The Impact of COVID-19 on Waste Infrastructure: Lessons Learned and Opportunities for a Sustainable Future.

The onset of the COVID-19 pandemic posed many global challenges, mainly in the healthcare sector; however, the impacts on other vital sectors cannot be overlooked. The waste sector was one of the significantly impacted sectors during the pandemic, as it dramatically changed the dynamics of waste generation. Inadequate waste management practices during COVID-19 shed light on the opportunities for developing systematic, sustainable, and resilient waste infrastructure in the future. This study aimed to exploit the learnings of COVID-19 to identify any potential opportunities in post-pandemic waste infrastructure. A comprehensive review on existing case studies was conducted to understand the waste generation dynamics and the waste management strategies during COVID-19. Infectious medical waste from healthcare facilities had the largest influx of waste compared with non-medical waste from residential and other sectors. This study then identified five key opportunities from a long-term operational perspective: considering healthcare waste sector as a critical area of focus; encouraging the integration and decentralization of waste management facilities; developing systematic and novel approaches and tools for quantifying waste; shifting towards a circular economy approach; and modernizing policies to improve the effectiveness of the post-pandemic waste management infrastructure.

Field-scale operation of methane biofiltration systems to mitigate point source methane emissions.

Methane biofiltration (MBF) is a novel low-cost technique for reducing low volume point source emissions of methane (CH4). MBF uses a granular medium, such as soil or compost, to support the growth of methanotrophic bacteria responsible for converting CH4 to carbon dioxide (CO2) and water (H2O). A field research program was undertaken to evaluate the potential to treat low volume point source engineered CH4 emissions using an MBF at a natural gas monitoring station. A new comprehensive three-dimensional numerical model was developed incorporating advection-diffusive flow of gas, biological reactions and heat and moisture flow. The one-dimensional version of this model was used as a guiding tool for designing and operating the MBF. The long-term monitoring results of the field MBF are also presented. The field MBF operated with no control of precipitation, evaporation, and temperature, provided more than 80% of CH4 oxidation throughout spring, summer, and fall seasons. The numerical model was able to predict the CH4 oxidation behavior of the field MBF with high accuracy. The numerical model simulations are presented for estimating CH4 oxidation efficiencies under various operating conditions, including different filter bed depths and CH4 flux rates. The field observations as well as numerical model simulations indicated that the long-term performance of MBFs is strongly dependent on environmental factors, such as ambient temperature and precipitation.

Effects of gas and moisture on modeling of bioreactor landfill settlement.

This manuscript describes a model that can predict settlement at variable moisture and pressure conditions as encountered in bioreactor landfills. In this model mechanical compression of municipal solid waste (MSW) was accounted with the help of laboratory compression tests. To model biodegradation-induced settlement, biodegradation of MSW was assumed to obey a first order decay equation. Richards equation was used to model moisture transport in the waste mass and mass balance was used to link settlement with gas pressure. The functionality of the numerical formulation was examined using a hypothetical bioreactor landfill. Four scenarios were analyzed to demonstrate how the proposed model can be used to analyze the settlement behavior of bioreactor landfills as well as dry landfills. The model predicted higher strains when moisture and gas pressures were incorporated into the settlement process. Results also indicated that the prediction capability of a MSW settlement model can be improved by coupling the settlement mechanisms with the generation and dissipation of gas pressure and the moisture distribution. The model is also able to predict landfill density values, and the predicted MSW wet density after 25 years agreed reasonably with those reported in literature.

Methane balance of a bioreactor landfill in Latin America.

This paper presents results from a methane (CH4) gas emission characterization survey conducted at the Loma Los Colorados landfill located 60 km from Santiago, Chile. The landfill receives approximately 1 million metric tons (t) of waste annually, and is equipped with leachate control systems and landfill gas collection systems. The collected leachate is recirculated to enable operation of the landfill as a bioreactor. For this study, conducted between April and July 2000, a total of 232 surface emission measurements were made over the 23-ha surface area of the landfill. The average surface flux rate of CH4 emissions over the landfill surface was 167 g x m(-2) x day(-1), and the total quantity of surface emissions was 13,320 t/yr. These values do not include the contribution made by "hot spots," originating from leachate pools caused by "daylighting" of leachate, that were identified on the landfill surface and had very high CH4 emission rates. Other point sources of CH4 emissions at this landfill include 20 disconnected gas wells that vent directly to the atmosphere. Additionally, there are 13 gas wells connected to an incinerator responsible for destroying 84 t/yr of CH4. The balance also includes CH4 that is being oxidized on the surface of the landfill by meth-anotrophic bacteria. Including all sources, except leachate pool emissions, the emissions were estimated to be 14,584 t/yr CH4. It was estimated that less than 1% of the gas produced by the decomposition of waste was captured by the gas collection system and 38% of CH4 generated was emitted to the atmosphere through the soil cover.

Evaluation of TENORMs field measurement with actual activity concentration in contaminated soil matrices.

The occurrence of technologically enhanced naturally occurring radioactive materials (TENORMs) concentrated through anthropogenic processes in contaminated soils at oil and gas facilities represent one of the most challenging issues facing the Canadian and US oil and gas industry today. Natural occurring radioactivity materials (NORMs) field survey techniques are widely used as a rapid and cost-effective method for ascertaining NORMs risks associated with contaminated soils and waste matrices as well other components comprising the environment. Because of potentially significant liability issues with Norms if not properly managed, the development of quantitative relationships between TENORMs field measurement techniques and laboratory analysis present a practical approach in facilitating the interim safe decision process since laboratory results can take days. The primary objective of this study was to evaluate the relationships between direct measurements of field radioactivity and various laboratory batch techniques using data collection technologies for NORM and actual laboratory radioactivity concentrations. The significance of selected soil characteristics that may improve or confound these relationships in the formulation of empirical models was also achieved as an objective. The soil samples used in this study were collected from 4 different locations in western Canada and represented a wide range in terms of their selected chemical and physical properties. Multiple regression analyses for both field and batch data showed a high level of correlation between radionuclides Ra-226 and Ra-228 as a function of data collection technologies and relevant soil parameters. All R2 values for the empirical models were greater than 0.80 and significant at P<0.05. The creation of these empirical models could be valuable in improving predictability of radium contamination in soils and therefore, reduce analytical costs as well as environmental liabilities.

Numerical model to predict settlements coupled with landfill gas pressure in bioreactor landfills.

Landfills settle due to its weight and biodegradation of waste. Biodegradation-induced settlement is a direct result of rearrangement of waste skeleton in response to the conversion of waste mass into landfill gases. Traditionally, the compressibility index based on settlement of clays is used to explain the settlement of waste. Literature review showed that there are limited research attempts of landfill settlement predictions by coupling with landfill gas generation and transport. This research describes a model which couples settlement in a bioreactor landfill with the generation and subsequent upward movement of landfill gases. The mass balance of the landfill gas was used to link settlement and gas pressures. In the absence of a closed-formed analytical solution, a computer program was developed to numerically predict the settlements and gas pressures in a bioreactor landfill using landfill geometry and waste properties. Explicitly computed settlement values were then used to predict the pressure profile implicitly. To test the mathematical formulations, a numerical exercise was performed using a single-cell hypothetical bioreactor landfill. The numerical simulation produced satisfactory trends of the settlement and the landfill gas pressure profiles.