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Volatile organic compounds (VOCs) are significant atmospheric pollutants that cause environmental and health risks. Waste gases polluted with multiple VOCs often need to be purified simultaneously in biofilters, which may lead to antagonistic, neutral, or synergistic effects on removal performance. Antagonism limits the application of biofilters to simultaneous treatment of multiple VOCs, while synergism has not yet been fully exploited. We review the interactions among multiple target pollutants and the changes in the bioavailability and biodegradability of substrates that are responsible for substrate interactions. Potential strategies for enhancing biofilter performance are then discussed. Finally, we propose further efforts to alleviate antagonism by enhancing bioavailability and biodegradability, and discuss possible challenges to take advantage of synergism. The structure of microbial populations plays an important role in the interactions between hydrophobic and hydrophilic VOCs, and the application of specific single species or mixed microorganisms may alter substrate interactions and consequently enhance removal performance. Enhancing the bioavailability of reluctant VOCs can better offset the negative interactions exerted by the cosubstrates. Strategies to alleviate the negative interactions among multiple VOCs will make it possible to employ biofilters for full-scale removal of multiple VOCs. Biofilter performance for hydrophobic VOCs can be enhanced by exploiting the synergistic interactions of hydrophilic substrates. Regulating operational parameters, such as changing the feeding loading rate for every component and alternating the use of some hydrophilic compounds, may be promising strategies.

Volatile organic compounds (VOCs) are of public concern due to their adverse health effects. Botanical air filtration is a promising technology for reducing indoor air contaminants, but the underlying mechanisms are not fully understood. This study assessed active botanical biofilters for their single-pass removal efficiency (SPRE) for benzene, ethyl acetate and ambient total volatile organic compounds (TVOCs), at concentrations of in situ relevance. Biofilters containing four plant species ( Chlorophytum orchidastrum , Nematanthus glabra , Nephrolepis cordifolia ‘duffii’ and Schefflera arboricola ) were compared to discern whether plant selection influenced VOC SPRE. Amongst all tested plant species, benzene SPREs were between 45.54 and 59.50%, with N. glabra the most efficient. The botanical biofilters removed 32.36–91.19% of ethyl acetate, with C. orchidastrum and S. arboricola recording significantly higher ethyl acetate SPREs than N. glabra and N. cordifolia . These findings thus indicate that plant type influences botanical biofilter VOC removal. It is proposed that ethyl acetate SPREs were dependent on hydrophilic adsorbent sites, with increasing root surface area, root diameter and root mass all associated with increasing ethyl acetate SPRE. The high benzene SPRE of N. glabra is likely due to the high wax content in its leaf cuticles. The SPREs for the relatively low levels of ambient TVOCs were consistent amongst plant species, providing no evidence to suggest that in situ TVOC removal is influenced by plant choice. Nonetheless, as inter-species differences do exist for some VOCs, botanical biofilters using a mixture of plants is proposed.

All odorants are volatile organic compounds (VOCs), i.e., low molecular weight compounds that easily evaporate at normal temperatures and pressure. Fungal VOCs are relatively understudied compared to VOCs of bacterial, plant, or synthetic origin. Much of the research to date on fungal VOCs has focused on their food and flavor properties, their use as indirect indicators of fungal growth in agriculture, or their role as semiochemicals for insects. In addition, research into fungal volatiles has also taken place to monitor spoilage, for purposes of chemotaxonomy, for use in biofilters and for biodiesel, to detect plant and animal disease, for “mycofumigation,” and with respect to plant health. As methods for the analysis of gas phase molecules have improved, it has become apparent that fungal VOC are more chemically varied and more biologically active than has generally been realized. In particular, there is increasing data that show that fungal VOCs frequently mediate interactions between organisms within and across different ecological niches. The goal of this mini review is to orchestrate data on fungal VOCs obtained from disparate disciplines as well as to draw attention to the ecological importance of fungal VOCs in signaling between different species. Technologies and approaches that are common in one area of research are often unknown in others, and the study of fungal VOCs would benefit from more cross talk between subdisciplines.

Microplastic (MP) pollution is a global environmental issue, and traditionally treated wastewater has been identified as a source of land-based microplastics into the aquatic environment. This study evaluated the performance of a pilot-scale biofilter to polish wastewater treatment plant (WWTP) effluent before it enters the environment. The filter was divided into four zones, allowing the concentration of microplastics to be followed through the filter. It was fed with secondary effluent from a conventional WWTP in Denmark. The raw effluent from the WWTP contained 917 items m−3 which corresponded to a mass concentration of 24.8 µg m−3. After the top layer of the biofilter, the concentration had decreased to a median value of 197 item m−3 and 2.8 µg m−3, indicating an overall removal efficiency of 79% in terms of particle number and 89% in terms of particle mass. We also observed a tendency that MP of larger size and higher particle mass were more likely to be retained. After the last filtration zone, all MP larger than 100 µm had been removed. The results of this study demonstrate that biofilters are able to lower the MP abundance in treated wastewater significantly, but a complete removal is not ensured, hence some MP, particularly small-sized ones, can still be discharged into the receiving environment.

Biofiltration is a water purification technology playing a pivotal role in producing safe drinking water. This technology attracts many interests worldwide due to its advantages, such as no addition of chemicals, a low energy input, and a high removal efficiency of organic compounds, undesirable taste and odours, and pathogens. The current review describes the microbial ecology of three biofiltration processes that are routinely used in drinking water treatment plants, i.e. (i) rapid sand filtration (RSF), (ii) granular activated carbon filtration (GACF), and (iii) slow sand filtration (SSF). We summarised and compared the characteristics, removal performance, and corresponding (newly revealed) mechanisms of the three biofiltration processes. Specifically, the microbial ecology of the different biofilter processes and the role of microbial communities in removing nutrients, organic compounds, and pathogens were reviewed. Finally, we highlight the limitations and challenges in the study of biofiltration in drinking water production, and propose future perspectives for obtaining a comprehensive understanding of the microbial ecology of biofiltration, which is needed to promote and optimise its further application. Key points • Biofilters are composed of complex microbiomes, primarily shaped by water quality . • Conventional biofilters contribute to address safety challenges in drinking water . • Studies may underestimate the active/functional role of microbiomes in biofilters .

This paper provides an overview of the Special Issue on Wastewater Treatment and Reuse: Past, Present, and Future. The papers selected for publication include advanced wastewater treatment and monitoring technologies, such as membrane bioreactors, electrochemical systems; denitrifying biofilters, and disinfection technologies. The Issue also contains articles related to best management practices of biosolids, the influence of organic matter on pathogen inactivation and nutrient removal. Collectively, the Special Issue presents an evolution of technologies, from conventional through advanced, for reliable and sustainable wastewater treatment and reuse.

Ecosystem services are the benefits that humans derive from ecosystems. Freshwater mussels perform many important functions in aquatic ecosystems, which can in turn be framed as the ecosystem services that they contribute to or provide. These include supporting services such as nutrient recycling and storage, structural habitat, substrate and food web modification, and use as environmental monitors; regulating services such as water purification (biofiltration); and provisioning and cultural services including use as a food source, as tools and jewelry, and for spiritual enhancement. Mussel-provided ecosystem services are declining because of large declines in mussel abundance. Mussel propagation could be used to restore populations of common mussel species and their ecosystem services. We need much more quantification of the economic, social, and ecological value and magnitude of ecosystem services provided by mussels, across species, habitats, and environmental conditions, and scaled up to whole watersheds. In addition, we need tools that will allow us to value mussel ecosystem services in a way that is understandable to both the public and to policy makers.

Current environmental concerns have led to a search of more environmentally friendly manufacturing methods; thus, natural fibers have gained attention in the 3D printing industry to be used as bio-filters along with thermoplastics. The utilization of natural fibers is very convenient as they are easily available, cost-effective, eco-friendly, and biodegradable. Using natural fibers rather than synthetic fibers in the production of the 3D printing filaments will reduce gas emissions associated with the production of the synthetic fibers that would add to the current pollution problem. As a matter of fact, natural fibers have a reinforcing effect on plastics. This review analyzes how the properties of the different polymers vary when natural fibers processed to produce filaments for 3D Printing are added. The results of using natural fibers for 3D Printing are presented in this study and appeared to be satisfactory, while a few studies have reported some issues.

The concept of recycling organic matter and waste nutrients back to agricultural land through the process of composting adheres to the basic principle of the circular economy. The studies on composting systems have laid a solid foundation for biodegradable solid waste management, and there are still significant gaps that require attention in future research. Addressing these gaps will lead to a more comprehensive understanding of composting processes, improved compost quality, and sustainable waste management practices with greater benefits for agriculture and the environment. The transition to a blended centralized and decentralized waste management system necessitates the conception of an adaptable system for waste management with higher quality compost production. Furthermore, countless agro-industrial products have emerged during this transition phase including commercial fertilizers, nitrogen fortifiers, phosphocompost, biofertilizers, compost tea, and compost biofilters that use compost as a base. The agro-industries might be engaged to participate in research and development in the forthcoming time to develop compost-based commodities. The current systematic study takes into account the long-term sustainability of composting systems harnessing compost valorization. In addition, this review highlights the various agro-industrial commodities that researchers should be concentrated on.

Polychaete assisted sand filters (PASFs) allow to combine a highly efficient retention of particulate organic matter (POM) present in aquaculture effluent water and turn otherwise wasted nutrients into valuable worm biomass, following an integrated multi-trophic aquaculture (IMTA) approach. This study evaluated the bioremediation and biomass production performances of three sets of PASFs stocked with ragworms ( Hediste diversicolor ) placed in three different locations of an open marine land-based IMTA system. The higher organic matter (OM) recorded in the substrate of the systems which received higher POM content (Raw and Df PASFs – filtered raw and screened by drum filter effluent, respectively) likely prompted a superior reproductive success of stocked polychaetes (final densities 2–7 times higher than initial stock; ≈1000–3000 ind. m −2 ). Bioremediation efficiencies of ≈70% of supplied POM (≈1.5–1.8 mg L −1 ) were reported in these systems. The PASFs with lower content of OM in the substrate (Df + Alg PASFs – filtered effluent previously screened by drum filter and macroalgae biofilter) differed significantly from the other two, with stocked polychaetes displaying a poorer reproductive success. The PASFs were naturally colonized with marine invertebrates, with the polychaetes Diopatra neapolitana , Terebella lapidaria and Sabella cf. pavonina being some of the species identified with potential for IMTA.