Effects of graphene oxide and reduced graphene oxide on acetoclastic, hydrogenotrophic and methylotrophic methanogenesis.

This study describes the effects of graphene oxide (GO) and reduced graphene oxide (rGO) on the acetoclastic, hydrogenotrophic and methylotrophic pathways of methanogenesis by an anaerobic consortium. The results showed that GO negatively affected the hydrogenotrophic and acetoclastic pathways at a concentration of 300 mg/L, causing a decrease of ~ 38% on the maximum specific methanogenic activity (MMA) with respect to the controls lacking GO. However, the presence of rGO (300 mg/L) promoted an improvement of the MMA (> 45%) achieved with all substrates, except for the hydrogenotrophic pathway, which was relatively insensitive to rGO.

Diazole and triazole inhibition of nitrification process in return activated sludge.

Azoles are emerging contaminants that are resistant to biodegradation during wastewater treatment. Their presence has been widely reported in wastewater effluents and receiving waters. In this work, the potential inhibition of nitrification process by six different azole compounds in wastewater treatment plants was investigated in batch bioassays.

Adaptation of granular sludge microbial communities to nitrate, sulfide, and/or p-cresol removal.

Effluents from petroleum refineries contain a toxic mixture of sulfide, nitrogen, and phenolic compounds that require adequate treatment for their removal. Biological denitrification processes are a cost-effective option for the treatment of these effluents, but the knowledge on the microbial interactions in simultaneous sulfide and phenol oxidation in denitrifying reactors is still very limited. In this work, microbial community structure and macrostructure of granular biomass were studied in three denitrifying reactors treating a mixture of inorganic (sulfide) and organic (p-cresol) electron donors for their simultaneous removal.

Gallium arsenide (GaAs) leaching behavior and surface chemistry changes in response to pH and O.

Gallium arsenide (GaAs) is a material widely used in electronic devices. Disposal of electronic waste containing GaAs in municipal solid waste landfills raises concerns about the public health and ecological risks associated with the potential release of toxic arsenic (As) species. In this study, different tests were performed to investigate the leaching behavior of particulate GaAs in aqueous solutions.

Adsorption and oxidation of 3-nitro-1,2,4-triazole-5-one (NTO) and its transformation product (3-amino-1,2,4-triazole-5-one, ATO) at ferrihydrite and birnessite surfaces.

The emerging insensitive munitions compound (IMC) 3-nitro-1,2,4-triazole-5-one (NTO) is currently being used to replace conventional explosives such as 1,3,5-trinitro-1,3,5-triazacyclohexane (RDX), but the environmental fate of this increasingly widespread IMC remains poorly understood. Upon release from unexploded solid phase ordinances, NTO exhibits high aqueous solubility and, hence, potential mobilization to groundwater. Adsorption and abiotic transformation at metal oxide surfaces are possible mechanisms for natural attenuation.

Oxidation of reduced daughter products from 2,4-dinitroanisole (DNAN) by Mn(IV) and Fe(III) oxides.

Abiotic transformation of anthropogenic compounds by redox-active metal oxides affects contaminant fate in soil. The capacity of birnessite and ferrihydrite to oxidize the insensitive munitions compound, 2,4-dinitroanisol (DNAN), and its amine-containing daughter products, 2-methoxy-5-nitro aniline (MENA) and 2,4-diaminoanisole (DAAN), was studied in stirred reactors at controlled pH (7.0).

Leaching of cadmium and tellurium from cadmium telluride (CdTe) thin-film solar panels under simulated landfill conditions.

A crushed non-encapsulated CdTe thin-film solar cell was subjected to two standardized batch leaching tests (i.e., Toxicity Characteristic Leaching Procedure (TCLP) and California Waste Extraction Test (WET)) and to a continuous-flow column test to assess cadmium (Cd) and tellurium (Te) dissolution under conditions simulating the acidic- and the methanogenic phases of municipal solid waste landfills.

Transferable Training Modules: Building Environmental Education Opportunities With and for Mexican Community Health Workers (Promotores de Salud).

Community health workers (promotores de salud) have the ability to empower communities to mitigate negative health outcomes. Current training efforts in environmental topics are lacking. This project addressed this gap by developing 4 transferable training modules on environmental health.

Adaptation of a methanogenic consortium to arsenite inhibition.

Arsenic (As) is a ubiquitous metalloid known for its adverse effects to human health. Microorganisms are also impacted by As toxicity, including methanogenic archaea, which can affect the performance of process in which biological activity is required ( stabilization of activated sludge in wastewater treatment plants). The novel ability of a mixed methanogenic granular sludge consortium to adapt to the inhibitory effect of arsenic (As) was investigated by exposing the culture to approximately 0.

Treatment of acid rock drainage using a sulfate-reducing bioreactor with zero-valent iron.

This study assessed the bioremediation of acid rock drainage (ARD) in flow-through columns testing zero-valent iron (ZVI) for the first time as the sole exogenous electron donor to drive sulfate-reducing bacteria in permeable reactive barriers. Columns containing ZVI, limestone or a mixture of both materials were inoculated with an anaerobic mixed culture and fed a synthetic ARD containing sulfuric acid and heavy metals (initially copper, and later also cadmium and lead). ZVI significantly enhanced sulfate reduction and the heavy metals were extensively removed (>99.

Recovery of palladium(II) by methanogenic granular sludge.

This is the first report that demonstrates the ability of anaerobic methanogenic granular sludge to reduce Pd(II) to Pd(0). Different electron donors were evaluated for their effectiveness in promoting Pd reduction. Formate and H2 fostered both chemically and biologically mediated Pd reduction.

Arsenic remediation by formation of arsenic sulfide minerals in a continuous anaerobic bioreactor.

Arsenic (As) is a highly toxic metalloid that has been identified at high concentrations in groundwater in certain locations around the world. Concurrent microbial reduction of arsenate (As(V) ) and sulfate (SO4 (2-) ) can result in the formation of poorly soluble arsenic sulfide minerals (ASM). The objective of this research was to study As biomineralization in a minimal iron environment for the bioremediation of As-contaminated groundwater using simultaneous As(V) and SO4 (2-) reduction.

Biotransformation and Degradation of the Insensitive Munitions Compound, 3-Nitro-1,2,4-triazol-5-one, by Soil Bacterial Communities.

Insensitive munitions (IM) are a new class of explosives that are increasingly being adopted by the military. The ability of soil microbial communities to degrade IMs is relatively unknown. In this study, microbial communities from a wide range of soils were tested in microcosms for their ability to degrade the IM, 3-nitro-1,2,4-triazol-5-one (NTO).

Biomineralization of arsenate to arsenic sulfides is greatly enhanced at mildly acidic conditions.

Arsenic (As) is an important water contaminant due to its high toxicity and widespread occurrence. Arsenic-sulfide minerals (ASM) are formed during microbial reduction of arsenate (As(V)) and sulfate (SO4(2-)). The objective of this research is to study the effect of the pH on the removal of As due to the formation of ASM in an iron-poor system.

Socially responsible mining: the relationship between mining and poverty, human health and the environment.

Increasing global demand for metals is putting strain on the ability of the mining industry to physically keep up with demand (physical scarcity). Conversely, social issues including the environmental and human health consequences of mining as well as the disparity in income distribution from mining revenues are disproportionately felt at the local community level. This has created social rifts, particularly in the developing world, between affected communities and both industry and governments.

Toxicity of TiO₂, ZrO₂, Fe⁰, Fe₂O₃, and Mn₂O₃ nanoparticles to the yeast, Saccharomyces cerevisiae.

The growing application of engineered nanomaterials is leading to an increased occurrence of nanoparticles (NPs) in the environment. Thus, there is a need to better understand their potential impact on the environment. This study evaluated the toxicity of nanosized TiO₂, ZrO₂, Fe(0), Fe₂O₃, and Mn₂O₃ towards the yeast Saccharomyces cerevisiae based on O₂ consumption and cell membrane integrity.

Toxicity assessment of inorganic nanoparticles to acetoclastic and hydrogenotrophic methanogenic activity in anaerobic granular sludge.

Release of engineered nanoparticles (NPs) to municipal wastewater from industrial and residential sources could impact biological systems in wastewater treatment plants. Methanogenic inhibition can cause failure of anaerobic waste(water) treatment. This study investigated the inhibitory effect of a wide array of inorganic NPs (Ag(0), Al₂O₃, CeO₂, Cu(0), CuO, Fe(0), Fe₂O₃, Mn₂O₃, SiO₂, TiO₂, and ZnO supplied up to 1500 mgL(-1)) to acetoclastic and hydrogenotrophic methanogenic activity of anaerobic granular sludge.

Fate of cerium dioxide (CeO2) nanoparticles in municipal wastewater during activated sludge treatment.

This study investigated the fate of nano-CeO(2) during municipal wastewater treatment using a laboratory-scale activated sludge (A/S) system fed with primarily-treated municipal wastewater and nano-CeO(2) (55.0 mg Ce/L). Nano-CeO(2) was highly removed during A/S treatment (96.

Low toxicity of HfO2, SiO2, Al2O3 and CeO2 nanoparticles to the yeast, Saccharomyces cerevisiae.

Increasing use of nanomaterials necessitates an improved understanding of their potential impact on environment health. This study evaluated the cytotoxicity of nanosized HfO(2), SiO(2), Al(2)O(3) and CeO(2) towards the eukaryotic model organism Saccharomyces cerevisiae, and characterized their state of dispersion in bioassay medium. Nanotoxicity was assessed by monitoring oxygen consumption in batch cultures and by analysis of cell membrane integrity.

Uranium bioremediation in continuously fed upflow sand columns inoculated with anaerobic granules.

Reductive precipitation of soluble hexavalent uranium (U(VI)) to insoluble tetravalent uranium (U(IV)) containing minerals is one of the more promising approaches to uranium remediation. The objective of this study was to evaluate the long-term performance of methanogenic granules for the continuous treatment of U(VI). For this purpose, three sand-packed columns inoculated with anaerobic biofilm were operated with or without ethanol and one column was exposed to nitrate co-contamination.

Cytotoxicity and physicochemical properties of hafnium oxide nanoparticles.

Nano-sized hafnium oxide (HfO(2)) particles are being considered for applications within the semiconductor industry. However, little is known about their cytotoxicity. The objective of this work was to assess several HfO(2) nanoparticles (NPs) samples for their acute cytotoxicity.

Assessment of in situ reductive dechlorination using compound-specific stable isotopes, functional gene PCR, and geochemical data.

Isotopic analysis and molecular-based bioassay methods were used in conjunction with geochemical data to assess intrinsic reductive dechlorination processes for a chlorinated solvent-contaminated site in Tucson, Arizona. Groundwater samples were obtained from monitoring wells within a contaminant plume comprising tetrachloroethene and its metabolites, trichloroethene, cis-1,2-dichloroethene, vinyl chloride, and ethene, as well as compounds associated with free phase diesel present at the site. Compound-specific isotope analysis was performed to characterize biotransformation processes influencing the transport and fate of the chlorinated contaminants.

Toxicity of fluoride to microorganisms in biological wastewater treatment systems.

Fluoride is a common contaminant in a variety of industrial wastewaters. Available information on the potential toxicity of fluoride to microorganisms implicated in biological wastewater treatment is very limited. The objective of this study was to evaluate the inhibitory effect of fluoride towards the main microbial populations responsible for the removal of organic constituents and nutrients in wastewater treatment processes.

Nitrate and nitrite inhibition of methanogenesis during denitrification in granular biofilms and digested domestic sludges.

Anaerobic bioreactors that can support simultaneous microbial processes of denitrification and methanogenesis are of interest to nutrient nitrogen removal. However, an important concern is the potential toxicity of nitrate (NO(3) (-)) and nitrite (NO(2) (-)) to methanogenesis. The methanogenic toxicity of the NO (x) (-) compounds to anaerobic granular biofilms and municipal anaerobic digested sludge with two types of substrates, acetate and hydrogen, was studied.

Anaerobic degradation of citrate under sulfate reducing and methanogenic conditions.

Citrate is an important component of metal processing effluents such as chemical mechanical planarization wastewaters of the semiconductor industry. Citrate can serve as an electron donor for sulfate reduction applied to promote the removal of metals, and it can also potentially be used by methanogens that coexist in anaerobic biofilms. The objective of this study was to evaluate the degradation of citrate with sulfate-reducing and methanogenic biofilms.