TECHNOLOGY UPDATE Bacteria spore removes dissolved metals Scientists from the Scripps Institution of Oceanography, La Jolla, Calif., have identified the probable mechanism of action that allows the spores of a particular marine bacteria to precipitate metal contaminants from seawater. The researchers, who presented their results last fall at the International Marine Biotechnology Conference in Italy, hope the marine bacteria may one day aid in recovering metals from polluted coastal waters and sediments. The bacteria being studied is an aerobic organism commonly found in California coastal waters. Currently known as Bacillus sp. strain SG-1, its species has not yet been named. The scientists located and cloned the bacterial gene that codes for the protein they believe is involved in oxidizing manganese—creating manganese oxides that allow the spores to bind to and oxidize other marine metal contaminants. The group is seeking to genetically manipulate the protein-mediated oxidation system thereby enhancing the utility of the for metal removal and recovery applications Under laboratory conditions the unaltered spores can accumulate up to six times their own weight in metals and they have been able to remove more than 90% of the toxic metals in contaminated seawater Bradley Tebo, the lead scientist on the research team, says that the metal-binding spores could be applied in situ to immobilize metals. To remediate metals-contaminated sea sediments, the sediments would have to be dredged and processed. As part of their research, the scientists used the bacterial spores to successfully remove copper from contaminated seawater from the San Diego Bay. The fact that it is the spore stage rather than the vegetative stage of the bacteria that oxidizes metal con-
taminants makes this organism particularly promising for use in biotechnological applications, the scientists believe. rJactenal spores are naturally resistant to physical and chemical stresses and can be recycled to perform their bioremediation activity repeatedly. Strain SG-I can oxidize several metals, including cadmium, zinc, and cobalt. The metal oxides produced are strong oxidants and good adsorbents. Because only the surface layers of marine waters tend to support aerobic bacteria, Tebo and his colleagues are also investigating the activities of anaerobic metals-reducing organisms that can transform soluble metals into insoluble ones. They are also investigating the possibility of treating industrial effluents with metalsoxidizing bacteria.
Waste acid recycling demonstrated in Japan A jointly funded U.S. Department of Energy and EPA program to promote the sale of U.S. environmental technologies overseas financed the first demonstration in Japan last November of a system for recycling spent acid. More than 30 Japanese companies participated in the demonstration of the Waste Acid Detoxification and Reclamation system, which was developed by Pacific Northwest National Laboratory. The system combines vacuum distillation technology with lightweight, corrosion-resistant equipment constructed from fluoropolymer materials. Spent acids are processed and separated into water, reclaimable metal crystals, and reusable acid. The Japanese demonstration was conducted using waste hydrochloric and nitric acids provided by Sumitomo Electric in Osaka. The waste acids were contaminated primarily with iron but also contained lower concentrations of chromium nickel and zinc. Southeast Asian countries closely
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regulate acid gas emissions from the region's electroplating, surface finishing, electronics, and steel industries. At least one company present at the demonstration, Tokyo Rope, plans to conduct an on-site test of the technology this year. The treatment process was able to recover 70% of each acid in the demonstration at the rate of 50-70 liters of acid per hour. According to its developers, the system can achieve upwards of 90% recovery. "In general, the fewer dissolved metals there are, the more acid can be recovered," said Pacific Northwest National Laboratory Senior Development Engineer Evan Jones. The process can be used with many types of mineral acid, including sulfuric, nitric, and hydrofluoric acids. Pacific Northwest National Laboratory staff estimate that the system saves between $1 and $5 in disposal and treatment costs for each gallon of treated spent acid The Waste Acid Detoxification and Reclamation systems are marketed worldwide by Viatec Recovery Systems of Richland, Wash. The largest of the three systems currently operating in the United States processes 1000 liters of metal-contaminated waste acid per hour.
Bioreactor reduces landfill volume Through a series of tests, the world's largest aerobic landfill bioreactor was able to reduce the volume of a capped landfill in Georgia by up to 12%. The evaluations of American Technologies, Inc.'s (ATI), decomposition-enhancing technology were funded by the nonprofit Southeastern Technology Center and supervised by the Department of Energy. ATI's aerobic landfill process was tested on 16 acres of a municipal sanitary waste site in Columbia County, Ga. The system collects and recirculates leachate through the landfill, which accelerates biodegra-
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