Low cost materials for fluoride removal from groundwater.

In several parts of the world, high fluoride concentrations in groundwater have been reported.Fluoride concentrations above the World Health Organization's (WHO) threshold level of 1.5 mg/L in drinkable water pose a health concern for communities and the environment. The distribution of fluoride is mainly related to the geological environment: rocks that contain fluorine, for example basalt, shale, and granite, release their respective minerals containing fluoride to the groundwater by dissolution. Excessive fluoride intake leads to dental and skeletal fluorosis, fragile bones, cancer, infertility, damage to the brain function, Alzheimer syndrome, and thyroid disorder. Cheap, abundant, and locally available fluoride removal techniques are needed to meet the requirement for fluoride-free drinking water in developing countries, especially in rural communities. Different conventional methods, such as membrane technologies, ion exchange, coagulation and precipitation techniques, are employed to remove fluoride from drinking water. However, only a few of these techniques can be applied at large-scale in developing countries due to their high investment costs, high maintenance and operating costs, and the possibility of producing toxic intermediates during the treatment process. Unlike conventional methods, adsorption is a promising technology due to its simple operation in a batch or continuous systems, simple design, low-cost of operation and wide range of locally available adsorbents. Adsorption is widely applied for removing fluoride from groundwater and wastewater, effectively maintaining water quality and taste. Based on the review, adsorption stands out as the best method for fluoride removal, considering surface modification and regeneration to increase the efficiency of adsorbent materials. This makes it an ideal solution for ensuring safe drinking water in resource-limited settings.

Auranofin loaded silk fibroin nanoparticles for colorectal cancer treatment.

Colorectal cancer (CRC) is the second most common cause of cancer related deaths worldwide and the prevalence in young people especially is increasing annually. In the search for innovative approaches to treat the disease, drug delivery systems (DDS) are promising owing to their unique properties, which allow improved therapeutic results with lower drug concentrations, overcoming drug resistance and at the same time potentially reducing side effects. Silk fibroin is a biopolymer that can be processed to obtain biocompatible and biodegradable nanoparticles that can be efficiently loaded by surface adsorption with small-molecule therapeutics and allow their transport and sustained release by modulating their pharmacokinetics. Auranofin (AF) has recently been repurposed for its strong anticancer activity and is currently in clinical trials. Its mechanism of action is through the inhibition of thioredoxin reductase enzymes, which play an essential role in several intracellular processes and are overexpressed in some tumours. Taking into account that AF has a low solubility in water, we propose silk fibroin nanoparticles (SFN) as AF carrier in order to improve its bioavailability, increasing cellular absorption and preventing its degradation or avoiding some resistance mechanisms. Here we report the preparation and characterization of a new formulation of AF-loaded silk fibroin nanoparticles (SFN-AF), its functionalization with FITC for the analysis of cellular uptake, as well as its cytotoxic activity against cell lines of human colorectal cancer (HT29 and HCT116) in both 2D and 3D cell cultures. 3D spheroid models provide a 3D environment which mimics the 3D aspects of CRC observed in vivo and represents an effective 3D environment to screen therapeutics for the treatment of CRC. The loaded nanoparticles showed a spherical morphology with a hydrodynamic diameter of ~ 160 nm and good stability in aqueous solution due to their negative surface charges. FESEM-EDX analysis revealed a homogeneous distribution of Au clusters with high electron density on the surface of the nanoparticles. SFN-AF incubated in phosphate buffer at 37 °C released 77% of the loaded AF over 10 days, showing an initial burst and then sustained release. Flow cytometry analysis showed that FITC-SFN-AF was efficiently internalized by both cell lines, which was confirmed by confocal microscopy imaging. SFN enhanced the cytotoxicity of AF in 2D cultures in both CRC lines. Promising results were also obtained in 3D culture paving the way for future application of this strategy as a therapy for CRC.

Enhanced pollution removal from canal water by coupling aeration to floating treatment wetlands.

Floating treatment wetlands (FTWs) are natural solutions for purifying polluted water, providing a green surface area and improving city landscape. This study investigated if the efficiency of FTWs can be improved by aeration for treating contaminated canal water. The three used plant species were Canna generalis, Phragmites australis, and Cyperus alternifolius. The experiment was carried out in three FTWs with aeration and three without aeration to compare the removal for COD, NH4+-N, E. coli, PO43--P, and Fe. In the aerated FTWs, air blowers were installed to run at two different air flow rates of 2.5 L min-1 (Batch 1) and 1.0 L min-1 (Batch 2). Aeration increased the dissolved oxygen concentrations in each tank, which came over 6.5 mg L-1 in both batches. This study sheds light on the positive impact of aeration has on COD and NH4+-N removal: these are nearly three-fold higher compared to non-aeration conditions and reached approximately 99% (1.7-log reduction) for E. coli removal. Additionally, the plant growth rate in the aerated FTWs was higher than in the non-aerated ones. The average shoot growth rate of Phragmites australis was 0.76 cm d-1 for the aerated FTW which was two-fold higher compared to the non-aerated one.

This article investigates the treatment performance of Floating Treatment Wetlands (FTWs) coupled with aeration to reduce the diffuse pollution in canal water. The results showed that the aeration enhanced the treatment of organics and nutrients, and the plant growth of the aerated FTWs was two-fold higher than that of non-aerated FTWs, which has a phytoremediation potential for treating canal water in Ho Chi Minh city.

Disentangling abiotic and biotic effects of treated wastewater on stream biofilm resistomes enables the discovery of a new planctomycete beta-lactamase.

BACKGROUND: Environmental reservoirs of antibiotic resistance pose a threat to human and animal health. Aquatic biofilms impacted by wastewater effluent (WW) are known environmental reservoirs for antibiotic resistance; however, the relative importance of biotic factors and abiotic factors from WW on the abundance of antibiotic resistance genes (ARGs) within aquatic biofilms remains unclear. Additionally, experimental evidence is limited within complex aquatic microbial communities as to whether genes bearing low sequence similarity to validated reference ARGs are functional as ARGs. RESULTS: To disentangle the effects of abiotic and biotic factors on ARG abundances, natural biofilms were previously grown in flume systems with different proportions of stream water and either ultrafiltered or non-ultrafiltered WW. In this study, we conducted deep shotgun metagenomic sequencing of 75 biofilm, stream, and WW samples from these flume systems and compared the taxonomic and functional microbiome and resistome composition. Statistical analysis revealed an alignment of the resistome and microbiome composition and a significant association with experimental treatment. Several ARG classes exhibited an increase in normalized metagenomic abundances in biofilms grown with increasing percentages of non-ultrafiltered WW. In contrast, sulfonamide and extended-spectrum beta-lactamase ARGs showed greater abundances in biofilms grown in ultrafiltered WW compared to non-ultrafiltered WW. Overall, our results pointed toward the dominance of biotic factors over abiotic factors in determining ARG abundances in WW-impacted stream biofilms and suggested gene family-specific mechanisms for ARGs that exhibited divergent abundance patterns. To investigate one of these specific ARG families experimentally, we biochemically characterized a new beta-lactamase from the Planctomycetota (Phycisphaeraceae). This beta-lactamase displayed activity in the cleavage of cephalosporin analog despite sharing a low sequence identity with known ARGs. CONCLUSIONS: This discovery of a functional planctomycete beta-lactamase ARG is noteworthy, not only because it was the first beta-lactamase to be biochemically characterized from this phylum, but also because it was not detected by standard homology-based ARG tools. In summary, this study conducted a metagenomic analysis of the relative importance of biotic and abiotic factors in the context of WW discharge and their impact on both known and new ARGs in aquatic biofilms. Video Abstract.

Mechanisms underlying the detrimental impact of micro(nano)plastics on the stability of aerobic granular sludge: Interactions between micro(nano)plastics and extracellular polymeric substances.

Microplastics (MPs) and nanoplastics (NPs) present in wastewater can pose a negative impact to aerobic granular sludge (AGS). Herein, this study found that MPs and NPs (20 mg/L) deteriorated the sludge settleability and granule integrity, resulting in a 15.7 % and 21.9 % decrease in the total nitrogen removal efficiency of the AGS system, respectively. This was possibly due to the reduction of the extracellular polymeric substances (EPS) content. The subsequent analysis revealed that tyrosine, tryptophan, and humic acid-like substances in EPS exhibited a higher propensity for chemisorption and inhomogeneous multilayer adsorption onto NPs compared to MPs. The binding of EPS onto the surface of plastic particles increased the electronegativity of the MPs, but facilitated the aggregation of NPs through reducing the electrostatic repulsion, thereby mitigating the adverse effects of MPs/NPs on the AGS stability. Additionally, comprehensive analysis of the extended Derjaguin-Landau-Verwey-Overbeek theory indicated that the suppressed aggregation of microorganisms was the internal mechanisms contributing to the inadequate stability of AGS induced by MPs/NPs. This study provides novel insights into the detrimental mechanisms of MPs/NPs on the AGS stability, highlighting the key role of EPS in maintaining the structural stability of AGS when exposed to MPs/NPs.

Microbial response to the chronic toxicity effect of graphene and graphene oxide nanomaterials within aerobic granular sludge systems.

Nanomaterials present in wastewater can pose a significant threat to aerobic granular sludge (AGS) systems. Herein, we found that compared to graphene nanomaterials (G-NMs), the long-term presence (95 days) of graphene oxide nanomaterials (GO-NMs) resulted in an increased proliferation of filamentous bacteria, poorer sedimentation performance (SVI30 of 74.1 mL/g) and smaller average particle size (1224.4 µm) of the AGS. In particular, the GO-NMs posed a more significant inhibitory effect to the total nitrogen removal efficiency of AGS (decreased by 14.3 %), especially for the denitrification process. The substantial accumulation of GO-NMs within the sludge matrix resulted in a higher level of reactive oxygen species in AGS compared to G-NMs, thereby inducing lactate dehydrogenase release, and enhancing superoxide oxidase and catalase activities. Such excessive oxidative stress could potentially result in a significant reduction in the activity of nitrogen metabolism enzymes (e.g., nitrate reductase and nitrite reductase) and the expression of key functional genes (e.g., nirS and nirK). Altogether, compared to G-NMs, prolonged exposure to GO-NMs had a more significant chronic toxicity effect on AGS systems. These findings implied that the presence of G-NMs and GO-NMs is a hidden danger to biological nitrogen removal and should receive more attention.

Deciphering the role of micro/nano-hydroxyapatite in aerobic granular sludge system: Effects on treatment performance and enhancement mechanism.

Hydroxyapatite (HAP), a mineral nucleus identified within aerobic granular sludge (AGS), plays a vital role in enhancing the AGS systems. However, the microscopic mechanism underlying their roles remains largely unexplored. Herein, a systematic investigation was carried out to elucidate the impact and enhanced mechanisms associated with HAP of different sizes, i.e. micro-HAP (mHAP) and nano-HAP (nHAP), on the aerobic granulation, nutrient removal and microbial diversity of AGS. Results showed that the presence of nHAP and mHAP significantly shortened the granulation process to 15 and 20 days, respectively. This might be ascribed to the fact that the large specific surface area of nHAP aggregates was conducive to microbial adhesion, biomass accumulation and sludge granulation. Compared with mHAP, the granules with nHAP showed better settlement performance, mechanical strength and larger diameter. The X-ray diffraction (XRD) and Raman spectrometer analysis confirmed the presence of HAP within the granules, which was found to stimulate the secretion of extracellular polymeric substance, improve the compactness of granule structure and suppress the growth of filamentous bacteria, thereby contributing to a stable AGS system. The presence of HAP, especially nHAP, effectively enriched the functional microorganisms, such as nitrifying and denitrifying bacteria (e.g. Candidatus_Competibacter) and phosphorus accumulating organisms (e.g. Flavobacterium), leading to the improved nutrient removal efficiencies (COD > 96%, TN > 76%, and TP > 74%). Further analysis revealed the up-regulation of functional enzymes (e.g. nitrite oxidoreductase and polyphosphate kinase) involved in nutrient metabolism, underlying the inherent mechanisms for the excellent nutrient removal. This study deepens the understanding of granulation mechanisms from the perspective of mineral cores, and proposes an economically feasible strategy for rapid initiation and stabilization of AGS reactors.

Floating treatment wetlands to improve the water quality of the Hang Bang canal, Ho Chi Minh City, Vietnam: Effect of plant species.

Floating treatment wetlands (FTWs) are artificial platforms that allow aquatic emergent plants to grow in water. Aquatic macrophytes and microorganisms attached to plant roots contribute to the remediation of the contaminated water through physicochemical and biological processes. The pollutant removal treatment performance is affected by various factors, including the plant species. In this study, several plant species, i.e. Canna generalis, Phragmites australis, Pennisetum purpureum, Cyperus alternifolius rottb, Kyllinga brevifolia rottb, and Cyperus ordoratus were investigated for their potential to clean-up water from the Hang Bang canal in Ho Chi Minh City (Vietnam). Canna generalis, Phragmites australis, and Cyperus alternifolius were found to be suitable for FTWs with the highest performance compared to that of other plant species investigated. The organic and nitrogen removal rates amounted to 48-70 g COD m-3 d-1 and 0.7-1.2 g N m-3 d-1, respectively, whereas the reduction of pathogens was around 1.86-3.00 log. Furthermore, FTW systems bring other benefits such as improving ecosystem functioning and biodiversity, producing value-added products from plant biomass, as well as attracting the attention of communities, thus increasing social acceptance of environmental technology interventions.

Nitrate Chemodenitrification by Iron Sulfides to Ammonium under Mild Conditions and Transformation Mechanism.

Autotrophic denitrification utilizing iron sulfides as electron donors has been well studied, but the occurrence and mechanism of abiotic nitrate (NO3-) chemodenitrification by iron sulfides have not yet been thoroughly investigated. In this study, NO3- chemodenitrification by three types of iron sulfides (FeS, FeS2, and pyrrhotite) at pH 6.37 and ambient temperature of 30 °C was investigated. FeS chemically reduced NO3- to ammonium (NH4+), with a high reduction efficiency of 97.5% and NH4+ formation selectivity of 82.6%, but FeS2 and pyrrhotite did not reduce NO3- abiotically. Electrochemical Tafel characterization confirmed that the electron release rate from FeS was higher than that from FeS2 and pyrrhotite. Quenching experiments and density functional theory calculations further elucidated the heterogeneous chemodenitrification mechanism of NO3- by FeS. Fe(II) on the FeS surface was the primary site for NO3- reduction. FeS possessing sulfur vacancies can selectively adsorb oxygen atoms from NO3- and water molecules and promote water dissociation to form adsorbed hydrogen, thereby forming NH4+. Collectively, these findings suggest that the NO3- chemodenitrification by iron sulfides cannot be ignored, which has great implications for the nitrogen, sulfur, and iron cycles in soil and water ecosystems.

Lactic acid fermentation of food waste at acidic conditions in a semicontinuous system: effect of HRT and OLR changes.

Lactic acid production through fermentation is an established technology, however, improvements are necessary to reduce the process costs and to decrease its market price. Lactic acid is used in many industrial sectors and its market has increased in the last decade for its use as the raw material for polylactic acid product. Using food waste as a cheap and renewable substrate, as well as fermentation at uncontrolled pH, helps to make the production cheaper and to simplify the downstream purification process. Lactic acid production at acidic conditions and the role of varying organic loading rate (OLR) and hydraulic retention time (HRT) were tested in two different semicontinuous batch fermentation systems. Reactor performances indicated that lactic acid fermentation was still possible at pH < 3.5 and even up to a pH of 2.95. The highest lactic acid production was recorded at 14-day HRT, 2.14 g VS/L·day OLR, and pH 3.11 with a maximum lactic acid concentration of 8.72 g/L and a relative yield of 0.82 g lactate/g carbohydrates. The fermentation microbial community was dominated by Lactobacillus strains, the organism mainly responsible for lactic acid conversion from carbohydrates. This study shows that low pH fermentation is a key parameter to improve lactic acid production from food waste in a semicontinuous system. Acidic pH favored both the selection of Lactobacillus strains and inhibited VFA producers from utilizing lactic acid as primary substrate, thus promoting the accumulation of lactic acid. Finally, production yields tend to decrease with high OLR and low HRT, while lactic acid production rates showed the opposite trend.

Effect of Rhodococcus opacus PD630 on selenium phytoremediation by Brassica oleracea.

The purpose of this study was to evaluate the potential of microbial-enhanced Brassica oleracea for the phytoremediation of seleniferous soils. The effect of selenite (Se(IV)) and selenate (Se(VI)) on B. oleracea (1-100 mg.L-1) was examined through germination (7 d) and pot (30 d) trials. Microbial analysis was conducted to verify the toxic effect of various Se concentrations (1-500 mg.L-1) on Rhodococcus opacus PD360, and to determine if it exhibits plant growth promoter traits. R. opacus PD630 was found to tolerate high concentrations of both Se(IV) and Se(VI), above 100 mg.L-1. R. opacus PD630 reduced Se(IV) and Se(VI) over 7 days, with a Se conversion efficiency between 60 and 80%. Germination results indicated lower concentrations (0-10 mg.L-1) of Se(IV) and Se(VI) gave a higher shoot length (> 4 cm). B. oleracea accumulated 600-1,000 mg.kg-1 dry weight (DW) of Se(IV) and Se(VI), making it a secondary accumulator of Se. Moreover, seeds inoculated with R. opacus PD360 showed increased Se uptake (up to 1,200 mg Se.kg-1 DW). In addition, bioconcentration and translocation factors were greater than one. The results indicate a synergistic effect between R. opacus PD630 and B. oleracea for Se phytoextraction from polluted soils.

This article examines how Brassica oleracea may be used to improve seleniferous soils and how Rhodococcus opacus can be added to increase biofortification. The research shows great potential for combining Brassica species with bacterial isolates to remove selenium from heavily contaminated soils.

Selenite (IV) and selenate (VI) uptake and accumulation capacity of Lemna minor L. from an aquatic medium.

The uptake of sodium selenite (Se(IV)) and sodium selenate (Se(VI)) from aqueous medium by Lemna minor L. and the influence of different Se concentrations on its growth, morphological and ultrastructural characteristics were studied. L. minor was grown at different concentrations (1, 3, 5 and 10 mg L-1) of Se(IV) and Se(IV). The Se(IV) concentration in the plant tissue ranged between 77.7 (± 4.3) to 453 (± 0) mg kg-1 DW. The Se(VI) concentration in plant tissues ranged between 117 (± 11) to 417 (± 2) mg kg-1 DW. The highest bioconcentration factor for Se(VI) was 127 (± 7) at 3 mg/L, with a Se removal efficiency of 44%. For Se(IV), the highest bioconcentration factor was 77.7 (± 4.3) at 1 mg L-1, which had a Se removal efficiency of 23%. Growth of L. minor was suppressed at 10 mg L-1 Se in both forms. The addition of Se promoted the formation of starch granules in L. minor which occupied a chloroplast area of 74% for Se(IV) and 77% for Se(VI). The efficient uptake of both Se forms by L. minor indicates the potential application of this species for phytoremediation of Se laden wastewaters and its use as an alternative feedstock in biofuel production.

Effect of copper, arsenic and nickel on pyrite-based autotrophic denitrification.

Pyritic minerals generally occur in nature together with other trace metals as impurities, that can be released during the ore oxidation. To investigate the role of such impurities, the presence of copper (Cu(II)), arsenic (As(III)) and nickel (Ni(II)) during pyrite mediated autotrophic denitrification has been explored in this study at 30 °C with a specialized microbial community of denitrifiers as inoculum. The three metal(loid)s were supplemented at an initial concentration of 2, 5, and 7.5 ppm and only Cu(II) had an inhibitory effect on the autotrophic denitrification. The presence of As(III) and Ni(II) enhanced the nitrate removal efficiency with autotrophic denitrification rates between 3.3 [7.5 ppm As(III)] and 1.6 [7.5 ppm Ni(II)] times faster than the experiment without any metal(loid) supplementation. The Cu(II) batches, instead, decreased the denitrification kinetics with 16, 40 and 28% compared to the no-metal(loid) control for the 2, 5 and 7.5 ppm incubations, respectively. The kinetic study revealed that autotrophic denitrification with pyrite as electron donor, also with Cu(II) and Ni(II) additions, fits better a zero-order model, while the As(III) incubation followed first-order kinetic. The investigation of the extracellular polymeric substances content and composition showed more abundance of proteins, fulvic and humic acids in the metal(loid) exposed biomass.

Deciphering anaerobic ethanol metabolic pathways shaped by operational modes.

Efficient anaerobic digestion requires the syntrophic cooperation among diverse microorganisms with various metabolic pathways. In this study, two operational modes, i.e., the sequencing batch reactor (SBR) and the continuous-flow reactor (CFR), were adopted in ethanol-fed systems with or without the supplement of powdered activated carbon (PAC) to examine their effects on ethanol metabolic pathways. Notably, the operational mode of SBR and the presence of CO2 facilitated ethanol metabolism towards propionate production. This was further evidenced by the dominance of Desulfobulbus, and the increased relative abundances of enzymes (EC: 1.2.7.1 and 1.2.7.11) involved in CO2 metabolism in SBRs. Moreover, SBRs exhibited superior biomass-based rates of ethanol degradation and methanogenesis, surpassing those in CFRs by 53.1% and 22.3%, respectively. Remarkably, CFRs with the extended solids retention time enriched high relative abundances of Geobacter of 71.7% and 70.4% under conditions with and without the addition of PAC, respectively. Although both long-term and short-term PAC additions led to the increased sludge conductivity and a reduced methanogenic lag phase, only the long-term PAC addition resulted in enhanced rates of ethanol degradation and propionate production/degradation. The strategies by adjusting operational mode and PAC addition could be adopted for modulating the anaerobic ethanol metabolic pathway and enriching Geobacter.

New insights into syntrophic ethanol oxidation: Effects of operational modes and solids retention times.

Anaerobic ethanol oxidation relies on syntrophic interactions among functional microorganisms to become thermodynamically feasible. Different operational modes (sequencing batch reactors, SBRs, and continuous flow reactors, CFRs) and solids retention times (SRT, 25 days and 10 days) were employed in four ethanol-fed reactors, named as SBR25d, SBR10d, CFR25d, and CFR10d, respectively. System performance, syntrophic relationships, microbial communities, and metabolic pathways were examined. During the long-term operation, 2002.7 ± 56.0 mg COD/L acetate was accumulated in CFR10d due to the washout of acetotrophic methanogens. Microorganisms with high half-saturation constants were enriched in reactors of 25-day SRT. Moreover, ethanol oxidizing bacteria and acetotrophic methanogens with high half-saturation constants could be acclimated in SBRs. In SBRs, Syner-01 and Methanothrix dominated, and the low SRT of 10 days increased the relative abundance of Geobacter to 38.0%. In CFRs, the low SRT of 10 days resulted in an increase of Desulfovibrio among syntrophic bacteria, and CFR10d could be employed in enriching hydrogenotrophic methanogens like Methanobrevibacter.

Effect of different inocula on the granulation process, reactor performance and biodiesel production of algal-bacterial granular sludge (ABGS) under low aeration conditions.

The algal-bacterial granular sludge (ABGS) system is a prospective wastewater treatment technology, but few studies focused on the effects of different inoculum types on the establishment of the ABGS system under low aeration conditions (step-decrease superficial gas velocity from 1.4 to 0.5 cm/s). Results from this study indicated that compared with other inocula, the ABGS formed by co-inoculating aerobic granular sludge (AGS) and targeted algae (Chlorella) exhibited a shorter granulation period (shortened by 15 days), higher total nitrogen (89.4%) and PO43--P (95.0%) removal efficiencies, and a greater yield of fatty acid methyl esters (FAMEs) (9.04 mg/g MLSS). This was possibly attributed to that the functional bacteria (e.g. Thauera, Gemmobacter and Rhodobacter) in the inoculated AGS facilitated the ABGS granulation. The inoculated algae promoted their effective enrichment under illumination conditions and enhanced the production of extracellular polymeric substances, thus improving the stability of ABGS. The enriched algae were attached to the outer layer of the granules, which could provide sufficient oxygen for bacterial metabolism, revealing the inherent mechanisms for the good stability of ABGS under low aeration intensity. Overall, the rapid granulation of ABGS can be achieved by inoculating optimal inocula under low aeration conditions, which is convenient and economically feasible, and motivates the application of algal-bacterial consortia.

Biofilm metagenomic characteristics behind high coulombic efficiency for propanethiol deodorization in two-phase partitioning microbial fuel cell.

Hydrophobic volatile organic sulfur compounds (VOSCs) are frequently found during sewage treatment, and their effective management is crucial for reducing malodorous complaints. Microbial fuel cells (MFC) are effective for both VOSCs abatement and energy recovery. However, the performance of MFC on VOSCs remains limited by the mass transfer efficiency of MFC in aqueous media. Inspired by two-phase partitioning biotechnology, silicone oil was introduced for the first time into MFC as a non-aqueous phase (NAP) medium to construct two-phase partitioning microbial fuel cell (TPPMFC) and augment the mass transfer of target VOSCs of propanethiol (PT) in the liquid phase. The PT removal efficiency within 32 h increased by 11-20% compared with that of single-phase MFC, and the coulombic efficiency of TPPMFC (11.01%) was 4.32-2.68 times that of single-phase MFC owing to the fact that highly active desulfurization and thiol-degrading bacteria (e.g., Pseudomonas, Achromobacter) were attached to the silicone oil surface, whereas sulfur-oxidizing bacteria (e.g., Thiobacillus, Commonas, Ottowia) were dominant on the anodic biofilm. The outer membrane cytochrome-c content and NADH dehydrogenase activity improved by 4.15 and 3.36 times in the TPPMFC, respectively. The results of metagenomics by KEGG and COG confirmed that the metabolism of PT in TPPMFC was comprehensive, and that the addition of a NAP upregulates the expression of genes related to sulfur metabolism, energy generation, and amino acid synthesis. This finding indicates that the NAP assisted bioelectrochemical systems would be promising to solve mass-transfer restrictions in low solubility contaminates removal.

Influence of pH, Heat Treatment of Inoculum, and Selenium Oxyanions on Concomitant Selenium Bioremediation and Volatile Fatty Acid Production from Food Waste.

Developing novel strategies to enhance volatile fatty acid (VFA) yield from abundant waste resources is imperative to improve the competitiveness of biobased VFAs over petrochemical-based VFAs. This study hypothesized to improve the VFA yield from food waste via three strategies, viz., pH adjustment (5 and 10), supplementation of selenium (Se) oxyanions, and heat treatment of the inoculum (at 85 °C for 1 h). The highest VFA yield of 0.516 g COD/g VS was achieved at alkaline pH, which was 45% higher than the maximum VFA production at acidic pH. Heat treatment resulted in VFA accumulation after day 10 upon alkaline pretreatment. Se oxyanions acted as chemical inhibitors to improve the VFA yield at pH 10 with non-heat-treated inoculum (NHT). Acetic and propionic acid production was dominant at alkaline pH (NHT); however, the VFA composition diversified under the other tested conditions. More than 95% Se removal was achieved on day 1 under all the conditions tested. However, the heat treatment was detrimental for selenate reduction, with less than 15% Se removal after 20 days. Biosynthesized Se nanoparticles were confirmed by transmission and scanning electron microscopy and and energy dispersive X-ray analyses. The heat treatment inhibited the presence of nonsporulating bacteria and methanogenic archaea (Methanobacteriaceae). High-throughput sequencing also revealed higher relative abundances of the bacterial families (such as Clostridiaceae, Bacteroidaceae, and Prevotellaceae) that are capable of VFA production and/or selenium reduction.

Integrated bioprocess for Se(VI) remediation using duckweed: Coupling selenate removal to biogas production.

The use of phytoremediation as a method for wastewater treatment or removal of pollutants is garnering significant interest and duckweed (DW), a free floating macrophyte, depicts significant potential for the removal of nutrients and toxic compounds from contaminated waters. The present work aimed to develop an integrated process for remediating selenate (Se(VI)) using DW biomass and subsequent use of Se(VI) enriched DW for biogas production. The main objective is to extend the application of selenium (Se) enriched DW biomass for biogas production. Se(VI) enriched DW biomass (Se-DW) gave higher methane production (48.38 ± 3.6 mL gCOD-1) than control DW biomass (C-DW) (24.46 ± 3.6 mL gCOD-1). To further enhance methane production, three pre-treatment approaches (acid, alkali and hydrothermal) were assessed and the solid and liquid fractions obtained after pre-treatment were used as a substrate. Pre-treatments increased biogas production in both Se-DW and C-DW than untreated conditions. Liquid fractions gave higher biogas production than solid fractions. In Se-DW, highest biogas production was observed in hydrothermal pre-treated Se-DW, while in C-DW, acid pre-treatment gave higher biogas production. Methane production was shown to be enhanced up to a Se(VI) concentration of 1.7 mg L-1, whereas a concentration beyond this lowered biogas production.

Simultaneous removal of sulfide and bicarbonate from synthetic wastewater using an algae-assisted microbial fuel cell.

The anaerobic digestion (AD) process is one of the most practiced technologies for the remediation of organic waste and maximization of energy recovery in terms of biogas or biomethane. The presence of other gaseous components in biogas, e.g. CO2 and H2S, often makes its direct application in engines and electricity production unsuitable. This work aimed to develop and utilize an algae-assisted microbial fuel cell (AMFC) for the purification of biogas by removing both CO2 and H2S and simultaneous bioelectricity generation. In addition to biogas clean-up, elemental sulfur recovery and CO2 utilization for algae cultivation add value to the proposed AMFC process. Experiments were performed with both sulfide and bicarbonate in their dissolved form, in the respective anodic and cathodic chambers of the AMFC. The sulfide concentration was varied from 100 to 800 mg/l and the AMFC exhibited a sulfide removal efficiency exceeding 97% at all concentrations tested. The process efficiency dropped, however, at sulfide concentrations above 300 mg/l in terms of both sulfide removal and power output. The AMFC performed best at 400 mg/l sulfide by exhibiting a power density of 24.99 mW/m3 and sulfide removal efficiency of 98.87%. The system exhibited columbic efficiency (CE %) in the range of 7.85-80%. The total alkalinity representing CO2, carbonate and bicarbonate levels in the algae-based system was reduced by 49.54%. The electrical energy recovered from the AMFC was 0.1 kWh/m3 and the total energy recovery, which is the sum of the electrical and algal lipid energy, amounted to 7.25 kWh/m3.