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Using Electrokinetics To Clean Waste Sites

Cleaning contaminated soils through electrokinensis--electrically transferring water and dissolved contaminants with uniform, controlled movement--has traditionally been an expensive procedure that required off-site cleaning as a final step. Philip Brodsky, B. Mason Hughes, and Sa Ho at Monsanto Co., St. Louis, Mo., developed the Lasagna Process with DuPont, Houston, Texas, and GE Research and Development Center, Schenectady, N.Y., to make electrokinesis less disruptive and more affordable.

In conventional electrokinesis, water pumped in at the anode travels by electroosmosis to the cathode, causing electromigration of contaminants. Contaminated water is pumped to the surface and taken offsite for treatment.

The Lasagna Process pumps water from the cathode back to the anode in a closed loop. It derives its name from the different layers of its configuration. The granular electrode layers form the ends of the stack and can be oriented either vertically or horizontally to each other. A degradation zone is stacked on top of each electrode, and sandwiched in the middle is the contaminated soil.

This solves several problems. First, the Lasagna Process can move contaminants into treatment zones where they can be decontaminated in situ. The time and expenses of off-site processes are eliminated. Second, poles can be reversed in the Lasagna Process for multiple passes through the soil. Pole reversal combined with water recycling eliminates pH and ionic gradient buildup as well as stopping soil drying from nonuniform voltage gradients. The Lasagna Process is also unique because it performs well on both non-permeable (high in clay and silt content) and permeable soils.

The Lasagna Process is effective for organics, metals, and mixed wastes including trichloroethylene, perchloroethylene, dichloroethylene, and vinyl chloride.

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Technology Burns Diesel Fuel Cleanly

Nitrogen oxides (NOx) and particulate matter from diesel engines pose challenging environmental problems, especially in urban. areas. Argonne Clean-Diesel Technology, a new operating regime for diesel engines, breaks previous technological barriers to reduce both forms of pollution.

Developers Ramesh Poola and Raj Sekar at the DOE's Argonne (Ill.) National Laboratory combined oxygen-enriched combustion, retarded injection timing, and a higher fuel flow rate to accomplish this feat on an EMD 567 locomotive research engine. The changes in injection timing and fuel flow reduce NOx emissions by 15%; particulate matter is reduced by 60% by the oxygen-enriched combustion.

Because fuel is burned more completely with every piston stroke this technology also increases engine power by 18% and fuel economy by 2-10%.

Intake air is enriched by 23% via polymer-coated fiber tubes 10 times shorter and using 60% less power than competitive membranes. Vehicles retrofitted with this technology could meet EPA emissions standards for 2004.

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Microwaves Replace Weather Balloons

Radiosondes, the instruments that collect data from weather balloons, represent technology that is 80 years old and error-prone. The Radiometrics Microwave Profiler (MP-3000), from Radiometrics Corp., Boulder, Colo., updates the measurement of atmospheric temperature and water-vapor profiles by providing more types of data more accurately on a more reliable platform.

The instrument, developed by Fredrick Solheim, calculates temperature and water-vapor profiles to a height of 10 km and low-resolution water profiles of one or two cloud layers from microwave radiation emitted from the atmosphere in different frequency bands.

Atmospheric water and oxygen have unique emission spectra that vary with temperature, density, and pressure. By observing atmospheric emissions, the MP-3000 can determine profiles of temperature, water vapor, and liquid water, as well as total water vapor and liquid along a path. The MP-3000 has the additional benefit of seeing through fog, smoke, and clouds.

The data provided by the MP-3000 are useful for atmospheric research, weather forecasting, aircraft icing hazard detection, and precipitation forecasts.

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Process Creates Better Biosolids

A two-stage anaerobic digestion process for wastewater treatment plants produces biosolids that are safe and beneficial to the environment. The Temperature-Phased Anaerobic Digestion (TPAD) process, created by Richard Dague at Iowa State Univ., Ames, with help from William Harris and Sandra Kaiser, is the first anaerobic digestion process that does not produce biosolids that have to be incinerated or disposed of in landfills.

Traditionally sludge would cook at 35 [degrees] C. TPAD prefaces this with a cooking step at 55 [degrees] C before allowing the sludge to flow into the cooler tank. This addition kills almost all fecal coliform, eliminates foaming, yields more methane, and concentrates end products by 10% more than the original method. The final products have no offensive smell and can be used for soil fertilization and conditioning.

The method processes the same amount of sludge in tanks that are half the size and eliminates the costs of landfill space and incineration.

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Robot Inspects Full Fuel Tanks

Maverick is the only robot certified to inspect aboveground storage tanks containing hazardous, potentially explosive fuel. Designed by researchers at the DOE's Idaho National Engineering and Environmental Lab, Idaho Falls, and Solex Robotics Systems Inc., Houston, Texas, Maverick does not produce any sparks and is completely submersible. The size of a suitcase, it easily fits through manways on top of the tanks, is self-righting, and moves on four traction wheels at walking speed. Its instruments include a multichannel ultrasonic sensor system to map and correlate metal thickness data, a video system to view the tank bottom, and position-tracking sensors that give the locations of both problem spots and the robot. Maverick performs floor, sidewall, and chine inspections in real time. Data goes through a 4.5-cm tether to a control trailer, where technicians can remotely control Maverick's movement.

Maverick eliminates the need for hand-probe inspections, which traditionally disable tanks for four-week periods. The robotic inspection also costs three times less than a manual inspection while providing much more data.

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Process Turns Dilute Ammonia Into Fertilizer

The Centrate Ammonia Recover (CAR) Process is currently the only way to remove environmentally harmful ammonia from wastewater, turn it into commercial fertilizer, and leave no secondary waste.

The process starts with centrate, liquid from centrifuged, anaerobically digested sewage sludge, which gets selectively absorbed onto ion exchange columns. Ammonia from this stream is selectively adsorbed by a proprietary resin loaded with zinc onto the same type of columns used for ion exchange, at a rate of 10 g of ammonia per liter of resin. The columns are regenerated with a low-pH solution of sulfuric acid, and zinc sulfate that concentrates the ammonia to 15,000 ppm. This concentrated solution is then evaporated to 60,000 ppm and cooled to form zinc ammonium sulfate crystals. These easy-to-separate double-salt crystals get roasted to drive the ammonia into a sulfuric acid scrubber. That forms ammonium sulfate, which can be sold as fertilizer.

This process removes over 90% of ammonia from wastewater. The technology was developed by researchers at the DOE's Pacific Northwest National Laboratory, Richland, Wash.; Battelle Columbus (Ohio) Operations, and ThermoEnergy Environmental Corp., Richland, Wash.

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Carbon Air Filter Cleans Self

The Self-Cleaning Carbon Air Filter, developed by Kirk Wilson, Timothy Burchell, and Roddie Judkins at the DOE's Oak Ridge (Tenn.) National Laboratory, is the first and only carbon air filter that automatically cleans itself. Other carbon cleaners are loose granules that have to be changed when they fill up. The Self-Cleaning filter is a monolith of electrically conductive, activated carbon fiber composite that can be reused several times.

When the filter is full, an electric current passes through it in the automatic cleaning cycle. Built-up pollutants are released into a purge airstream and exhausted outdoors. To do this, the filter reverses the airflow and draws air from indoors through the pollutant-filled filter to exhaust it outside. When cleaning is complete, the filter automatically returns to normal operation. The carbon filters can be used for many cycles before they need to be replaced.

The Self-Cleaning Carbon Air Filter also yields a lower pressure drop than other filters, thus saving fan energy.

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Heat Pump Conserves Indoor Heat

The Frostless Heat Pump, from researchers at the DOE's Oak Ridge (Tenn.) National Laboratory, avoids wasting heated indoor air for defrosting outdoor heat-exchange coils in cold weather. This is in contrast to conventional heat pumps, which reverse the airflow to melt the frost using indoor air. When this happens, indoor temperatures temporarily drop despite supplemental resistance-heating elements that switch on.

The Frostless Heat Pump avoids this problem by adding a moderate amount of heat to the accumulator. This both increases the temperature of the refrigerant entering the outdoor coil and increases heating capacity, the latter being due to the fact that most of the heat to the accumulator is delivered to the indoor coil. This not only keeps the outdoor coil warmer--and therefore less likely to frost up--but also can heat a house faster, and thereby shut off the cycle before frost forms. Frost formation can be retarded down to 1 [degree] C.

If frost does form, the pump does not reverse airflow to defrost. Instead, it shuts off the indoor fan and uses accumulator heat to defrost the outdoor coil.

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Title Annotation:innovations in environmental processes and products
Publication:R & D
Geographic Code:1USA
Date:Sep 1, 1999
Previous Article:Energy.
Next Article:Imaging.

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