News
Enzyme Could Overcome Industrial Bleaching Waste Problems
Department of Energy's Idaho National Engineering and Environmental Laboratory (INEEL) scientists have discovered an enzyme that may transform industrial bleaching from environmentally problematic to environmentally green.
Chemical engineer Vicki Thompson and biologists William Apel and Kastli Schaller discovered that the catalase enzyme from a Thermus brockianus microbe, which thrives in the depths of a Yellowstone National Park hot springs pool, flourishes in both a high-temperature and high-pH (basic or alkaline) environment.
Catalase enzymes chemically alter hydrogen peroxide into natural products -- water and oxygen. Industry is increasingly using peroxide in industrial bleaching processes and needs an environmentally friendly process to handle process wastes. The T. brockianus catalase works well in the hot, alkaline process wastewater where commercially available catalase enzymes do not, so researchers believe it could be the answer.
Industries such as textile and pulp and paper have started shifting away from toxic, carcinogenic chemical bleaching processes to more environmentally friendly hydrogen peroxide-based bleaching. Until INEEL discovered the T. brockianus enzyme, there were only a few options available for dealing with the wastewater.
Industry can chemically treat the water to break hydrogen peroxide down, but that practically cancels out the environmental benefit. Or they can heavily dilute wastewater with even more water, but that increases the volume of wastewater. Using catalase to break down hydrogen peroxide is a good alternative, but commercially available catalase enzymes require much cooler wastewater temperatures and lower pH conditions. This costs industry significant energy, time and money.
However, researchers have found that the T. brockianus catalase likes these extreme conditions, performing best at temperatures around 90 degrees Celsius and in highly alkaline pH of more than 9. In laboratory tests, it functioned well for as long as 360 hours under these conditions compared to a mere 15 minutes to 20 minutes for other commercially available catalases.
"We didn't anticipate such extreme stability from the catalase, even though it's a thermophilic enzyme," said Thompson. Thermophiles are heat-tolerant microorganisms.
"High-temperature stability makes this enzyme potentially viable and economically attractive for industrial applications," said Apel. "This new catalase is lasting for days where the typical performance limit for many industrial-use enzymes is a mere 10 hours."
For the T. brockianus catalase, breaking down hydrogen peroxide in an industrial setting is an everyday task. Within a microorganism, the enzyme's normal role is to break down hydrogen peroxide that is naturally produced by cellular activity. This protects cells from oxidative stress, or the biological equivalent of rust.
The next step to commercial development of T. brockianus catalase is to establish enzyme production at industrially relevant volumes, including identifying the gene that encodes the T. brockianus catalase and inserting it into a microbe that is easily grown in large quantities. Then researchers can use already established technology to attach the enzyme to tiny polymer beads and pack them into columns that will filter industrial wastewater.
The team is currently discussing the industrial possibilities of this catalase with a major hydrogen peroxide manufacturer.
The INEEL is a science-based, multi-program national laboratory dedicated to supporting the U.S. Department of Energy's missions in environment, energy, science and national defense. For more information on this or any other INEEL study, go to www.inel.gov .
Worm Study at Superfund Site Finds Polluted Riverbed Can Recover
A study released in August 2003 by scientists at Stony Brook University reveals that a highly polluted riverbed, once dredged of the pollutants, can recover its original environmental health.
The study focuses on Foundry Cove, a small tidal bay and Superfund site opposite West Point Military Academy, near Cold Spring, N.Y., on the Hudson River.
Prior to 1994, Foundry Cove was one of the most polluted sites in the world. For decades, a battery factory had used the cove and the adjacent Hudson River to dispose of hundreds of tons of metal-contaminated wastes, raising the cadmium concentration of the bottom sediment to as much as 25 percent near a factory outlet pipe and over one percent cadmium in much of the cove.
Over two decades of cadmium pollution had caused dramatic effects of the biota. The most common species, an aquatic worm related to earthworms, was still abundant, but the species had become dominated by mutants that were resistant to cadmium toxicity.
In the study, led by Professor Jeffrey S. Leviton of Stony Brook University, researchers found that this resistance arose from very strong natural selection, producing rapid adaptation of the population to the high cadmium concentrations, which could now survive the new toxic conditions. The mutants that took over were not only resistant to cadmium, they even absorbed it at high rates and could transfer the toxic metal through the food web.
The Stony Brook scientists have shown a dramatic and rapid reversal of resistance toward a nearly complete recovery at Foundry Cove, following a Superfund clean-up. After only eight years since the clean-up, Leviton's team has shown that worms in the cove now are not different in resistance from those in areas that had not experienced pollution. For the first few years, worms were still resistant, despite the fact that the cadmium had been removed. By this year, however, worms in the cove now are no different in resistance than those in other areas. Their bodies are no longer laden with cadmium, and the sediment is very low in cadmium concentration -- even lower than a nearby cove not near the battery factory.
Fish-Friendly Culverts in the Making
While successfully channeling water under roadbeds, tens of thousands of culverts that lay beneath Pacific Northwest roadways also are acting as barriers to juvenile salmon by preventing the upstream passage required for growth and development, according to recent research.
To find a more "fish friendly" design for future stream crossings and for the thousands of retrofits expected to be completed in coming years, the Washington State Department of Transportation (WSDOT) has hired Pacific Northwest National Laboratory (PNNL) to design and install a culvert test bed in southwestern Washington.
"We're blending the expertise of hydraulics engineers, mechanical engineers, statisticians, fish biologists and fish-behavior specialists to find a solution to a problem that faces the entire Northwest, and has implications for culverts throughout the country," said Walter Pearson, PNNL fish behaviorist and program manager.
Located at the Washington Department of Fish and Wildlife Skookumchuck Hatchery near Tenino, Wash., the one-of-a-kind system allows scientists to adjust and measure the hydraulic conditions -- water velocity, turbulence and depth -- of various culvert designs. By assessing different slopes and flow regimes, scientists can determine how these conditions influence fish behavior and the ability of the fish to pass through a variety of culvert designs being considered as retrofits.
"There are hundreds of possibilities for bed configurations," Pearson said. "A particular design may stop passing fish at some flow rate or some slope and that's what we'll be looking for. This will help us design stream crossings that accommodate fish in all life stages."
With tens of millions of dollars allotted to improving culvert fish passageways in Washington State alone, transportation agencies are interested in quickly receiving research results. "Testing culvert designs in a controlled setting will help us better understand how we can meet fish passage needs in a variety of conditions," said Jon Peterson, from WSDOT's Environmental Services Office.
U.S. Representative Norm Dicks (D-Wash.) has recognized the need for greater federal involvement in removing these barriers to fish passage, initiating a new program to identify problems and replacing culverts that obstruct salmon migration on national forests and other federal lands. However, he said better science is required, and that a culvert test bed is needed for a more thorough understanding of the dynamics of stream flow and how adjustments based on credible data gathering will help improve culvert design and construction.
Attempts to retrofit culverts are not new. Baffles, weirs, ladders and other physical structures have been added to enhance fish passage over the years, but there is insufficient data to demonstrate the effectiveness of these efforts. "Investing in this system provides WSDOT with improved scientific data to ensure that we're spending money on solutions for fish passage that will work to provide long-term benefits to our environment," said Peterson.
A transportation consortium, which includes the states of California, Oregon, Washington and Alaska, along with the Federal Highway Administration pooled funds totaling $1.16 million to contract with PNNL to conduct the first phase of a five-year, $3.4 million interdisciplinary program. Scientists with extensive natural resources and hydraulics expertise were selected from PNNL's Marine Sciences Laboratory in Sequim, Wash., and from PNNL's Hydrology Group in Richland, Wash., to design, install and operate the culvert test bed. PNNL recently completed installation of the test bed, has tested the mechanics of the device and is currently performing hydraulic characterization.
Aussie Arsenic-Eating Bacteria Could Purify Water
Australian microbiologist Joanne Santini of Melbourne's LaTrobe University hopes an arsenic-eating bacteria discovered in her country's gold mines could one day be used to remediate contaminated water.
Santini's research group is working out how to use the bacteria to clean up contaminated wastewater in Australian and overseas mining environments and drinking wells in Bangladesh and West Bengal, India.
"If the iron guts of bacteria that can eat arsenic without dying could be harnessed to process this waste, less damage would be done to the environment and hopefully, one day, fewer people on the subcontinent will get sick," Santini said.
"It is theoretically cheaper and safer to use bacteria to clean up environmental mess than it is to use dangerous and expensive chemical methods that employ chlorine or hydrogen peroxide," she added.
Arsenic occurs naturally in rocks and in this form is harmless. But when exposed to air and water, the substance becomes soluble and toxic to plants, animals and humans. Mining and boring rock for drinking wells can expose the rock-bound arsenic to air and water and turn it into two toxic forms: arsenate and arsenite.
Arsenate is easy and safe to get rid of, but arsenite is not. It's this form that Santini hopes can be removed through the use of arsenite-munching bacteria on a mass scale. One bacterium, NT-26, eats arsenite and excretes arsenate.
"In order to know how to best use these microbes for bioremediation, we must first study how they eat arsenite," Santini said. "We can't just plunk them into a biological reactor and hope for the best."
This news section originally appeared in the November/December 2003 issue of Water & Wastewater, Volume 3, Number 6.
This article originally appeared in the 11/01/2003 issue of Environmental Protection.