Process condensate wastewaters from two fixed-bed gasijiers have been treated successfully using a laboratory-scale, fixed-film, fluidized-bed bioreactor. Both dilute (1 to 2% raw wastewater) and more concentrated (50% stripped wastewater) were treated continuously for periods of one to three months. Biological activity was stable, recovery from upsets was rapid, and reaction rates were high due to the high concentration of microorganisms retained on the support particles. Removal of phenolics exceeded 99%, and removal of chemical oxygen demand was typically 75 to 85% for the 50% stripped wastewater with a hydraulic residence time in the bed of -5 to 7 h. Sludge production rates were comparable to rates in suspended growth systems.

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Most coal gasification processes will use large quantities of water and generate wastewaters that require treatment prior to discharge or reuse. A major wastewater source in many gasification processes is the raw quench condensate [ I ] . These wastewaters are characterized by high concentrations of suspended solids, ammonia, organics (notably phenols), tars, and oils. Treatment of these wastewaters may require a train of operations, such as clarification, extraction of tars and oils, hydrogen sulfide and ammonia stripping, removal of organics, and final polishing.The major portion of the dissolved organics can be removed by using conventional biooxidation processes such as activated sludge [2] or trickle filters. However, these conventional processes require relatively large capital investments and large land areas, are subject to environmental stress (temperature, rainfall), and may produce environmental stress (aerosols, odors). An alternative technology for biooxidation of dissolved organics is the fixed-film, fluidized-bed bioreactor. This technology, which is currently under development at Oak Ridge National Laboratory [3-6XORNL), offers several advantages relative to conventional biooxidation technologies. Lower capital costs are projected since the high density of retained cells enables high organic removal rates at low hydraulic retention times and thus permits smaller reactors. The fixed films are expected to provide improved resistance to shock and toxins relative to suspended growth systems, as evidenced by work done at ORNL with similar fixed-film systems. Health and environmental effects associated with open-air systems are minimized by the use of closed-reactor systems with off-gas control.Process development work is being carried out to demonstrate the technical feasibility of this process for coal gasification wastewaters. Two laborator scale bioreactors have been constructed and successfulcoperated for more than 1 year to treat synthetic wastewaters. Dilute actual wastewaters have been treated continuously for approximately 9 months. Bioreactor performance, batch kinetic studies, and development, characterization, and preservation of the microbial culture are described in this report. EXPERIMENTAL PROCEDURES Eioreactor DesignThe laboratory-scale bioreactor, shown in Figure 1, is a glass column 5 cm ID and 1.5 m tall with a water jacket for temperature control. There is a solids disengaging zone at the top, with an angled effluent discharge arm to allow solids to return to the main column. Recycle of solids or liquid is possible if desired. Two reactor systems of this type have been operated.The solid support particles chosen for the initial process development work are 30-60 mesh anthracite coal. The wastewater treatment industry has historically used coal for fixed-film processes, and considerable earlier work at ORNL with other biological fluidized-bed applications indicated that anthracite coal is especially effective for retaining stable fixed films. Coal is less dense than sand (another co...

Pumping tests have shown that a 24 wt % slurry of CST in water can be transported at fluid velocities of 4.3 ftls (45 gpm in a 2-in. pipe) with no visible settling of the CST particles, while a 5 wt 1% slurry will stay suspended at a velocity of 3.8 Ms. The CST was easily mobilized after purposely plugging sections of pipe. The CST particles were rapidly broken up by a centrifugal pump into very small particles (<150 Km, with the majority being <1 .um). A progressing cavity (Moyno) pump caused less damage to the CST particles.Slurries of CST in water showed low abrasivity to 304L stainless steel and moderate abrasivity to A106 mild steel. A slurry of CST in median supemate (2.9 MNaOH plus other salts) showed low abrasivity to A106 steel, so the higher abrasivity result for CST in water was probably caused by oxidative corrosion. Sludge simukmt slurries showed low abrasivity, but mixtures of sludge and zeolite showed moderate abrasively.Storage of cesiurn-loaded CST in supemate simukmts has shown possible leaching of the cesium from the CST into median and high-concentration (13.5 illNaOH) supemate sirnulants at 80°C. There was no measurable leaching after 105 days in any of the simukmts at 25 'C, or in lowconcentration simulant (0.01 MNaOEl) at 80"C.Mixtures of CST in SRS sludge simulants have shown minimal tendency to cause caking or hard layers. Supernate sinmkmts that cover the range of solutions in the SRS high-level waste storage tanks have shown minimal effect on the particle size of the CST sorbent.

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