This study focused on the syngenetic control of polychlorinated-ρ-dibenzodioxins and dibenzofurans (PCDD/Fs) and heavy metals by field stabilization/solidification (S/S) treatment for municipal solid waste incineration fly ash (MSWIFA) and multi-step leachate treatment. Modified European Community Bureau of Reference (BCR) speciation analysis and risk assessment code (RAC) revealed the medium environment risk of Cd and Mn, indicating the necessity of S/S treatment for MSWIFA. S/S treatment significantly declined the mass/toxic concentrations of PCDD/Fs (i.e., from 7.21 to 4.25 μg/kg; from 0.32 to 0.20 μg I-TEQ/kg) and heavy metals in MSWIFA due to chemical fixation and dilution effect. The S/S mechanism of sodium dimethyldithiocarbamate (SDD) and cement was decreasing heavy metals in the mild acid-soluble fraction to reduce their mobility and bioavailability. Oxidation treatment of leachate reduced the PCDD/F concentration from 49.10 to 28.71 pg/L (i.e., from 1.60 to 0.98 pg I-TEQ/L) by suspension absorption or NaClO oxidation decomposition, whereas a so-called “memory effect” phenomena in the subsequent procedures (adsorption, press filtration, flocculating settling, slurry separation, and carbon filtration) increased it back to 38.60 pg/L (1.66 pg I-TEQ/L). Moreover, the multi-step leachate treatment also effectively reduced the concentrations of heavy metals to 1–4 orders of magnitude lower than the national emission standards. Furthermore, the PCDD/Fs and heavy metals in other multiple media (soil, landfill leachate, groundwater, and river water) and their spatial distribution characteristics site were also investigated. No evidence showed any influence of the landfill on the surrounding liquid media. The slightly higher concentration of PCDD/Fs in the soil samples was ascribed to other waste management processes (transportation and unloading) or other local source (hazardous incineration plant). Therefore, proper management of landfills and leachate has a negligible effect on the surrounding environment.

Polybrominated dibenzo-p-dioxins/furans (PBDD/Fs) and polychlorinated dibenzo-p-dioxins/furans (PCDD/Fs) share similar toxicities and thermal origins, e.g., municipal solid waste incinerator (MSWI). Recently, PBDD/Fs from MSWI attracted rising concern because their important precursors, i.e., brominated flame retardants (BFRs), were frequently found in various wastes for landfill or MSWI feedstock. So far, however, little is known about PBDD/Fs and their associated risks in the vicinal environments of MSWI. Here we analyzed PBDD/Fs and PCDD/Fs in 29 soil samples collected around a multiyear large-scale MSWI, and compared their spatial distributions, sources and risks. PBDD/Fs demonstrated comparable concentrations and toxic equivalent quantities (TEQs) to PCDD/Fs in these samples. Spatially, both the concentrations of PBDD/Fs and PCDD/Fs decreased outwards from the MSWI, and exhibited significant linear correlations with the distances from the MSWI in the southeast downwind soil, suggesting the influence of the MSWI on its vicinal soil environment. However, the existence of other dioxin sources concealed its influence beyond 6 km. PBDD/Fs in the soils were characterized by highly-brominated PBDFs, especially Octa-BDF, and their sources were diagnosed as the MSWI and diesel exhaust; PCDD/Fs, however, were dominated by highly-chlorinated PCDDs, particularly Octa-CDD, and were contributed individually or jointly by the MSWI, automobile exhaust and pentachlorophenol (PCP)/Na-PCP. The non-carcinogenic risks of dioxins in all the soil samples were acceptable, but their carcinogenic risks in 17% of the samples were unacceptable. These samples were all located close to the MSWI and highways, therefore, the land use of these two high-risk zones should be cautiously planed.

Organic fraction municipal solid waste (OFMSW) has a high potential for energy and value-added product recovery due to its carbon- and nutrient-rich composition; however, traditional value chains have treated OFMSW as an undesired by-product. This study focuses on value chain optimisation to assist the transition to resource recovery value chains. To achieve this, this work combined two stage stochastic mathematical optimisation with geographical spatial analysis and time series waste generation analysis. Existing infrastructure in England, including anaerobic digestion plants and road transportation networks, were included in the model. To account for uncertainty in waste generation, multiple scenarios and their associated probabilities were developed based on environmental variables. The optimisation problem was solved to further advance the understanding of economically optimal waste-to-resource value chains under waste generation variability. The pertinent decision variables included sizing, technology selection, waste flows and location of thermochemical treatment sites. The model highlights the potential reduction in system profitability as a result of different operating constraints, such as minimum plant operating capacity factors and landfill taxation. The latter was shown to have the largest impact on profitability as overconservative systems designs were implemented to hedge against the waste variability. Such computer-aided models offer opportunities to overcome the challenges posed by waste generation variability and waste to resource value chain transformation.

Many types of contaminants of emerging concern (CECs), including per- and poly-fluoroalkyl substances (PFAS), have been found in leachate of operating municipal landfills. However, there is only limited information on CECs presence in leachate of historic landfills (≥3 decades since closure, often lacking engineered liners or leachate collection systems) at concentrations that may pose a risk to nearby wells and surface water ecosystems. In this study, 48 samples of leachate-impacted groundwater were collected from 20 historic landfills in Ontario, Canada. The CECs measured included artificial sweeteners (ASs), PFAS, organophosphate esters (OPE), pharmaceuticals, bisphenols, sulfamic acid, perchlorate, and substituted phenols. The common presence of the AS saccharin, a known indicator of old landfill leachate, combined with mostly negligible levels of the AS acesulfame, an indicator of modern wastewater, revealed that most samples were strongly influenced by leachate and not cross-contaminated by wastewater (which can contain these same CECs). Several landfills, including ones closed in the 1960s, had total PFAS concentrations similar to those previously measured at modern landfills, with a maximum observed here of 12.7 μg/L. Notably elevated concentrations of several OPE, sulfamic acid, cotinine, and bisphenols A and S were found at many 30-60 year-old landfills. There was little indication of declining concentrations with landfill age, suggesting historic landfills can be long-term sources of CECs to groundwater and that certain CECs may be useful tracers for historic landfill leachate. These findings provide guidance on which CECs may require monitoring at historic landfill sites and wastewater treatment plants receiving their effluent.

Composting is a solid waste management alternative that avoids the emission of methane associated with its disposal in landfill and reduces or eliminates the need for chemical fertilisers if compost is applied. The main objective of this study was to analyse the environmental burdens of composting as a way to achieve a more circular valorisation of wine waste. To do so, with the purpose of identifying optimal operational conditions and determining the “hotspots” of the process, the life cycle assessment (LCA) methodology was used. The consumption of diesel fuel in machinery was determined to be the main critical point in the environmental effects of the system, followed by the transport and distribution of the compost. After the application of compost instead of mineral fertilisers, corn, tomato and strawberry crops would have a better environmental performance in most impact categories. In this sense, a maximum improvement of 65% in terrestrial ecotoxicity is achieved in strawberry cultivation. In light of the results obtained, it is demonstrated that composting is a suitable way of organic waste valorisation according to Circular Economy principles.

Multi-layered engineered landfill consists of the bottom liner layer (mainly bentonite clay (B)) upon which the hazardous wastes are dumped. In current practice, sand (S) is mixed with bentonite to mitigate the adverse effects of using bentonite alone in the liner layer. Incorporation of waste and unutilized fly ash (FA) as an amendment material to B has been explored in terms of its hydro-mechanical properties, but not gauged its adsorption potential. Indian subcontinent primarily relies on the thermal power source, and FA dumps have already reached its full capacity. The objective of this study is to explore the adsorption characteristics of four B-FA composite mixes sourced within India, considering Pb²⁺ as a model contaminant. The effect of fly ash type, fly ash amendment rate and adsorbate concentration was explored in the current study and juxtaposed with B-S mixes, based on 960 batch adsorption tests. Both B-FA and B-S mixes reached equilibrium adsorption capacity within 65 min. At higher adsorbate concentrations (commonly observed in the liner), B-FA mixes exhibited superior adsorption capacity, mainly one mixed with Neyvelli fly ash (NFA). The effect of higher amendment rate had little impact on the adsorption capacity at different concentration, but gradually decreased the percentage removal of Pb²⁺. The B-S mix showed a drastic decrease in percentage removal at higher adsorbate concentration among all tested mixes. Systematic characterization including geotechnical properties, microstructure and chemical analysis was also done to interpret the obtained results. Both Freundlich and Langmuir models fitted the isotherm data well for all B-FA mixes. The maximum adsorption capacity from the isotherm was correlated to easily measurable Atterberg limits by two empirical relationships.

A mass balance approach to quantify methane (CH4) emission of four co-located landfills by means of airborne measurements and dispersion modelling was proposed and assessed. By flying grids at different heights above the landfills, atmospheric CH4 densities and wind components were measured along the edges and inside the study atmospheric volume, in order to calculate mass flows in the along- and across-wind directions. A steady-state Gaussian dispersion model was applied to build the concentration fields associated to unit emission from each landfill, while the contribution of each one to the total emission was assessed using a General Linear Model approach, minimizing the difference between measured and modeled mass flows. Results showed that wind spatial and temporal variability is the main factor controlling the accuracy of the method, as a good agreement between measured and modeled mass flows was mainly found for flights made in steady wind conditions. CH4 emissions of the entire area ranged from 213.5 ± 33.5 to 317.9 ± 90.4 g s−1 with a mean value of 252.5 ± 54.2 g s−1. Contributions from individual sources varied from 17.5 to 40.1 g m−2 day−1 indicating a substantial heterogeneity of the different landfills, which differed in age and waste composition. The proposed method was validated against tower eddy covariance flux measurements made at one of the landfills, revealing an overall agreement within 20%.

With the rapid development of urbanization and industrialization, the peri-urban areas are often the sites for waste dumps, which may exacerbate the occurrence and spread of antibiotic resistance from waste to soil bacteria. However, the profiles of antibiotic resistomes and the associated factors influencing their dissemination in peri-urban areas have not been fully explored. Here, we characterized the antibiotic resistance genes (ARGs) in peri-urban arable and pristine soils in four seasons at the watershed scale, by using high-throughput qPCR. ARGs in peri-urban soils were diverse and abundant, with a total of 222 genes were detected in the peri-urban soil samples. The arable soil harbored more diverse ARGs compared to the pristine soils, and nearly all the ARGs detected in the pristine soils were also detected in the farmlands. A random forest prediction showed that the overall patterns of ARGs clustered closely with the landuse type. Mantel test and partial redundancy analysis indicated that bacterial community variation is a major contributor to antibiotic resistome alteration. Significant positive correlation was found between the abundance of ARGs and mobile genetic elements (MGEs), suggesting potential mobility of ARGs in peri-urban areas. Our results extend knowledge of the resistomes compositions in peri-urban areas, and suggest that anthropogenic activities driving its spatial and temporal distribution.

Determining sources of heavy metals in soils, sediments and groundwater is important for understanding their fate and transport and mitigating human and environmental exposures. Artificially imported fill, natural sediments and groundwater from 240 ha of reclaimed land at Fishermans Bend in Australia, were analysed for heavy metals and other parameters to determine the relative contributions from different possible sources. Fishermans Bend is Australia's largest urban re-development project, however, complicated land-use history, geology, and multiple contamination sources pose challenges to successful re-development. We developed a method for heavy metal source separation in groundwater using statistical categorisation of the data, analysis of soil leaching values and fill/sediment XRF profiling. The method identified two major sources of heavy metals in groundwater: 1. Point sources from local or up-gradient groundwater contaminated by industrial activities and/or legacy landfills; and 2. contaminated fill, where leaching of Cu, Mn, Pb and Zn was observed. Across the precinct, metals were most commonly sourced from a combination of these sources; however, eight locations indicated at least one metal sourced solely from fill leaching, and 23 locations indicated at least one metal sourced solely from impacted groundwater. Concentrations of heavy metals in groundwater ranged from 0.0001 to 0.003 mg/L (Cd), 0.001–0.1 mg/L (Cr), 0.001–0.2 mg/L (Cu), 0.001–0.5 mg/L (Ni), 0.001–0.01 mg/L (Pb), and 0.005–1.2 mg/L (Zn). Our method can determine the likely contribution of different metal sources to groundwater, helping inform more detailed contamination assessments and precinct-wide management and remediation strategies.

Rapid urbanization and economic growth has led to significant increase in municipal solid waste generation in India during the last few decades and its management has become a major issue because of poor waste management practices. Solid waste generated is deposited into open dumping sites with hardly any segregation and processing. Carbon dioxide (CO₂), methane (CH₄) and nitrous oxide (N₂O) are the major greenhouse gases that are released from the landfill sites due to the biodegradation of organic matter. In this present study, CH₄ and CO₂ emissions from a landfill in north-east India are estimated using a flux chamber during September, 2015 to August, 2016. The average emission rates of CH₄ and CO₂ are 68 and 92 mg/min/m², respectively. The emissions are highest in the summer whilst being lowest in winter. The diurnal variation of emissions indicated that the emissions follow a trend similar to temperature in all the seasons. Correlation coefficients of CH₄ and temperature in summer, monsoon and winter are 0.99, 0.87 and 0.97, respectively. The measured CH₄ in this study is in the range of other studies around the world. Modified Triangular Method (MTM), IPCC model and the USEPA Landfill gas emissions model (LandGEM) were used to predict the CH₄ emissions during the study year. The consequent simulation results indicate that the MTM, LandGEM-Clean Air Act, LandGEM-Inventory and IPCC models predict 1.9, 3.3, 1.6 and 1.4 times of the measured CH₄ emission flux in this study. Assuming that this higher prediction of CH₄ levels observed in this study holds well for other landfills in this region, a new CH₄ emission inventory (Units: Tonnes/year), with a resolution of 0.1⁰ × 0.1⁰ has been developed. This study stresses the importance of biodegradable composition of waste and meteorology, and also points out the drawbacks of the widely used landfill emission models.