Evaluating the Ecological Footprint of Landfills: A Framework and Case Study of Fargo, North Dakota.

There is growing interest in better understanding the environmental impacts of landfills and optimizing their operation. Accordingly, we developed a holistic framework to calculate a landfill's Ecological Footprint (EF) and applied that to the Fargo, North Dakota, landfill. Parallelly, the carbon footprint and biocapacity of the landfill were calculated. We calculated the EF for six scenarios (i.e., cropland, grazing land, marine land, inland fishing ground, forest land, and built land as land types) and six operational strategies typical for landfills. Operational strategies were selected based on the variations of landfill equipment, the gas collection system, efficiency, the occurrence of fugitive emissions, and flaring. The annual EF values range from 124 to 213,717 global hectares depending on land type and operational strategy. Carbon footprints constituted 28.01-99.98% of total EF, mainly driven by fugitive emissions and landfill equipment. For example, each percent increase in Fargo landfill's fugitive emissions caused the carbon footprint to rise by 2130 global hectares (4460 tons CO2e). While the landfill has biocapacity as grazing grass in open spaces, it remains unused/inaccessible. By leveraging the EF framework for landfills, operators can identify the primary elements contributing to a landfill's environmental impact, thereby minimizing it.

Impacts of the COVID-19 pandemic on landfilling and recycling in the city of Fargo, North Dakota, USA.

The COVID-19 pandemic impacted different aspects of human lifestyle, including waste generation and management. The landfilled and recycled waste volume from the City of Fargo's annual solid waste report between 2019 and 2021 was critically analyzed to understand these impacts. The analysis showed a 4.5% increase in the residential waste volume in 2020 compared to 2019 and 2021, suggesting a pandemic-induced lockdown effect. The monthly residential waste volume was approximately 5-15% greater during the mandatory quarantine period (April - November 2020) than in 2019 and 2021. Commercial waste volume decreased by 12% during 2020 and then sharply increased in 2021 as commercial facilities reopened. The total recycling volume increased slightly by 2.5% in 2020 compared to 2019 and 2021. Cardboard recycling showed a 5.8% increase in 2020 from 2019 and a 13% increase in 2021 compared to 2020. This was presumably caused by the reliance on online shopping during the pandemic and becoming habituated to online shopping. The COVID-19 pandemic did not significantly impact other classes of recycled waste volumes. In summary, COVID-19 affected landfilling and recycling in different capacities in the City of Fargo. The data will contribute to the global understanding of the impact of COVID-19 on solid waste management practices.Implications: The COVID-19 pandemic impacted waste generation and management. In Fargo, USA, the monthly residential waste volume increased by up to 15% during the mandatory quarantine period in 2020 compared to the same period in 2019 and 2021. Conversely, the monthly commercial waste volume decreased during the mandatory quarantine period in 2020. The commercial waste volume increased in 2021 as commercial activities became normal. The cardboard recycling increased significantly because people became used to online shopping during the lockdown, and the practice continues. The findings will contribute to the global understanding of the impact of COVID-19 on solid waste management practices.

Formation of disinfection byproducts during Fenton's oxidation of chloride-rich landfill leachate.

Because of the production of chlorine species in leachate during Fenton's oxidation, harmful disinfection byproducts (DBP) can be formed but this has not been well studied before. Herein, we have investigated five classes of DBP: trihalomethanes, haloacetic acids, haloacetonitriles, haloketones, and halonitromethanes during Fenton's oxidation of landfill leachates. The results show that the DBP concentration increased with the increase of [H2O2]: [Cl-] ratio due to the increased concentration of chlorine species. The highest total DBP concentration was 4860 µg L-1 at [H2O2]: [Cl-] = 4.0 and the lowest was 84 µg L-1 at [H2O2]: [Cl-] = 0.25. Both the DBP concentration and DBP toxicity increased with the increase of the [H2O2]: [Fe2+] ratio, because of the increased concentration and lifetime of the chlorine species. Most of the DBP were formed during the first minute of the reaction and stayed stable up to 3 h, indicating that DBP may not be preferred targets of hydroxyl radicals in the presence of a large amount of organics. In most cases, trihalomethanes dominated the DBP concentration, while haloacetonitriles dominated the total additive toxicity. This study has provided important implications to understand DBP formation during Fenton's oxidation.

Treatment of leachate organic matter through sunlight driven processes.

Leachate organic matter (LOM) from mature, stabilized landfills is recalcitrant in nature resulting from high concentrations of humic substances, such as humic acids and other complex organic matter. This research focused on the behavior and fate of LOM in aquatic sun-lit systems to address the extent and mechanisms of LOM photodegradation by exposing leachate to natural sunlight in central Florida for a period of 90 days. Transformation processes were measured using ultraviolet-visible (UV-Vis) spectroscopy, fluorescence excitation-emission matrix spectroscopy, size-exclusion chromatography, and chemical oxygen demand over the test period. Results of the study suggest that photolytic, and in some cases biological, reactions were responsible for the reduction of LOM demonstrated by the transformation of high molecular weight recalcitrant material to lower molecular weight material, loss of fluorescence and color, and reduction of UV254 absorbance.

Impact of organic matter from leachate discharged to wastewater treatment plants on effluent quality and UV disinfection.

There are growing concerns over the negative effects of leachate organic matter (LOM) on ultraviolet (UV) disinfection and effluent quality when leachate is co-treated with domestic wastewater. In this study, the effects of LOM on wastewater effluent quality were evaluated through field studies at wastewater treatment plants (WWTPs) that receive and do not receive leachate. Impacts of leachate on effluent quality were determined through UV measurements at 254 nm (UV254), fluorescence measurements, and the quantification of conventional parameters which included nutrient and organic constituent concentrations. Results showed that some leachate impacts can be observed using UV254 spectroscopy in wastewater influent and effluent when present at volumetric contributions as low as 0.01%. In addition, leachate impacted wastewater samples showed a higher dissolved organic nitrogen and dissolved organic carbon concentrations in the effluent relative to effluents from WWTPs without leachate. At leachate volumetric contributions greater than or equal to 0.1% (0.10-14.8%), UV254 transmittance in wastewater effluents was below 65%. A typical guideline for effective UV disinfection at WWTPs is above 65% transmittance. Furthermore, fluorescence characterization of leachate-impacted wastewater showed a higher intensity of humic-like peaks relative to wastewater without leachate. This research provided a better understanding of the potential implications of accepting leachate at WWTPs. These effects, however, can be managed by ensuring that leachate discharge is maintained at acceptable volumetric contributions and evenly spread out over the discharge period.

Conventional and fourier transform infrared characterization of waste and leachate during municipal solid waste stabilization.

Solid waste and leachate samples from bench-scale anaerobic bioreactors and flushing bioreactors (FBs), containing mature waste were characterized using Fourier Transform Infrared Spectroscopy (FTIR) to provide a better understanding of the changes in waste characteristics when waste transitions from mature to stabilized. Humic acid (HA) extracted from mature waste and waste removed from the FBs were characterized using FTIR and 13C nuclear magnetic resonance. FBs were operated under three different treatment scenarios (flushing with clean water, recirculation of leachate treated by chemical oxidation, and recirculation of leachate treated by chemical oxidation with waste aeration. FTIR spectra of FB waste and leachate supported the stabilization of waste that occurred after the additional treatment. There was a shift in the dominance of organic to inorganic functional groups when compared to changes in conventional parameters that aligned with published values on waste stability. HA extracted from the mature waste were dominated by aliphatic carbon and aromatic carbon was less intense. Treatment by flushing resulted in a decrease in aliphatic carbon and an increase in aromatic carbon. HA extracted from reactors with oxidized leachate recirculation and aeration decreased in aliphatic carbon content, with minimal change in aromatic carbon. Therefore, the additional treatment did not result in an increase in the reactivity potential of the HA which aligns with FTIR and principal component analysis. Results suggest that spectroscopic techniques could be used to assess the stability of waste samples as opposed to more time-consuming analyses.

A review of the fate of engineered nanomaterials in municipal solid waste streams.

Significant knowledge and data gaps associated with the fate of product-embedded engineered nanomaterials (ENMs) in waste management processes exist that limit our current ability to develop appropriate end-of-life management strategies. This review paper was developed as part of the activities of the IWWG ENMs in Waste Task Group. The specific objectives of this review paper are to assess the current knowledge associated with the fate of ENMs in commonly used waste management processes, including key processes and mechanisms associated with ENM fate and transport in each waste management process, and to use that information to identify the data gaps and research needs in this area. Literature associated with the fate of ENMs in wastes was reviewed and summarized. Overall, results from this literature review indicate a need for continued research in this area. No work has been conducted to quantify ENMs present in discarded materials and an understanding of ENM release from consumer products under conditions representative of those found in relevant waste management process is needed. Results also indicate that significant knowledge gaps associated with ENM behaviour exist for each waste management process investigated. There is a need for additional research investigating the fate of different types of ENMs at larger concentration ranges with different surface chemistries. Understanding how changes in treatment process operation may influence ENM fate is also needed. A series of specific research questions associated with the fate of ENMs during the management of ENM-containing wastes have been identified and used to direct future research in this area.

Evaluation of leachate dissolved organic nitrogen discharge effect on wastewater effluent quality.

Nitrogen is limited more and more frequently in wastewater treatment plant (WWTP) effluents because of the concern of causing eutrophication in discharge waters. Twelve leachates from eight landfills in Florida and California were characterized for total nitrogen (TN) and dissolved organic nitrogen (DON). The average concentration of TN and DON in leachate was approximately 1146mg/L and 40mg/L, respectively. Solid-phase extraction was used to fractionate the DON based on hydrophobic (recalcitrant fraction) and hydrophilic (bioavailable fraction) chemical properties. The average leachate concentrations of bioavailable (bDON) and recalcitrant (rDON) DON were 16.5mg/L and 18.4mg/L, respectively. The rDON fraction was positively correlated, but with a low R2, with total leachate apparent color dissolved UV254, chemical oxygen demand (COD), and humic acid (R2 equals 0.38, 0.49, and 0.40, respectively). The hydrophobic fraction of DON (rDON) was highly colored. This fraction was also associated with over 60% of the total leachate COD. Multiple leachate and wastewater co-treatment simulations were carried out to assess the effects of leachate on total nitrogen wastewater effluent quality using removals for four WWTPs under different scenarios. The calculated pass through of DON suggests that leachate could contribute to significant amounts of nitrogen discharged to aquatic systems.

Application of landfill treatment approaches for stabilization of municipal solid waste.

This research sought to compare the effectiveness of three landfill enhanced treatment approaches aimed at removing releasable carbon and nitrogen after anaerobic landfilling including flushing with clean water (FB 1), leachate recirculation with ex-situ treatment (FB 2), and leachate recirculation with ex-situ treatment and in-situ aeration (FB 3). After extensive treatment of the waste in the FB scenarios, the overall solids and biodegradable fraction were reduced relative to the mature anaerobically treated waste. In terms of the overall degradation, aeration did not provide any advantage over flushing and anaerobic treatment. Flushing was the most effective approach at removing biodegradable components (i.e. cellulose and hemicellulose). Leachate quality improved for all FBs but through different mechanisms. A significant reduction in ammonia-nitrogen occurred in FB 1 and 3 due to flushing and aeration, respectively. The reduction of chemical oxygen demand (COD) in FB 1 was primarily due to flushing. Conversely, the reduction in COD in FBs 2 and 3 was due to oxidation and precipitation during Fenton's Reagent treatment. A mass balance on carbon and nitrogen revealed that a significant fraction still remained in the waste despite the additional treatment provided. Carbon was primarily converted biologically to CH4 and CO2 in the FBs or removed during treatment using Fenton's Reagent. The nitrogen removal occurred through leaching or biological conversion. These results show that under extensive treatment the waste and leachate characteristics did meet published stability values. The minimum stability values achieved were through flushing although FB 2 and 3 were able to improve leachate quality and solid waste characteristics but not to the same extent as FB 1.

Evaluation of monitoring indicators for the post-closure care of a landfill for MSW characterized with low lignin content.

To understand the applicability of the termination indicators for landfill municipal solid waste (MSW) with low initial lignin content, four different accelerated landfill stabilization techniques were applied to anaerobic landfilled waste, including anaerobic flushing with water, anaerobic flushing with Fenton-treated leachate, and aerobic flushing with Fenton-treated and UV/H2O2-treated leachate. Termination indicators, including total organic carbon (TOC), ammonia-N (NH4(+)-N), the ratio of UV absorbance at 254 nm to TOC concentration (SUVA254), fluorescence spectra of leachate, methane production, oxygen consumption, lignocellulose content, and humus-like content were evaluated. Results suggest that oxygen consumption related indicators used as a termination indicator for low-lignin-content MSW were more sensitive than methane consumption related indicators. Aeration increased humic acid (HA) and (HA+FA)/HyI content by 2.9 and 1.7 times compared to the anaerobically stabilized low-lignin-content MSW. On the other hand, both the fulvic acid (FA) and hydrophilic (HyI) fractions remained constant regardless of stabilization technique. The target value developed for low-lignin-content MSW was quite different than developed countries mainly due to low residual biodegradable organic carbon content in stabilized low-lignin-content MSW.

Behavior of engineered nanoparticles in landfill leachate.

This research sought to understand the behavior of engineered nanoparticles in landfill leachate by examining the interactions between nanoparticles and leachate components. The primary foci of this paper are the effects of ZnO, TiO2, and Ag nanoparticles on biological landfill processes and the form of Zn, Ti, and Ag in leachate following the addition of nanoparticles. Insight into the behavior of nanoparticles in landfill leachate was gained from the observed increase in the aqueous concentrations over background for Zn, Ti, and Ag in some tested leachates attributed to leachate components interacting with the nanoparticle coatings resulting in dispersion, dissolution/dissociation, and/or agglomeration. Coated nanoparticles did not affect biological processes when added to leachate; five-day biochemical oxygen demand and biochemical methane potential results were not statistically different when exposed to nanoparticles, presumably due to the low concentration of dissolved free ionic forms of the associated metals resulting from the interaction with leachate components. Chemical speciation modeling predicted that dissolved Zn in leachate was primarily associated with dissolved organic matter, Ti with hydroxide, and Ag with hydrogen sulfide and ammonia; less than 1% of dissolved Zn and Ag was in the free ionic form, and free ionic Ti and Ag concentrations were negligible.