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.

Microbial degradation of low-density polyethylene, polyethylene terephthalate, and polystyrene by novel isolates from plastic-polluted environment.

Biodegradation is an eco-friendly measure to address plastic pollution. This study screened four bacterial isolates that were capable of degrading recalcitrant polymers, i.e., low-density polyethylene, polyethylene terephthalate, and polystyrene. The unique bacterial isolates were obtained from plastic polluted environment. Dermacoccus sp. MR5 (accession no. OP592184) and Corynebacterium sp. MR10 (accession no. OP536169) from Malaysian mangroves and Bacillus sp. BS5 (accession no. OP536168) and Priestia sp. TL1 (accession no. OP536170) from a sanitary landfill. The four isolates showed a gradual increase in the microbial count and the production of laccase and esterase enzymes after 4 weeks of incubation with the polymers (independent experiment set). Bacillus sp. BS5 produced the highest laccase 15.35 ± 0.19 U/mL and showed the highest weight loss i.e., 4.84 ± 0.6% for PS. Fourier transform infrared spectroscopy analysis confirmed the formation of carbonyl and hydroxyl groups as a result of oxidation reactions by enzymes. Liquid chromatography-mass spectrometry analysis showed the oxidation of the polymers to small molecules (alcohol, ethers, and acids) assimilated by the microbes during the degradation. Field emission scanning electron microscopy showed bacterial colonization, biofilm formation, and surface erosion on the polymer surface. The result provided significant insight into enzyme activities and the potential of isolates to target more than one type of polymer for degradation.

Black Vulture (Coragyps atratus) feathers as bioindicators of exposure to metals and metalloids contamination in urban, semi-urban, and rural areas from Campeche state, Mexico.

Landfills are sources of soil, water, and air pollution due to the release of toxic compounds such as metals and metalloids. In both tropical and temperate environments, scavenger birds such as the Black Vulture (Coragyps atratus) that have learned to use these sites as a feeding area are probably exposed to metals, metalloids and other "persistent bioaccumulative toxic substances (PBTs)" released in open dumpsite (OD) and sanitary landfill (SL). The objective of this study is to evaluate the presence and distribution of toxic metals (Al, Sn, Hg, Cu, Pb, Cd, Cr) and As in OD and SL from urban, semi-urban and rural localities in Campeche, México, using molting feathers of C. atratus as bioindicators. A total of 125 Black Vulture primary and secondary wing feathers were collected from OD and SL. Metals were determined by voltammetry through acid digestion. The highest levels of metals occurred in landfills in urban, semi-urban, and rural localities. The elements with the highest concentrations were Al, with an average of 35.67 ± 33.51 µg g-1 from rural environments, and As, with 16.20 ± 30.06 µg g-1 from the urban localities. Mercury was the only element that had a very homogeneous distribution between the three environments we studied. In general, Pb, Hg, Cu and Cd were the elements that presented the lowest concentrations with 0.32 ± 0.35, 0.16 ± 0.22, 0.14 ± 0.31 and 0.06 ± 0.10 µg g-1, respectively regardless of any particular location or environment. Black Vultures from dumpsites are good bioindicators of what humans consume in urban, semi-urban, and rural environments. However, the conservation of vultures is of great importance since these scavenger birds perform ecosystem services by feeding on decomposing organic material.

Toxicity assessment of sanitary landfill leachate before and after Fenton treatment process.

Sanitary landfills are widely accepted and promoted as the environmentally friendly way to properly dispose of solid waste. However, a harmful aspect is the leachate generation and management, which are currently recognized as one of the greatest challenges in the environmental engineering field. Due to the high leachate recalcitrance, Fenton treatment has been accepted as a viable and efficient treatment process, which significantly reduces the organic matter: 91 % of COD; 72 % of BOD5; and 74 % of DOC. However, the acute toxicity of leachate must be assessed, mainly after the Fenton process, with the view of performing a low-cost biological post-treatment of the effluent. Despite the high redox potential, degrading 185 organic chemicals compounds identified in raw leachate, the present work reports a removal efficiency of almost 84 %, counting 156 organic compounds removed, and almost 16 % of persistent compounds. After Fenton treatment, 109 organic compounds were identified, beyond the persistent fraction of almost 27 %, wherein 29 organic compounds remained unchanged after Fenton treatment, counting 80 new short chain and lower complexity organic compounds formed. Despite the biogas production ratio increase (3-6 times), and significant enhancement of the biodegradable fraction susceptible to oxidation in respirometric test, a higher reduction in the oxygen uptake rate (OUR) was identified after Fenton treatment due to persistent compounds and their bioaccumulation. Additionally, the D. magna bioindicator parameter indicated that treated leachate is three times more toxic than raw leachate.

Assessing the preference and spatial dependence of a solid waste management system in Nepal: A choice experiment approach.

This study deploys a choice experiment method to estimate the preference and willingness to pay for a better solid waste management system in Siddharthanagar municipality in Nepal. A primary survey of 611 households was conducted, and the results from the Generalized Multinomial Logit Model (GMNL) indicate a public preference for a better waste management service. Significant heterogeneity in household preferences is evident after accommodating each choice selection's preference certainty in the GMNL model. On average, households prefer to pay the highest amount for constructing and maintaining a sanitary landfill, which is Nepalese Rupee (NPR) 158/month (USD 1.43). The geographic distribution of the marginal willingness to pay (MWTP) by hot spot analysis from the geocoded location also indicates spatial heterogeneity across the study area. The MWTP for each waste management attribute is spatially autocorrelated, and household awareness and attitude significantly impact this spatial dependence. Overall, both the choice models result and spatial analyses indicate the policy should be targeted at a localized level to increase awareness concerning the proper management of solid waste.

Landfill siting for municipal solid waste using remote sensing and geographic information system integrated analytic hierarchy process and simple additive weighting methods from the point of view of a fast-growing metropolitan area in GAP area of Turkey.

The site selection process for municipal solid wastes (MSW) plays an important role in environmental impact studies by allowing the use of environmental design criteria in city and country planning. This process also includes the subject of urban planning due to its impact on the economy, ecology, and environmental health of the region. Urban growth is a phenomenon that is difficult to stop or limit in line with environmental, social, and economic changes and development. Therefore, the selection of solid waste landfill is of great importance in terms of ensuring a sustainable urban future. In the study, Landsat 5 and Landsat 8 satellite images, base map, soil, and geology maps were used for the integration of geospatial data. Each layer specified in the map has been formed using the spatial analysis potential of the ArcGIS10.5 software. In these digitized layers, weight scoring was made using the comparison matrix and the final suitability map was produced. All digital layers established in the generated maps were arranged according to the analytical hierarchy method (AHP) and subjected to the simple additive weighting (SAW) method. The results indicated that 13.51% of the total area was suitable for a sanitary landfill. As a result of this study, urban growth, population projection, and domestic solid waste volume of Sanliurfa province were determined. According to the 25-year population projection, the population in 2045 was approximately 4,471,938 people, and the cumulative waste volume was 27,415,627 m3. In addition, as a result of accepting the wastes of three metropolitan districts and seven district municipalities to the sanitary landfill, only "first candidate area" is the most and has been deemed appropriate. Given the ecological and environmental challenges (proximity to the city center, etc.) associated with the existing MSW sanitary landfill facility in Sanliurfa, the results of this study show that the geographic information system (GIS) integrated AHP and SAW method is an effective tool to assist decision makers to properly plan towards achieving a sustainable environment.

Solar photo-Fenton oxidation of mature landfill leachate: empirical model and chemical inferences.

In this study, a stochastic model was applied to investigate the degradation of landfill leachate by solar photo-Fenton processes. The coefficient of determination (R2) between experimental and predicted data ranged from 0.9958-0.9995. The optimal conditions for the initial phase (lasting 5-22 min) were high Fe2+ level, low pH level, and intermediate H2O2 level. For the second phase, optimal leachate degradation percentages were obtained by maintaining the pH, increasing H2O2, and decreasing Fe2+ to the lowest level. Determination of optimal reaction conditions (such as pH, Fe2+, and H2O2 values) for both degradation phases is of paramount importance for process scale-up. The major contribution of this study was the development of a tool that considers the effects of one or more reactions on organic carbon degradation. This was achieved by assessing the significance of the effects of experimental conditions on model parameters for the fast and slow steps of leachate degradation by advanced oxidation processes.

[Reasons for consultation and healthcare strategies analyzed from a neighborhood dermatological assistance device. Qualitative research: Skin problems. Qualitative research. / Motivos de consulta y estrategias de atención analizados a partir de un dispositivo barrial de asistencia dermatológica. Investigación cualitativa: Afecciones de la piel. Investigación cualitativa.

Aim of study: identify consultation reasons, experiences with seeking dermatological assistance and skin care strategies within neighbours from an urban deprived settlement in Buenos Aires province, Argentina. This setting lies onto a sanitary landfill with a high index of environmental contamination. Materials and methods: a dermatological health care team from the main local hospital designed a dermatological assistance device (DAD), in cooperation with social leaders and institutions of the neighborhood. The DADs included walks around the neighborhood for attending those who could not get a consultation. The experiences were evaluated through a qualitative research strategy, developed from the theoretical framework of Sociocultural Epidemiology. Those who attended the DADs were interviewed. Ethnographic field notes were also recorded. Multiple accessibility barriers to the public health care system were identified and self care practices were also recognized. Results: The most frequent consultations to the DADs were for "pimples", "stains'' and "lumps" on exposed areas of the skin. These lesions generated discomfort or pain, or even affected the interviewees aesthetically or emotionally. Most of them were associated to extremely dry skin and a high sun exposure, in connection with the lack of shade in the neighbourhood. An initiative to plant trees was promoted in order to prevent sun radiation-induced dermatoses. Conclusion: the reflective immersion of the dermatology team in the realm of the neighborhood daily life enabled the development of attention strategies grounded on the perceived needs of the population.

Objetivo: analizar motivos de consulta, experiencias y formas de atención de las afecciones dermatológicas de la población de un asentamiento de la Provincia de Buenos Aires, ubicado sobre un relleno sanitario con altos índices de contaminación ambiental. Materiales y métodos: investigación cualitativa, mediante entrevistas en profundidad a vecinos/as y elaboración de registros etnográficos de las recorridas. La investigación se realizó en el contexto de un dispositivo de atención dermatológica, planificado en conjunto con referentes barriales, bajo el marco teórico de la Epidemiología Sociocultural. Resultados: se identificaron múltiples barreras de accesibilidad a la atención dermatológica en el sistema público de salud, y prácticas de autoatención como el uso de cremas, medidas de higiene y uso de elementos de protección personal para trabajos que significaban un riesgo para la salud. Las consultas al dispositivo más frecuentes fueron "granos", "manchas", "bultitos" en zonas visibles del cuerpo, que generaban molestia, dolor y/o afectaban estética y emocionalmente a lo/as entrevistado/as. Estas consultas se relacionaban principalmente con piel extremadamente seca y patologías por alta exposición solar, coincidiendo con la escasez de sombra en el barrio. Para prevenir patologías relacionadas a la exposición solar, se impulsó una iniciativa para plantar árboles. Conclusión: a partir de la inmersión reflexiva del equipo de atención, en las experiencias de atención de lo/as habitantes del barrio, se desplegaron estrategias según las necesidades percibidas por la población.

Population dynamics of microbial species under high and low ammonia nitrogen in the alternate layer bioreactor landfill (ALBL) approach.

Anaerobic landfill process is still believed to be a complex ecosystem due to the lack of knowledge on the functional activities of microbial species. This research sought to introduce a novel landfill bioreactor, named here as the alternate layer bioreactor landfill (ALBL) of fresh MSW (FW) and stabilized waste (CT) to avoid inhibitory conditions for the microbial species in anaerobic landfill. The stabilized waste layer in the bottom of landfill cell significantly changed microbial ecology of fresh MSW which in turn reduced the concentrations of NH4-N (29-31%) and VFAs (33-38%) in the ALBL approach, compared to fresh MSW disposal in sanitary landfill. The reduction of NH4-N favored early onset of methanogenesis within 6 weeks and methane (CH4) content of landfill gas increased from 11% to 40-50% (v/v), owing to the coexistence of Methanosarcinales (36-50%) and Methanomicrobiales (26-28%) archaea. The acetoclastic methanogenesis was achieved by reducing NH4-N toxicity in the ALBL.

Persistent impacts of an abandoned non-sanitary landfill in its surroundings.

The inadequate disposal of solid waste, a common practice in developing countries, can represent an important pollution source since the closure of these deposits typically does not include the adoption of monitoring, isolation, or remediation techniques. Even so, several disposal areas are abandoned, without performing long-term monitoring in order to evaluate the depletion of contaminants' concentrations. This research aimed at comparing current and historical physicochemical data of water resources surrounding a non-sanitary landfill situated in a Guarani Aquifer recharge zone. The primary objective was to recognize whether significant changes in contaminants concentrations occurred, as well as if the area still poses a significant threat to the environment, 20 years after ending disposing activities. Samples from eight monitoring wells and three surface water points (upstream and downstream to the deposit) were evaluated in the periods of 1996-1997 and 2016-2019. The parameters pH, electrical conductivity (EC), alkalinity, chemical oxygen demand (COD), oxidation-reduction potential (ORP), chloride, nitrate, iron, manganese, calcium, and magnesium were investigated. Contamination has been detected in the landfill surroundings since the ending of the waste disposal (1996-1997), even though its intensity reduced within short distances from the waste mass. Nevertheless, no statistical variation occurred in 20 years' time considering COD, chloride, calcium, magnesium, and ORP. Moreover, increases of EC, pH, alkalinity, iron, and manganese concentrations were observed for the years of 2016-2019. The results indicate that the evaluated contaminants do not suffer depletion in the surroundings of non-sanitary landfills in sandy aquifers, considering a time span of 20 years. This study also suggests that those areas need to be adequately remediated to permit other future land uses.

Sanitary landfill site selection using multi-criteria decision analysis and analytical hierarchy process: A case study in Azuay province, Ecuador.

Despite environmental regulations in Ecuador, particularly in the Province of Azuay, the solid waste final disposal management is still a socio-environmental problem, worsened by weak governance processes. The province has three sanitary landfills with almost expired service lives. The site selection was based on circumstantial reasons, which makes landfills more likely to cause environmental pollution and, therefore, have negative implications for public health. The largest landfill serves Cuenca and also leases service to other small cities. The remaining two are small and, accordingly, have limited technology and fewer resources. In this context, the main aim of this study is to evaluate the terrain of the province to find the most suitable area for landfill siting. A multi-criteria decision analysis, integrated with a geographical information system and analytical hierarchy process methodology, was conducted. Fourteen factors and seven constraints were simultaneously analysed, divided into technical, environmental, social, and economic categories; 15 of these criteria were from the Ecuadorian Unified Text of the Secondary Legislation of the Environmental Ministry. According to the results, 76.17% of the territory is not suitable for landfill implementation, and the unrestricted area represents the remaining 23.83%. The highest landfill suitability index (70-81%) is located in the south of the province in Santa Isabel, Oña, and Nabón cantons, which are dry and clay-rich areas.

Emerging contaminants removal from effluents with complex matrices by electrooxidation.

The electrooxidation of methiocarb and bisphenol A was studied in complex matrices, namely, simulated and real sanitary landfill leachate samples, using a boron-doped diamond anode. With simulated sanitary landfill leachate samples, the influence of the type and ratio of carbon source (glucose/humic acid) and electrolyte (NaCl or Na2SO4) on the emerging contaminants removal was assessed. Using real sanitary landfill leachate, the influence of current density was evaluated. The experimental results showed that electrooxidation, using a boron-doped diamond anode, can be successfully utilized to degrade methiocarb and bisphenol A when present in complex matrices, such as sanitary landfill leachate, and that methiocarb is more easily oxidized than bisphenol A. Furthermore, it was found that the presence of chloride and high humic acid content increases emerging contaminants removal rate, showing that electrooxidation at boron-doped diamond is particularly adequate to solve the problems raised by sanitary landfill leachate, even when contaminated with emerging contaminants.

Carbonaceous decomposition of a recalcitrant effluent treated by the photo-Fenton process: a kinetic approach.

Natural effluents with marked variation in their chemical composition over decomposition time in the matrix from which they are generated have a complex composition and are not totally known in most cases. Landfill leachate can be considered an effluent with complex composition, requiring imminent and more comprehensive studies on organic load degradation. Such complexity of numerous organic compounds (most of them recalcitrant humic and fulvic substances) demands a large number of kinetic equations to satisfactorily describe the temporal evolution of such conversion. Thereby, this work aims to study a kinetic approach grounded on previously consolidated chemical reactions of radical generation through the photo-Fenton mechanism. A molar balance was developed for each species in a batch photo-Fenton process and the resulting ordinary differential equations were numerically solved in MATLABTM. The kinetic model satisfactorily described an organic load conversion of the effluent under the various experimental conditions studied herein. Experimental trends could be represented by a free-radical mechanism and a degradation rate equation of first order for organic carbon, hydroxyl radical and H+. The model fittings revealed a hydroxyl radical/organic carbon stoichiometric ratio of 2:1. The kinetic study has confirmed the importance of pH levels for the reaction medium, and indicated that degradation rate depends on the medium organic composition, which provided an exponential function of conversion for the degradation rate coefficient. The model simulations corroborated the positive effect of sunlight on the radical generation through [Formula: see text] decomposition reaction with a rate coefficient in the range 4 × 10-3-2 × 10-1 s-1.

[Particle Size Distribution and Population Characteristics of Airborne Bacteria Emitted from a Sanitary Landfill Site].

Sanitary landfill is a commonly-used method for solid waste disposal. In the process of landfilling, e. g. dumping, stacking, pushing, and compacting, a large number of bioaerosols with pathogenic bacteria will be generated. That can result in air pollution and significant harm to human health if these pathogens are released into the air. Sampling sites were set up in a domestic waste sanitary landfill in North China to collect airborne bacteria in the air. Airborne bacteria, particle size distributions, and populations were analyzed, and the influence of meteorological parameters (temperature, relative humidity (RH), and wind speed (WS)) on the emission of airborne bacteria was also investigated. Results showed that the concentrations of airborne bacteria in the working area and the coverage area were (5437±572) CFU·m-3 and (2707±396) CFU·m-3, respectively. The emission level in the leachate treatment area was the highest, with an average of 9460 CFU·m-3. The concentration of airborne bacteria showed clear seasonal variation, being was much higher in summer than that in the other seasons. Redundancy analysis (RDA) demonstrated that RH, temperature, and WS affected the number of airborne bacteria in the air. The peaks in the airborne particle size distribution were 2.1-4.7 µm in the working area and 0.65-2.1 µm in the coverage area. Most of the airborne bacteria released from the leachate treatment processes were larger than 4.7 µm. Moraxellaceae, Bacillus aerius, Arcobacter, and Aeromonas were potential or opportunistic pathogens detected from the airborne bacteria samples. Effective measures should be taken to reduce the amount of bacterial aerosol emitted to the air in landfill working areas and in the leachate of treatment areas. Operators of landfill machinery and leachate treatment facilities should consider personal protection measures and should reduce their exposure to microbial aerosols in order to prevent disease.

Long-term groundwater protection efficiency of different types of sanitary landfills: Data description.

Data presented in this paper are related to the research article "Long-term risk assessments comparing environmental performance of different types of sanitary landfills'' (Madon et al., 2019). Overall environmental risks were quantitatively assessed by calculating probabilities that an assumed aquifer lying directly below the landfill of a particular type will be polluted due to landfill-derived impacts as long as the pollution potential referring to each of the four types which were compared exists. A specific model was built for the purpose, described in the companion MethodX article (Madon et al., 2019). Uncertainty was taken in consideration by attributing input parameters required for modeling with probability distributions. When loosely defined groups of landfills are to be compared, which was the objective of the related research article, these distributions can be nothing but approximate and spread out, however, the values tend to cluster together around the averages which are characteristic for particular landfill types. Secondary data from scientific literature were mostly used to estimate probability density functions for the inputs, however, when referring to one of the four landfill types which were compared, primary data were used as well. The resultant outputs derived by running Monte Carlo simulations are given as time dependent variables. In this article, probability distributions for the outputs are graphically presented comparing environmental performance of different landfill types.

Performance of Electrochemical Processes in the Treatment of Reverse Osmosis Concentrates of Sanitary Landfill Leachate.

Electrochemical technologies have been broadly applied in wastewaters treatment, but few studies have focused on comparing the performance of the different electrochemical processes, especially when used to treat highly-polluted streams. The electrochemical treatment of a reverse osmosis concentrate of sanitary landfill leachate was performed by means of electrocoagulation (EC), anodic oxidation (AO) and electro-Fenton (EF) processes, and the use of different electrode materials and experimental conditions was assessed. All the studied processes and experimental conditions were effective in organic load removal. The results obtained showed that EC, with stainless steel electrodes, is the cheapest process, although it presents the disadvantage of sludge formation with high iron content. At high applied current intensity, AO presents the best treatment time/energy consumption ratio, especially if the samples' initial pH is corrected to 3. However, pH correction from natural to 3 deeply decreases nitrogen-containing compounds' removal. For longer treatment time, the EF process with a carbon-felt cathode and a BDD anode, performed at natural iron content and low applied current intensity, is the most favorable solution.

Long-term risk assessments comparing environmental performance of different types of sanitary landfills.

Landfilling of non-pretreated, mixed municipal solid and similar waste remains a major method of waste management in many parts of the world today, particularly in developing countries. Modern dry-type and bioreactor landfills are considered to be relatively safe facilities in contrast to less engineered sanitary landfills. However, highly-engineered landfills are often not applicable in low-income countries because of their high cost. Performance of low-cost types of sanitary landfills deserve further exploration, because uncontrollable dumpsites pose real long-term threats to aquifers and the most reliable means of improving the situation is by upgrading these sites into technically similar, but environmentally safe facilities. Risk assessments can provide some insight into differences in environmental performance between major types of low-cost and high-cost landfills simulating the essential landfill processes. The risk of contamination at a presumed aquifer that resides directly below a presumed landfill was quantitatively assessed in this study comparing long-term environmental performances of four different types of facilities. A risk assessment software tool which explicitly enables inclusion of uncertainty present in the estimates to generate results with a wide range of possible outcomes was used to fulfill this purpose. It was demonstrated that contaminants derived from a modern, dry-type landfill would likely leech into an aquifer with the greatest impact occurring several decades after landfill closure. However, a specifically designed and properly operated, passive semiaerobic above-ground landfill was shown to be a comparatively safe facility.

Vulnerability assessment of areas allocated for municipal solid waste disposal systems: a case study of sanitary landfill and incineration.

This study was conducted to assess the vulnerability of areas allocated for sanitary landfill in Nakhon Ratchasima and for incineration in Phuket, Thailand, and to investigate the factors contributing to their vulnerability. Analysis was conducted to develop a vulnerability index using a composite index approach and the Intergovernmental Panel on Climate Change (IPCC) framework approach, while correlation and t tests were applied to identify the relationships and differences between the two systems. Additionally, vulnerability indices were developed using the IPCC vulnerability definition. The results suggested that the vulnerability of the areas allocated for sanitary landfill and incineration were not significantly different. The factor that had the greatest impact on the vulnerability of the sanitary landfill was nuisance, while sub-component correlation analysis revealed that cadmium in groundwater was significantly negatively correlated with vulnerability (r = - 0.958, p < 0.05). Furthermore, the factor that had the greatest effect on vulnerability from incineration was leachate. Similarly, correlation analysis suggested that the chemical oxygen demand in leachate and solid waste residues was significantly positively correlated with vulnerability (r = 0.981, 0.975 respectively, p < .05). It is hoped that these findings can be used to establish measures for preventing environmental problems, as well as to prioritize and identify issues that need to be resolved urgently, and to help policy makers select appropriate systems for different regions of Thailand.

Linking nano-ZnO contamination to microbial community profiling in sanitary landfill simulations.

Nanomaterials (NMs) commercially used for various activities mostly end up in landfills. Reduced biogas productions reported in landfill reactors create a need for more comprehensive research on these greatly-diverse microbial pools. In order to evaluate the impact of one of the most widely-used NMs, namely nano-zinc oxide (nano-ZnO), simulated bioreactor and conventional landfills were operated using real municipal solid waste (MSW) for 300 days with addition nano-ZnO. Leachate samples were taken at different phases and analyzed by 16S rRNA gene amplicon sequencing. The bacterial communities were distinctly characterized by Cloacamonaceae (phylum WWE1), Rhodocyclaceae (phylum Proteobacteria), Porphyromonadaceae (phylum Bacteroidetes), and Synergistaceae (phylum Synergistetes). The bacterial community in the bioreactors shifted at the end of the operation and was dominated by Rhodocyclaceae. There was not a major change in the bacterial community in the conventional reactors. The methanogenic archaeal diversity highly differed between the bioreactors and conventional reactors. The dominance of Methanomicrobiaceae was observed in the bioreactors during the peak methane-production period; however, their prominence shifted to WSA2 in the nano-ZnO-added bioreactor and to Methanocorpusculaceae in the control bioreactor towards the end. Methanocorpusculaceae was the most abundant family in both conventional control and nano-ZnO-containing reactors.

Effects of biochar on bacterial communities in a newly established landfill cover topsoil.

Recent studies revealed the benefits of applying biochar in landfill final cover soil, such as adsorbing odorous compounds and promoting microbial methane oxidation. Most of these processes are related to the soil bacterial communities. However, the effects of biochar application on the overall bacterial community in newly established landfill cover soil are not yet understood, especially in field condition. The objective of the present field study is to investigate the effects of biochar on the diversity of soil bacterial community 3 months after incubation (short-term). Landfill final cover topsoil (0.6 m) was amended with 0 (control), 5, and 10% (w/w) of biochar derived from peanut-shell and wheat straw. Soil bacterial communities were analysed using the 16S rRNA-based T-RFLP approach. Biochar application significantly (p < 0.05) increased the diversity of soil bacterial communities. The Shannon diversity index of bacterial communities in soil amended with 5 and 10% of biochar was increased from 3.34 to 3.85 and 3.92, respectively. There were four bacterial phyla recorded found at both control and amended soils, namely Actinobacteria, Bacteroidetes, Firmicutes, and Proteobacteria. In addition, Gemmatimonadetes was found only in soil amended with 10% biochar. The interactions between soil bacterial communities and measured soil parameters including moisture content, electrical conductivity, total organic matter, total nitrogen and total phosphorus were found to be statistically non-significant (p > 0.05), according to the canonical correspondence analysis (CCA). This may be due to the highly heterogeneous nature of landfill soil. Results from this study revealed that short-term biochar application already altered the soil physicochemical properties and increased the diversity of soil bacterial communities.