Alix P. Rooker

Bio: Alix P. Rooker is an academic researcher from North Carolina State University. The author has contributed to research in topics: Leachate & Bioreactor landfill. The author has an hindex of 2, co-authored 2 publications receiving 1994 citations.

Present and long-term composition of msw landfill leachate: a review

Abstract: The major potential environmental impacts related to landfill leachate are pollution of groundwater and surface waters. Landfill leachate contains pollutants that can be categorized into four groups (dissolved organic matter, inorganic macrocomponents, heavy metals, and xenobiotic organic compounds). Existing data show high leachate concentrations of all components in the early acid phase due to strong decomposition and leaching. In the long methanogenic phase a more stable leachate, with lower concentrations and a low BOD/COD-ratio, is observed. Generally, very low concentrations of heavy metals are observed. In contrast, the concentration of ammonia does not decrease, and often constitutes a major long-term pollutant in leachate. A broad range of xenobiotic organic compounds is observed in landfill leachate. The long-term behavior of landfills with respect to changes in oxidation-reduction status is discussed based on theory and model simulations. It seems that the somewhere postulated enhanced release of accumulated heavy metals would not take place within the time frames of thousands of years. This is supported by a few laboratory investigations. The existing data and model evaluations indicate that the xenobiotic organic compounds in most cases do not constitute a major long-term problem. This may suggest that ammonia will be of most concern in the long run.

Critical evaluation of factors required to terminate the postclosure monitoring period at solid waste landfills.

Abstract: Regulations governing the disposal of solid waste in landfills specify that they must be monitored for 30 years after closure unless this period is extended by the governing regulatory authority. Given the wide range of conditions under which refuse is buried, technical criteria, rather than a specific time period, are preferable for evaluation of when it is acceptable to terminate postclosure monitoring. The objectives of this paper are to identify and evaluate parameters that can be used to define the end of the postclosure monitoring period and to present a conceptual framework for an investigation of whether postclosure monitoring can be terminated at a landfill. Parameters evaluated include leachate composition and leachate and gas production. Estimates of leachate production from closed landfills are used to assess the potential environmental impacts of a hypothetical release to surface water or groundwater. The acceptability of gaseous releases should be evaluated against criteria for odors, the potential for subsurface migration, and greenhouse gas and ozone precursor emissions. The approach presented here must be tested on a site-specific basis to identify additional data requirements and regulatory activity that might be required to prepare regulators for the large number of requests to terminate postclosure monitoring expected over the next 20 years. An approach in which the frequency and extent of postclosure monitoring is reduced as warranted by site-specific data and impact analysis should provide an effective strategy to manage closed landfills.

Advanced Oxidation Processes (AOPs) in Wastewater Treatment

Abstract: Advanced oxidation processes (AOPs) were first proposed in the 1980s for drinking water treatment and later were widely studied for treatment of different wastewaters. During the AOP treatment of wastewater, hydroxyl radicals (OH·) or sulfate radicals (SO4 ·−) are generated in sufficient quantity to remove refractory organic matters, traceable organic contaminants, or certain inorganic pollutants, or to increase wastewater biodegradability as a pre-treatment prior to an ensuing biological treatment. In this paper, we review the fundamental mechanisms of radical generation in different AOPs and select landfill leachate and biologically treated municipal wastewater as model wastewaters to discuss wastewater treatment with different AOPs. Generally, the treatment efficiencies rely heavily upon the selected AOP type, physical and chemical properties of target pollutants, and operating conditions. It would be noted that other mechanisms, besides hydroxyl radical or sulfate radical-based oxidation, may occur during the AOP treatment and contribute to the reduction of target pollutants. Particularly, we summarize recent advances in the AOP treatment of landfill leachate, as well as advanced oxidation of effluent organic matters (EfOM) in biologically treated secondary effluent (BTSE) for water reuse.

Hydrothermal carbonization of municipal waste streams.

Abstract: Hydrothermal carbonization (HTC) is a novel thermal conversion process that can be used to convert municipal waste streams into sterilized, value-added hydrochar. HTC has been mostly applied and studied on a limited number of feedstocks, ranging from pure substances to slightly more complex biomass such as wood, with an emphasis on nanostructure generation. There has been little work exploring the carbonization of complex waste streams or of utilizing HTC as a sustainable waste management technique. The objectives of this study were to evaluate the environmental implications associated with the carbonization of representative municipal waste streams (including gas and liquid products), to evaluate the physical, chemical, and thermal properties of the produced hydrochar, and to determine carbonization energetics associated with each waste stream. Results from batch carbonization experiments indicate 49–75% of the initially present carbon is retained within the char, while 20–37% and 2–11% of the carbon is ...