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CONSTRUCTION AND DEMOLITION DEBRIS
Control of Odors from Construction and Demolition Debris Landfills
Dr. Timothy Townsend, University of Florida
Construction and demolition (C&D) debris landfills sometimes experience odor problems as a result of reduced sulfur compounds produced in the landfill. The most notable reduced sulfur compound is hydrogen sulfide (H2S). The production of H2S and other reduced sulfur compounds has been linked to the disposal of gypsum wall-board. Previous research efforts have explored the occurrence of H2S at C&D debris landfills and in simulated laboratory experiments. Recent laboratory work has also examined the use of different types of cover soil to "filter" H2S from the gas before it leaves the landfill. This project expands this research to the field. The emissions of H2S from actual C&D debris landfills will be measured using a flux chamber. At one field site, different cover soil types will be used to assess the ability of various materials to attenuate H2S emissions.
Research Advancing the Management of Construction and Demolition Debris in Florida
Dr. Timothy Townsend, University of Florida
This project targets three tasks whose objectives are to advance the practice of C&D debris management in Florida.
Task 1: H2S Odors at C&D Debris Landfills - To examine the long term performance of soil amendments for mitigating hydrogen sulfide emissions from C&D debris landfills (in the field) and to evaluate factors impacting H2S control (in the field and in the lab).
Task 2: Engineered Wood - To examine potential environmental concerns associated with the inclusion of engineered wood products such as plywood and oriented strand board (OSB) in landscape mulch.
Task 3: Portland Cement Concrete - To compile all available federal and state specifications (and possibly international) regarding the reuse of crushed portland cement concrete for road base construction stone and to foster a dialogue between all appropriate parties to determine what actions are needed to overcome existing impediments.
Several landfill sites in Florida are experiencing elevated iron concentrations in the groundwater wells. The iron rich soil is being hypothesized as source of iron. Similarly the disposal of arsenic treated wood in unlined C&D landfills is a concern for potential groundwater contamination due to arsenic (As) leaching from the wood. The two issues are interrelated since changes to the redox conditions can have a strong impact on the fate of both As and Fe. The fate of As is very much tied to chemistry of iron; iron soils have a strong ability to adsorb arsenic from water. The fact that reducing condition under landfills may cause iron to be released suggests that As will also be released and might be more mobile than expected based on soil properties alone.
The primary objectives of this project are to quantify the contribution that soils beneath landfills can make to iron in groundwater and to evaluate the ability of soils beneath C&D debris landfills to retain and hold arsenic against leaching. Elevated iron concentrations have been noted at a growing number of facilities in the state, both lined and unlined, but the source of the iron is unknown. This study will attempt to relate the chemical, physical, and hydrologic properties of these soils to their iron releasing potential. The second issue is the fate of As from CCA-treated wood at C&D debris landfills. The ability of soils to retain arsenic depends on the chemical and physical properties of the soil as well as the chemical properties of the surrounding solution, such as redox potential and presence of organic and inorganic ligands. These factors will be quantified to the extent possible and utilized in an existing transport model to evaluate the leaching potential of arsenic beneath C&D Landfills.
