Biodegradation Process Research Articles

HISTORICAL HERITAGE IN ANTARCTICA, THE CASA MONETA MUSEUM: A FIRST APPROACH TO THE CHARACTERIZATION OF XYLOPHAGOUS FUNGI AND THEIR POTENTIAL ROLE IN WOOD DAMAGE

The Casa Moneta Museum is located at the base located at an isthmus located on Laurie Island in the South Orkney Islands archipelago. Currently, the museum shows signs of deterioration of the wood (discoloration, fibrous appearance and presence of mycelium) and it is necessary to characterize this mycobiota to analyze the potential role in the biodegradation process. An assessment of the potential risk associated with fungal communities could provide valuable information for taking conservation action at the Casa Moneta Museum. The aim of this work was to evaluate the extracellular oxidase production of fungi recovered from deteriorated wood at the museum and to analyze the biodegradation risk index of three sampled sites in the building. The enzymatic profile showed the potential degradation of Cadophora spp. and Tulasnella albida strains. The analysis performed integrated data on several parameters like occurrences, species diversity, dominant species, wind direction, relative humidity, growth temperature, type of dispersion propagules and substrate, indicating Site 2 has a major biodegradation risk index which suggests that this site should be the immediate target for conservation efforts.

Utilization of Sunflower Husk Ash in the Production of Polyurethane Materials

Energy produced from waste biomass is more environmentally friendly than that produced from fossil resources. However, the problem of managing waste from the thermal conversion of biomass arises. The overarching goal of this article was to propose a method of utilizing biomass ash (sunflower husk) as a filler that positively affects the properties of rigid polyurethane foams. The scope of the presented research is to obtain and characterize rigid polyurethane foams (RPUFs) with the addition of two types of fillers: sunflower husks (SHs) and sunflower husk ash (SHA). First, an analysis of the fillers was carried out. The carbon content of SHs (C~49%) was ten times higher in comparison to SHA’s carbon content (C~5%). The morphology of the fillers and the particle size distribution were determined, which showed that in the case of SHs, particles with a size of 500–1000 µm predominated, while in SHA, the particles were 1–20 µm. The content of inorganic compounds was also determined. Potassium and calcium compounds were the most abundant in both fillers. The second part of the research was the analysis of polyurethane materials with the addition of fillers. The obtained results indicate that filler addition had a positive effect on the dimensional stability of the foams by eliminating the risk of material shrinkage. The biodegradation process of polyurethane materials was also carried out. The reference foam weight loss after 8 weeks was ~10%, while the weight loss of the foam containing SHA was over 28%. Physical and mechanical properties, cell structure, and thermal stability tests were also carried out. The use of bio-waste fillers creates a possibility for the partial replacement of petrochemical products with environmentally friendly and recycled materials, which fits into the circular economy strategy.

Comparing the response of the indigenous microbial community to crude oil amendment in oxic versus hypoxic conditions

IntroductionThe Caspian Sea is the world’s largest landlocked saline lake which lies between Europe and Asia. This region is particularly known for its large-scale oil reserves, pipelines, and drilling activities, which have contributed to the environmental decline of this lake. In addition to pollution from the petroleum industry, drainage from various river basins brings an influx of residential, industrial, and agricultural effluents that induce eutrophication and hypoxic conditions in deeper, colder waters, creating an oxygen gradient. The temperature and oxygen stratification in this environment has presented a unique opportunity to investigate the potential of the biodegradative processes carried out by the indigenous microbial community. We believe these indigenous microbes possess different metabolic capabilities to degrade oil as they adapted to declining oxygen concentrations and temperatures with increasing depths over a prolonged period. Hence, community structure and composition will vary with depth.MethodsMicrocosms were set up to observe the indigenous microbial reaction after a 60 ppm native crude oil amendment over 115 days. Surface water microcosms were incubated at 28ºC and aerated while deep water microcosms were incubated at 8ºC under anaerobic conditions. These two environmental conditions represent the temperature and oxygen extremes along the gradient and were selected as we try to simulate the indigenous community’s response to this oil contamination. DNA was extracted and amplified from these microcosms and sequenced. Bioinformatic analysis was performed to track changes in the abundance of taxa present and biodiversity over different time points to show the progression of community structure.ResultsAll microcosms showed the presence of hydrocarbon-degrading phyla, whose presence is consistent with other reports from oil-enriched environments. However, distinct communities were observed in oxic versus hypoxic microcosms.ConclusionOrders of Bacteria related to sulfate and nitrogen cycling were found in hypoxic microcosms, indicating a possible mechanism for the anaerobic biodegradation of crude oil. GC-MS analysis of initial and final microcosms also provided evidence of degradation of hydrocarbon fractions in both warm, oxic and cold, hypoxic conditions.

Investigation of Mineral Oil and CuO Mixed Synthetic Oil in Compression Ignition Engines: A Comparison of Physicochemical Attributes

Mineral oil resources are depleting rapidly, and the slower conventional oil biodegradation process results in environmental pollution. To resolve this issue, cupric oxide (CuO) nanoparticles (1% wt) were introduced into a base oil to improve the lubricating capability of castor oil. In addition, 1% wt. sodium dodecyl sulfate was also blended with the base oil in order to attain the maximum dispersion stability of CuO nanoparticles in the castor oil. Afterward, thermophysical property, atomic absorption spectroscopy, and Fourier transform infrared radiation (FTIR) testing of the lubricant oil sample were performed before and after 100 h of engine operations at 75% throttle and 2200 rpm for each lubricant sample in order to check the capability of the novel oil with mineral oil. Compared with the natural mineral oil, the behavior of the CuO-based lubricant has essentially the same physical features, as measured according to ASTM standard methods. The physicochemical properties like (KV)40 °C, (KV)100 °C, FP, ash, and TBN decrease more in the case of the synthetic oil by 1.15, 1.11, 0.46, 1.1, and 1.2% than in the conventional oil, respectively. FTIR testing shows that the maximum peaks lie in the region of 500 to 1750 cm−1, which shows the presence of C=O, C-N, and C-Br to a maximum extent in the lubricant oil sample. AAS testing shows that the synthetic oil has 21.64, 3.23, 21.44, and 1.23% higher chromium, iron, aluminum, and zinc content. However, the copper and calcium content in the synthetic oil is 14.72 and 17.68%, respectively. It can be concluded that novel bio-lubricants can be utilized as an alternative to those applications that are powered by naturally produced mineral oil after adding suitable additives that further enhance their performance.

Unravelling biosynthesis and biodegradation potentials of microbial dark matters in hypersaline lakes

Biosynthesis and biodegradation of microorganisms critically underpin the development of biotechnology, new drugs and therapies, and environmental remediation. However, most uncultured microbial species along with their metabolic capacities in extreme environments, remain obscured. Here we unravel the metabolic potential of microbial dark matters (MDMs) in four deep-inland hypersaline lakes in Xinjiang, China. Utilizing metagenomic binning, we uncovered a rich diversity of 3030 metagenome-assembled genomes (MAGs) across 82 phyla, revealing a substantial portion, 2363 MAGs, as previously unclassified at the genus level. These unknown MAGs displayed unique distribution patterns across different lakes, indicating a strong correlation with varied physicochemical conditions. Our analysis revealed an extensive array of 9635 biosynthesis gene clusters (BGCs), with a remarkable 9403 being novel, suggesting untapped biotechnological potential. Notably, some MAGs from potentially new phyla exhibited a high density of these BGCs. Beyond biosynthesis, our study also identified novel biodegradation pathways, including dehalogenation, anaerobic ammonium oxidation (Anammox), and degradation of polycyclic aromatic hydrocarbons (PAHs) and plastics, in previously unknown microbial clades. These findings significantly enrich our understanding of biosynthesis and biodegradation processes and open new avenues for biotechnological innovation, emphasizing the untapped potential of microbial diversity in hypersaline environments.

The enhancement of waste PET particles enzymatic degradation with a rotating packed bed reactor

Polyethylene terephthalate (PET) is widely used, and biodegradation of waste PET results in a residue-free process, generating recyclable products, thereby contributing to the advancement of a more recyclable plastics lifecycle. Extensive research has been conducted on the modification and evolution of enzyme for PET degradation. As a solid-liquid heterogeneous reactions of PET degradation, the slow diffusion rate of the enzyme from liquid to solid PET surface leading to a slow reaction rate. Enhancement of mass transfer would accelerate PET degradation. Rotating packed bed (RPB) is a mass transfer enhancement reactor, but shear strength generated by the enzyme molecule knocking on rotator of RPB leads to enzyme denaturation. To address this issue, shear strength resistance agents were introduced in this study. With the protection of β-cyclodextrin combined with kieselguhr, PET particle degradation rate of 95% was achieved under the optimum conditions in 24 h, which was improved by 30% compared to that in stirred tank reactor. The results of this work demonstrated that the mass transfer greatly influenced the PET biodegradation process. RPB combined with the function of shear strength resistance agents could greatly improve the efficiency of the biodegradation process. This study provides a reference for the scaling up of PET degradation, and holds significant promise in the broader context of combatting plastic pollution challenges and advancing sustainable solutions for plastic waste.

Marine Copepods as a Microbiome Hotspot: Revealing Their Interactions and Biotechnological Applications

Copepods are the most abundant organisms in marine zooplankton and the primary components of the food chain. They are hotspots for highly adaptable microorganisms, which are pivotal in biogeochemical cycles. The microbiome, encompassing microorganisms within and surrounding marine planktonic organisms, holds considerable potential for biotechnological advancements. Despite marine microbiome research interests expanding, our understanding of the ecological interactions between microbiome and copepods remains limited. This review intends to give an overview of the recent studies regarding the microbiome associated with marine copepods, with particular focus on the diversity of bacteria and fungi. The significance of copepod-associated microbiomes in different contexts, such as aquaculture and biodegradation processes, was evaluated. The ability of the microbiome to mitigate harmful bacterial growth in cultured organisms was also explored. The microbiome associated with copepods has demonstrated efficacy in reducing the proliferation of detrimental bacteria in aquaculture, paving the way for the commercial utilization of natural zooplankton in fish rearing. Additionally, copepod-associated microbiomes may play a role in addressing marine environmental challenges, such as the bioremediation of polluted marine matrices. Overall, this review represents a basis for investigating intricate copepod-associated microbiomes and their diverse applications, enhancing our comprehension of the ecological and evolutionary significance of marine microbiomes.

Application of laccase produced by marine actinomycetes in accelerating the rate of biodegradation of polyethylene

Although plastic is very useful in modern life, its widespread use could impair human sustainability. Improper plastic waste management generates greenhouse gases and harmful waste. Plastics and its associated by-products, such as microplastics, accumulate on land and in the oceans causing harm to human and ecological health. An environmentally friendly solution, such as enzymes-mediated biocatalytic depolymerization, is required for efficient management of the large amount of waste generated around the world. Actinomycetes are less explored for commercial biodegradation processes but have attracted attention since they constitute a significant proportion of the soil and aquatic flora and because of their ability to degrade complex materials. This study involves identification of laccase-producing marine actinomycetes and examining the possibility of accelerating the rate of biodegradation of polyethylene by treating with laccase enzyme. The polyethylene test material treated with laccase enzyme for 30 days shows 9.36 percent rate of biodegradation, which was six times higher than the rate of biodegradation of an untreated one. The change in the chemical structure of the polyethylene was studied using Fourier transform infrared spectroscopy. After treatment with laccase enzyme, the carbonyl index of the polyethylene test material increased to 1.25 indicating that the polymer was oxidized, and post biodegradation study showed that the carbonyl index decreased to 0.66 which confirms the concept that oxidized polymer was utilized by the microorganisms. The laccase-producing isolate A-09 showed 99 percent identity as Streptomyces rubiginosus based on molecular fingerprinting.

Effect of pro‐oxidants on the aerobic biodegradation, disintegration, and physio‐mechanical properties of compostable polymers

AbstractBiodegradable polymers are gaining momentum to resolve the globally acknowledged plastic waste problem. Understanding, characterizing, and developing new generations of biodegradable plastics is crucial to provide industries with alternative green materials that can fully satisfy biodegradation rates and lifetime specifications. This study evaluates the influence of metal pro‐oxidant additives on the degradation properties of various biodegradable polymer systems. For this purpose, iron (III) stearate (FeSt3) and bismuth oxide (Bi2O3), as oxidant agents, were incorporated into poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) (PHBV), poly(butylene adipate‐co‐terephthalate) (PBAT), cellulose acetate (CA), poly(lactic acid) (PLA), and thermoplastic starch (TPS) bioplastics. The material performances and biodegradability properties due to the additives on the resulting bioplastic formulations were investigated. A mechanism was proposed in which both pro‐oxidant additives can accelerate the thermo‐oxidation processes under composting conditions and cleave the polymer chains into smaller fragments to stimulate the biodegradation rate through microorganisms' activity. The study revealed that both pro‐oxidant additives, FeSt3 and Bi2O3, effectively improved the biodegradation process for all tested polymers except TPS, which already had a very high biodegradation rate. The observed change in the barrier and mechanical properties due to the additives were within tolerable limits of corresponding neat polymers.

Novel derivative compound produced from carbofuran insecticide degradation and transformation promoted by Pseudomonasfluorescens

Carbofuran insecticide is one of the insecticides most often used by Indonesian farmers. The United Nations Environment Program (UNEP) 2011 in the decision of UNEP/FAO/RC/CRC.11/6, agreed that the active ingredient Carbofuran is dangerous to human health and the environment. P. fluorescens bacteria are known to be able to remediate carbofuran-contaminated soil. This study examines more deeply the biodegradation and biotransformation processes of Carbofuran in P. fluorescens bacteria. The research was carried out at the Laboratory of Plant Diseases, Faculty of Agriculture, Brawijaya University; Analytical Chemistry Laboratory, State Polytechnic of Malang; and Analytical Chemistry Laboratory, Udayana University from February to August 2020. The results showed that P. fluorescens was able to degrade the insecticide Carbofuran in liquid media up to 82 % and the growth of P. fluorescens bacteria reached 2.9 x 1012 CFU/mL, bacteria P. fluorescens is able to degrade the insecticide Carbofuran in a mixture of soil and compost up to 85 % and the growth of P. fluorescens bacteria reaches 7.5 x 1013 CFU/mL, resulting in Carbofuran insecticide derivatives from the biotransformation process, there are 3-hydroxy-7-phenol; 2,3-dihydro-1-benzofuran-2,2,7-triol; (2Z)-2-[(2Z)-pent-2-en-1-ylidene]butane-1,4,4-trio; 7-phenol; 2,2,3-trihydroxy-2,3-dihydro-1-benzofuran-7-yl hydrogen carbonate; 2,2-dimethyl-2,3-dihydro-1-benzofuran-7-yl acetate; 7-(hydroxymethoxy)-2,3-dihydro-1-benzofuran-2,2,3,5-tetrol; 3-hidroksi-2-fenilpropil Carbamat; 2-(3-hydroperoxy-2-hydroxyphenyl)ethane-1,1-diol, 3-keto-7-fenol; 4-hydroxy-2,2-dimethyl-2,3-dihydro-1H-inden-1-one; 3-hydroxy-carbofuran; and 7-methoxy-2,2-dimethyl-2,3-dihydro-1-benzofuran-3,5-diol. Carbofuran derivative compounds from the biodegradation of P. fluorescens bacteria are less toxic than the active ingredient Carbofuran.

Investigation on the effect of several parameters involved in the biodegradation of polyethylene (PE) and low-density polyethylene (LDPE) under various seawater environments

This work investigates the biodegradation of polyethylene (PE) and low-density polyethylene (LDPE) and the leaching of their harmful additives. Micro/macro-plastics of both types were subjected to different laboratory-controlled conditions for 3 months. Gas Chromatography-Mass Spectroscopy (GC–MS) results revealed that leachate concentrations ranged from 0.40 ± 0.07 μg/L to 96.36 ± 0.11 μg/L. It was concluded that the additives' leaching process was promoted by light. However, light was not the only factor examined; microorganisms, pH, salinity, aeration/mixing and temperature influenced the biodegradation process, too. GC–MS results showed a prodigious impact on the biodegradation process when Pseudomonas aeruginosa was added to the artificial seawater compared to plastics exposed to light/air only. Scanning Electron Microscopy (SEM) micrographs demonstrated a significant alteration in the plastics' morphologies. Similarly, Fourier-Transform Infrared Spectroscopy (FTIR) spectra showed obvious changes in plastics characteristic peaks, especially microplastics. Furthermore, it was shown that PE was more susceptible to degradation/biodegradation than LDPE. Inductively Coupled Plasma-Optical Emission Spectroscopy (ICP-OES) findings showed that some toxic metals were present in water samples after experiments, with concentrations above the permissible limits. For instance, bio-augmentation/bio-stimulation experiments showed that the concentrations of Pb, Sr, and Zn were 0.59 mg/L, 70.09 mg/L, and 0.17 mg/L, respectively; values above the permissible limits. It is crucial to emphasise that plastics must be meticulously engineered to avoid environmental and human impacts, originated from their degradation by-products. Furthermore, a holistic approach engaging stakeholders, researchers, policymakers, industries and consumers, is essential to effectively tackle the global challenge of marine plastic pollution.

Biodegradation and Utilization of the Pesticides Glyphosate and Carbofuran by Two Yeast Strains

The widespread use of synthetic pesticides in agricultural practice is associated with the risk of environmental pollution, damage to non-target organisms, and harm to the health of consumers due to the presence of pesticides in the resulting products. Metabolically active microbial species play a significant role in eliminating harmful chemicals from the environment. The two yeast strains used in this study are Trichosporon cutaneum R57 and Candida tropicalis V1. Both strains showed growth and development in the presence of the pesticides glyphosate and carbofuran used as the sole carbon sources. The gas-chromatographic analysis performed showed that C. tropicalis V1 reached 76% of 0.3 g/L glyphosate biodegradation in 192 h. At the same time, the amount of glyphosate decreased by about 58% in the culture of T. cutaneum R57. During the glyphosate biodegradation process, the presence of the intermediate metabolites methylglycine and glycine was revealed. Strain T. cutaneum R57 demonstrated nearly total biodegradation of 0.3 g/L carbofuran in 192 h of cultivation. Strain C. tropicalis V1 showed a slow decrease (23.4%) of the same amount of carbofuran during 192 h. Pyruvic acid and carbofuran-7-phenol have been found to be intermediate metabolites in the breakdown of carbofuran. This report provides new information on the potential of yeasts to participate in environmental pesticide cleanup processes.

Exploring genetic landscape of low-density polyethylene degradation for sustainable troubleshooting of plastic pollution at landfills

Plastic pollution increases globally due to the high volume of its production and inadequate mismanagement, leading to dumps in landfills affecting terrestrial and aquatic ecosystems. Landfills, as sink for plastics, leach various toxic chemicals and microplastics into the environment. We scrutinized the genetic expression for low-density polyethylene (LDPE) degradation via microorganisms to investigate cell viability and metabolic activities for biodegradation and genetic profiling. Samples were collected from the Pirana waste landfill at Ahmedabad, Gujarat, which is one of the largest and oldest municipal solid waste (MSW) dump sites in Asia. Results analyzed that isolated bacterial culture PN(A)1 (Bacillus cereus) is metabolically active on LDPE as carbon source during starvation conditions when incubated for up to 60 days, which was confirmed via 2,3,5-triphenyl-tetrazolium chloride (TTC) reduction test, reported cell viability and LDPE degradation. Abrasions, surface erosions, and cavity formations were analyzed via scanning electron microscopy (SEM), whereas the breakdown of high molecular polymers converted to low molecules, i.e., depolymerization, was also observed via Fourier-transform infrared (FTIR) spectroscopy over 90 days, along with changes in functional groups of carboxylic acids and aldehyde as well as the formation of polysulfide, aliphatic compounds, aromatic ethers, alcohols, and ether linkages. Further, transcriptomic analysis was performed via DESeq2 analysis to understand key gene expression patterns and pathways involved in LDPE degradation. During the initial phase of LDPE degradation, genes related to biological processes, like membrane transportation, ABC transporters, carbon and lipid metabolism, fatty acid degradation/oxidation, and TCA cycle, are likely to indicate pathways for stress response and molecular functions, like oxidoreductase, catalytic, lyase, transferase, and hydrolase activities were expressed. Interlinking between metabolic pathways indicates biodegradation process that mineralizes LDPE during subsequent incubation days. These pathways can be targeted for increasing the efficiency of LDPE degradation using microbes in future studies. Thus, considering microbial-mediated biodegradation as practical, eco-friendly, and low-cost alternatives, healthy biomes can degrade polymers in natural environments explored by understanding the genetic and enzymatic expression, connecting their role in the process to the likely metabolic pathways involved, thereby increasing the rate of their biodegradation.

A mini review on synthetic and biosurfactants: origin and structure, physicochemical properties, applications, cost of production, toxicity, biodegradability and environmental effects

Abstract A comparison is made between synthetic and biosurfactants in terms of their origin, structure, physico-chemical properties, applications, production costs, toxicity, biodegradability and environmental impact. It is shown that the chemical structure of surfactants synthesised by living organisms is more complicated than that of those produced by classical methods. The reduction in water surface tension induced by synthetic and biosurfactants is almost the same. Due to their origin and structure, biosurfactants are preferred in medical, cosmetic and food applications, mainly because they are less toxic than synthetic surfactants. Synthetic surfactants require more time and special environmental conditions to start the biodegradation process compared to biosurfactants, which can easily start biodegradation under normal physical conditions. This mini-review highlights this new category of surfactants (biosurfactants). It also provides a comparison between synthetic and biosurfactants is provided using the available data reported in the literature.

A review of the recent progress in biotrickling filters: packing materials, gases, micro-organisms, and CFD.

Organic pollutants in the air have serious consequences on both human health and the environment. Among the various methods for removing organic pollution gas, biotrickling filters (BTFs) are becoming more and more popular due to their cost-effective advantages. BTF can effectively degrade organic pollutants without producing secondary pollutants. In the current research on the removal of organic pollutants by BTF, improving the performance of BTF has always been a research hotspot. Researchers have conducted studies from different aspects to improve the removal performance of BTF for organic pollutants. Including research on the performance of BTF using different packing materials, research on the removal of various mixed pollutant gases by BTF, research on microbial communities in BTF, and other studies that can improve the performance of BTF. Moreover, computational fluid dynamics (CFD) was introduced to study the microscopic process of BTF removal of organic pollutants. CFD is a simulation tool widely used in aerospace, automotive, and industrial production. In the study of BTF removal of organic pollutants, CFD can simulate the fluid movement, mass transfer process, and biodegradation process in BTF in a visual way. This review will summarize the development of BTFs from four aspects: packing materials, mixed gases, micro-organisms, and CFD, in order to provide a reference and direction for the future optimization of BTFs.

Biodegradation of pyrene by bacterial consortia: Impact of natural surfactants and iron oxide nanoparticles

Polycyclic aromatic hydrocarbons (PAHs) are potentially hazardous compounds that could cause a severe impact on many ecosystems. They are very challenging to remove using conventional methods due to their hydrophobic nature. However, this issue can be resolved by utilizing surface-active molecules to increase their bioavailability. In this study, pyrene was chosen as the PAH compound to explore its degradability by the effect of individual bacterial strains (Pseudomonas stutzeri NA3 and Acinetobacter baumannii MN3) and mixed consortia (MC) along with natural surfactant derived from Sapindus mukorossi and iron oxide nanoparticles (NPs). Additionally, fatty acids esters, dipeptides, and sugar derivative groups were identified as potent bioactive components of natural surfactants. Various techniques, such as XRD, VSM, TEM, and FE-SEM with EDX, were utilized to characterize the pristine and Fenton-treated iron oxide NPs. The analytical results confirmed that the Fe3O4 crystal phase and spherical-shaped NPs exhibited excellent magnetic properties. The impact of natural surfactants and iron oxide NPs has significantly contributed to the biodegradation process, resulting in a prominent decrease in chemical oxygen demand (COD) levels. Gas chromatography-mass spectrometry (GC-MS) analysis showed that biodegradation systems produced primary hydrocarbon intermediates, which underwent oxidative degradation through Fenton treatment. Interestingly, synthesized iron oxide NPs effectively produced hydroxyl radical (•OH) during the Fenton reaction, which was confirmed by electron paramagnetic resonance (EPR) spectra, and the pristine iron oxide NPs underwent a material transformation observed. The study demonstrated an integrated approach for biodegradation and the Fenton reaction process to enhance the pyrene degradation efficiency (90%) compared to other systems. Using natural surfactants and iron oxide NPs in aquatic environments serves as a crucial platform at the interface of microorganisms and contaminated oil products. This interaction offers a promising solution for PAHs bioremediation.

A parsimonious approach to predict regions affected by sewer-borne contaminants in urban aquifers

Leaky urban drainage networks (UDNs) exfiltrating wastewater can contaminate aquifers. Detailed knowledge on spatiotemporal distributions of water-dissolved, sewer-borne contaminants in groundwater is essential to protect urban aquifers and to optimize monitoring systems. We evaluated the effect of UDN layouts on the spreading of sewer-borne contaminants in groundwater using a parsimonious approach. Due to the UDN’s long-term leakage behavior and the existence of non-degradable sewer-borne contaminants (equivalent to a conservative and constant contaminant source), we employed a concept of horizontal line sources to mimic the UDN layout. This does not require the consideration of bio-degradation processes or temporal delay and effectively bypasses the vadose zone, thus reducing computational requirements associated with a full simulation of leakages. We used a set of synthetic leakage scenarios which were generated using fractals and are based on a real-world UDN layout. We investigated the effects of typical leakage rates, varying groundwater flow directions, and UDN’s layouts on the shape of the contaminant plume, disregarding the resulted concentration. Leakage rates showed minimal effects on the total covered plume area, whereas 89% of the variance of the plume’s geometry is explained by both the UDN’s layout (e.g., length and level of complexity) and groundwater flow direction. We demonstrated the potential of applying this approach to identify possible locations of groundwater observation wells using a real UDN layout. This straightforward and parsimonious method can serve as an initial step to strategically identify optimal monitoring systems locations within urban aquifers, and to improve sewer asset management at city scale.

Preparation of antistatic and biodegradable packaging of PLA/PHBV blend‐based glassy carbon and graphene nanoplatelets composites

AbstractGlassy carbon (GC) and graphene nanoplatelets (GNP) were used as fillers for the preparation of antistatic and biodegradable composites based on poly (lactic acid)/poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) (PLA/PHBV) blend. In this work, PLA/PHBV (80/20) blends with the addition of different GC contents (0.1, 0.3, and 0.5 wt%) were prepared by melt mixing using a twin‐screw extruder, and specimens were injection molded. Furthermore, hybrid composites were prepared with the addition of 5 wt% of GNP and different GC contents (0.1, 0.3, and 0.5 wt%) using the same processing. The effect of the addition of GC and GNP on the mechanical, electrical, and electromagnetic properties and its effect on the biodegradability of the PLA/PHVB blend was evaluated. The simultaneous addition of GC (0.3 and 0.5 wt%) and GNP (5 wt%) significantly increases the elastic modulus and decreases the electrical resistivity, becoming suitable for electrostatic discharge protection packaging applications. The hybrid composite GC0.5/GNP5 reached a maximum value of total attenuation (4.5 dB), which corresponds to 60% EMI shielding. The degree of crystallinity affects biodegradability more than the type or presence of carbon material. After 110 days of anaerobic biodegradation, the hybrid composite exhibited 10% biodegradability due to the high degree of crystallinity that hinders the biodegradability process. The hybrid composites with the addition of GC and GNP are very promising for use in antistatic packaging.

Assessing Biodegradation Processes of Atrazine in Constructed Wetland Using Compound-Specific Stable Isotope Analysis

To bridge the gap between lab-scale microcosm research and field application in the compound-specific stable isotope analysis (CSIA) of atrazine, we studied the characteristics of carbon and nitrogen isotope fractionation in the atrazine degradation processes within a constructed wetland. In the wetland, we observed multiple element (C, N) isotope fractionation parameters, such as kinetic isotope effects and dual isotope slopes. These parameters are very consistent with those observed in the cultivation of AtzA- or TrzN-harboring strains, suggesting a similarity in the pathway and reaction mechanism of atrazine biodegradation between the two settings. However, we recorded variable carbon (εC: −3.2 ± 0.6‰ to −4.3 ± 0.6‰) and nitrogen isotope fractionation (εN: 1.0 ± 0.3‰ to 2.2 ± 0.3‰) across different phases. This variance could lead to an over- or underestimation of the biodegradation extent of atrazine when employing the large or small enrichment factor of the carbon isotope. Intriguingly, the estimation accuracy improved considerably when using the enrichment factor (−4.6‰) derived from the batch cultivation of the pore water. This study advances the application of CSIA in tracking atrazine biodegradation processes in ecosystems, and it also underlines the importance of the careful selection and application of the enrichment factor in quantifying the intrinsic biodegradation of atrazine in ecosystems.

Insights into electro-bioremediation of PAH-contaminated soil under polarity reversal conditions: Effect of effective current intensity and soil properties on microbial function

Electrical stimulation during electro-bioremediation has the potential to enhance the biodegradation of polycyclic aromatic hydrocarbons (PAHs) in soil. In this study, we investigated the effective current intensity, referred to as the “window condition,” which promotes the activity of functional microflora. Electro-bioremediation was performed on PAH-contaminated soil using various polarity reversal frequencies (PRF) to study the remediation mechanism. The “window condition” in this study was 20–40 mA. The enhancement of PAH degradation, particularly that of high-PAHs, increased with higher PRF, which accompanied the increasing ratio of the “window condition” to the overall electrification time (RWC). Electro-bioremediation with a 10-minute (EBPR-10 m) and 30-minute (EBPR-30 m) polarity reversal (PR) periods achieved the highest ratios of PAH degradation at 43.9±2.3 % and 37.9±1.8 %, respectively, with RWC of 0.4919 and 0.4056, respectively, after 60 days. The increase in PRF improved the soil physicochemical properties, which were conducive to maintaining effective electrokinetic and biodegradation processes. Redundancy analysis (RDA) and Pearson correlation analyses demonstrated that soil electrical conductivity (EC), dissolved organic carbon (DOC), temperature, and the proportion of macroparticle components (0.195–2.500 um) in soil colloids (Ps/Po) were key factors in explaining the persistence of microbial abundance and community structure. Structural equation models (SEMs) further illustrated the mechanism behind the enhanced PAH biodegradation, including (i) the direct stimulation of microbial activity because of increased RWC and (ii) the indirect optimization of microbial function by improving soil physicochemical properties under optimal PRF.