Aerobic Biodegradation Research Articles

Aerobic and anaerobic biodegradation of synthetic drilling fluids in marine deep-water offshore environments: Process variables and empirical investigations

In this study, the aerobic and anaerobic biodegradation tendencies of a newly developed synthetic ester drilling fluid named “SEEP Mixture synthetic fluid” in marine deep-water environment were experimentally studied. The results were compared with a GTL and LASF synthetic hydrocarbon fluids. A modified Oxygen (O2) Consumption and a gas pressure measurement technique were used for biodegradation evaluation in the aerobic and anaerobic digesters respectively. The tested drilling fluids were exposed to the sea water inoculum for a period of 28 and 60 days in the different digester designs. An empirical investigation of the influence of some paramount biodegradation factors among others such as reaction temperature, dissolved oxygen concentration, time, chemical and inoculum concentrations was conducted.The biodegradation levels in SEEP mixture synthetic fluid and reference chemical sample were already above 60% during the 10-day window period under aerobic condition which shows that the new ester fluid (SEEP mixture) is inherently-readily biodegradable under aerobic condition. The ultimate biodegradability degrees of the new fluid were 81.50% and 76.10 % in aerobic and anaerobic pathways respectively. The rates of biodegradation were higher in the aerobic than in anaerobic medium in all the tested fluid chemicals. However, the GTL and LASF fluids (SHBF & SEBF) were not readily biodegradable in both microbial consortia. The rate of aerobic and anaerobic biodegradation has a positive linear relationship with incubation time and temperature but an inverse relationship with substrate concentration. Finally, Lower oxygen concentration in sea water reduces aerobic biodegradation while anaerobic transformation is grossly dependent on the availability of alternative electron acceptor ions such as NO3−, SO42−, Fe3＋ Mn4+, and CO32− and methanogens in the sea water.

Effect of methyl substituents on the biodegradation of two-ring polycyclic aromatic hydrocarbons in crude oil identified by aerobic biodegradation simulations

Existing studies determining the effects of substituted methyl groups on polycyclic aromatic hydrocarbon biodegradation were mostly limited to an individual compound or a class of compounds. The simultaneous transformation of the multiple series of methyl-substituted two-ring polycyclic aromatic hydrocarbons (61 compounds) in crude oil through laboratory simulations has been examined, including naphthalenes, fluorenes, biphenyls, and dibenzofurans. The biodegradation sequences were in the order of dimethylnaphthalenes > trimethylnaphthalenes > biphenyls > dibenzofurans, tetramethylnaphthalenes > pentamethylnaphthalenes > fluorenes. Polycyclic aromatic hydrocarbon biodegradation was depending on both the number and the position of methyl substituents. For naphthalenes, fluorenes, biphenyls, and dibenzofurans, the more methyl groups in the parent compound, the more resistant it was to biodegradation. Among the polycyclic aromatic hydrocarbons with the same number of methyl groups, the more ortho-methyl substitutes, the more challenging it was to be decomposed. In the case of dimethylnaphthalenes or trimethylnaphthalenes with the same number of methyl and ortho-methyl substituents, their biodegradability reduced as the number of α substituents increased. The number of ortho-methyl substituents had a greater impact than that of α/β substituents. The relative significance of these two factors has not been confirmed in previous studies.

Migration, Transformation, and Toxicity of Quaternary Ammonium Antimicrobial Agents in the Environment

Quaternary ammonium compounds (QACs) are one type of widely used cationic biocide, and their usage amount is growing rapidly due to the flu and COVID-19 pandemic. Many QACs were released into the environment in or after the course of their use, and thus they were widely detected in water, sediment, soil, and other environmental media. QACs have stronger surface activity and non-specific biotoxicity, which poses a potential threat to the ecosystem. In this study, the environmental fate and potential toxicity of QACs were documented in terms of their migration and transformation process, biological toxicity effects, and the main mechanisms of bacterial resistance to QACs. Aerobic biodegradation was the main natural way of eliminating QACs in the environment, and the reaction was mainly initiated by the hydroxylation of C atoms at different positions of QACs and finally mineralized to CO2and H2O through decarboxylation, demethylation, and β-oxidation reaction. Toxicological studies showed that QACs at environmental concentrations could not pose acute toxicity to the selected biotas but threatened the growth and reproduction of aquatic organisms like Daphnia magna. Their toxicity effects depended on their molecular structure, the tested species, and the exposed durations. Additionally, our team first investigated the toxicity effects and mechanisms of QACs toward Microcystis aeruginosa, which showed that QACs depressed the algae growth through the denaturation of photosynthetic organelles, suppression of electron transport, and then induction of cell membrane damage. In the environment, the concentrations of QACs were always lower than their bactericidal concentrations, and their degradation could induce the formation of a concentration gradient, which facilitated microbes resistant to QACs. The known resistance mechanisms of bacteria to QACs mainly included the change in cell membrane structure and composition, formation of biofilm, overexpression of the efflux pump gene, and acquisition of resistance genes. Due to the similar targets and mechanisms, QACs could also induce the occurrence of antibiotic resistance, mainly through co-resistance and cross-resistance. Based on the existing data, future research should emphasize the toxicity effect and the potential QACs resistance mechanism of microorganisms in real environmental conditions.

Congener-specificity, dioxygenation dependency and association with enzyme binding for biodegradation of polybrominated diphenyl ethers by typical aerobic bacteria: Experimental and theoretical studies

Polybrominated diphenyl ethers (PBDEs) are a group of organic pollutants that have attracted much concerns of scientific community over the ubiquitous distribution, chemical persistence and toxicological risks in the environment. Though a great number of aerobic bacteria have been isolated for the rapid removal of PBDEs, the knowledge about biodegradation characteristics and mechanism is less provided yet. Herein, the congener-specificity of aerobic biodegradation of PBDEs by typical bacteria, i.e. B. xenovorans LB400 was identified with the different biodegradation kinetics, of which the changes were largely hinged on the bromination pattern. The more bromination isomerically at ortho-sites other than meta-sites or the single bromination at one of aromatic rings might always exert the positive effect. The biodegradation of PBDEs should be thermodynamically constrained to some extent because the calculated Gibbs free energy changes of initial dioxygenation by quantum chemical method increased with the increase of bromination. Within the transition state theory, the high correlativity between the apparent biodegradation rates and Gibbs free energy changes implied the predominance and rate-limiting character of initial dioxygenation, while the regioselectivity of dioxygenation at the ortho/meta-sites was also manifested for the more negative charge population. The molecular binding with the active domain of dioxygenase BphA1 in aerobe was firstly investigated using docking approach. As significantly illustrated with the positive relationship, the higher binding affinity with BphA1 should probably signify the more rapid biodegradation. Besides the edge-on π-π stacking of PBDEs with F227 or Y277 and π-cation formulation with histidines (H233, H239) in BphA1, the reticular hydrophobic contacts appeared as the major force to underpin the high binding affinity and rapid biodegradation of PBDEs. Overall, the experimental and theoretical results would not only help understand the aerobic biodegradation mechanism, but facilitate enhancing applicability or strategy development of engineering bacteria for bioremediation of PBDEs in the environment.

Multilayer Sheets Based on Double Coatings of Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) on Paper Substrate for Sustainable Food Packaging Applications

This work reports on the development and performance evaluation of newly developed paper sheets coated, on both sides, with thin films of biodegradable poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) for applications of food packaging. For this, PHBV/paper/PHBV multilayers were first prepared by the thermo-sealing technique, optimizing the process variables of temperature and time. Thereafter, the multilayer sheets were characterized in terms of their morphological, optical, thermal, mechanical, and barrier properties and compared with equivalent paper structures double coated with high-barrier multilayer films of petrochemical polymers. The results indicated that the double coatings of PHBV successfully improved the mechanical resistance and ductility, protected from moisture, and also reduced the aroma and oxygen permeances of paper, having a minimal effect on its optical and thermal properties. Finally, the compostability of the resultant multilayer sheets was analyzed, confirming that the presence of the PHBV coatings slightly delayed the aerobic biodegradation and disintegration of paper.

NSO-bearing compounds in severely–extremely biodegraded crude oil revealed by ESI(-) FT-ICR MS

The heavy oil is essentially comprised of asphaltene and nitrogen, sulphur, and oxygen-bearing (NSO) compounds, which records the alteration processes of aerobic biodegradation. In this study, six biodegraded oils were geochemically examined using Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) in negative-ion electrospray ionization (ESI(-)) mode to decipher the NSO heteroatom compounds molecular compositions. The results reveal that the NSO compounds, especially those strongly resistant to biodegradation, i.e., alcohol/phenols, carboxylic acids with various alkyl substitution, naphthenic acids with 2 to 5 naphthenic/aromatic rings, nitrogen- and sulphur-bearing carboxylic acids, and hydroxy acids (O3) and dibasic acids (O4) are enriched in biodegraded oils. The O1, N1O1, and O1S1 classes appear in trace amounts in severely to extremely biodegraded oils (PM > 7) but are abundant in moderately biodegraded oils (PM < 7), implying the alcohol group generated by biodegradation are further oxidized to form a carboxylic acid with the progressively biodegraded process. Abnormal enrichment of O2 and O4 classes was trapped in the severely–extremely biodegraded oils, implying the generation of additional monobasic acid/dibasic acids during microbial aerobic degradation of crude oils. Besides, the relative content of monocyclic naphthenic acid (DBE = 2) gradually decreased with biodegradation level, while those of the bicyclic-, tricyclic-, and tetracyclic–naphthenic acid (DBE = 3-5) showed an increasing trend. The newly developed proxies of NSO compounds (i.e., the ratios of biodegradation products with different numbers of oxygen atoms of the specified compound, and the O2, O3, O4, and O5 classes with various DBE values and/or various carbon numbers) agreed well with the existing biodegradation indicators (i.e., C2925-NH/C30H, C2117-NT/C23TT, C27DS/C27RS, and C28TAS/C21TAS), confirming the availability of ESI(-) FT-ICR MS to distinguish the biodegraded oils with high resolution.

Ethylated analogue of Zingerone: A new and eco-respectful preservative in cosmetics.

This article describes the eco-design of a new preservative in cosmetics based on bio-inspiration of natural extracts from traditional medicines. In order to reach the multiple specification targets, various structures have been synthesized and evaluated to select the one demonstrating broad antimicrobial spectrum with favorable environmental profile and application potential to a wide variety of formulas. In order to evaluate the antimicrobial activity of the synthesized structures, the method of the challenge test consisting in an artificial contamination of the sample with collection microbial strains and evaluation of the number of revivable microorganisms was used to select the most promising candidate. Validation of its antimicrobial potential was later confirmed on Gram positive and Gram negative bacteria, yeast and mold with measurement of its Minimum Inhibitory Concentration (MIC) in comparison with known preservatives. Environmental impact assessment of the selected candidate was achieved with the help of ready biodegradability and aquatic ecotoxicity tests performed according to appropriate Organization tes a strfor Economic Co-operation and Development (OECD) and European Union (EU) guidelinesy. Bio-inspired from turmeric and ginger extracts, an ethylated analog of Zingerone (EZ) with the chemical name 4-(3-ethoxy-4-hydroxyphenyl)butan-2-one demonstrates the strongest activity on Escherichia coli, Enterococcus faecalis, Pseudomonas aeruginosa and Candida albicans. Moreover, EZ shows a solubility in water two times higher than that of Zingerone thus increasing its interest as a potential preservative. Finally, its assessment of ready biodegradability and aquatic ecotoxicity in OECD-EU tests with a favorable environmental profile confirms its unique interest and fully justifies its use in cosmetic formulas as an eco-respectful preservative. Bio-inspiration based on technologies without noteworthy side effects but also on eco-design, particularly through the use of measures of potential environmental impact very upstream of a development, are two fundamental elements for the launching of new eco-friendly cosmetic ingredients. This approach has thus validated the strong potential of EZ as a preservative of eco-respectful formulas. The selection of EZ is also a very good example of the achievement of two key objectives targeted by cosmetic companies for the development of a novel active ingredient: environmental performance and technical performance.

Integrated anaerobic-aerobic biodegradation of mixed chlorinated solvents by electrolysis coupled with groundwater circulation in a simulated aquifer.

Chlorinated solvents are widespread subsurface contaminants that are often present as complex mixtures. Complete biodegradation of mixed chlorinated solvents remains challenging because the optimal redox conditions for biodegradation of different chlorinated solvents differ significantly. In this study, anaerobic and aerobic conditions were integrated by electrolysis coupled with groundwater circulation for biodegradation of a mixture of chloroform (CF, 8.25mg/L), 1,2-dichloroethane (DCA, 7.01mg/L), and trichloroethylene (TCE, 4.56mg/L). A two-dimensional tank was filled with field sandy and silty-clayed sediments to simulate aquifer conditions, a pair of electrodes was installed between an injection well and abstraction well, and groundwater circulation transported cathodic H2 and anodic O2 to produce multiple redox conditions. Microbial community analysis demonstrated that the system constructed a habitat suitable for the co-existence of aerobic and anaerobic microbes. After 50days of treatment, 93.1%, 100%, and 87.3% of CF, 1,2-DCA, and TCE were removed without observed intermediates, respectively. Combined with compound specific isotope analysis, the degradation of 1,2-DCA and CF was mainly attributed to aerobic oxidation and reductive dechlorination, respectively, and TCE was removed by both aerobic and anaerobic biodegradation. Our findings provide a new and efficient strategy for in situ bioremediation of groundwater contaminated by mixed chlorinated solvents.

Degradation kinetics of aromatic VOCs polluted wastewater by functional bacteria at laboratory scale

Reaction kinetics in biodegradation process is the basis and key of bioremediation technology, which can be used to predict the interaction between microorganisms and environmental states in the system. In this study, the kinetic model (Monod, Moser, Tessier and Cotonis) and kinetic parameters of aerobic biodegradation of functional bacteria in simulated wastewater polluted by aromatic volatile organic compounds (VOCs) were determined by shaking flask experiment. Monod, Moser, Tessier and Contois models were used to fit the experimental data and determine the kinetic parameters based on nonlinear regression analysis. Experimental results demonstrated that the removal rate of aromatic VOCs at 72 h was between 34.78 and 99.75% depending on the initial concentration of aromatic VOCs. The specific growth rate μ and degradation rate q increased with the increase of substrate concentration. The model of Monod, Moser and Tessier could be used to simulate microbial growth and substrate degradation in simulated aromatic VOCs polluted wastewater. Then the model and corresponding kinetic parameters were used to predict the limit concentration of biodegradation and provide theoretical support for the subsequent dynamic simulation and field engineering.

Unraveling the key driving factors involved in cometabolism enhanced aerobic degradation of tetracycline in wastewater

Cometabolism has shown great potential in increasing the engineering feasibility of microalgae-based biotechnologies for the aerobic treatment of antibiotics-polluted wastewaters. Yet, the underlying mechanisms involved in improved microalgal performance remain unknown. In this study, we incorporated transcriptomics, gene network analysis, and enzymatic activities with cometabolic pathways of tetracycline (TC) by Chlorella pyrenoidosa to identify the key driving factors. The results demonstrated that cometabolism constructed a metabolic enzymes-photosynthetic machinery to improve the electron transport chain and activities of catalytic enzymes, which resulted in subsequent 100% removal of TC. Coupling formation dynamics of the intermediates with roles of identified metabolic enzymes, degradation of TC can be induced by de/hydroxylation, de/hydrogenation, bond-cleavage, decarboxylation, and deamination. Evaluation of 18 antibiotics’ removal in reclaimed water showed cometabolism decreased the total concentrations of these antibiotics from 495.54 ng L−1 to 221.80 ng L−1. Our findings not only highlight the application potential of cometabolism in increasing engineering feasibility of microalgal degradation of antibiotics from wastewaters, but also provide the unique insights into unraveling the “black-box” of cometabolisms in aerobic biodegradation.

The effect of nitrification inhibitors on the aerobic biodegradation of tetracycline antibiotics in swine wastewater

The aerobic biotreatment process for the dual goals of antibiotic removal and ammonia retainment for the field-return-based treatment of swine wastewater was optimized by adding 2-chloro-6-trichloromethylpyridine (TCMP), commonly used as a nitrogen fertilizer synergist. The results show that the dosage of 5–10 mg/L TCMP daily effectively inhibited nitrification. The COD and tetracycline antibiotics (TCs) in the absence of TCMP was removed by 91% and 76%, and became 87% and 78% with 5 mg/L TCMP and 83% and 70% with 10 mg/L TCMP, respectively. The removal efficiency of four TCs generally followed a decreasing trend of chlortetracycline (CTC) > doxycycline (DC) > tetracycline (TC) > oxytetracycline (OTC). A dosage of 5 mg/L TCMP daily inhibited ammonia nitrification effectively and only slightly affected the removal of conventional organic pollutants and TCs. The contribution of volatilization and hydrolysis to the removal of TCs was negligible. The overall removal efficiency of four TCs in removal pathway experiments was 98%, 94%, 97%, and 96% for OTC, CTC, DC, and TC, of which 69%, 41%, 56%, and 62% was contributed by absorption, and 29%, 53%, 41%, and 34% was contributed by biodegradation, respectively. This study may have significant implications for the proper management of livestock wastewater intended to be used as fertilizers, which aims to reduce the exposure risk of antibiotics and preserve its nutrient value.

Biodegradation of micro sized nylon 6, 6 using Brevibacillus brevis a soil isolate for cleaner ecosystem

The increasing accumulation of microplastic constitutes pathogens and hazardous chemicals posing a great threat to the ecosystem. Biodegradation is an eco-friendly strategy for the removal of these contaminants. The present investigation demonstrates bioremediation of nylon 6, 6 microplastics (NMPs) for the first time using a soil isolate called Brevibacillus brevis (B.brevis) by shake flask assay. 22 w/w % weight loss of nylon 6, 6 microplastics was noticed after 35 d of incubation with B.brevis. Upon interaction with microplastics, a change in the shape of the bacterium (rod to round) could be observed along with the size reduction of the microorganism. In the case of NMPs incubated in presence of this bacterium, irregular shapes of NMPs with cracks and holes could be visualized using SEM and TEM. TGA and FTIR analysis reported the disappearance of intermolecular hydrogen bonding of nylon 6, 6 posts microbial interaction. The release of various organic acids and enzyme/enzymatic activities of the bacterium was found to be higher in the presence of NMPs. The mass spectrometric analysis confirmed the release of adipic acid and hexamethylenediamine derivatives during aerobic biodegradation, indicating NMPs being the only carbon source for the growth of B.brevis in the reaction environment. The study addresses B.brevis as a viable bacterial source for the degradation of NMPs while at the same time attempting to understand the mechanism involved. A biodegradation pathway for B.brevis induced NMP degradation has been also proposed for the first time. This finding promises a potential approach for reducing the accumulation of nylon 6, 6 in the environment.

Persistence of N-oxides transformation products of tertiary amine drugs at lab and field studies.

This work aimed at studying the formation and persistence of N-oxides transformation products (TPs) of tertiary amine drugs by combining laboratory and field studies relevant for surface water. A monitoring study using passive samplers was first achieved for assessing attenuation of selected pharmaceuticals and their related N-oxides and N-, O-dealkylated TPs (i.e., venlafaxine, tramadol, amisulpride and sulpiride) along a 1.7 km river stretch between two sampling sites. This study revealed the stability of tramadol-N-oxide, amisulpride-N-oxide and the fast dissipation of O-desmethylvenlafaxine-N-oxide, as well as the significance of N-oxidized TPs in comparison to N-dealkylated TPs and parent compounds in river. Lab-scale experiments were then implemented for a better understanding of their mechanisms of formation and degradation under aerobic water/sediment testing and under simulated solar photochemistry. N-oxidation reactions were always a minor transformation pathway under both degradation conditions with respect to N-and O-dealkylation reactions. The amount of generated N-oxides were similar for venlafaxine, tramadol and sulpiride and peaked in the 8.4–12.8% and <4% of their initial concentration (100 μg/L), during photodegradation and biodegradation experiments, respectively. Other transformation pathways such as hydroxylation and α-C-hydroxylation followed by oxidation to amide or dehydration were also identified. Investigated N-oxides TPs (except O-desmethylvenlafaxine-N-oxide) were found stable under solar photolysis and aerobic biodegradation with a very slight reverse reaction to parent compound observed for tramadol-N-oxide and amisulpride-N-oxide. Lab-scale degradation experiments were not able to anticipate the high occurrence levels of N-oxide compounds in the environment. This was most likely due to faster degradation kinetics and/or higher sorption to sediment of parent compounds and dealkylated TPs over N-oxide TPs, resulting in higher relative accumulation of the latter.

Contrasting regulatory effects of organic acids on aerobic vinyl chloride biodegradation in etheneotrophs.

Vinyl chloride (VC) is a common groundwater pollutant generated during anaerobic biodegradation of chlorinated solvents (e.g., trichloroethene (TCE) or tetrachloroethene (PCE)). Aerobic VC biodegradation by etheneotrophs can support anaerobic PCE and TCE bioremediation to achieve complete removal in situ. However, anaerobic bioremediation strategies necessitate biostimulation with electron donors that are fermented in situ, generating organic acids that could influence aerobic VC biodegradation processes. We examined the effect of organic acids (lactate, acetate, propionate, and butyrate) on aerobic VC biodegradation by VC-assimilating etheneotrophs Mycobacterium strain JS60 and Nocardioides strain JS614. Strain JS60 grew on all organic acids tested, while strain JS614 did not respond to lactate. VC-grown strain JS60 fed VC and one or more organic acids showed carbon catabolite repression (CCR) behavior where VC biodegradation occurred only after organic acids were depleted. In contrast, CCR was not evident in VC-grown strain JS614, which degraded VC and organic acids simultaneously. Acetate-grown JS60 showed similar CCR behavior when fed VC and a single organic acid, except that extended lag periods (5-12days) occurred before VC oxidation ensued. Acetate-grown JS614 fed VC and either acetate or butyrate displayed 5-8day lag periods before simultaneous VC and organic acid biodegradation. In contrast, acetate-grown JS614 degraded VC and propionate without a significant lag, suggesting a regulatory link between propionate and VC oxidation in JS614. Different global regulatory mechanisms controlling VC biodegradation in the presence of organic acids in etheneotrophs have implications for developing combined anaerobic-aerobic bioremediation strategies at chlorinated ethene-contaminated sites. KEY POINTS: • With organic acids present, VC utilization was repressed in JS60, but not in JS614 • Strain JS60 grew readily on lactate, while strain JS614 did not • Propionate alleviated lag periods for VC utilization in acetate-grown JS614.

Acesulfame Anoxic Biodegradation Coupled to Nitrate Reduction by Enriched Consortia and Isolated Shinella spp.

Acesulfame (ACE) is considered to be an emerging pollutant associated with growing concerns. Although aerobic biodegradation of ACE has been observed in wastewater treatment plants worldwide and verified in pure cultures, limited information is available on ACE biodegradation under anoxic conditions, which are ubiquitous in natural environments. Here, we found that ACE could be mineralized completely via a process coupled with nitrate reduction by enriched consortia, with the highest degradation rate of 9.95 mg ACE/g VSS·h-1. Meanwhile, three novel ACE-degrading strains affiliated with Shinella were isolated, examined, and sequenced, revealing that the isolates could utilize ACE as the sole carbon source under both aerobic and anoxic conditions, with maximum degradation rates of 30.3 mg ACE/g VSS·h-1 and 8.92 mg ACE/g VSS·h-1, respectively. Additionally, the biodegradation of ACE was suspected to be a plasmid-mediated process based on comparative genomic analysis. In ACE-degrading consortia, 83 near-complete metagenome-assembled genomes (MAGs) were obtained via Illumina and Nanopore sequencing, showing that Proteobacteria and Bacteroidetes were the dominant phyla. Moreover, nine MAGs affiliated with Hyphomicrobiales were proposed to be the major ACE degraders in the enrichments. This study demonstrated that ACE could be degraded under anoxic conditions, providing novel insights into ACE biodegradation in the environment.

Polymethyl methacrylate-g-carboxy-methylcellulose as an amphiphilic coating material for slow-release fertilizer

In the perspective of preparing coating material of water-soluble fertilizer with controlled and slow-release property, polymethyl methacrylate (PMMA) was grafted from carboxymethyl cellulose (CMC) through in-situ polymerization using potassium persulfate (KPS) as initiator. The prepared copolymers (PMMA-g-CMC) were fully characterized using Transform Infrared Spectroscopy (FTIR), Thermogravimetric analysis (TGA), Differential Scanning Calorimetry (DSC), Dynamic light scattering (DLS), X-Ray diffraction (XRD), Brunauer Emmett Teller (BET), Scanning electron microscopy (SEM) and mechanical tensile testing. The molecular weight (Mn) was also evaluated using the size exclusion chromatography (SEC). Next, conventional water-soluble diammonium phosphate (DAP) fertilizer was coated by the prepared copolymers using laboratory rotary drum. The coating effectiveness was evaluated in terms of its uniformity and thickness. The successfully coated nanomaterials significantly delay the release rate of nitrogen (N) and phosphorus (P) in water and soil, compared to their release using uncoated fertilizers. Finally, aerobic biodegradation of the coating agent was also demonstrated.

Fate &amp; transport of vinyl chloride in soil vapor

AbstractVinyl chloride (VC) is a common risk driver in vapor intrusion (VI) studies. At many sites, initial screening shows potential indoor air impacts for VC at unacceptable levels. During follow‐up site characterization, however, the VI pathway for VC is rarely if ever found to be complete. This paper sets forth a conceptual model for understanding these results and summarizes data from several field sites to illustrate the concepts. VC can be formed under anaerobic conditions via reductive dechlorination of tetrachloroethylene or trichloroethylene. The ultimate fate of any VC that is produced depends on the amount of available oxygen. If sufficient oxygen is available, VC will readily undergo aerobic biodegradation. Data are presented for multiple field sites to illustrate the fate and transport of VC. The sites are drawn from various regions of the United States and cover a range of conditions. At these sites, VC was detected at relatively high concentrations in groundwater. It may also have been detected in deeper soil gas, but generally was fully attenuated before reaching shallow soil depths. Indoor air results were consistently non‐detect. The behavior is also discussed for sites with very shallow groundwater, where VC was found in some subslab soil gas samples but not in the overlying indoor air.

Classification and Regression Machine Learning Models for Predicting Aerobic Ready and Inherent Biodegradation of Organic Chemicals in Water.

Machine learning (ML) is viewed as a promising tool for the prediction of aerobic biodegradation, one of the most important elimination pathways of organic chemicals from the environment. However, available models only have small datasets (<3200 records), make binary classification predictions, evaluate ready biodegradability, and do not incorporate experimental conditions (e.g., system setup and reaction time). This study addressed all these limitations by first compiling a large database of 12,750 records, considering both ready and inherent biodegradation under different conditions, and then developing regression and classification models using different chemical representations and ML algorithms. The best regression model (R2 = 0.54 and root mean square error of 0.25) and classification model (the prediction accuracy from 85.1%) achieved very good performance. The model interpretation indicated that the models correctly captured the effects of chemical substructures, following the order of C═O > O═C-O > OH > CH3 > halogen > branching > N > 6-member ring. The consideration of chemical speciation based on pKa and α notations did not affect the regression model performance but significantly improved the classification model performance (the accuracy increased to 87.6%). The models also showed large applicability domains and provided reasonable predictions for more than 98% of over 850,000 environmentally relevant chemicals in the Distributed Structure-Searchable Toxicity database. These robust, trustable models were finally made widely accessible through two free online predictors with graphical user interface.

Synthesis and Characterization of a Biodegradable and Robust Film Using Gracilarialichenoides and Sargassumhorneri for Packaging Applications

In this study, a biodegradable and mechanically robust film was synthesized using seaweeds (Gracilarialichenoides and Sargassumhorneri), and its physicochemical and mechanical properties were characterized. In addition, its applicability in the packaging area was studied. A synthetic process including cleaning, drying, softening, pulping, and forming was developed. The microscopic morphology of the developed biodegradable film was similar to wood-based paper. In order to characterize its chemical composition and structure, FE-SEM, FT-IR, GC-MS, and TGA analyses have been performed. In addition, an aerobic biodegradability test was performed in accordance with ISO 14855-1:2012. From those experimental studies, it was shown that the major ingredient of the developed material is cellulose and other bio-originated organic substances. The developed seaweed-based film has excellent biodegradability which is 17 times higher than biodegradable polybutylene succinate (PBSe, hereafter) film, and seven times higher than other seaweed-based film in literature. The tensile strength of the film was enhanced by more than 40% compared with other seaweed-based film of previous studies. A hazardous material test was conducted in accordance with IEC62321, and the result indicated that all of the concerned toxic material was estimated to be under the method detection limit (MDL). Based on the aforementioned results, a prototype egg carton was successfully developed in accordance with ISO 534.

REMEDIATION OF PALM OIL MILL EFFLUENT (POME) USING SELECTED BIOLOGICAL TECHNIQUES: A MINI REVIEW

Undoubtedly, industrial activities have produced a large amount of waste, which has significantly contributed to the global environmental problem. The palm oil sector, which is considered a water-intensive industry, is one of the industrial sectors that have become a major source of severe water pollution concerns. Normally, 50% of the freshwater used during the extraction of crude palm oil will end up in the production of undesirable liquid waste. Thus, proper regulation and enforcement are required to control the discharge of such waste to ensure the sustainability of water resource management. Based on research databases such as Scopus, ScienceDirect, Web of Science and PubMed the total number of publications focused on palm oil mill effluent (POME) treatment has increased significantly over the past five years. The increase in publications shows the growing concern about the POME issue among the scientific community. This mini review focuses on selected biological treatment techniques for remediation of POME focusing on ponding systems, bioadsorption, activated sludge, microorganism and plant, aerobic biodegradation and integrated/hybrid treatment strategies. The summary of optimum operating conditions, characteristics of the treatment system, properties of materials and performance of each treatment are discussed in detail. To achieve a high level of contaminant removal performance, it is critical to discover the synergistic effect between the treatment procedures, materials employed, operational cost, and circumstances.