Co-Removal of Perfluorooctanoic Acid and Nitrate from Water by Coupling Pd Catalysis with Enzymatic Biotransformation.

PFAS (poly- and per-fluorinated alkyl substances) represent a large family of recalcitrant organic compounds that are widely used and pose serious threats to human and ecosystem health. Here, palladium (Pd0)-catalyzed defluorination and microbiological mineralization were combined in a denitrifying H2-based membrane biofilm reactor to remove co-occurring perfluorooctanoic acid (PFOA) and nitrate. The combined process, i.e., Pd-biofilm, enabled continuous removal of ∼4 mmol/L nitrate and ∼1 mg/L PFOA, with 81% defluorination of PFOA. Metagenome analysis identified bacteria likely responsible for biodegradation of partially defluorinated PFOA: Dechloromonas sp. CZR5, Kaistella koreensis, Ochrobacterum anthropic, and Azospira sp. I13. High-performance liquid chromatography-quadrupole time-of-flight mass spectrometry and metagenome analyses revealed that the presence of nitrate promoted microbiological oxidation of partially defluorinated PFOA. Taken together, the results point to PFOA-oxidation pathways that began with PFOA adsorption to Pd0, which enabled catalytic generation of partially or fully defluorinated fatty acids and stepwise oxidation and defluorination by the bacteria. This study documents how combining catalysis and microbiological transformation enables the simultaneous removal of PFOA and nitrate.

Coremoval of Energetics and Oxyanions via the In Situ Coupling of Catalytic and Enzymatic Destructions: A Solution to Ammunition Wastewater Treatment.

Ammunition wastewater contains toxic nitrated explosives like RDX and oxyanions like nitrate and perchlorate. Its treatment is challenged by low efficiency due to contaminant recalcitrance and high cost due to multiple processes needed for separately removing different contaminant types. This paper reports a H2-based low-energy strategy featuring the treatment of explosives via catalytic denitration followed by microbial mineralization coupled with oxyanion reduction. After a nitrate- and perchlorate-reducing biofilm incapable of RDX biodegradation was coated with palladium nanoparticles (Pd0NPs), RDX was rapidly denitrated with a specific catalytic activity of 8.7 gcat-1 min-1, while biological reductions of nitrate and perchlorate remained efficient. In the subsequent 30-day continuous test, >99% of RDX, nitrate, and perchlorate were coremoved, and their effluent concentrations were below their respective regulation levels. Detected intermediates and shallow metagenome analysis suggest that the intermediates after Pd-catalytic denitration of RDX ultimately were enzymatically utilized by the nitrate- and perchlorate-reducing bacteria as additional electron donor sources.

Para-Chlorophenol (4-CP) Removal by a Palladium-Coated Biofilm: Coupling Catalytic Dechlorination and Microbial Mineralization via Denitrification.

Rapid dechlorination and full mineralization of para-chlorophenol (4-CP), a toxic contaminant, are unfulfilled goals in water treatment. Means to achieve both goals stem from the novel concept of coupling catalysis by palladium nanoparticles (PdNPs) with biodegradation in a biofilm. Here, we demonstrate that a synergistic version of the hydrogen (H2)-based membrane biofilm reactor (MBfR) enabled simultaneous removals of 4-CP and cocontaminating nitrate. In situ generation of PdNPs within the MBfR biofilm led to rapid 4-CP reductive dechlorination, with >90% selectivity to more bioavailable cyclohexanone. Then, the biofilm mineralized the cyclohexanone by utilizing it as a supplementary electron donor to accelerate nitrate reduction. Long-term operation of the Pd-MBfR enriched the microbial community in cyclohexanone degraders within Clostridium, Chryseobacterium, and Brachymonas. In addition, the PdNP played an important role in accelerating nitrite reduction; while NO3- reduction to NO2- was entirely accomplished by bacteria, NO2- reduction to N2 was catalyzed by PdNPs and bacterial reductases. This study documents a promising option for efficient and complete remediation of halogenated organics and nitrate by the combined action of PdNP and bacterial catalysis.

H2-Based Membrane Catalyst-Film Reactor (H2-MCfR) Loaded with Palladium for Removing Oxidized Contaminants in Water.

Scalable applications of precious-metal catalysts for water treatment face obstacles in H2-transfer efficiency and catalyst stability during continuous operation. Here, we introduce a H2-based membrane catalyst-film reactor (H2-MCfR), which enables in situ reduction and immobilization of a film of heterogeneous Pd0 catalysts that are stably anchored on the exterior of a nonporous H2-transfer membrane under ambient conditions. In situ immobilization had >95% yield of Pd0 in controllable forms, from isolated single atoms to moderately agglomerated nanoparticles (averaging 3-4 nm). A series of batch tests documented rapid Pd-catalyzed reduction of a wide spectrum of oxyanions (nonmetal and metal) and organics (e.g., industrial raw materials, solvents, refrigerants, and explosives) at room temperature, owing to accurately controlled H2 supply on demand. Reduction kinetics and selectivity were readily controlled through the Pd0 loading on the membranes, H2 pressure, and pH. A 45-day continuous treatment of trichloroethene (TCE)-contaminated water documented removal fluxes up to 120 mg-TCE/m2/d with over 90% selectivity to ethane and minimal (<1.5%) catalyst leaching or deactivation. The results support that the H2-MCfR is a potentially sustainable and reliable catalytic platform for reducing oxidized water contaminants: simple synthesis of an active and versatile catalyst that has long-term stability during continuous operation.

The Nature and Oxidative Reactivity of Urban Magnetic Nanoparticle Dust Provide New Insights into Potential Neurotoxicity Studies.

The recent discovery of magnetic nanoparticles (NPs) in human brain tissue has raised concerns regarding their source and neurotoxicity. As previous studies have suggested that magnetite in urban dust may be the source, we collected urban magnetic dust and thoroughly characterized the nature of ambient urban magnetic dust particles prior to investigating their neurotoxic potential. In addition to magnetite, magnetic dust contained an abundance (∼40%) of elemental iron (Fe0). The coexistence of magnetite and elemental iron was found in magnetic dust particles of inhalable (<10 µm) and nanoscale (<200 nm) size ranges with these particles small enough to enter the human brain via the respiratory tract and olfactory bulbs. The magnetic dust also contained nonferrous water-soluble metals (particularly Cu) that can induce formation of reactive oxygen species (ROS). Previous studies used engineered pure-magnetite for in vitro ROS studies. However, while magnetite was present in all magnetic dust particles collected, engineered pure-magnetite was relatively unreactive and contributed minimally to the generation of ROS. We fill a critical knowledge gap between exposure to heterogeneous ambient iron-particles and in vitro experiments with engineered versus ambient, incidental iron-bearing nanoscale minerals. Our work points to the need to further investigate the presence and properties of magnetic NPs in respirable dust with respect to their potential role in neurodegeneration.

Constructing models for Crohn's disease diagnosis and prediction of infliximab non-response based on angiogenesis-related genes.

Background: Angiogenesis response plays a crucial role in the occurrence and development of Crohn's disease (CD) and may involve the mechanism of infliximab non-response. However, the role of angiogenesis-related genes in Crohn's disease has not been comprehensively studied. This study aimed to explore the expression profiles of angiogenesis-related genes in CD patients and construct models for disease diagnosis and prediction of infliximab non-response. Methods: CD-related microarray datasets were collected from the GEO database. Unsupervised consensus clustering analysis was performed based on differentially expressed angiogenesis-related genes to divide CD samples into two distinct clusters. Weighted gene co-expression network analysis (WGCNA) was conducted on the clusters to identify angiogenesis-related module. Based on the differentially expressed genes in the module, machine learning algorithms were employed to further identify hub genes and construct a disease diagnostic model. Subsequently, treatment outcome-related genes were extracted from these hub genes, and a predictive model for infliximab non-response in CD patients was ultimately built. Results: Based on angiogenesis-related genes, we identified two distinct CD clusters (C1 and C2). Compared to C1, the metabolic pathways in C2 were significantly upregulated, and there was a higher abundance of cell clusters such as M1 macrophages and plasma cells. Additionally, C2 showed a poorer response to infliximab. Furthermore, a predictive model for infliximab non-response in CD patients was constructed based on the hub genes, and it was successfully validated using an external dataset. Conclusion: Comprehensive analysis of angiogenesis-related genes revealed different clusters of CD, which exhibited differential response rates to infliximab. The construction of models provides a reference for disease diagnosis and drug selection, aiding in clinical decision-making.

A two-stage design enhanced biodegradation of high concentrations of a C16-alkyl quaternary ammonium compound in oxygen-based membrane biofilm reactors.

Quaternary ammonia compounds (QAC), such as hexadecyltrimethyl-ammonium (CTAB), are widely used as disinfectants and in personal-care products. Their use as disinfectants grew during the SARS-CoV-2 (COVID-19) pandemic, leading to increased loads to wastewater treatment systems and the environment. Though low concentrations of CTAB are biodegradable, high concentrations are toxic to bacteria. Sufficient O2 delivery is a key to achieve high CTAB removal, and the O2-based Membrane Biofilm Reactor (O2-MBfR) is a proven means to biodegrade CTAB in a bubble-free, non-foaming manner. A strategy for achieving complete biodegradation of high-concentrations of CTAB is a two-stage O2-MBfR, in which partial CTAB removal in the Lead reactor relieves inhibition in the Lag reactor. Here, more than 98 % removal of 728 mg/L CTAB could be achieved in the two-stage MBfR, and the CTAB-removal rate was 70 % higher than for a one-stage MBfR with the same O2-delivery capacity. CTAB exposure shifted the bacterial community toward Pseudomonas and Stenotrophomonas as the dominant genera. In particular, P. alcaligenes and P. aeruginosa were enriched in the Lag reactor, as they were capable of biodegrading the metabolites of initial CTAB monooxygenation. Metagenomic analysis also revealed that the Lag reactor was enriched in genes for CTAB and metabolite oxygenation, due to reduced CTAB inhibition.

A synergistic platform enables co-oxidation of halogenated organic pollutants without input of organic primary substrate.

While co-oxidation is widely used to biodegrade halogenated organic pollutants (HOPs), a considerable amount of organic primary substrate is required. Adding organic primary substrates increases the operating cost and also leads to extra carbon dioxide release. In this study, we evaluated a two-stage Reduction and Oxidation Synergistic Platform (ROSP), which integrated catalytic reductive dehalogenation with biological co-oxidation for HOPs removal. The ROSP was a combination of an H2-based membrane catalytic-film reactor (H2-MCfR) and an O2-based membrane biofilm reactor (O2-MBfR). 4-chlorophenol (4-CP) was used as a model HOP to evaluate the performance of ROSP. In the MCfR stage, zero-valent palladium nanoparticles (Pd0NPs) catalyzed reductive hydrodechlorination that converted 4-CP to phenol, with a conversion yield over 92%. In the MBfR stage, the phenol was oxidized and used as a primary substrate that supported the co-oxidation of residual 4-CP. Genomic DNA sequencing revealed that phenol produced from 4-CP reduction enriched bacteria having genes for functional enzymes for phenol biodegradation in the biofilm community. In the ROSP, over 99% of 60 mg/L 4-CP was removed and mineralized during continuous operation: Effluent 4-CP and chemical oxygen demand concentrations were below 0.1 and 3 mg/L, respectively. H2 was the only added electron donor to the ROSP, which means no extra carbon dioxide was produced by primary-substrate oxidation.

The structure of biodegradable surfactants shaped the microbial community, antimicrobial resistance, and potential for horizontal gene transfer.

While most household surfactants are biodegradable in aerobic conditions, their biodegradability may obscure their environmental risks. The presence of surfactants in a biological treatment process can lead to the proliferation of antimicrobial-resistance genes (ARG) in the biomass. Surfactants can be cationic, anionic, or zwitterionic, and these different classes may have different effects on the proliferation ARG. Cationic hexadecyltrimethyl-ammonium (CTAB), anionic sodium dodecyl sulfate (SDS), and zwitterionic 3-(decyldimethylammonio)-propanesulfonate inner salt (DAPS) were used to represent the three classes of surfactants in domestic household clean-up products. This study focused on the removal of these surfactants by the O2-based Membrane Biofilm Reactor (O2-MBfR) for hotspot scenarios (∼1 mM) and how the three classes of surfactants affected the microbial community's structure and ARG. Given sufficient O2 delivery, the MBfR provided at least 98% surfactant removal. The presence and biodegradation for each surfactant uniquely shaped the biofilms' microbial communities and the presence of ARG. CTAB had by far the strongest impact and the higher ARG abundance. In particular, Pseudomonas and Stenotrophomonas, the two main genera in the biofilm treating CTAB, were highly correlated to the abundance of ARG for efflux pumps and antibiotic inactivation. CTAB also led to more functional genes relevant to the Type-IV secretion system and protection against oxidative stress, which also could encourage horizontal gene transfer. Our findings highlight that the biodegradation of quaternary ammonium surfactants, while beneficial, can pose public health concerns from its ability to promote the proliferation of ARG.

Identifying biodegradation pathways of cetrimonium bromide (CTAB) using metagenome, metatranscriptome, and metabolome tri-omics integration.

Traditional research on biodegradation of emerging organic pollutants involves slow and labor-intensive experimentation. Currently, fast-developing metagenome, metatranscriptome, and metabolome technologies promise to expedite mechanistic research on biodegradation of emerging organic pollutants. Integrating the metagenome, metatranscriptome, and metabolome (i.e., tri-omics) makes it possible to link gene abundance and expression with the biotransformation of the contaminant and the formation of metabolites from this biotransformation. In this study, we used this tri-omics approach to study the biotransformation pathways for cetyltrimethylammonium bromide (CTAB) under aerobic conditions. The tri-omics analysis showed that CTAB undergoes three parallel first-step mono-/di-oxygenations (to the α, ß, and ω-carbons); intermediate metabolites and expressed enzymes were identified for all three pathways, and the ß-carbon mono-/di-oxygenation is a novel pathway; and the genes related to CTAB biodegradation were associated with Pseudomonas spp. Four metabolites - palmitic acid, trimethylamine N-oxide (TMAO), myristic acid, and betaine - were the key identified biodegradation intermediates of CTAB, and they were associated with first-step mono-/di-oxygenations at the α/ß-C. This tri-omics approach with CTAB demonstrates its power for identifying promising paths for future research on the biodegradation of complex organics by microbial communities.

Reductive destruction of multiple nitrated energetics over palladium nanoparticles in the H2-based membrane catalyst-film reactor (MCfR).

Nitrated energetics are widespread contaminants due to their improper disposal from ammunition facilities. Different classes of nitrated energetics commonly co-exist in ammunition wastewater, but co-removal of the classes has hardly been documented. In this study, we evaluated the catalytic destruction of three types of energetics using palladium (Pd0) nano-catalysts deposited on H2-transfer membranes in membrane catalyst-film reactors (MCfRs). This work documented nitro-reduction of 2,4,6-trinitrotoluene (TNT), as well as, for the first time, denitration of hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) and pentaerythritol tetranitrate (PETN) over Pd0 at ambient temperature. The catalyst-specific activity was 20- to 90-fold higher than reported for other catalyst systems. Nitrite (NO2-) released from RDX and PETN also was catalytically reduced to dinitrogen gas (N2). Continuous treatment of a synthetic wastewater containing TNT, RDX, and PETN (5 mg/L each) for more than 20 hydraulic retention times yielded removals higher than 96% for all three energetics. Furthermore, the concentrations of NO2- and NH4+ were below the detection limit due to subsequent NO2- reduction with > 99% selectivity to N2. Thus, the MCfR provides a promising strategy for sustainable catalytic removal of co-existing energetics in ammunition wastewater.

Increased expression of antibiotic-resistance genes in biofilm communities upon exposure to cetyltrimethylammonium bromide (CTAB) and other stress conditions.

Quaternary ammonium compounds (QAC, e.g., cetyltrimethylammonium bromide, (CTAB)) are widely used as surfactants and disinfectants. QAC already are commonly found in wastewaters, and their concentration could increase, since QAC are recommended to inactivate the SARS-CoV-2 (COVID-19) virus. Exposure of bacteria to QAC can lead to proliferation of antibiotic resistance genes (ARG). In particular, O2-based membrane biofilm reactors (O2-MBfRs) achieved excellent CTAB biodegradation, but ARG increased in their biofilms. Here, we applied meta-transcriptomic analyses to assess the impacts of CTAB exposure and operating conditions on microbial community's composition and ARG expression in the O2-MBfRs. Two opportunistic pathogens, Pseudomonas aeruginosa and Stenotrophomonas maltophilia, dominated the microbial communities and were associated with the presence of ARG. Operating conditions that imposed stress on the biofilms, i.e., limited supplies of O2 and nitrogen or a high loading of CTAB, led to large increases in ARG expression, particularly for genes conferring antibiotic-target protection. Important within the efflux pumps was the Resistance-Nodulation-Division (RND) family, which may have been active in exporting CTAB from cells. Oxidative stress appeared to be the key factor that triggered ARG proliferation by selecting intrinsically resistant species and accentuating the expression of ARG. Our findings suggest that means to mitigate the spread of ARG, such as shown here in a O2-based membrane biofilm reactor, need to consider the impacts of stressors, including QAC exposure and stressful operating conditions.

Impact of acetic acid addition on nitrogen speciation and bacterial communities during urine collection and storage.

The rate of urea hydrolysis in nonwater urinals is influenced by the volume of urination events and the frequency of urinal use. Inhibition of urea hydrolysis with acetic acid addition has been demonstrated at the laboratory scale but it was not able to fully represent the conditions of a real restroom with real urine collection. The goal of this study was to understand the effects of acid addition for control of urea hydrolysis on nutrient concentrations and bacterial communities in human urine during collection and storage. Three control logics were used to determine the schedule of acid addition: (i) acid addition after every urination event, (ii) acid addition during periods of high building occupancy, and (iii) acid addition during periods of low building occupancy. Wifi logins were used to approximate building occupancy and to create the control logics used in the study. All three control logics were able to inhibit urea hydrolysis. The bacterial communities were identified to determine the impact of acid addition on the community structure. The collection of urine by nonwater urinals alone did not reduce the presence of enteric bacteria commonly found when collecting urine with urine-diverting toilets. Acid addition reduced the community diversity and created conditions for higher relative abundances of the order Enterobacteriales. Finally, results from stored acidified urine showed that urea hydrolysis inhibition is reversible and is influenced by the amount of acid added at the urinal. The amount of acid added can influence the rate of hydrolysis in the storage tanks and can be used to select for urea- or ammonia-nitrogen for nutrient recovery. This study is the first of its kind to inhibit urea hydrolysis in nonwater urinals in a real restroom with real urine, and is the first to identify the bacterial communities in urine collected solely with nonwater urinals.

Real Gas Model Parameters for High-Density Combustion from Chemical Kinetic Model Data.

Low emissions and high efficiencies can be realized in combustion systems that operate at high-pressure and low-temperature conditions (high densities). The design of such engines relies on accurate models of the physical processes involved. Under these conditions, the ideal gas model widely used in computational fluid dynamics (CFD) simulations fails to properly capture the relation among pressure, density, and temperature as well as inter-relations among other thermodynamic and transport properties. As such, discrepancies between experimental observations and CFD simulations cannot only be traced to uncertainties from experiments, turbulent, or combustion models. This paper offers a possible solution to the implementation of the real gas equation of state models in combustion simulations. The large number of species in combustion simulations requires effort to provide the relevant real gas properties. A method is suggested for incorporating these properties in simulations based on available transport and thermodynamic data of chemical kinetic models. This attempt also brings out an often-ignored problem in existing chemical kinetic models in the literature, namely, the nonsystematic assignment of transport properties for various species. To clearly demonstrate the need for real gas models in reacting flows, simulations are carried out of a high-pressure n-heptane jet into a quiescent chamber of air based on ideal gas and real gas models. The defects of the ideal gas model are revealed, and the proposed method of property estimation is justified as a convenient solution.