The "Microplastome" - A Holistic Perspective to Capture the Real-World Ecology of Microplastics.

Microplastic pollution, an emerging pollution issue, has become a significant environmental concern globally due to its ubiquitous, persistent, complex, toxic, and ever-increasing nature. As a multifaceted and diverse suite of small plastic particles with different physicochemical properties and associated matters such as absorbed chemicals and microbes, future research on microplastics will need to comprehensively consider their multidimensional attributes. Here, we introduce a novel, conceptual framework of the "microplastome", defined as the entirety of various plastic particles (<5 mm), and their associated matters such as chemicals and microbes, found within a sample and its overall environmental and toxicological impacts. As a novel concept, this paper aims to emphasize and call for a collective quantification and characterization of microplastics and for a more holistic understanding regarding the differences, connections, and effects of microplastics in different biotic and abiotic ecosystem compartments. Deriving from this lens, we present our insights and prospective trajectories for characterization, risk assessment, and source apportionment of microplastics. We hope this new paradigm can guide and propel microplastic research toward a more holistic era and contribute to an informed strategy for combating this globally important environmental pollution issue.

Effect-based monitoring of two rivers under urban and agricultural influence reveals a range of biological activities in sediment and water extracts.

Chemical contaminants, such as pesticides, pharmaceuticals and industrial compounds are ubiquitous in surface water and sediment in areas subject to human activity. While targeted chemical analysis is typically used for water and sediment quality monitoring, there is growing interest in applying effect-based methods with in vitro bioassays to capture the effects of all active contaminants in a sample. The current study evaluated the biological effects in surface water and sediment from two contrasting catchments in Aotearoa New Zealand, the highly urbanised Whau River catchment in Tamaki Makaurau (Auckland) and the urban and mixed agricultural Koreti (New River) Estuary catchment. Two complementary passive sampling devices, Chemcatcher for polar chemicals and polyethylene (PED) for non-polar chemicals, were applied to capture a wide range of contaminants in water, while composite sediment samples were collected at each sampling site. Bioassays indicative of induction of xenobiotic metabolism, receptor-mediated effects, genotoxicity, cytotoxicity and apical effects were applied to the water and sediment extracts. Most sediment extracts induced moderate to strong estrogenic and aryl hydrocarbon (AhR) activity, along with moderate toxicity to bacteria. The water extracts showed similar patterns to the sediment extracts, but with lower activity. Generally, the polar Chemcatcher extracts showed greater estrogenic activity, photosynthesis inhibition and algal growth inhibition than the non-polar PED extracts, though the PED extracts showed greater AhR activity. The observed effects in the water extracts were compared to available ecological effect-based trigger values (EBT) to evaluate the potential risk. For the polar extracts, most sites in both catchments exceeded the EBT for estrogenicity, with many sites exceeding the EBTs for AhR activity and photosynthesis inhibition. Of the wide range of endpoints considered, estrogenic activity, AhR activity and herbicidal activity appear to be the primary risk drivers in both the Whau and Koreti Estuary catchments.

Microplastics and Tire Wear Particles in Urban Stormwater: Abundance, Characteristics, and Potential Mitigation Strategies.

Stormwater has been identified as a pathway for microplastics (MPs), including tire wear particles (TWPs), into aquatic habitats. Our knowledge of the abundance of MPs in urban stormwater and potential strategies to control MPs in stormwater is still limited. In this study, stormwater samples were collected from microlitter capture devices (inlet and outlet) during rain events. Sediment samples were collected from the material captured in the device and from the inlet and outlet of a constructed stormwater wetland. MP (>25 µm) concentration in stormwater varied across different locations ranging from 3.8 to 59 MPs/L in raw and 1.8 to 32 MPs/L in treated stormwater, demonstrating a decrease after passage through the device (35-88% removal). TWPs comprised ∼95% of all particles, followed by polypropylene (PP) and poly(ethylene terephthalate) (PET). The concentration of TWPs ranged from 2.5 to 58 TWPs/L and 1450 to 4740 TWPs/kg in stormwater and sediment, respectively. A higher abundance of MPs was found in the sediment at the inlet of the constructed wetland compared to the outlet, indicating a potential role of wetlands in removing MPs from stormwater. These findings suggest that both constructed wetlands and microlitter capture devices can mitigate the transport of MPs from stormwater to the receiving waterways.

Airborne Microplastics in Indoor and Outdoor Environments of a Developing Country in South Asia: Abundance, Distribution, Morphology, and Possible Sources.

Airborne microplastics (AMPs) have been reported in indoor and outdoor air in high-income countries and are expected to be a significant contributor to daily microplastic (MP) exposure for human beings. To date, there are only a handful of studies in lower-middle-income countries. In this study, AMPs from 5000 to 50 µm were sampled across selected areas of Sri Lanka using an active sampling technique. Suspected AMPs were further characterized using Fourier transform infrared spectroscopy. MP concentrations were higher indoors compared to outdoor air (0.13-0.93, compared to 0.00-0.23 particles/m3, respectively). The types of indoor MPs were related to indoor-generating sources, and the occupant's lifestyles. The highest outdoor MP abundance was found near an industrial zone, followed by urban and inland locations in high-density areas. The dominant size range of MPs was 100-300 µm, and the only shapes observed indoors and outdoors were fibers (98%) and fragments. Polyethylene terephthalate was the most prominent MP type, followed by polyester, indicating that textile fibers could be the major source of these AMPs. This study provides the first report on AMPs in Sri Lanka. Considering population growth and industrialization, further research should evaluate possible trends and health risks upon inhalation.

Impact of Microplastic Beads and Fibers on Waterflea (Ceriodaphnia dubia) Survival, Growth, and Reproduction: Implications of Single and Mixture Exposures.

There is limited knowledge regarding the adverse effects of wastewater-derived microplastics, particularly fibers, on aquatic biota. In this study, we examined the acute (48 h) and chronic (8 d) effects of microplastic polyester fibers and polyethylene (PE) beads on freshwater zooplankton Ceriodaphnia dubia. We also assessed the acute response of C. dubia to a binary mixture of microplastic beads and fibers for the first time. Acute exposure to fibers and PE beads both showed a dose-dependent effect on survival. An equitoxic binary mixture of beads and fibers resulted in a toxic unit of 1.85 indicating less than additive effects. Chronic exposure to lower concentrations did not significantly affect survival of C. dubia, but a dose-dependent effect on growth and reproduction was observed. Fibers showed greater adverse effects than PE beads. While ingestion of fibers was not observed, scanning electron microscopy showed carapace and antenna deformities after exposure to fibers, with no deformities observed after exposure to PE beads. While much of the current research has focused on microplastic beads, our study shows that microplastic fibers pose a greater risk to C. dubia, with reduced reproductive output observed at concentrations within an order of magnitude of reported environmental levels.

Wastewater treatment plant effluent as a source of microplastics: review of the fate, chemical interactions and potential risks to aquatic organisms.

Wastewater treatment plant (WWTP) effluent has been identified as a potential source of microplastics in the aquatic environment. Microplastics have recently been detected in wastewater effluent in Western Europe, Russia and the USA. As there are only a handful of studies on microplastics in wastewater, it is difficult to accurately determine the contribution of wastewater effluent as a source of microplastics. However, even the small amounts of microplastics detected in wastewater effluent may be a remarkable source given the large volumes of wastewater treatment effluent discharged to the aquatic environment annually. Further, there is strong evidence that microplastics can interact with wastewater-associated contaminants, which has the potential to transport chemicals to aquatic organisms after exposure to contaminated microplastics. In this review we apply lessons learned from the literature on microplastics in the aquatic environment and knowledge on current wastewater treatment technologies, with the aim of identifying the research gaps in terms of (i) the fate of microplastics in WWTPs, (ii) the potential interaction of wastewater-based microplastics with trace organic contaminants and metals, and (iii) the risk for aquatic organisms.

Evaluating the retention of airborne microplastics on plant leaf: Influence of leaf morphology.

Airborne microplastics (AMPs) have been identified in both indoor and outdoor environments and account for a large portion of an individual's daily exposure to microplastics. Thus, it is crucial to find effective methods to capture and control the levels of AMPs and ultimately reduce human exposure. While terrestrial plants have been recognized for their effectiveness in capturing airborne particles, little is known about their ability to capture AMPs. This study investigated the ability of 8 natural plant species and 2 artificial plants to capture AMPs, as well as the influence of leaf morphology on this retention. Plant leaves were exposed to AMPs for two weeks, and deposited AMPs were characterized using a Micro-Fourier Transform Infrared (µ-FTIR)spectroscopy. Selected cleaned leaves were further digested, and the presence of subsurface AMPs was confirmed using µ-Raman spectroscopy. Results revealed that AMPs were retained on the leaves of all selected plant species at concentrations ranging from 0.02 to 0.87 n/cm2. The highest average concentration was observed on an artificial plant with fenestrated leaves, followed by natural plant species with trichomes and leaflets. The lowest concentration was observed on a natural plant with smooth leaves. The majority (90%) of retained AMPs were fibres, and the remaining were fragments. Polyethylene terephthalate (PET) was the prominent polymer type. Additionally, AMP fragments were observed in the leaf subsurface in one selected species, likely retained within the leaf cuticles. The results suggest that plant leaves can indiscriminately retain AMPs on their surfaces and act as temporary sinks for AMPs. Additionally, indoor plants may provide a useful functional role in reducing indoor AMP concentrations, although longer-term studies are needed to ascertain their retention capacity more accurately over time and to evaluate the capability of indoor plants to act as a suitable, cost-effective candidate for reducing AMPs.

Microplastics and other anthropogenic fibres in large apex shark species: Abundance, characteristics, and recommendations for future research.

Microplastics and microfibres are found ubiquitously in global oceans as well as marine organisms from different trophic levels. However, little is known about the presence of microplastics and microfibres in marine megafauna, such as sharks. This study provided the first investigation of the presence of microplastics and other anthropogenic fibres (i.e., cellulose based fibres) in intestine and muscle samples of four large apex shark species in Australian coastal waters. Microplastics and other anthropogenic fibres were found in 82% of the analysed intestine samples. The mean abundance in intestine samples was 3.1 ± 2.6 particles/individual, which corresponded to 0.03 ± 0.02 particles/g of intestine, across all shark species. The size of particles ranged from 190 to 4860 µm in length with 92% being fibrous in shape and the rest fragments. FTIR spectroscopy identified that 70% of fibres were cellulose-based followed by polyethylene terephthalate (PET), while the fragments were polyethylene and polypropylene. In shark muscles, 60% of samples contained microplastics and other anthropogenic fibres, again with the majority being cellulose-based fibres followed by PET fibres. Methodological differences hinder a more comprehensive assessment of microplastic contamination across studies. Additionally, we identified some challenges which should be factored in for future studies looking at the presence of microplastics as well as other anthropogenic fibres in these large marine organisms. Overall, the findings provide first evidence of microplastics and other anthropogenic fibres not only in the intestines, but also in muscle tissues of large apex shark species.

Exploring the co-exposure effects of environmentally relevant microplastics and an estrogenic mixture on the metabolome of the Sydney rock oyster.

In aquatic environments the concurrent exposure of molluscs to microplastics (MPs) and estrogens is common, as these pollutants are frequently released by wastewater treatment plants into estuaries. Therefore, this study aimed to evaluate the independent and co-exposure impacts of polyethylene microplastics (PE-MPs) and estrogenic endocrine-disrupting chemicals (EEDCs) at environmentally relevant concentrations on polar metabolites and morphological parameters of the Sydney rock oyster. A seven-day acute exposure revealed no discernible differences in morphology; however, significant variations in polar metabolites were observed across oyster tissues. The altered metabolites were mostly amino acids, carbohydrates and intermediates of the Kreb's cycle. The perturbation of metabolites were tissue and sex-specific. All treatments generally showed an increase of metabolites relative to controls - a possible stimulatory and/or a potential hormetic response. The presence of MPs impeded the exposure of adsorbed and free EEDCs potentially due to the selective feeding behaviour of oysters to microplastics, favouring algae over similar-sized PE-MPs, and the formation of an eco/bio-corona involving faeces, pseudo-faeces, natural organic matter, and algae.

Polyethylene microplastics induced lipidomic responses in Chironomus tepperi: A two-generational exploration.

Microplastics (MPs) accumulating in freshwater sediment have raised concerns about potential risks to benthic dwelling organisms, yet few studies have examined the long-term impacts caused by MP exposure. This study investigated alterations to lipid profiles in an Australian freshwater invertebrate, Chironomus tepperi, induced by polyethylene MP fragments (1-45 µm) at environmentally relevant concentrations (125, 250, 500 and 1000 MPs/kg sediment), using a two-generational experimental design. In the parental generation, the relative abundance of triacylglycerols, total fatty acids and unsaturated fatty acids exhibited apparent hormetic patterns, with low-concentration stimulation and high-concentration inhibition observed. The overall trend in these lipid classes is consistent with previously observed changes to polar metabolite profiles, indicating that ingestion of MPs could inhibit nutrient assimilation from food leading to disruption of energy availability. In the first filial generation continuously exposed to MPs, however, abundance of cholesterol and total fatty acids increased with increasing exposure concentrations, suggesting different effects on energy metabolism between the parental generation and offspring. No differences in the lipidome were observed in first filial larvae that were not exposed, implying that MPs pose negligible carry-over effects. Overall, the combined results of this study together with a preceding metabolomics study provide evidence of a physical effect of MPs with subsequent impacts to bioenergetics. Nevertheless, future research is required to explore the potential long-term impacts caused by MPs, and to unravel the impacts of the surfactant control as a potential contributor to the observed hormetic response, particularly for studies exploring sub-lethal effects of MP exposure using sensitive omics techniques.

Comprehensive assessment of microplastics in Australian biosolids: Abundance, seasonal variation and potential transport to agroecosystems.

Striving towards a circular economy, the application of treated sewage sludge (biosolids) to land is an opportunity to improve the condition of the soil and add essential nutrients, in turn reducing the need for fertilisers. However, there is an increasing concern about microplastic (MP) contamination of biosolids and their transport to terrestrial ecosystems. In Australia, agriculture is the largest biosolids end-user, however, there is limited understanding of MPs in Australian biosolids. Also, while the method to isolate MPs from biosolid is established, a need to extract and analyse MPs more efficiently is still pressing. In this study, we comprehensively quantified and characterised MPs in 146 biosolids samples collected from thirteen wastewater treatment plants (WWTPs) including different seasons. We have optimised an oxidative-enzymatic purification method to overcome current limitations for MP identification in complex samples and accurately report MPs in biosolids. This method enabled removal of >93 % of dry weight of organic material and greatly facilitated the MPs instrumental analysis. The concentration of MPs (>20 µm) in all biosolids samples ranged from 11 to 150 MPs/g dry weight. Abundance of MPs was affected by seasons with higher abundance of MPs usually found during cold and wet seasons. Despite seasonal variations, polyethylene terephthalate, polyurethane and polymethyl methacrylate were the most abundant polymers. Smaller MPs (20 to 200 µm) comprised >70 % of all detected MPs with a clear negative linear relationship observed between MP size and abundance. Per capita concentration of MPs in biosolids across all studied WWTPs was 0.7 to 21 g MPs per person per year. Therefore, biosolids are an important sink and source of MPs to agroecosystems, emphasising the need to more comprehensively understand the fate, impact and risks associated with MPs on agricultural soils.

Microplastics in Australian indoor air: Abundance, characteristics, and implications for human exposure.

Studies on airborne microplastics (AMPs) have reported higher abundance of AMPs in indoor air compared to outdoors. Most people spend more time indoors compared to outdoors, and it is therefore important to identify and quantify AMPs in indoor air to understand human exposure to AMPs. This exposure can vary among different individuals as they spend their time in different locations and different activity levels, and thus experience different breathing rates. In this study, AMPs ranging from 20-5000 µm were sampled across different indoor sites of Southeast Queensland using an active sampling technique. The highest indoor MP concentration was observed at a childcare site (2.25 ± 0.38 particles/m3), followed by an office (1.20 ± 0.14 particles/m3) and a school (1.03 ± 0.40 particles/m3). The lowest indoor MP concentration was observed inside a vehicle (0.20 ± 0.14 particles/m3), comparable to outdoor concentrations. The only shapes observed were fibers (98%) and fragments. MP fibers ranged from 71 to 4950 µm in length. Polyethylene terephthalate was the prominent polymer type at most sites. Using our measured airborne concentrations as inhaled air concentrations, we calculated the annual human exposure levels to AMPs using scenario-specific activity levels. Males between the ages of 18 to 64 were calculated to have the highest AMP exposure at 3187 ± 594 particles/year, followed by males ≥65 years at 2978 ± 628 particles/year. The lowest exposure of 1928 ± 549 particles/year was calculated for females between the ages of 5 to 17. This study provides the first report on AMPs for various types of indoor locations where individuals spend most of their time. Considering acute, chronic, industrial, and individual susceptibility, more detailed human inhalation exposure levels to AMPs should be estimated for a realistic appraisal of the human health risk, including how much of the inhaled particles are exhaled. SYNOPSIS: Limited research exists on the occurrence and the associated human exposure levels to AMPs in indoor locations where people spend most of their time. This study reports on the occurrence of AMPs at indoor locations and associated exposure levels using scenario-specific activity levels.

Metabolomic responses in freshwater benthic invertebrate, Chironomus tepperi, exposed to polyethylene microplastics: A two-generational investigation.

The accumulation of microplastics (MPs) in sediments could pose risks to benthic organisms and their progeny. Here, we examined effects on traditional apical endpoints along with changes to whole body metabolite profiles induced by irregular shaped polyethylene MPs (1-45 µm) at environmentally relevant concentrations (125, 250, 500 and 1000 MPs/kg sediment) in Chironomus tepperi using a two-generation exposure regime. Survival and emergence of C. tepperi were negatively affected in the parental generation at the two highest concentrations, whereas endpoints associated with growth were only impacted at 1000 MPs/kg sediment. Metabolites associated with several amino acid and energy metabolism pathways were present at lower abundances at the highest exposure concentration suggesting an overall impact on bioenergetics which relates to the inhibition of food acquisition or nutrient assimilation caused by ingestion of MPs, rather than a traditional receptor-mediated toxicity response. In contrast, no significant effects on apical endpoints were observed in the continuous exposure of first filial generation, and lactic acid was the only metabolite that differed significantly between groups. Larvae in unexposed conditions showed no differences in survival or metabolite profiles suggesting that effects in the parental generation do not carry over to the next filial generation. The findings provide evidence on the underlying impacts of MP ingestion and potential adaption to MP exposure of C. tepperi.

Systematic assessment of data quality and quality assurance/quality control (QA/QC) of current research on microplastics in biosolids and agricultural soils.

Although a growing number of studies have reported microplastics (MPs) in biosolids and soils, there are significant differences in the concentrations found across different regions worldwide. This has raised questions about the quality of studies due to a lack of standardized sampling and analysis methods for detecting MPs in such complex samples. In this study, we applied a systematic quantitative literature review (SQLR) methodology to analyze studies reporting MPs in sludge/biosolids and agricultural soils. We also assessed the quality of individual studies on MPs in sludge/biosolids and soils based on the inclusion of quality assurance/quality control (QA/QC) procedures. There is limited understanding about MPs in soils with a history of biosolid application with only 9% of publications reporting MPs in biosolid-amended soil. There was almost eight orders of magnitude difference (3.4 × 10-5 to 9.4 × 103 particles/g) between the highest concentrations of MPs in sludge/biosolid samples compared to the lowest virgin soil samples. The literature shows a consistency in the polymer types (polyester, PP and PE) and morphotypes (fibres and fragments) of MPs most frequently detected in biosolids and soils, suggesting a potential role of biosolids in soils MP pollution. Despite the large variations in the sizes of MPs, there was a negative correlation between the lowest size detected and concentrations reported. This indicates that current concentrations of MPs are influenced by the detection size. Our assessment shows that the majority of studies to-date lack critical QA/QC measures, particularly field blank, positive control and method validation. This highlights an urgent need for quality improvement of future research in this field to produce reliable data, ultimately crucial to assess the risk of MPs and derive suitable environmental guidelines. It is recommended that MPs studies methodically include QA/QC protocols at every step of the process to ensure the integrity of the data that is published.

Microplastics profile in constructed wetlands: Distribution, retention and implications.

Wastewater and stormwater are both considered as critical pathways contributing microplastics (MPs) to the aquatic environment. However, there is little information in the literature about the potential influence of constructed wetlands (CWs), a commonly used wastewater and stormwater treatment system. This study was conducted to investigate the abundance and distribution of MPs in water and sediment at five CWs with different influent sources, namely stormwater and wastewater. The MP abundance in the water samples ranged between 0.4 ± 0.3 and 3.8 ± 2.3 MP/L at the inlet and from 0.1 ± 0.0 to 1.3 ± 1.0 MP/L at the outlet. In the sediment, abundance of MPs was generally higher at the inlet, ranging from 736 ± 335 to 3480 ± 4330 MP/kg dry sediment and decreased to between 19.0 ± 16.4 and 1060 ± 326 MP/kg dry sediment at the outlet. Although no significant differences were observed in sediment cores at different depth across the five CWs, more MPs were recorded in silt compared to sandy sediment which indicated sediment grain size could be an environmental factor contributing to the distribution of MPs. Polyethylene terephthalate (PET) fibres were the dominant polymer type found in the water samples while polyethylene (PE) and polypropylene (PP) fragments were predominantly recorded in the sediment. While the size of MPs in water varied across the studied CWs, between 51% and 64% of MPs in the sediment were smaller than 300 µm, which raises concerns about the bioavailability of MPs to a wider range of wetland biota and their potential ecotoxicological effects. This study shows that CWs can not only retain MPs in the treated water, but also become sinks accumulating MPs over time.

An audit of microplastic abundance throughout three Australian wastewater treatment plants.

Wastewater treatment plants (WWTPs) have been identified as an important pathway of microplastics to the environment. Most studies have focused on wastewater effluent, but generally only a small fraction of microplastics entering WWTPs are present in treated effluent. Instead, the majority of microplastics are expected to be retained in the sludge. To our knowledge, there is limited information on microplastics in sludge/biosolids from Australian WWTPs, despite 75% of biosolids produced in Australia being used for agriculture. This study evaluated the abundance of microplastics throughout the treatment trains of three WWTPs in Australia. The fate of microplastics >25 µm during treatment and their release to the environment was evaluated using an audit approach. The highest microplastic concentrations were detected in the influent, with fibres the dominant form of microplastic found. The screening and grit removal process preceding primary treatment removed 69-79% of microplastics, with these microplastics transported to landfill. Only 0.2-1.8% of the total microplastics in the influent were present in the final effluent, while 8-16% were retained in biosolids. This equates to between 22.1 × 106 to 133 × 106 microplastic particles per day released in effluent, between 864 × 106 to 1020 × 106 microplastic particles per day in biosolids, and between 4100 × 106 to 9100 × 106 microplastic particles per day transported to landfill. This study shows for the first time that most microplastics are retained during the initial screening and grit removal process with the load of microplastics going to landfill an order of magnitude greater than that in biosolids. Landfills may thus be an important sink (and potential future source) of microplastics from wastewater.

Environmentally relevant concentrations of polyethylene microplastics negatively impact the survival, growth and emergence of sediment-dwelling invertebrates.

Microplastics are a widespread environmental pollutant in aquatic ecosystems and have the potential to eventually sink to the sediment, where they may pose a risk to sediment-dwelling organisms. While the impacts of exposure to microplastics have been widely reported for marine biota, the effects of microplastics on freshwater organisms at environmentally realistic concentrations are largely unknown, especially for benthic organisms. Here we examined the effects of a realistic concentration of polyethylene microplastics in sediment on the growth and emergence of a freshwater organism Chironomus tepperi. We also assessed the influence of microplastic size by exposing C. tepperi larvae to four different size ranges of polyethylene microplastics (1-4, 10-27, 43-54 and 100-126 µm). Exposure to an environmentally relevant concentration of microplastics, 500 particles/kgsediment, negatively affected the survival, growth (i.e. body length and head capsule) and emergence of C. tepperi. The observed effects were strongly dependent on microplastic size with exposure to particles in the size range of 10-27 µm inducing more pronounced effects. While growth and survival of C. tepperi were not affected by the larger microplastics (100-126 µm), a significant reduction in the number of emerged adults was observed after exposure to the largest microplastics, with the delayed emergence attributed to exposure to a stressor. While scanning electron microscopy showed a significant reduction in the size of the head capsule and antenna of C. tepperi exposed to microplastics in the 10-27 µm size range, no deformities to the external structure of the antenna and mouth parts in organisms exposed to the same size range of microplastics were observed. These results indicate that environmentally relevant concentrations of microplastics in sediment induce harmful effects on the development and emergence of C. tepperi, with effects greatly dependent on particle size.

Biocatalytic degradation of pharmaceuticals, personal care products, industrial chemicals, steroid hormones and pesticides in a membrane distillation-enzymatic bioreactor.

Laccase-catalyzed degradation of a broad spectrum of trace organic contaminants (TrOCs) by a membrane distillation (MD)-enzymatic membrane bioreactor (EMBR) was investigated. The MD component effectively retained TrOCs (94-99%) in the EMBR, facilitating their continuous biocatalytic degradation. Notably, the extent of TrOC degradation was strongly influenced by their molecular properties. A significant degradation (above 90%) of TrOCs containing strong electron donating functional groups (e.g., hydroxyl and amine groups) was achieved, while a moderate removal was observed for TrOCs containing electron withdrawing functional groups (e.g., amide and halogen groups). Separate addition of two redox-mediators, namely syringaldehyde and violuric acid, further improved TrOC degradation by laccase. However, a mixture of both showed a reduced performance for a few pharmaceuticals such as primidone, carbamazepine and ibuprofen. Mediator addition increased the toxicity of the media in the enzymatic bioreactor, but the membrane permeate (i.e., final effluent) was non-toxic, suggesting an added advantage of coupling MD with EMBR.