9.1 ± 1.3 kg/y) and 42% (8.0 ± 5.7 kg/y) via tributaries and WWTPs, respectively, consistent with emissions deposited and subsequently washed-off of urban surfaces and emissions to the sewage system. PAHs loadings of 1600 ± 280 kg/y (71%) from tributaries were strongly associated with vehicle transportation and impervious surfaces. PCM loadings were 83% (±140 kg/y) from WWTP final effluent, reflecting their use in personal care products. Opportunities for source reduction lie in reducing the current inventories of in-use PCBs and PBDE-containing products, reducing vehicle emissions of PAHs and use of PAHs in the transportation network (e.g., pavement sealants), and improving wastewater treatment technology.

Polybrominated diphenyl ethers in sewage sludge and treated biosolids: effect factors and mass balance

Polybrominated diphenyl ether (PBDE) flame retardants have been consistently detected in sewage sludge and treated biosolids. Two hundred and eighty-eight samples including primary sludge (PS), waste biological sludge (WBS) and treated biosolids from fifteen wastewater treatment plants (WWTPs) in Canada were analyzed to investigate the factors affecting accumulation of PBDEs in sludge and biosolids. Factors examined included environmental/sewershed conditions and operational parameters of the WWTPs. PBDE concentrations in PS, WBS and treated biosolids were 230-82,000 ng/g, 530-8800 ng/g and 420-6000 ng/g, respectively; BDE-209,-99, and -47 were the predominant congeners. Concentrations were influenced by industrial input, leachate, and temperature. Several examinations including the measurement of BDE-202 indicated minimal debromination during wastewater treatment. Estimated solids-liquid distribution coefficients were moderately correlated to hydraulic retention time, solids loading rate, mixed liquor suspended solids, solids retention time, and removal of organic solids, indicating that PBDE partitioning to solids can be optimized by WWTPs' operational conditions. Solids treatment type strongly affected PBDE levels in biosolids: 1.5 times increase after solids digestion, therefore, digestion efficiency could be a potential factor for variability of PBDEs concentration. In contrast, alkaline treatment reduced PBDE concentrations in biosolids. Overall, mass balance approaches confirmed that PBDEs were removed from the liquid stream through partitioning to solids. Variability of PBDE levels in biosolids could result in different PBDEs burdens to agricultural land, and different exposure levels to soil organisms.