Biofilm Barriers for Waste Containment

Principal Investigators
J.P. Turner, L.E. Bulla, and Q.D. Skinner, University of Wyoming

Abstract

Goal: The principal objective of this project is to determine--through a series of carefully controlled bench-scale tests designed to measure changes in hydraulic conductivity of soils treated with ultramicrobacteria compared to untreated soils--the feasibility of using biologically modified soils as waste containment barriers.

Rationale: The U.S. Environmental Protection Agency (EPA) is responsible for developing standards and regulations governing design, operation, and maintenance of landfills, surface impoundments, and waste piles used to treat, store, or dispose of hazardous wastes. A good deal of EPA effort, therefore, is focused on design and performance of waste containment systems. All such systems include one or more barriers to prevent transport of contaminants into the environment. Performance of contaminant barriers depends upon many factors, including type of wastes being contained, materials used to construct the barrier and their compatibility with the waste materials, quality of construction, and long-term durability under adverse environmental conditions. Materials used for barriers should be inexpensive, have low hydraulic conductivity and low molecular diffusivity, and must be durable enough to last for tens and possibly hundreds of years. This project will involve developing new, low-cost barrier materials bioengineered for waste containment.

Approach: In order to determine the feasibility of using biologically modified soils as waste containment barriers, a series of bench-scale tests will be performed to measure changes in hydraulic conductivity of soils treated with ultramicrobacteria (UMB) compared to untreated soils. The project will investigate the range of biological conditions under which UMBs have the ability to reduce soil hydraulic conductivity. Based on results of bench-scale tests, investigators will establish the range of physical and biological parameters most likely to result in successful application of biofilm technology to the design and construction of field-scale waste barriers. Finally, feasibility of using biofilm barriers at the prototype scale will be tested.

Status: A medium-grained quartz sand has been selected as the soil to be used. This soil has a high hydraulic conductivity and is relatively free of organic material and easily compacted into specimens which can be placed into a permeameter cell without any special handling. Initial tests have been conducted with the bacterium klebsiella pneumoniae. This bacterium is an excellent biofilm producer, but it has the potential to cause pneumonia in humans. Bierjerinckia, another biofilm-producing bacterium that is not pathogenic to humans, is an excellent candidate for further research. Three biofilm-treated soils have been tested. Similar behavior has been observed in specimens tested with klebsiella and bierjerinckia. This project is in its first year.

Clients/Users: Results of this project will be of interest to the U.S. Environmental Protection Agency, U.S. Department of Defense, environmental contractors, regulators, and the mining and agriculture industries.

Key words: biofilms, hydraulic conductivity, ultramicrobacteria, waste containment, barriers

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