by Rebecca Wallace Before the catastrophic hurricane season of 2005 drew widespread attention to the issue of flood-related pollution, researchers from the Forest Products Laboratory (FPL) and the University of North Dakota (UND) began studying the problem of indoor air pollution that can follow massive flooding. Personal experience is what drew Drs. Evguenni Kozliak and Wayne Seames of the UND Chemistry and Chemical Engineering departments toward this complex form of pollution. In April 1997, the Red River flooded Grand Forks, North Dakota, spurring long-lasting indoor air pollution problems. During the flood, fuel oil tanks in residential basements ruptured and spilled their contents into the floodwaters. The volatile mixture was absorbed into concrete walls and wood building materials and became embedded in these porous materials. After the flood, slow evaporation of the oil and water continued, releasing hydrocarbons into the air and exposing residents to indoor air pollution for years to come. When chemicals are absorbed into building materials such as wood or concrete, common remediation techniques such as heating or washing are ineffective. The chemicals can become trapped along with water inside the porous spaces of the solid materials, making them inaccessible to common treatments. Complete removal of the contaminated materials is also common, although it can be nearly impossible when the entire foundation of a structure is affected by pollution. In search of a feasible solution to this problem, UND researchers went looking for anyone who had information on decontamination methods and the unique properties of building materials. Their search led to a partnership with FPL. "When flooding causes massive damage to large sections of buildings, traditional methods of remediation, such as material removal, are no longer feasible," said Dr. Charles Frihart, research chemist and head of the Wood Adhesives Science and Technology unit at FPL. "Our partnership and research with UND started focusing on removing the contaminants instead of the materials themselves." Eventually, the research evolved into two different approaches to addressing this particular cause of indoor air pollution. Cleaning Contaminated Materials With Tiny Organisms One route the decontamination research has taken is the potential for bioremediation—the process of applying bacteria that have the ability to degrade contaminants directly to the affected building materials. UND researchers had successfully completed a feasibility study on bioremediation of concrete, so researchers wanted to expand those existing protocols to wood, which has a significantly different pore structure than concrete. Achieving this required fundamental research to fully understand how bioremediation would work for wood. "One interesting aspect of this research is that the migration rate of chemicals through wood is not well known," said Frihart. "Much has been learned about driving large amounts of chemicals into wood, for example by pressure-treating, for the purpose of preservation. However, little is known about what happens in terms of migration when chemicals simply come in contact with wood." To test the effectiveness of bioremediation, researchers contaminated various-sized specimens of southern yellow pine with pollutants, chosen based on their solubility in water and volatility. The specimens were then treated with bacteria under various controlled conditions, and the efficiency of the bacteria at removing the pollutants was analyzed. Based on their findings, researchers were able to develop a parametric equation describing the penetration of various chemicals in wood and to create protocols for the effective removal of chemicals from wood using bioremediation. And Cleaning Air With…Sunlight? A typical approach to indoor air purification is the physical removal of contaminated air by ventilation. Unfortunately, current methods are inefficient and waste energy. Seeing improved air filtration as a promising remediation method, FPL and UND researchers began focusing on photoremediation. Photoremediation involves a photocatalyst, such as titanium dioxide, which is activated by a light source. A photocatalyst exposed to ultraviolet light—such as that in sunlight—generates reactive radicals capable of oxidizing any organic matter, rendering it harmless. Modified properly, photocatalysts can perform this important function without producing any toxic byproducts such as ozone or hydrogen peroxide. Preliminary research led FPL and UND scientists to the formulation of an efficient titanium dioxide-based photocatalyst that is currently being patented. Researchers used this formulation in the development of a novel indoor air purification device that has been demonstrated at bench-scale. A Very Viable Technology The next step for both the bioremediation and photoremediation projects is scaling them to real-world applications. Researchers will be testing commercially relevant bioremediation methods on full-scale wood and concrete samples, such as basement walls and subflooring. They will also be designing and constructing a full-scale indoor air purifier, which is expected to be complete by fall 2006. "Developing an air filtration system using photoremediation is a very viable technology," said Frihart. "It is one of the most promising aspects of this research as far as it having a direct impact on people affected by indoor air pollution." Frihart added that the results of this research will benefit a large segment of the population, not only those affected by flood-related indoor air pollution. "By adding this technology to existing electrostatic purifiers currently on the market, we will be able to address all types of indoor air pollutants with one filtration system," he said. "This includes everything from chemical pollutants to biological contaminants such as mold and dust mites, which many people are allergic to." And with that development on the horizon, perhaps we'll all be able to breathe a little easier. (Originally published in Newsline Fall 2006)
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