The ability of the biological fluidized bed (BFB) process configuration to intensify biological reaction rates through accumulation of high concentrations of active biomass has brought attention to the technology for the past twenty years. Over 80 commercial, media based BFB reactors have been installed in North America and Europe. Currently there is much interest in systems in which granular activated carbon (GAC) is used as the fluidizing media for treatment of contaminated waters and wastewaters. This paper provides a historical review of the development of the technology together with information on design and commercial application of the technology in North America.

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The membrane biological reactor (MBR) system consists of a suspended-growth biological reactor combined with a membrane ultrafiltration unit process. It is particularly attractive in situations where long solids retention times are required, and physical retention and subsequent hydrolysis are critical to achieving biological degradation of pollutants. In order to develop full scale process design information, a large pilot system was operated for eleven months. The pilot project involved assessing performance and developing design information for the system in the treatment of wastewater from two General Motors (GM) facilities. The pilot system results provided a basis for design of a full scale, demonstration MBR system for treatment of industrial wastewater. Case history information is presented in this paper on the design of the MBR system and subsequent operation and performance. Despite certain design issues, the system has met or exceeded performance expectations.zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA Water Environ. Res., 66, 133 (1994).

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The operation of a number of small and large scale biological fluidized bed pilot plants over the past ten years has resulted in the derivation of process and component information for design of commercial facilities. The General Motors (GM) Corporation represents the single, largest industrial user of the technology in the United States. Ten fluidized bed reactors are located at GM automotive manufacturing facilities. Nine of the reactors are designed to treat wastewaters originating from metalworking operations pretreated for removal of petroleum oils. The other reactor is designed for treatment of sanitary waste-water. In 1984 and 1985, GM completed extensive pilot plant studies and on the basis of the results selected the aerobic fluidized bed (AFB) process configuration for full scale implementation at various plant sites. The fluidized bed reactors located at the sites range in reactor volume from approximately 60 to 730 m3. The pilot plant results which formed the basis for process design of the full scale reactors involved operation of 77 l fluidized bed reactors. Operating information and performance results were derived from evaluation of full scale GM fluidized bed reactors located at the New Departure Hyatt (NDH) plant in Sandusky, Ohio and the Oldsmobile engine plant in Lansing, Michigan. The full scale results were compared to the pilot plant results with the objective of understanding the effects of scale-up on system operation and performance. A comparable level of reactor attached volatile solids (VS) was measured in the pilot and full scale reactors. Biomass net yield coefficients were higher in the full scale reactors, likely due to differences in the composition of the wastewater fed to the full scale versus the pilot scale units. Oxygen utilization coefficients were comparable. The full scale performance results compared favorably with results from the pilot plant studies on the basis of the relationship between effluent quality and reactor solids retention time (SRT).

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Common practice for design of biological wastewater treatment systems involves evaluation of certain fixed structure systems at several alternative conditions. This study considered optimization of both the structure and the design of the system using the structural parameter system synthesis technique. The system was composed of a trickling filter, an activated sludge aeration vessel, and a secondary clarifier. Results of optimal synthesis indicated that the activated sludge system was the most cost effective system for the specific set of process parameters employed. The same conclusion was reached by optimizing several systems with different structures.

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