Microplastic contamination in filter-feeding oyster Saccostrea cuccullata: Novel insights in a marine ecosystem.

Microplastic (MP) pollution has become a pressing global concern. Oysters are well-known filter feeders who ingest food by filtering microscopic particles suspended in the surrounding water. Along with organic matter, filter-feeding also causes accidental ingestion of MP by oysters. Hence, the aim of the current investigation is to understand the MP contamination in filter-feeding oysters. A total of 500 specimens of oyster Saccostrea cuccullata collected from the intertidal zone of five sampling locations on the Gujarat coast, India. Specimens underwent analysis following established protocols. Each specimen was found to exhibit MP contamination, showing an abundance of 2.72 ± 1.98 MPs/g. A negative relationship was found between shell length and MP abundance. Predominantly, fibers were documented across all study sites. Black, blue, and red-colored MPs with 1-2 mm sizes were most dominant. MP polymer composition was identified as polyethylene terephthalate and polypropylene. Findings provide baseline information on levels of MPs contamination, which can be used to monitor future effects of MP pollution.

Exploring nature's filters: Peat-mineral mix for low and high-strength oilfield produced water reclamation.

Nature-based solutions are encouraged for treating oilfield produced water from oil and gas extraction, a crucial undertaking that aligns with the Canadian oil sands industry's ambitious goal of zero waste, and the globally recognized Sustainable Development Goals (SDGs) pertaining to water conservation and ecosystem preservation. This study explored the use of peat-mineral mix (PMM), a leftover of inevitable oil sands mining, for treating low and high-strength wastewaters during biofiltration, which contained large molecular weight (44.3 kDa), which include alcohols, aliphatics, aromatics, and ketones, and can impart high toxicity to both fauna and flora (MicroTox: 99 %). The breakthrough curve indicated an effective initial adsorption phase driven by advection within the column dynamics. For complete organics removal and mechanistic insights, the wastewater was re-circulated in a continuous mode for up to 42 days. Here, we found that chemical oxygen demand was reduced from ∼85,000 mg/L to ∼965 mg/L). Kinetics investigations along with physicochemical characterization of PMM and wastewater suggested that chemisorption and anaerobic digestion contributed to the overall removal of contaminants. Chemisorption, led by hydrogen bonding and hydrophobic interactions, was the dominant mechanism, with a limited contribution from physical adsorption (surface area: 2.85 m2/g). The microbial community within the PMM bed was rich/diverse (Shannon > 6.0; Chao1 > 600), with ∼ 50 % unclassified phylotypes representing 'microbial dark matter'. High electric conductivity (332.1 µS cm-1) of PMM and the presence of Geobacter, syntrophs, and Methanosaeta suggest that direct interspecies electron transfer was likely occurring during anaerobic digestion. Both low and high-strength wastewaters showed effective removal of dissolved organics (e.g., naphthenic acids, acid extractable fraction, oil and grease content), nutrients, and potentially toxic metals. The successful use of PMM in treating oilfield produced water offers promising avenues for embracing nature-based remediation solutions at oil refining sites.

Chemical structure of hydrocarbons significantly affects removal performance and microbial responses in gas biotrickling filters.

The control of emissions of short-chain hydrocarbons with different structures is critical for the petrochemical industry. Herein, three two-carbon-containing (C2) hydrocarbons, ethane, ethylene, and acetylene, were chosen as pollutants to study the effects of chemical structure of hydrocarbons on removal performance and microbial responses in biotrickling filters. Results showed that the removal efficiency (RE) of C2 hydrocarbons followed the sequence of acetylene > ethane > ethylene. When the inlet loading rate was 30 g/(m3·h) and the empty bed residence time was 60 s, the RE of ethane, ethylene, and acetylene was 57 ± 4.0 %, 49 ± 1.0 %, and 84 ± 2.7 %, respectively. The high water solubility resulted in the high removal of C2 hydrocarbons, while a low surface tension enhanced the removal of C2 hydrocarbons. Additionally, the microbial community, enzyme activity, and extracellular properties of microorganisms also contributed to the difference in C2 hydrocarbon removal. These results could be referred for the effective control of light hydrocarbon emissions.

Removal of organic micropollutants in biologically active filters: A systematic quantitative review of key influencing factors.

Biofiltration utilizes natural mechanisms including biodegradation and biotransformation along with other physical processes for the removal of organic micropollutants (OMPs) such as pharmaceuticals, personal care products, pesticides and industrial compounds found in (waste)water. In this systematic review, a total of 120 biofiltration studies from 25 countries were analyzed, considering various biofilter configurations, source water types, biofilter media and scales of operation. The study also provides a bibliometric analysis to identify the emerging research trends in the field. The results show that granular activated carbon (GAC) either alone or in combination with another biofiltration media can remove a broad range of OMPs efficiently. The impact of pre-oxidation on biofilter performance was investigated, revealing that pre-oxidation significantly improved OMP removal and reduced the empty bed contact time (EBCT) needed to achieve a consistently high OMP. Biofiltration with pre-oxidation had median removals ranging between 65% and >90% for various OMPs at 10-45 min EBCT with data variability drastically reducing beyond 20 min EBCT. Biofiltration without pre-oxidation had lower median removals with greater variability. The results demonstrate that pre-oxidation greatly enhances the removal of adsorptive and poorly biodegradable OMPs, while its impact on other OMPs varies. Only 19% of studies we reviewed included toxicity testing of treated effluent, and even fewer measured transformation products. Several studies have previously reported an increase in effluent toxicity because of oxidation, although it was successfully abated by subsequent biofiltration in most cases. Therefore, the efficacy of biofiltration treatment should be assessed by integrating toxicity testing into the assessment of overall removal.

Deodorizing bacterial consortium: community analysis of biofilms and leachate water collected from an air biofiltration system in a piggery.

Intensive livestock production is a source of water, soil, and air contamination. The first aspect that negatively affects the quality of life of residents in the vicinity of piggeries is malodorous aerosols, which are not only responsible for discomfort but can be an etiological factor in the development of various diseases during prolonged exposure. One of the proven and efficient ways to counteract odor emissions is the usage of air biofiltration. The purpose of this study was to qualitatively analyze the bacterial community colonizing the biofilm of a biofilter operating at an industrial piggery in Switzerland. The study material consisted of biofilm and leachate water samples. The microbiological analysis consisted of DNA isolation, amplification of the bacterial 16S rRNA gene fragment (V3-V4), preparation of a library for high-throughput sequencing, high-throughput NGS sequencing, filtering of the obtained sequencing reads, and evaluation of the species composition in the studied samples. The investigation revealed the presence of the following bacterial genera: Pseudochelatococcus, Methyloversatilis, Flexilinea, Deviosia, Chryseobacterium, Kribbia, Leadbetterella, Corynebacterium, Flavobacterium, Xantobacter, Tessaracoccus, Staphylococcus, Thiobacillus, Enhydrobacter, Proteiniclasticum, and Giesbergeria. Analysis of the microbial composition of biofilters provides the opportunity to improve the biofiltration process.

Simultaneous removal of NOM and sulfate in a bioelectrochemical integrated biofilter treating reclaimed water.

Biofiltration is an environmentally 'green' technology that is compatible with the recently proposed sustainable development goals, and which has an increasingly important future in the field of water treatment. Here, we explored the impacts of bioelectrochemical integration on a bench-scale slow rate biofiltration system regarding its performance in reclaimed water treatment. Results showed that the short-term (<3 months) integration improved the removal of natural organic matter (NOM) (approximately 8.8%). After long-term (5 months and thereafter) integration, the cathodic charge transfer resistance was found to have a significant reduction from 2662 to 1350 Ω. Meanwhile, bioelectrochemical autotrophic sulfate (SO42-) reduction (over 27.6% reduction) through the syntrophic metabolism between hydrogen oxidation strains (genus Hydrogenophaga) and sulfate-reducing microbes (genera Dethiobacter, Desulfovibrio, and Desulfomicrobium) at the cathodic region was observed. More significantly, the microbial-derived chromophoric humic substances were found to act as electron shuttles at the cathodic region, which might facilitate the process of bioelectrochemical SO42- reduction. Overall, this study provided valuable insights into the potential application of bioelectrochemical-integrated biofilter for simultaneous reduction of NOM and SO42- treating reclaimed water.

Addition of (bio)surfactants in the biofiltration of hydrophobic volatile organic compounds in air.

The removal of volatile organic compounds (VOCs) in air is of utmost importance to safeguard both environmental quality and human well-being. However, the low aqueous solubility of hydrophobic VOCs results in poor removal in waste gas biofilters (BFs). In this study, we evaluated the addition of (bio)surfactants in three BFs (BF1 and BF2 mixture of compost and wood chips (C + WC), and BF3 filled with expanded perlite) to enhance the removal of cyclohexane and hexane from a polluted gas stream. Experiments were carried out to select two (bio)surfactants (i.e., Tween 80 and saponin) out of five (sodium dodecyl sulfate (SDS), Tween 80, surfactin, rhamnolipid and saponin) from a physical-chemical (i.e., decreasing VOC gas-liquid partitioning) and biological (i.e., the ability of the microbial consortium to grow on the (bio)surfactants) point of view. The results show that adding Tween 80 at 1 critical micelle concentration (CMC) had a slight positive effect on the removal of both VOCs, in BF1 (e.g., 7.0 ± 0.6 g cyclohexane m-3 h-1, 85 ± 2% at 163 s; compared to 6.7 ± 0.4 g cyclohexane m-3 h-1, 76 ± 2% at 163 s and 0 CMC) and BF2 (e.g., 4.3 ± 0.4 g hexane m-3 h-1, 27 ± 2% at 82 s; compared to 3.1 ± 0.7 g hexane m-3 h-1, 16 ± 4% at 82 s and 0 CMC), but a negative effect in BF3 at either 1, 3 and 9 CMC (e.g., 2.4 ± 0.4 g hexane m-3 h-1, 30 ± 4% at 163 s and 1 CMC; compared to 4.6 ± 1.0 g hexane m-3 h-1, 43 ± 8% at 163 s and 0 CMC). In contrast, the performance of all BFs improved with the addition of saponin, particularly at 3 CMC. Notably, in BF3, the elimination capacity (EC) and removal efficiency (RE) doubled for both VOCs (i.e., 9.1 ± 0.6 g cyclohexane m-3 h-1, 49 ± 3%; 4.3 ± 0.3 g hexane m-3 h-1, 25 ± 3%) compared to no biosurfactant addition (i.e., 4.5 ± 0.4 g cyclohexane m-3 h-1, 23 ± 3%; hexane 2.2 ± 0.5 g m-3 h-1, 10 ± 2%) at 82 s. Moreover, the addition of the (bio)surfactants led to a shift in the microbial consortia, with a different response in BF1-BF2 compared to BF3. This study evaluates for the first time the use of saponin in BFs, it demonstrates that cyclohexane and hexane RE can be improved by (bio)surfactant addition, and it provides recommendations for future studies in this field.

Engineering green wall botanical biofiltration to abate indoor volatile organic compounds: A review on mechanisms, phyllosphere bioaugmentation, and modeling.

Indoor air pollution affects the global population, especially in developed countries where people spend around 90% of their time indoors. The recent pandemic exacerbated the exposure by relying on indoor spaces and a teleworking lifestyle. VOCs are a group of indoor air pollutants with harmful effects on human health at low concentrations. It is widespread that plants can remove indoor VOCs. To this day, research has combined principles of phytoremediation, biofiltration, and bioremediation into a holistic and sustainable technology called botanical biofiltration. Overall, it is sustained that its main advantage is the capacity to break down and biodegrade pollutants using low energy input. This differs from traditional systems that transfer VOCs to another phase. Furthermore, it offers additional benefits like decreased indoor air health costs, enhanced work productivity, and well-being. However, many disparities exist within the field regarding the role of plants, substrate, and phyllosphere bacteria. Yet their role has been theorized; its stability is poorly known for an engineering approach. Previous research has not addressed the bioaugmentation of the phyllosphere to increase the performance, which could boost the system. Moreover, most experiments have studied passive potted plant systems at a lab scale using small chambers, making it difficult to extrapolate findings into tangible parameters to engineer the technology. Active systems are believed to be more efficient yet require more maintenance and knowledge expertize; besides, the impact of the active flow on the long term is not fully understood. Besides, modeling the system has been oversimplified, limiting the understanding and optimization. This review sheds light on the field's gains and gaps, like concepts, experiments, and modeling. We believe that embracing a multidisciplinary approach encompassing experiments, multiphysics modeling, microbial community analysis, and coworking with the indoor air sector will enable the optimization of the technology and facilitate its adoption.

Insights into the roles of biochar pores toward alleviating antibiotic resistance genes accumulation in biofiltration systems.

Biofiltration systems would harbor and spread various antibiotic resistance genes (ARGs) when treating antibiotic micro-pollution, constituting a potential ecological risk. This study aimed to investigate the effects of biochar pores on ARG emergence and related microbial response mechanisms in bench-scale biofiltration systems. Results showed that biochar pores effectively reduced the absolute copies of the corresponding ARGs sul1 and sul2 by 54.1% by lowering the sorbed-SMX's bioavailability compared to non-porous anthracite. An investigation of antimicrobial resistomes revealed a considerable decrease in the abundance and diversity of ARGs and mobile gene elements. Metagenomic and metaproteomic analysis demonstrated that biochar pores induced the changeover of microbial defense strategy against SMX from blocking SMX uptake by EPS absorbing to SMX biotransformation. Microbial SOS response, antibiotic efflux pump, EPS secretion, and biofilm formation were decreased. Functions related to SMX biotransformation, such as sadABC-mediated transformation, xenobiotics degradation, and metabolism, were significantly promoted.

Antibiotic resistance genes and the association with bacterial community in biofilms occurring during the drinking water granular activated carbon (GAC) sandwich biofiltration.

The granular activated carbon (GAC) sandwich modification to slow sand filtration could be considered as a promising technology for improved drinking water quality. Biofilms developed on sand and GAC surfaces are expected to show a functional diversity during the biofiltration. Bench-scale GAC sandwich biofilters were set-up and run continuously with and without antibiotic exposure. Surface sand (the schmutzdecke) and GAC biofilms were sampled and subject to high-throughput qPCR for antibiotic resistance gene (ARG) analysis and 16 S rRNA amplicon sequencing. Similar diversity of ARG profile was found in both types of biofilms, suggesting that all ARG categories decreased in richness along the filter bed. In general, surface sand biofilm remained the most active layer with regards to the richness and abundance of ARGs, where GAC biofilms showed slightly lower ARG risks. Network analysis suggested that 10 taxonomic genera were implicated as possible ARG hosts, among which Nitrospira, Methyloversatilis and Methylotenera showed the highest correlation. Overall, this study was the first attempt to consider the whole structure of the GAC sandwich biofilter and results from this study could help to further understand the persistence of ARGs and their association with the microbial community in drinking water biofiltration system.

Narrow host range phages infect essential bacteria for water purification reactions in groundwater-fed rapid sand filters.

Biofiltration is used worldwide to provide safe potable water due to its low energy demand and excellent treatment performance. For instance, in Denmark, over 95% of drinking water is supplied through groundwater-fed rapid sand filters (RSF). Bacteriophages, viruses that infect bacteria, have been shown to shape the taxonomic and functional composition of microbial communities across a range of natural and engineering systems. However, phages in the biofiltration systems are rarely studied, despite the central role microbes play in water purification. To probe this, metagenomic data from surface water, groundwater and mixed source water biofiltration units (n = 26 from China, Europe and USA) for drinking water production were analysed to characterize prokaryotic viruses and to identify their potential microbial hosts. The source water type and geographical location are found to exert influence on the composition of the phageome in biofilters. Although the viral abundance (71,676 ± 17,841 RPKM) in biofilters is only 14.4% and 17.0% lower than those of the nutrient-rich wastewater treatment plants and fresh surface waters, the richness (1,441 ± 1,046) and diversity (Inverse Simpson: 91 ± 61) in biofiltration units are significantly less by a factor of 2-5 and 3-4, respectively. In depth analysis of data from 24 groundwater-fed RSFs in Denmark revealed a core phageome shared by most RSFs, which was consistently linked to dominant microbial hosts involved in key biological reactions for water purification. Finally, the high number of specific links detected between phages and bacterial species and the large proportion of lytic phages (77%) led to the conjecture that phages regulate bacterial populations through predation, preventing the proliferation of dominant species and contributing to the established functional redundancy among the dominant microbial groups. In conclusion, bacteriophages are likely to play a significant role in water treatment within biofilters, particularly through interactions with key bacterial species.

Betaproteobacteria are a key component of surface water biofilters that maintain sustained manganese removal in response to fluctuations in influent water temperature.

The health risks associated with manganese (Mn) in drinking water, and an improved understanding of Mn accumulation within, and subsequent release from, distribution systems, have increased the need for robust, sustainable treatment options to minimize Mn concentrations in finished water. Biofiltration is an established and effective method to remove Mn in groundwater however, Mn removal in surface water biofilters is an emerging treatment process that has not been extensively studied. Seasonal variations in water temperature can present an operational challenge for surface water biofilters which may see reduced Mn removal under colder conditions. This study examined the microbiomes of surface water biofilters at three utilities (ACWD WTP, WTP B, and WTP D) which all experienced similar seasonal fluctuations in influent water temperature. High Mn removal was observed at the ACWD WTP for much of the year, but Mn removal decreased with a concurrent decrease in the influent water temperature (58% ± 22%). In contrast, both WTP B and WTP D achieved year-round Mn removal (84% ± 5% and 93% ± 8% respectively). Marker gene (16S rRNA) sequencing analysis of the biofilter microbiomes identified a high abundance of Betaproteobacteria in WTP B and WTP D (37% ± 12% and 21% ± 3% respectively), but a low abundance of Betaproteobacteria in the ACWD WTP (2% ± 2%). The microbiomes of new bench-scale biofilters, in operation at the ACWD WTP, were also investigated. The abundance of Betaproteobacteria was significantly greater (p < 0.05) after the biofilters had acclimated than before acclimation, and differential abundance analysis identified 6 genera within the Betaproteobacteria class were enriched in the acclimated microbiome. Additionally, the acclimated biofilters were able to maintain high Mn removal performance (87% ± 10%) when the influent water temperature decreased to 10 °C or less. Further analysis of previously published studies found the abundance of Betaproteobacteria was also significantly greater (p < 0.001) in biofilters with sustained Mn removal than in biofilters which did not treat for Mn as a contaminant, despite differences in design scale, source water, and media type. Microbiome network analysis identified multiple co-occurrence relationships between Betaproteobacteria and Mn oxidizing bacteria in the WTP B and WTP D biofilters, suggesting indirect contributions by Betaproteobacteria to biological Mn oxidation. These co-occurrence relationships were not present in the full-scale ACWD WTP microbiome. Whether the role of Betaproteobacteria in biological Mn oxidation is direct, indirect, or a combination of both, they are consistently present at a high abundance in both groundwater and surface water biofilters with sustained Mn removal, and their absence may contribute to the seasonal fluctuations in Mn removal observed at the ACWD WTP. This new insight to Betaproteobacteria and their role in Mn biofiltration could contribute to water innovation and design that would improve the reliability of Mn removal.

Species-specific influence of powdery mildew mycelium on the efficiency of PM accumulation by urban greenery.

Particulate matter (PM) is one of the most important air pollutants, especially in urban areas. The efficiency of PM biofiltration by plants depends on the morphological features of the foliage. More PM is deposited on complex leaves, covered with thick wax layer, trichomes, epidermal glands, and convex venation. Very few literature reports suggest that also the presence of mycelium of nonparasitic and saprophytic fungi positively affects the accumulation of PM on the leaves. In this work, to our best knowledge, for the first time the effect of the mycelium of the parasitic powdery mildew on the efficiency of PM accumulation by urban greenery was studied. Uninfested and fungus-infested leaves of Acer negundo L., Malus domestica Borkh Quercus robur L., and Berberis vulgaris L. were harvested in July in the center of Warsaw city. The effect of powdery mildew infection on PM accumulation was species-specific. A higher amount of PM on leaves not infected with powdery mildew was found in M. domestica and Q. robur, while in A. negundo and B. vulgaris more PM was accumulated on leaves infected with fungus. All species (except A. negundo) accumulated more of the PM of 0.2-2.5-µm and 2.5-10-µm size fractions on leaves not infected with powdery mildew. One of the greatest consequences of the presence of powdery mildew mycelium on the foliage is most probably reduction of the direct involvement of waxes in PM accumulation and retention processes.

Impacts of freshwater mussels on planktonic communities and water quality.

Live Freshwater Mussels (FMs) have remarkable characteristics to support other species and the ecosystem. The objective of the study was to identify the planktonic composition; dye absorbance by living FMs; analyze the water quality indicators; and determine the heavy metals from FMs of different rivers in Bangladesh. In order to assess the planktonic composition, planktons were collected from the experimental ponds and then identified under the microscope. Methyl blue (MB) and methyl red (MR) dye absorbance were assessed using live FMs. After co-cultivating Silver barb (Barbonymus gonionotus) with FMs, water quality indicators (including pH, DO, hardness, total dissolved solids, ammonia, nitrite, and nitrate) were recorded. For determining heavy metals (Cu, Cr, Cd, Pb, Zn), mussels (Lamellidens marginalis) samples were collected from different rivers of Bangladesh. The findings of the study showed that the planktons were significantly (p < 0.01) greater in the 'Fish' group, compared to the 'Mussels' and 'Mussels + Fish' groups. Also, the MB and MR dye absorption were significantly higher (p < 0.01) in mussels, indicating that live FMs can accumulate hazardous dyes. Furthermore, the hardness value in the 'Mussels' and 'Mussels + Fish' groups were significantly (p < 0.01) greater than in the 'Fish' group. In addition, the values of nitrite and nitrate in the 'Fish' group were also significantly (p < 0.05) greater than those in the 'Mussels + Fish' group. The heavy metals content in the mussels of the Buriganga river was significantly (p < 0.05) higher compared to the mussels of the Rupsha and Brahmaputra rivers. This study revealed that the live FMs have the profound potential to consume plankton, absorb hazardous wastewater dyes, and maintain good water quality which may serve as the ecological indicators in freshwater environment.

Transformation from biofiltration unit to hybrid constructed wetland-microbial fuel cell: Improvement of wastewater treatment performance and energy recovery.

This study aimed to compare the performance of biofiltration, constructed wetland, and constructed wetland microbial fuel cell (CW-MFC). The transformation from a biofiltration unit to a hybrid CW-MFC was demonstrated with the advantages of improvement of wastewater treatment while generating electricity simultaneously. The introduction of plants to the upper region of the bioreactor enhanced the DO level by 0.8 mg/L, ammonium removal by 5 %, and COD removal by 1 %. The integration of electrodes and external circuits stimulated the degradation rate of organic matter in the anodic region (1 % without aeration and 3 % with aeration) and produced 5.13 mW/m3 of maximum power density. Artificial aeration improved the nitrification efficiency by 38 % and further removed the residual COD to an efficiency of 99 %. The maximum power density was also increased by 3.2 times (16.71 mW/m3) with the aid of aeration. In treating higher organic loading wastewater (3M), the maximum power density showed a significant increment to 78.01 mW/m3 (4.6-fold) and the COD removal efficiency was 98 %. The ohmic overpotential dominated the proportion of total loss (67-91 %), which could be ascribed to the low ionic conductivity. The reduction in activation and concentration loss contributed to the lower internal resistance with the additional aeration and higher organic loading. Overall, the transformation from biofiltration to a hybrid CW-MFC system is worthwhile since the systems quite resemble while CW-MFC could improve the wastewater treatment as well as recover energy from the treated wastewater.

The Minus Approach Can Redefine the Standard of Practice of Drinking Water Treatment.

Chlorine-based disinfection for drinking water treatment (DWT) was one of the 20th century's great public health achievements, as it substantially reduced the risk of acute microbial waterborne disease. However, today's chlorinated drinking water is not unambiguously safe; trace levels of regulated and unregulated disinfection byproducts (DBPs), and other known, unknown, and emerging contaminants (KUECs), present chronic risks that make them essential removal targets. Because conventional chemical-based DWT processes do little to remove DBPs or KUECs, alternative approaches are needed to minimize risks by removing DBP precursors and KUECs that are ubiquitous in water supplies. We present the "Minus Approach" as a toolbox of practices and technologies to mitigate KUECs and DBPs without compromising microbiological safety. The Minus Approach reduces problem-causing chemical addition treatment (i.e., the conventional "Plus Approach") by producing biologically stable water containing pathogens at levels having negligible human health risk and substantially lower concentrations of KUECs and DBPs. Aside from ozonation, the Minus Approach avoids primary chemical-based coagulants, disinfectants, and advanced oxidation processes. The Minus Approach focuses on bank filtration, biofiltration, adsorption, and membranes to biologically and physically remove DBP precursors, KUECs, and pathogens; consequently, water purveyors can use ultraviolet light at key locations in conjunction with smaller dosages of secondary chemical disinfectants to minimize microbial regrowth in distribution systems. We describe how the Minus Approach contrasts with the conventional Plus Approach, integrates with artificial intelligence, and can ultimately improve the sustainability performance of water treatment. Finally, we consider barriers to adoption of the Minus Approach.

Prolonged operation of a methane biofilter from acclimation to the failure stage.

Global warming needs immediate attention to reduce major greenhouse gas emissions such as methane (CH4). Bio-oxidation of dilute CH4 emissions in packed-bed bioreactors such as biofilters has been carried out over recent years at laboratory and large scales. However, a big challenge is to keep CH4 biofilters running for a long period. In this study, a packed-bed lab-scale bioreactor with a specialized inorganic-based filter bed was successfully operated over four years for CH4 elimination. The inoculation of the bioreactor was the active leachate of another CH4 biofilter which resulted in a fast acclimation and removal efficiency (RE) reached 80% after seven weeks of operation for CH4 inlet concentrations ranging from 700 to 800 ppmv and an empty bed residence time (EBRT) of 6 min. During four years of operation, the bioreactor often recorded REs higher than 65% for inlet concentrations in the range of 1900-2200 ppmv and an EBRT of 6 min. The rate and interval of the nutrient supply played an important role in maintaining the bioreactor's high performance over the long operation. Forced shutdowns were unavoidable during the 4-year operation and the bioreactor fully tolerated them with a partial recovery within one week and a progressive recovery over time. In the end, the bioreactor's filter bed started to deteriorate due to a long shutdown of twelve weeks and the extended operation of four years when the RE dropped to below 8% with no sign of returning to its earlier performance.

Control of odor emissions from livestock farms: A review.

Odor emission seriously affects human and animal health, and the ecological environment. Nevertheless, a systematic summary regarding the control technology for odor emissions in livestock breeding is currently lacking. This paper summarizes odor control technology, highlighting its applicability, advantages, and limitations, which can be used to evaluate and identify the most appropriate methods in livestock production management. Odor control technologies are divided into four categories: dietary manipulation (low-crude protein diet and enzyme additives in feed), in-housing management (separation of urine from feces, adsorbents used as litter additive, and indoor environment/manure surface spraying agent), manure management (semi-permeable membrane-covered, reactor composting, slurry cover, and slurry acidification), and end-of-pipe measures for air treatment (wet scrubbing of the exhaust air from animal houses and biofiltration of the exhaust air from animal houses or composting). Findings of this paper provide a theoretical basis for the application of odor control technology in livestock farms.

Long-term biofiltration of gaseous N,N-dimethylformamide: Operational performance and microbial diversity analysis at different conditions.

N,N-Dimethylformamide (DMF) is an organic solvent produced in large quantities worldwide. It is considered as a hazardous air pollutant and its emission should be controlled. However, only a limited number of studies have been performed on the removal of gaseous DMF by biological technologies. In this paper, we evaluate the removal of DMF under mesophilic and thermophilic conditions in a lab-scale biofilter for 472 days. The results show that, at ambient temperature, the biofilter achieved an average removal efficiency (RE) of 99.7 ± 0.3 % at Inlet Loads (ILs) up to 297 ± 52 g DFM m-3 h-1 (Empty Bed Residence Time (EBRTs) of 10.7 s). However, a decrease in EBRT (6.4 s) led to an unstable outlet concentration and, thus, to a drop in the biofilter performance (average RE: 90 ± 9 %). Moreover, an increase in temperature up to 65 °C led to a gradual decrease in RE (till 91 ± 7 %). Microbial analysis indicates that once the microorganisms encountered DMF, Rhizobiaceae dominated followed by Alcaligenaceae. Afterwards, a strong decrease in Rhizobiaceae was observed at every increase in temperature, and at 65 °C, the taxa were more heterogeneous. Overall, our experimental results indicate that biofiltration is a promising technique to remove DMF from waste gas streams.

Pilot-scale biofiltration of 1,4-dioxane at drinking water-relevant concentrations.

1,4-Dioxane is a drinking water contaminant of emerging concern. Because conventional and many advanced drinking water treatment technologies are ineffective for 1,4-dioxane removal, cost-effective technologies for the removal of 1,4-dioxane at drinking water-relevant concentrations are needed. In this research, a gravity-fed, cometabolic biofiltration system was developed to degrade 1,4-dioxane that was spiked into coagulated, settled surface water at a concentration of ∼10 µg/L. Objectives were to determine whether cometabolic degradation of trace levels of 1,4-dioxane can be sustained using n-butane as primary substrate and whether filter media properties and empty bed contact time (EBCT) affect biofiltration efficiency. A mixed culture of bacteria derived from the Cape Fear River basin and previously enriched using isobutane served as inoculum for biologically active filters. Two granular activated carbons (GACs) with different grain sizes and one carbonaceous resin were used as attachment media, and n-butane served as the primary substrate for biologically active filters. Non-inoculated controls with the same media were evaluated in parallel to distinguish between biological and adsorptive removals of 1,4-dioxane. For the duration of the pilot study (>3 months), 1,4-dioxane was degraded in inoculated biofilters receiving n-butane. In control filters containing larger and smaller grain GAC, 1,4-dioxane broke through completely within 750 and 1250 bed volumes, respectively, corresponding to 15 to 30 days of operation at an EBCT of 30 min. 1,4-Dioxane removal increased with increasing EBCT in all biologically active filters. At an EBCT of 30 min, the biologically active GAC filter containing the larger-grain GAC removed on average 87% of 1,4-dioxane at pseudo steady-state. When the hydraulic loading rate was decreased to achieve an overall EBCT of 60 min, 1,4-dioxane was removed to <1 µg/L in the biologically active GAC filter containing the larger-grain GAC. Activity-based labeling showed the presence of catalytically active monooxygenases in backwash water from biologically active filters that degraded 1,4-dioxane. Amplicon sequencing results showed that while taxa shifted after the initial inoculation of biologically active filters, taxa in biologically active filters remained more similar to the inoculum than those in the non-inoculated control filters. Overall, results of this research demonstrate that cometabolic degradation of 1,4-dioxane at trace levels is possible for extended periods of time in inoculated biofilters that receive n-butane as primary substrate.