Insights into the stabilization of landfill by assessing the diversity and dynamic succession of bacterial community and its associated bio-metabolic process

Effects of different types of municipal solid waste incineration slag on landfill stabilization and related microbiological mechanism

Municipal solid waste incineration slag has the potential to accelerate the stabilization of landfills, but the effects of key slag components (i.e., alkaline substances and ferromagnetic substances) on the landfilling process have not been systematically studied. Therefore, landfill bioreactors containing different types of incineration slag, including a control group (CK), raw slag (RS), iron-rich slag (FM), and alkali-rich slag (AL), mixed with refuse at 5% and 10% ratios, were established. The results showed that the addition of RS was superior than FM and AL in accelerating refuse degradation, and the degree of stabilization was significantly better at a high slag addition ratio (10%) than at a low ratio (5%). Addition of 10% RS was most effective in DOM removal in the leachate, which was mainly because the raw slag had a high content of alkaline substances (46.78%) and a relatively low content of ferromagnetic substances (7.01%). The addition of RS and AL increased the bacterial population in the early and middle stages of landfilling, but the addition of 10% FM resulted in a decrease in bacterial population. The dominant genus was Lactobacillus in the early stage of landfilling, while Clostridium and Petrimonas were the dominant genera in the late and final stages of landfilling in the slag addition systems, and alkaline substances played a vital role in the succession of bacterial community. The addition of slag promoted the abundance of amino acid metabolism and carbohydrate metabolism pathways involved in refuse degradation.

Study on the growth and decline patterns and environmental drivers of pathogens during the stabilization process of simulated landfilling municipal solid waste

Waste and leachate in landfills are substantial reservoirs of pathogens, however information about the risk of pathogen contamination during the stabilization process under different landfill conditions is very limited. In this study, dynamic changes of culturable pathogens, bacteria community, and human bacterial pathogens (HBPs) during the stabilization process under different landfill conditions were investigated, and the environmental drivers were explored. Results showed that total coliforms, Enterococcus, and Staphylococcus aureus were the dominant pathogens detected in waste and leachate samples. During the landfill stabilization process, the concentration of culturable pathogens peaked at the hydrolysis-acidification stage (3.6 × 105 CFU·g-1) in the anaerobic condition, fluctuated from 4.18 × 104 to 5.35 × 105 CFU·g-1 in the anaerobic leachate-recirculation condition, and kept rising (from 4.18 × 104 to 2.12 × 106 CFU·g-1) in the micro-aerobic condition. Moreover, HBPs abundance and diversity in the waste and leachate under micro-aerobic conditions were higher than those under the other two conditions, suggesting a higher risk of pathogen contamination. Sulfate and pH were significantly (p < 0.05) correlated with the composition of bacterial communities and HBPs, likely serving as the major environmental driving factors. Additionally, the interactions between HBPs and functional bacterial groups tended towards cooperative symbiotic relationships, with hydrolytic-acidogenic bacteria promoting the growth and proliferation of most pathogens. These findings will help to understand the changes and environmental drivers of pathogens during landfill stabilization, which will provide a theoretical basis for the risk prevention and control of pathogens in waste disposal.

Characteristics of microplastics in typical poultry farms and the association of environment microplastics colonized-microbiota, waterfowl gut microbiota, and antibiotic resistance genes

Microplastics (MPs) pollution is a growing global environmental concern. MPs serve as ecological niches for microbial communities, which may accelerate the spread of antibiotic resistance genes (ARGs), posing risks to the breeding industry. While studies on MPs in aquatic organisms are common, research on farmed poultry is limited. This study investigates MPs in poultry farm environments and waterfowl intestines for the first time. MPs were isolated via density separation and analyzed for characterization in soil, pond water, and waterfowl intestines. Metagenomics was used to investigate the association between environment MPs colonized-microbiota and waterfowl gut microbiota. Our findings reveal that MPs are abundant in soil (6.75 ± 2.78 items/g d.w.), pond water (0.94 ± 0.28 items/g w.w.), and poultry intestines (45.35 ± 19.52 items/g w.w.), primarily appearing as fragmented particles sized 20-50 μm. MPs abundance in intestines correlates with environmental levels. Colonized-microbiota on MPs are linked to poultry intestinal microbiota, with greater diversity and microbial functions. Network analysis reveals that Corynebacterium plays a key role in MPs and poultry intestinal. Polymyxin resistance exhibits high clustering. Procrustes analysis reveals correlations between MPs, bacteria, and ARGs in the farming environment. Overall, MPs in poultry farms may facilitate pathogen and ARGs transmission, posing risks to animal gut health.

Metagenomic insights into the functional potential of non-sanitary landfill microbiomes in the Indian Himalayan region, highlighting key plastic degrading genes

Solid waste management in the Indian Himalayan Region (IHR) is a growing challenge, intensified by increasing population and tourism, which strain non-sanitary landfills. This study investigates microbial diversity and functional capabilities within these landfills using a high-throughput shotgun metagenomic approach. Physicochemical analysis revealed that the Manali and Mandi landfill sites were under heavy metal contamination and thermal stress. Taxonomic annotation identified a dominance of bacterial phyla, including Proteobacteria, Actinobacteria, Bacteroidetes, and Firmicutes, with genera like Pseudomonas and Bacillus prevalent. Squeezemeta analysis generated 9,216,983 open reading frames (ORFs) across the sampling sites, highlighting diverse metabolic potentials for heavy metal resistance and degrading organic, xenobiotics and plastic wastes. Hierarchical clustering and principal component analysis (PCA) identified distinct gene clusters in Manali and Mandi landfill sites, reflecting differences in pollution profiles. Functional redundancy of landfill microbiome was observed with notable xenobiotic and plastic degradation pathways. This is the first comprehensive metagenomic assessment of non-sanitary landfills in the IHR, providing valuable insights into the microbial roles in degrading persistent pollutants, plastic waste, and other contaminants in these stressed environments.

Deciphering the driving mechanism of microbial community for rapid stabilization and lignocellulose degradation during waste semi-aerobic bioreactor landfilling with multifunctional microbial inoculum

Owing to the massive refractory lignocellulose and leachate-organic loads, the stabilization of municipal solid waste (MSW) landfill is often prolonged, resulting in environmental burdens. Herein, various assembled multifunctional microbial inoculums (MMIs) were introduced into the semi-aerobic bioreactor landfill (SABL) to investigate the bioaugmentation impacts. Compared to control (CK) and other MMIs treatments (G1-G3), LD + LT + DM inoculation (G4) significantly increased volatile solids degradation (9.72-45.03 %), while reducing chemical oxygen demand (COD) content (10.34-51.85 %) and ammonia nitrogen concentration (80.71-90.95 %) in the leachate. G4 also exhibited significantly higher degradation of cellulose and hemicellulose, achieving 0.99 and 1.94 times higher efficiency than CK, respectively. Microbial analysis revealed that LD + LT + DM reshaped microbial communities composition of SABL, with most of the introduced microorganisms (Enterobacter, Sphingobacterium, Streptomyces, etc.) successfully colonizing, and stimulating indigenous functional microbes associated with organic matter decomposition. Additionally, microbial interactions were strengthened in G4, accompanied by the higher abundance of 11 biomarkers and enzymes involved in lignocellulose degradation and ammonia nitrogen conversion. Overall, LD + LT + DM maximized MMI function by reconstructing synergistic core microbes. These findings highlight the superiority of LD + LT + DM in simultaneously regulating the microbial composition of lignocellulose-rich waste landfills, expediting MSW decomposition, improving leachate treatment, and mitigating odor emissions, offering valuable insights for efficient MSW management.

Insights into bioaerosol contamination in the process of mineralized refuse mining: Microbial aerosolization behavior and potential pathogenicity

The landfill mining process is a main source of anthropogenic bioaerosol release, posing potential risks to the health of occupationally exposed personnel and nearby residents. In this study, microbial aerosolization behavior and potential pathogenicity during the landfill mining process were systematically investigated. The highest concentration of bacterial aerosols was measured in the refuse mining area, with a value of 5968 ± 1608 CFU/m3, while the highest concentration of fungal aerosols was 1196 ± 370 CFU/m3 in the refuse screening area. The bacterial and fungal aerosols were distributed primarily in the particle size ranges of 4.7-7.0 µm and > 7.0 µm, respectively. The pathogenic microbes Arthrobacter, Bacillus, Arthrobotrys and Aspergillus had high bioaerosol aerosolization capacities, with aerosolization indices of 100-329, 31-62, 2-14 and 1-11, respectively, when released from mineralized refuse. There are more than 100 types of pathogenic bacteria in bioaerosols. The microorganisms Lysobacter, Luteimonas and Mycolicibacterium, which carry virulence factor genes (VFGs) (pilG, Rv0440, pilT, etc.), can spread VFGs, aggravate bioaerosol pollution, and threaten the health of workers and nearby residents. This research will help further the understanding of bioaerosol contamination behaviors and potential pathogenicity risks from landfill mining activities.

Biostimulation accelerates landfill stabilization and resource utilization efficiency, providing feasible technical support for the overall lifecycle management of landfills

Although sanitary landfill is one of the principal municipal solid waste (MSW) treatment and disposal methods, its limitations, such as insufficient use of resources, long stability time, and high risk of environmental pollution, must be urgently resolved. The effect of multifunctional microbial community (MMC) inoculation on MSW landfill process was investigated using simulated anaerobic bioreactor landfill (ABL), and composition and microbial community structure of waste, leachate water quality, and gas production were monitored. MMC inoculation significantly accelerated lignocellulose degradation, and the (Hemicellulose content + Cellulose content)/Lignin content ((C + H)/L) of MMC inoculation treatment was 0.89 ± 0.04 on day 44, which was significantly lower than that of the control group (1.14 ± 0.02). At the end of the landfill process, the reductive organic matter, ammonia nitrogen, and volatile fatty acids in the leachate of the MMC group decreased to 9400.00 ± 288.68, 332.78 ± 5.77, and 79.33 ± 6.44 mg L-1, respectively, significantly lower than those of the control group (24,167.00 ± 208.17, 551.14 ± 5.60, and 156.33 ± 8.22 mg L-1). Meanwhile, MMC inoculation increased the methane production to 118.12 ± 5.42 L kg-1 of dry matter, significantly higher than the output of the control group (60.60 ± 2.24 L kg-1). MMC inoculation optimized the microbial community structure in ABL and increased lignocellulose-degrading microorganisms (Brevundimonas, Cellvibrio, Leifsonia, and Devosia) and methanogen (Methanosaeta and Methanoculleus) abundance in the middle stage of landfill. Moreover, MMC introduction improved the abundance of carbon metabolism enzymes and increased saprophytic fungal abundance by 30.09% in the middle stage of landfill. Overall, these findings may help in developing an effective method to increase the lifespan of landfills and enhance their post-closure management.

Pathways and contributions of sulfate reducing-bacteria to arsenic cycling in landfills

Sulfate-reducing bacteria (SRB) are generally found in sanitary landfills and play a role in sulfur (S) and metal/metalloid geochemical cycling. In this study, we investigated the influence of SRB on arsenic (As) metabolic pathways in refuse-derived cultures. The results indicated that SRB promote As(III) methylation and are beneficial for controlling As levels. Heterotrophic and autotrophic SRB showed significant differences during As cycling. In heterotrophic SRB cultures, the As methylation rate increased with As(III) concentration in the medium and reached a peak (85.1%) in cultures containing 25 mg L-1 As(III). Moreover, 4.0-12.6% of SO42- was reduced to S2-, which then reacted with As(III) to form realgar (AsS). In contrast, autotrophic SRB oxidized As(III) to less toxic As(V) under anaerobic conditions. Heterotrophic arsM-harboring SRB, such as Desulfosporosinus, Desulfocurvibacter, and Desulfotomaculum, express As-related genes and are considered key genera for As methylation in landfills. Thiobacillus are the main autotrophic SRB in landfills and can derive energy by oxidizing sulfur compounds and metal(loid)s. These results suggest that different types of SRB drive As methylation, redox reaction, and mineral formation in landfills. These study findings have implications for the management of As pollutants in landfills and other contaminated environments.

Unleashing the power of acetylacetone: Effective control of harmful cyanobacterial blooms with ecological safety

Harmful algal blooms resulting from eutrophication pose a severe threat to human health. Acetylacetone (AA) has emerged as a potential chemical for combatting cyanobacterial blooms, but its real-world application remains limited. In this study, we conducted a 42-day evaluation of AA's effectiveness in controlling blooms in river water, with a focus on the interplay between ecological community structure, organism functional traits, and water quality. At a concentration of 0.2 mM, AA effectively suppressed the growth of Cyanobacteria (88 %), Bacteroidia (49 %), and Alphaproteobacteria (52 %), while promoting the abundance of Gammaproteobacteria (5.0 times) and Actinobacteria (7.2 times) that are associated with the degradation of organic matter. Notably, after dosing of AA, the OD680 (0.07 ± 0.02) and turbidity (8.6 ± 2.1) remained at a satisfactory level. AA induced significant disruptions in two photosynthesis and two biosynthesis pathways (P < 0.05), while simultaneously enriching eight pathways of xenobiotics biodegradation and metabolism. This enrichment facilitated the reduction of organic pollutants and supported improved water quality. Importantly, AA treatment decreased the abundance of two macrolide-related antibiotic resistance genes (ARGs), ereA and vatE, while slightly increased the abundance of two aminoglycoside-related ARGs, aacA and strB. Overall, our findings establish AA as an efficient and durable algicide with favorable ecological safety. Moreover, this work contributes to the development of effective strategies for maintaining and restoring the health and resilience of aquatic ecosystems impacted by harmful algal blooms.

Physiochemical and biological characteristics of fouling on landfill leachate treatment systems surface

Fouling of landfill leachate, a biofilm formation process on the surface of the collection system, migration pipeline and treatment system causes low efficiency of leachate transportation and treatment and increases cost for maintenance of those facilities. In addition, landfill leachate fouling might accumulate pathogens and antibiotic resistance genes (ARGs), posing threats to the environment. Characterization of the landfill leachate fouling and its associated environmental behavior is essential for the management of fouling. In this study, physicochemical and biological properties of landfill leachate fouling and the possible accumulation capacity of pathogens and ARGs were investigated in nitrification (aerobic condition) and denitrification (anaerobic condition) process during landfill leachate biological treatment, respectively. Results show that microbial (bacterial, archaeal, eukaryotic, and viral) community structure and function (carbon fixation, methanogenesis, nitrification and denitrification) differed in fouling under aerobic and anaerobic conditions, driven by the supplemental leachate water quality. Aerobic fouling had a higher abundance of nitrification and denitrification functional genes, while anaerobic fouling harbored a higher abundance of carbon fixation and methanogenesis genes. Both forms of leachate fouling had a higher abundance of pathogens and ARGs than the associated leachate, suggesting the accumulation capacity of fouling on biotic pollutants. Specifically, aerobic fouling harbored three orders of magnitude higher multidrug resistance genes mexD than its associated leachate. This finding provides fundamental knowledge on the biological properties of leachate fouling and suggests that leachate fouling might harbor significant pathogens and ARGs.

Metagenomics insights into the effect of co-landfill of incineration fly ash and refuse for bacterial community succession and metabolism pathway of VFAs production

With the development of incineration technologies, incineration has become the most common treatment method of municipal solid waste in China. However, stabilized fly ash may enter landfills during the transition from landfill to incineration, which caused uncertain impact on landfill waste stabilization. Two simulated co-landfill columns were constructed based on different co-landfill methods (layer co-landfill and mixed co-landfill) to investigate the effect of stabilized fly ash co-landfilled municipal solid waste for bacterial community succession and change in metabolic pathways during hydrolysis-acidogenesis stage. The mixed co-landfill method resulted in higher degree of organic matter degradation, and the concentrations of volatile fatty acids (VFA) and chemical oxygen demand (COD) in leachate were higher. The dominant phyla were Firmicutes in the layered co-landfill column and Bacteroidetes in mixed co-landfill column. The dominant genera for the total bacterial composition and VFA production were different, Pseudomonas and Propionibacterium, Proteiniphilum and unclassified Bacteroides were the dominant genera responsible for VFA generation in the layered and mixed co-landfill columns. The genes for butyrate production were enriched in the layered co-landfill column, whereas those related to acetate production were enriched in mixed co-landfill column. However, the layered co-landfill inhibited the microbial metabolic activity at the end of the co-landfill process.

Influence of leachate microenvironment on the occurrence of phthalate esters in landfills

Phthalate esters (PAEs) are added to various products as plasticizers. Plastic waste containing PAEs enters landfills as they age with use. However, the influence of microenvironmental changes on the occurrence of PAEs during landfill stabilization is still unknown. In this study, we evaluated the relationship between the physical and chemical properties of leachate, the structure of bacterial communities and the chemical structure of dissolved organic matter (DOM), and the occurrence of PAEs and the mechanism underlying their responses to changes. Landfill leachate in different stabilization states had high Cl- and NH4+ contents and its metal element (Cr, Pb, and Zn) contents generally decreased with the increase in landfill ages. Proteobacteria, Bacteroidetes, and Firmicutes were important phyla and had an average relative abundance of 68.63%. The lignin/carboxylate-rich alicyclic molecule structure was the main component of DOM (56%-64%). Of the 6-priority controlled PAEs in leachate, di-n-butyl phthalate was the most abundant (1046 μg L-1), while butyl phthalate was not detected. The results showed that pH, the relative abundance of Chloroflexi, and the value of SUVA254 can directly influence the occurrence of PAEs in leachate. The positive and negative effects vary depending on the PAE content and molecular weight. DBP and DEHP have higher environmental risks in the aquatic system. These results are intended to provide a scientific basis for the evolutionary characterization of the microenvironment in complex environmental systems and the control of novel contaminants, such as PAEs.

Micro-aeration and leachate recirculation for the acceleration of landfill stabilization: Enhanced hydrolytic acidification by facultative bacteria

The long duration of landfill stabilization is one of the challenges faced by municipalities. In this paper, a combination of micro-aeration and leachate recirculation is used to achieve rapid degradation of organic matter in landfill waste. The results showed that the content of volatile fatty acids (VFAs) in the hydrolysis phase increased significantly and could enter the methanogenic phase quickly. Until the end of the landfill, the removal rates of chemical oxygen demand (COD), total phosphorus (TP) and ammonia nitrogen (NH4+-N) by micro-aeration and leachate recirculation reached 80.17 %, 48.30 % and 48.56 %, respectively, and the organic matter degradation rate reached 50 %. Micro-aeration and leachate recirculation enhanced the abundance of facultative hydrolytic bacteria such as Rummeliibacillus and Bacillus and the oxygen tolerance of Methanobrevibacter and Methanoculleus. Micro-aeration and leachate recirculation improved the organic matter degradation efficiency of landfill waste by promoting the growth of functional microorganisms.

Impact of incineration slag co-disposed with municipal solid waste on methane production and methanogens ecology in landfills

Co-landfill of incineration slag and municipal solid waste (MSW) is a main method for disposal of slag, and it has the potential of promoting methane (CH₄) production and accelerating landfill stabilization. Four simulated MSW landfill columns loaded with different amount of slag (A, 0%; B, 5%; C, 10%; D, 20%) were established, and the CH₄ production characteristics and methanogenic mechanisms were investigated. The maximum CH₄ concentration in columns A, B, C and D was 10.8%, 23.3%, 36.3% and 34.3%, respectively. Leachate pH and refuse pH were positively correlated with CH₄ concentration. Methanosarcina was the dominant genus with abundance of 35.1%∼75.2% and it was positively correlated with CH₄ concentration. CO₂-reducing and acetoclastic methanogenesis were the main types of methanogenesis pathway, and the methanogenesis functional abundance increased with slag proportion during stable methanogenesis process. This research can help understanding the impact of slag on CH₄ production characteristics and microbiological mechanisms in landfills.

Arsenic methylation behavior and microbial regulation mechanisms in landfill leachate saturated zones

Arsenic (As) is a potential contaminant in landfill. As methylation has been considered as a detoxification mechanism to address this problem. In this study, microcosm incubation was used to simulate leachate saturation zone (LSZ) and other landfill zones scenarios to explore the As methylation behavior. The As methylation rate of LSZ is 11.75%, which is slightly higher than that of other zone of landfill (10.87%). However, the difference was greatly increased by the addition of moderate content of As(III), with values of 29.25% in LSZ and 4.61% in other zones. The microbial community structure varied greatly between zones and a higher abundance of arsM was observed in the LSZ, which enhanced As methylation. Based on the annotated As functional genes from the KEGG database, the microbial As methylated pathway was summarized. Higher relative abundances of gst and arsC promoted the formation of more trivalent As substrates, stimulating the methylation behavior for As detoxification in the LSZ. According to microbial arsM contribution analysis, unclassified_p__Gemmatimonadetes, unclassified_p__Actinobacteria, unclassified_o_Hydrogenophilales, and Intrasporangium were the primary As methylation bacteria in the LSZ, while unclassified_f__Chitinophagaceae and unclassified_c_Gammaproteobacteria were the primary contributors in other landfill zones. These results highlight the specific As methylation process in the LSZ, and these insights could improve the control of As contamination in landfill sites.

Dynamic processes in conjunction with microbial response to unveil the attenuation mechanisms of tris (2-chloroethyl) phosphate (TCEP) in non-sanitary landfill soils

Although the environmental and health risks of chlorinated organophosphate esters (OPEs-Cl) have drawn much attention, its environmental behaviors have been insufficiently characterized. As a notable sink of this emerging contaminant, non-sanitary landfills, which may decompose/accumulate OPEs-Cl, is of particular concern. In the present study, the dynamic processes of the typical OPEs-Cl, tris(2-chloroethyl) phosphate (TCEP), in non-sanitary landfill soils were analyzed under anaerobic condition, and the microbial taxa involved in these processes were explored. Our results showed that TCEP could be simultaneously reduced by abiotic and biotic processes, as it was reduced by 73.9% and 65.5% over the 120-day experiment in landfill humus and subsoil, respectively. Notably, the degradation of TCEP was significantly (p < 0.05) enhanced under the stress of a high TCEP concentration (10 μg g^-1), while its ecological consequences were found insignificant regarding the microbial diversity and community structure and the typical soil redox processes, including Fe(III)/SO₄^2- reduction and methanogenesis, in both soils. The microbial diversity of subsoil was significantly lower, and acetate was an important factor in changing microbial communities in landfill soils. The microbes in the family Nocardioidaceae and genus Pseudomonas might contribute to in the degradation of TCEP in landfill humus and subsoil, respectively. The metabolism related to sulfur and sulfate respiration were significantly (p < 0.05) correlated with TCEP reduction, and Desulfosporosinus were found as a potentially functional microbial taxon in TCEP degradation in both soils. The results could advance our understanding of the environmental behavior of OPEs-Cl in landfill-like complex environments.

Characteristic pollutants and microbial community in underlying soils for evaluating landfill leakage

Leachate leakage poses a serious environmental risk to the safety of surrounding soils and groundwater. A much faster approach to reflect landfill leakage is the premise to mitigate the ecological risk of landfills. In this study, two landfills (BJ and WZ) were selected to investigate the leaching characteristics of various pollutants along the vadose soil depths. The physiochemical properties of underlying soils including NO₃^--N, NO₂^--N, NH₄⁺-N, OM, TN, EC and Cl^- exhibited a typical leaching dynamic along the depths. Among them, TN, NH₄⁺-N, OM, NO₃^--N, and EC might be used as characteristic pollutants to evaluate the leachate leakage issues in landfilled sites. The genera Thiopseudomonas, Acinetobacter, Pseudomonas, and Hydrogenispora dominated in underlying soils. Compared to BJ samples, a more diverse and active microbiome capable of carbon and nitrogen cycles was observed in WZ samples, which was mainly ascribed to nutrients and elements contained in different types of soils. Among the environmental factors, nitrogenous compounds, SO₄^2-, pH and EC had significant effects on the microbial community structures in the underlying soils. The relative abundances of Hydrogenispora and Caldicoprobacter might be used as characteristic microorganisms to evaluate the leachate leakage issues in landfilled sites. These results provided a deep insight into effects of leachate leakage in underlying soils, especially the pollutants vertical distribution and the corresponding microbial community structures.

Viral community in landfill leachate: Occurrence, bacterial hosts, mediation antibiotic resistance gene dissemination, and function in municipal solid waste decomposition

A municipal solid waste (MSW) landfill is a significant source of antibiotic resistance, pathogens and viruses and also a habitat for microbial consortia that perform MSW decomposition. Viruses are of great significance in ecological interactions such as MSW decomposition and antibiotic resistance gene (ARG) transmission. In this study, the viral community structure and the associated driver, the linkage of viruses and their bacterial hosts, the virus-associated ARG dissemination and virtual community function on MSW decomposition were investigated in landfill leachate from seven cities, China. The seven cities include four megacities, two large-scale cities and one small-scale city, representing the leachate characters of China. The results showed that the leachates were dominated by the phage families Siphoviridae, Myoviridae and Podoviridae (91.7 ± 3.6) %. Their putative hosts were the important MSW decomposers Lactobacillus, Pseudomonas, Clostridium, Proteiniphilum, and Bacteroides. The structure of the viral community was significantly affected by pH (P = 0.007, analyzed by RDA) and the bacterial community (R = 0.83, P < 0.001, analyzed by Mantel test). The relative abundance of ARGs showed a strong correlation (R > 0.8, P < 0.01) with viral family, suggesting that viruses play an important role in ARGs dissemination. Phage regulate bacterial population abundance through top-down effects, thus participating in MSW decomposition. These results demonstrate that viral community are involve in ARGs transmission and dissemination and mediate MSW decomposition in landfill.

Bisphenol S degradation in soil and the dynamics of microbial community associated with degradation

Bisphenol S (BPS) has been widely applied as a replacement for BPA in industrial application, leading to the frequent detection in the environment. However, its impact on soil microbial communities has not been well reported. Here, effects of BPS exposure on soil microbial communities in the presence of polystyrene (PS) microplastics were revealed. Rapid degradation of BPS occurred with a degradation rate of up to 98.9 ± 0.001 % at 32 d. The presence of BPS reduced the diversity of soil microbial communities, and changed community structures. After BPS treatment, Proteobacteria, and its members Methylobacillus, Rhodobacteraceae and Mesorhizobium became dominant, and were considered as potential biomarkers indicating BPS contamination. Co-occurrence network analysis revealed the increased relationships of certain groups of microbes after BPS treatment. The resultant low stability and resilience towards environment disturbance of microbial community networks implied the biotoxicity of BPS towards soil ecosystems. The degradation and biotoxicity of BPS (p > 0.05) in soil was not affected by the presence of PS. Our findings showed that exposure to BPS could reshape soil microbial communities and impair the robustness of microbial co-occurrence networks.

Characterization of anaerobic oxidation of methane and microbial community in landfills with aeration

Landfills are the third largest source of anthropogenic CH₄ emissions. Anaerobic oxidation of methane (AOM) activity and communities of methane-oxidizing bacteria were investigated in three informal landfills in this study, namely, BJ, CH and SZ landfills, among which BJ and CH represent traditional anaerobic landfills, while the SZ landfill was subjected to aeration to accelerate waste stabilization. The AOM rates of the investigated landfilled wastes ranged from 3.66 to 23.91 nmol g^-1 h^-1. Among the three landfills, the AOM rate was highest in the SZ-1-Top sample, which was closest to the aeration pipe. Among the possible electron acceptors for AOM, including NO₃^-, NO₂^-, SO₄^2- and Fe³⁺, the NO₂^--N content was the only variable that was positively correlated with the AOM rate. Compared with α-Proteobacteria methanotrophs, γ-Proteobacteria methanotrophs were more abundant in the landfilled waste, especially Methylobacter, which was detected in nearly all samples. Members of the family Methylomirabilaceae, including Candidatus Methylomirabilis, were also detected in the SZ-1 and SZ-2-Bot samples. The relative abundance of the main methanotrophs in the families Methylomonadaceae, Methylococcaceae, Rokubacteriales and Methylomirabilaceae, the genus Methylocystis and the phylum NC10 were all positive correlations with the contents of NO₂^--N in the landfilled waste samples. Additionally, significantly positive correlations were observed between the AOM rates and the relative abundance of the main methanotrophs except for the family Methylococcaceae. This indicated that aeration could enhance the conversion of nitrogen compounds in the landfilled waste, in which the high contents of NO₂^--N could stimulate the growth of methanotrophs and increase AOM rate. These findings are helpful for understanding the mechanisms of CH₄ oxidation in landfills and for taking effective measures to mitigate CH₄ emissions from landfills.

Insights into the landfill leachate properties and bacterial structure succession resulting from the colandfilling of municipal solid waste and incineration bottom ash

Four simulated bioreactors were loaded with only MSW, 5 % BA + MSW, 10 % BA + MSW and 20 % BA + MSW to investigate the leachate property and bacterial community change trends during the colandfilling process. The results showed that with increasing BA addition proportion (5 %∼20 %), the leachate oxidation-reduction potential (ORP) was lower, the leachate pH quickly entered the neutral stage, and the chemical oxygen demand (COD), volatile fatty acids (VFA), NH₄⁺-N, Ca²⁺ and SO₄^2- presented faster downward trends. The leachate SUVA₂₅₄ and E_300/400 confirmed that BA can accelerate the leachate humification process. BA can quickly increase bacterial diversity, and the higher the addition proportion of BA, the more significant the change in microbial community structure during the landfilling process. The leachate pH and COD greatly influenced the bacterial community structure. A low BA proportion can increase metabolism pathway abundance during the initial stage, but a high BA proportion had an inhibitory effect on the metabolism pathway.

Booming microplastics generation in landfill: An exponential evolution process under temporal pattern

Landfills are the main plastic sinks and microplastics (MPs) sources in the anthropogenic terrestrial system. Understanding the dynamic process of generating MPs is a prerequisite to reducing their potential risk, which remains unexplored because of the complex stabilization process of landfills. In this study, we investigated the evolution process of MPs generated in a partitioned landfill, with well-recorded disposal ages of over 30 years. Considering the initial plastic proportions in fresh landfilled waste, the occurrence of MPs increased exponentially with the disposal age. A booming generation of MPs occurred from 71.3 ± 17.7 items/(g plastic) to 653.1 ± 191.5 items/(g plastic). The generation rates of MPs varied greatly depending on the individual polymer types, with polyethylene (PE) having the highest generation rate of 28.4 items/(g plastic) per year at 31 years, compared to that of polypropylene (PP) and polystyrene (PS) at 15.0 and 9.6 items/(g plastic) per year, respectively. The variation in the carbonyl index indicated that environmental oxidation might facilitate the fragmentation of plastic waste. The relative abundance of plastic-degrading microbes increased more than three times in the plastisphere after 30 years of landfilling, indicating that the potential biodegradation might be a nonnegligible driver for plastic fragmentation after long-term natural acclimatization. This study revealed the dynamic evolution process of MPs in landfills and predicted the booming stage, which might provide an important guideline for reducing the leakage risk of MPs during the reclamation of old landfills or dumping sites.

Freeze-thaw vacuum treatment of landfill sludge: Mechanism of uneven frost heaving and dewatering performance

The method of freeze-thaw combined with vacuum pretreatment for landfill sludge (LS) has attracted extensive attention. However, most of the existing approaches are based on small-scale laboratory testing, and further testing studies must be performed to realize in situ treatment. To enhance the practicality of such approaches, the range of temperature effects on LS was analysed after field freeze-thaw model testing. After the freeze-thaw model test, samples were transported to the laboratory for unidirectional oedometer tests, and the remaining samples were retained in the field to continue vacuum model testing for exploring the differences in the consolidation and drainage effect of the LS. Results show that temperature changes during freeze-thaw process affect the distribution of sludge and water in the model boxes, resulting in frost heave and the appearance of "extrusion rings". In addition, the coefficient of consolidation obtained from the unidirectional oedometer test shows that the consolidation coefficient is generally larger near the freezing tubes at a lower temperature. The settlement determined from the field vacuum preloading test shows that the subsequent vacuum consolidation settlement is larger at the position with a lower elevation of the frozen sludge surface. The comparison indicates that the consolidation and drainage effect in the field is not as significant as that in the laboratory. The findings can provide reference to optimize the field conditions during the in situ engineering practice of sludge treatment.