A methodology to screen priority toxins in pollutant release inventories.

Pollutant release inventories are used for environmental policy making to reduce toxic pollutants, even though the quantity-based inventory analysis does not take into account the relative toxicity of pollutants. To overcome this limit, life cycle impact assessment (LCIA)-based inventory analysis was developed but still has a high uncertainty from modelling the site- and time-specific fates and transports of pollutants. Thus, this study develops a methodology to evaluate toxicity potentials based on the concentration of pollutants in the exposure to humans in order to circumvent the uncertainty and subsequently screen priority toxins in pollutant release inventories. This methodology combines (i) analytical measurement of the concentration of the pollutants exposed to humans; (ii) application of toxicity effect characterization factors for pollutants; and (iii) identification of priority toxins and industries based on the toxicity potential evaluation results. To demonstrate the methodology, a case study is considered, evaluating toxicity potentials from the ingestion of heavy metals in seafood organisms and then identifying priority toxins and industry sectors in a pollutant release inventory. The results of the case study show that the methodology-based priority pollutant is different from the quantity- and LCIA-based ones. Therefore, the methodology can contribute to making effective environmental policy.

Unique selectivity and rapid uptake of molybdenum-disulfide-functionalized MXene nanocomposite for mercury adsorption.

A heterogeneous nanoadsorbent composed of two-dimensional Ti3C2Tx MXene nanosheets (MX) functionalized with nanolayered molybdenum disulfide (MoS2/MX-II) was synthesized by a facile hydrothermal treatment method and used to remove toxic mercuric ions (Hg2+). Mercury was adsorbed by the synergistic action of the sulfur (disulfide) and the oxygenated terminal groups of Ti3C2Tx in the MoS2-MX-II composite. Ultrasonication increased the surface area and interlayer distance of the Ti3C2Tx nanosheets, which enhanced the removal capability of the composite. As a result, 50 µmol/L of Hg2+ was reduced to 0.01 µmol/L in just 120 s, which is unprecedented kinetic behavior for mercury adsorption. Furthermore, the Langmuir adsorption isotherm fitted well with the adsorption data and revealed a maximum adsorption capacity of 7.16 mmol/g. To provide a practical demonstration of MoS2/MX-II, it was applied to mercury-contaminated wastewater, whose results showed that MoS2/MX-II was capable of removing Hg2+ at the ppb level with a distribution coefficient of 7.87 × 105 mL/g in the co-presence of various metal ions. Hydrothermal stability tests and SEM analysis confirmed the stability of MoS2-MX-II after it adsorbed a high concentration of Hg2+. Furthermore, MoS2-MX-II exhibited excellent recyclability as 0.08 mM of Hg2+ was completely removed even after five cycles. The results suggest the practical applicability of this type of heterogeneous nanocomposite for water purification.

Potential environmental impacts from the metals in incandescent, compact fluorescent lamp (CFL), and light-emitting diode (LED) bulbs.

Artificial lighting systems are transitioning from incandescent to compact fluorescent lamp (CFL) and light-emitting diode (LED) bulbs in response to the U.S. Energy Independence and Security Act and the EU Ecodesign Directive, which leads to energy savings and reduced greenhouse gas emissions. Although CFLs and LEDs are more energy-efficient than incandescent bulbs, they require more metal-containing components. There is uncertainty about the potential environmental impacts of these components and whether special provisions must be made for their disposal at the end of useful life. Therefore, the objective of this study is to analyze the resource depletion and toxicity potentials from the metals in incandescent, CFL, and LED bulbs to complement the development of sustainable energy policy. We assessed the potentials by examining whether the lighting products are to be categorized as hazardous waste under existing U.S. federal and California state regulations and by applying life cycle impact-based and hazard-based assessment methods (note that "life cycle impact-based method" does not mean a general life cycle assessment (LCA) but rather the elements in LCA used to quantify toxicity potentials). We discovered that both CFL and LED bulbs are categorized as hazardous, due to excessive levels of lead (Pb) leachability (132 and 44 mg/L, respectively; regulatory limit: 5) and the high contents of copper (111,000 and 31,600 mg/kg, respectively; limit: 2500), lead (3860 mg/kg for the CFL bulb; limit: 1000), and zinc (34,500 mg/kg for the CFL bulb; limit: 5000), while the incandescent bulb is not hazardous (note that the results for CFL bulbs excluded mercury vapor not captured during sample preparation). The CFLs and LEDs have higher resource depletion and toxicity potentials than the incandescent bulb due primarily to their high aluminum, copper, gold, lead, silver, and zinc. Comparing the bulbs on an equivalent quantity basis with respect to the expected lifetimes of the bulbs, the CFLs and LEDs have 3-26 and 2-3 times higher potential impacts than the incandescent bulb, respectively. We conclude that in addition to enhancing energy efficiency, conservation and sustainability policies should focus on the development of technologies that reduce the content of hazardous and rare metals in lighting products without compromising their performance and useful lifespan.

Potential environmental impacts of light-emitting diodes (LEDs): metallic resources, toxicity, and hazardous waste classification.

Light-emitting diodes (LEDs) are advertised as environmentally friendly because they are energy efficient and mercury-free. This study aimed to determine if LEDs engender other forms of environmental and human health impacts, and to characterize variation across different LEDs based on color and intensity. The objectives are as follows: (i) to use standardized leachability tests to examine whether LEDs are to be categorized as hazardous waste under existing United States federal and California state regulations; and (ii) to use material life cycle impact and hazard assessment methods to evaluate resource depletion and toxicity potentials of LEDs based on their metallic constituents. According to federal standards, LEDs are not hazardous except for low-intensity red LEDs, which leached Pb at levels exceeding regulatory limits (186 mg/L; regulatory limit: 5). However, according to California regulations, excessive levels of copper (up to 3892 mg/kg; limit: 2500), Pb (up to 8103 mg/kg; limit: 1000), nickel (up to 4797 mg/kg; limit: 2000), or silver (up to 721 mg/kg; limit: 500) render all except low-intensity yellow LEDs hazardous. The environmental burden associated with resource depletion potentials derives primarily from gold and silver, whereas the burden from toxicity potentials is associated primarily with arsenic, copper, nickel, lead, iron, and silver. Establishing benchmark levels of these substances can help manufacturers implement design for environment through informed materials substitution, can motivate recyclers and waste management teams to recognize resource value and occupational hazards, and can inform policymakers who establish waste management policies for LEDs.

Priority screening of toxic chemicals and industry sectors in the U.S. toxics release inventory: a comparison of the life cycle impact-based and risk-based assessment tools developed by U.S. EPA.

Life Cycle Impact Assessment (LCIA) and Risk Assessment (RA) employ different approaches to evaluate toxic impact potential for their own general applications. LCIA is often used to evaluate toxicity potentials for corporate environmental management and RA is often used to evaluate a risk score for environmental policy in government. This study evaluates the cancer, non-cancer, and ecotoxicity potentials and risk scores of chemicals and industry sectors in the United States on the basis of the LCIA- and RA-based tools developed by U.S. EPA, and compares the priority screening of toxic chemicals and industry sectors identified with each method to examine whether the LCIA- and RA-based results lead to the same prioritization schemes. The Tool for the Reduction and Assessment of Chemical and other environmental Impacts (TRACI) is applied as an LCIA-based screening approach with a focus on air and water emissions, and the Risk-Screening Environmental Indicator (RSEI) is applied in equivalent fashion as an RA-based screening approach. The U.S. Toxic Release Inventory is used as the dataset for this analysis, because of its general applicability to a comprehensive list of chemical substances and industry sectors. Overall, the TRACI and RSEI results do not agree with each other in part due to the unavailability of characterization factors and toxic scores for select substances, but primarily because of their different evaluation approaches. Therefore, TRACI and RSEI should be used together both to support a more comprehensive and robust approach to screening of chemicals for environmental management and policy and to highlight substances that are found to be of concern from both perspectives.

Adsorption of a cationic dye, methylene blue, on to chitosan hydrogel beads generated by anionic surfactant gelation.

Chitosan hydrogel beads (CSB) formed by sodium dodecyl sulphate (SDS) gelation were used for the removal of a cationic dye, methylene blue (MB), from aqueous solutions. The adsorption capacity of chitosan beads (CB) formed by alkali gelation was low because of charge repulsions between the chitosan (CS) and the MB. The adsorption capacity of CSB (4 g/L SDS gelation) for MB (100 mg/L) was 129.44 mg/g, and it decreased significantly with increasing SDS concentration during gelation. This decrease was a result of increased density of the CSB membrane materials. The CSB membrane materials formed with the 4 g/L SDS gelation showed the highest volumetric adsorption capacity. The MB adsorption on to CB and CSB increased with increasing values for the initial pH of solution. Data from both CB and CSB showed good fit to Sips isotherm models, and the maximum adsorption capacity of CSB (226.24 mg/g) was higher than that of CB (99.01 mg/g).

Nickel ferrite/MXene-coated carbon felt anodes for enhanced microbial fuel cell performance.

In recent years, the modification of electrode materials for enhancing the power generation of microbial fuel cells (MFCs) has attracted considerable attention. In this study, a conventional carbon felt (CF) electrode was modified by NiFe2O4 (NiFe2O4@CF), MXene (MXene@CF), and NiFe2O4-MXene (NiFe2O4-MXene@CF) using facile dip-and-dry and hydrothermal methods. In these modified CF electrodes, the electrochemical performance considerably improved, while the highest power density (1385 mW/m2), which was 5.6, 2.8, and 1.4 times higher than those of CF, NiFe2O4@CF, and MXene@CF anodes, respectively, was achieved using NiFe2O4-MXene@CF. Furthermore, electrochemical impedance spectroscopy and cyclic voltammetry results confirmed the superior bioelectrochemical activity of a NiFe2O4-MXene@CF anode in a MFC. The improved performance could be attributed to the low charge transfer resistance, high conductivity and number of catalytically active sites of the NiFe2O4-MXene@CF anode. Microbial community analysis demonstrated the relative abundance of electroactive bacteria on a NiFe2O4-MXene@CF anodic biofilm rather than CF, MXene@CF, and NiFe2O4@CF anodes. Therefore, these results suggest that combining the favorable properties of composite materials such as NiFe2O4-MXene@CF anodes can open up new directions for fabricating novel electrodes for renewable energy-related applications.

Urban water infrastructure optimization to reduce environmental impacts and costs.

Urban water planning and policy have been focusing on environmentally benign and economically viable water management. The objective of this study is to develop a mathematical model to integrate and optimize urban water infrastructures for supply-side planning and policy: freshwater resources and treated wastewater are allocated to various water demand categories in order to reduce contaminants in the influents supplied for drinking water, and to reduce consumption of the water resources imported from the regions beyond a city boundary. A case study is performed to validate the proposed model. An optimal urban water system of a metropolitan city is calculated on the basis of the model and compared to the existing water system. The integration and optimization decrease (i) average concentrations of the influents supplied for drinking water, which can improve human health and hygiene; (ii) total consumption of water resources, as well as electricity, reducing overall environmental impacts; (iii) life cycle cost; and (iv) water resource dependency on other regions, improving regional water security. This model contributes to sustainable urban water planning and policy.

Environmental indicators for communication of life cycle impact assessment results and their applications.

Life cycle impact assessment (LCIA) is performed to quantitatively evaluate all environmental impacts from products, systems, processes and services. However, LCIA does not always provide valuable information for choosing among alternatives with different specifications, functionalities and lifetimes. The objectives of this study are (1) to propose environmental indicators to evaluate environmental efficiency and value qualitatively and quantitatively on the basis of analogies to financial and economic indicators, and (2) to present the application of the indicators. Incremental evaluation using a reference is employed to obtain the environmental indicators. The environmental efficiency indicators are conceptually based on the ratios of reduced environmental burdens returned to environmental burdens required: environmental return on investment, environmental payback period and environmental internal rate of return. The environmental value indicator is the sum of all reduced and required environmental burdens: i.e., environmental net present value. All the environmental indicators can be used to compare and rank the environmental efficiencies or values of alternatives. The environmental efficiency indicators can be applied to a new environmental labeling. The concept of eco-efficiency labeling is developed by combining the environmental efficiency indicators with financial indicators. A case study is performed to illustrate the necessity and importance of the environmental indicators. These environmental indicators can help easily communicate LCIA results in the field of environmental management.

Effect of rGO loading on Fe3O4: A visible light assisted catalyst material for carbamazepine degradation.

Carbamazepine (CBZ), an anticonvulsant drug, is one of the most recalcitrant pharmaceuticals detected in wastewater. For the photocatalytic degradation of CBZ, visible light assisted heterogeneous Fenton-like hybrid composites were synthesized via a co-precipitation method by anchoring magnetite (Fe3O4) with reduced graphene oxide (rGO). The rGO loading not only reduced the aggregation of Fe3O4 nanoparticles, but also increased the adsorption capacity of the hybrid composites. The mass ratio of rGO in the composites substantially affected CBZ photocatalytic degradation and a 10 wt% rGO loading (rGF10) provided nearly complete CBZ degradation within 3 h. Moreover, the addition of rGO reduced the charge recombination of the bare Fe3O4 nanoparticles and provided more accessible reactive sites, enhancing the degradation capacity. The visible light excited Fe3O4 nanoparticles yielded reactive species such as hydroxyl radicals (·OH), holes (h+), and superoxide radicals (O2·-) during the photodegradation process that were evaluated by using specific scavengers during the degradation experiment. The hybrid catalyst was effective under wide pH ranges (from 3 to 9) and showed faster degradation rates in the acidic condition. The composites were magnetically separable, easily regenerated, and exhibited considerably high photocatalytic activity up to five cycles.

Environmental effects of the technology transformation from hard-disk to solid-state drives from resource depletion and toxicity management perspectives.

Solid-state drives (SSDs) are used as data storage systems in various electronic devices in place of hard-disk drives (HDDs) due to their higher speed and durability and lower noise and power consumption. Although SSDs have these advantages, the environmental consequences of the technology transformation from HDD to SSD need to be examined from resource depletion and toxicity management perspectives because most electronic components and devices contain rare, precious, and toxic metals. Thus, the objective of this study was to assess and compare resource depletion and toxicity potentials from metals in an HDD and an SSD on a same capacity basis. The environmental impact potentials were evaluated based on the metal contents and masses of the drives and environmental impact characterization factors used in life cycle impact assessments. The SSD had 86% to 94% lower resource depletion potentials than the HDD, due primarily to the lower contents of Au, Cu, Pd, Ru, and Pt, whereas the SSD had 33% higher potential for only In. The SSD also had 87% to 94% lower toxicity potentials due primarily to the lower contents of Ni, Pb, Cu, and Cr. Thus, this study showed that the technology transformation is environmentally desirable to conserve resources and to protect human and ecological health. Integr Environ Assess Manag 2019;15:292-298. © 2019 SETAC.

Investigating the role of anodic potential in the biodegradation of carbamazepine in bioelectrochemical systems.

Anode potential is a critical factor in the biodegradation of organics in bioelectrochemical systems (BESs), but research on these systems with complex recalcitrant co-substrates at set anode potentials is scarce. In this study, carbamazepine (CBZ) biodegradation in a BES was examined over a wide range of set anode potentials (-200 to +600 mV vs Ag/AgCl). Current generation and current densities were improved with the increase in positive anode potentials. However, at a negative potential (-200 mV), current generation was higher as compared to that for +000 and +200 mV. The highest CBZ degradation (84%) and TOC removal efficiency (70%) were achieved at +400 mV. At +600 mV, a decrease in CBZ degradation was observed, which can be attributed to a low number of active bacteria and a poor ability to adapt to high voltage. This study signified that BESs operated at optimum anode potentials could be used for enhancing the biodegradation of complex and recalcitrant contaminants in the environment.

Development of a new Cr(VI)-biosorbent from agricultural biowaste.

Among useless but abundant agricultural biowastes such as banana skin, green tea waste, oak leaf, walnut shell, peanut shell and rice husk, in this study, banana skin was screened as the most efficient biomaterial to remove toxic Cr(VI) from aqueous solution. X-ray photoelectron spectroscopy (XPS) study revealed that the mechanism of Cr(VI) biosorption by banana skin was its complete reduction into Cr(III) in both aqueous and solid phases and partial binding of the reduced-Cr(III), in the range of pH 1.5-4 tested. One gram of banana skin could reduce 249.6 (+/-4.2)mg of Cr(VI) at initial pH 1.5. Namely, Cr(VI)-reducing capacity of banana skin was four times higher than that of a common chemical Cr(VI)-reductant, FeSO(4).7H(2)O. To diminish undesirable/serious organic leaching from the biomaterial and to enhance removal efficiency of total Cr, its powder was immobilized within Ca-alginate bead. The developed Cr(VI)-biosorbent could completely reduce toxic Cr(VI) to less toxic Cr(III) and could remove almost of the reduced-Cr(III) from aqueous phase. On the basis of removal mechanisms of Cr(VI) and total Cr by the Cr(VI)-biosorbent, a kinetic model was derived and could be successfully used to predict their removal behaviors in aqueous phase. In conclusion, our Cr(VI)-biosorbent must be a potent candidate to substitute for chemical reductants as well as adsorbents for treating Cr(VI)-bearing wastewaters.

Reliable evidences that the removal mechanism of hexavalent chromium by natural biomaterials is adsorption-coupled reduction.

For the last few decades, over 200 papers have been published in the Cr(VI) biosorption research field. Most early studies have claimed that Cr(VI) was removed from aqueous phase through an anionic adsorption, but this approach has been lost old original position. It has been newly explained that these findings were misinterpreted due to errors in measuring the concentrations of different chromium species in the aqueous phase, insufficient contact time required for equilibrium and the lack of information about the oxidation state of the chromium bound to biomaterials. Although 'adsorption-coupled reduction' is now widely accepted as the mechanism of Cr(VI) biosorption by natural biomaterials, a number of researchers still believe that Cr(VI) is removed by anionic adsorption onto the biomaterials. Therefore, the objective of this study was to show reliable evidences that the removal mechanism of Cr(VI) by natural biomaterials is 'adsorption-coupled reduction'. Sixteen natural biomaterials were used to study the Cr(VI) biosorption. Not only Cr(VI) but also total Cr in the aqueous phase were analyzed. X-ray photoelectron spectroscope was also used to verify the oxidation state of the chromium bound to the biomaterials. Finally, the removal behavior of Cr(VI) by each biomaterial was described by a kinetic model based on a redox reaction.

Column study on Cr(VI)-reduction using the brown seaweed Ecklonia biomass.

The potential use of the brown seaweed, Ecklonia, biomass as a bioreductant for reducing Cr(VI) was examined in a continuous packed-bed column. The effects of the operating parameters, such as influent Cr(VI) concentration, influent pH, biomass concentration, flow rate and temperature, on the Cr(VI) reduction were investigated. Increases in the influent Cr(VI) concentration and flow rate or a decrease in the biomass concentration inside the column led to a higher breakthrough of the Cr(VI) ions in the effluent. Particularly, the influent pH and temperature most significantly affected on the breakthrough curve of Cr(VI); a decrease in the influent pH or an increase in the temperature enhanced the Cr(VI) reduction in the column. For process application, a non-parametric model using neural network was used to predict the breakthrough curves of the column. Finally, the potential of the column packed with Ecklonia biomass for Cr(VI) detoxification was demonstrated.

Potential resource and toxicity impacts from metals in waste electronic devices.

As a result of the continuous release of new electronic devices, existing electronic devices are quickly made obsolete and rapidly become electronic waste (e-waste). Because e-waste contains a variety of metals, information about those metals with the potential for substantial environmental impact should be provided to manufacturers, recyclers, and disposers to proactively reduce this impact. This study assesses the resource and toxicity (i.e., cancer, noncancer, and ecotoxicity) potentials of various heavy metals commonly found in e-waste from laptop computers, liquid-crystal display (LCD) monitors, LCD TVs, plasma TVs, color cathode ray tube (CRT) TVs, and cell phones and then evaluates such potentials using life cycle impact-based methods. Resource potentials derive primarily from Cu, Sb, Ag, and Pb. Toxicity potentials derive primarily from Pb, Ni, and Hg for cancer toxicity; from Pb, Hg, Zn, and As for noncancer toxicity; and from Cu, Pb, Hg, and Zn for ecotoxicity. Therefore, managing these heavy metals should be a high priority in the design, recycling, and disposal stages of electronic devices.

Application of a combined three-stage system for reclamation of tunnel construction wastewater.

A combined three-stage system, (1) coagulation (2) zeocarbon filtration and (3) membrane filtration, a combination of microfiltration (MF) and reverse osmosis (RO), was investigated for reclamation of tunnel construction wastewater having a salinity of 10.8-12.9‰ and a concentration of suspended solids (SS) in the range of 264-1084 mg/L. The initial stages - coagulation, zeocarbon filtration and MF - served as a precursor to RO membrane filtration to successfully reduce water contaminants to less than 0.2 nephelometric turbidity units (NTU) of turbidity, thereby minimizing the potential for fouling. The RO system subsequently removed over 99% of remaining pollutants including ionic substances, resulting in less than 0.02 NTU turbidity, less than 0.04 mg/L total nitrogen (TN) and less than 0.01 mg/L total phosphorus (TP). Also, addition of an RO system markedly reduced high salt concentrations (high chloride (Cl(-)) concentrations) in the wastewater, exceeding 99% salt elimination. Thus, reclaimed water from our combined system met and exceeded currently regulatory quality standards for wastewater reuse (turbidity ≤ 2.0 NTU; TN ≤ 10 mg/L; TP ≤ 0.5 mg/L; Cl(-) ≤ 250 mg/L).

Casein hydrolytic peptides mediated green synthesis of antibacterial silver nanoparticles.

A green route based on the casein hydrolytic peptides (CHPs) has been established for the synthesis of highly stable and smaller sized (10±5nm) silver nanoparticles (AgNPs), without producing any type of toxic byproducts. The formation of AgNPs was triggered by the addition of an aqueous NaOH solution due to the catalytic properties of OH(-) and/or hydration of the functional groups of CHPs. The 99% transformation of Ag ions (9mM) in 20mL reaction mixture into identical AgNPs using substantially low concentration of CHPs (0.3%, wt/v), indicates that the present system is suitable for the "low volume high concentration" nanosynthesis. The AgNPs obtained by CHPs showed the minimum inhibitory concentration at 24.5ppm against both gram positive and gram negative bacterial cultures with a 96-well titer plate assay. The AgNPs possibly interact with the cell wall structures of pathogenic bacteria, Escherichia coli, causing changes in the cell morphology and the formation of porous structures, as observed by scanning electron microscopy. This eco-friendly process for the bio-mimetic production of AgNPs is a nontoxic and a competitive alternative to existing physical and chemical methods for the production of nano-scale inorganic materials.

Potentials of macroalgae as feedstocks for biorefinery.

Macroalgae, so-called seaweeds, have recently attracted attention as a possible feedstock for biorefinery. Since macroalgae contain various carbohydrates (which are distinctively different from those of terrestrial biomasses), thorough assessments of macroalgae-based refinery are essential to determine whether applying terrestrial-based technologies to macroalgae or developing completely new technologies is feasible. This comprehensive review was performed to show the potentials of macroalgae as biorefinery feedstocks. Their basic background information was introduced: taxonomical classification, habitat environment, and carbon reserve capacity. Their global production status showed that macroalgae can be mass-cultivated with currently available farming technology. Their various carbohydrate compositions implied that new microorganisms are needed to effectively saccharify macroalgal biomass. Up-to-date macroalgae conversion technologies for biochemicals and biofuels showed that molecular bioengineering would contribute to the success of macroalgae-based biorefinery. It was concluded that more research is required for the utilization of macroalgae as a new promising biomass for low-carbon economy.