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EXPANDED BED BIOLOGICAL TREATMENT
Citation:
Oppelt, E., J. Smith, AND W. Feige. EXPANDED BED BIOLOGICAL TREATMENT. U.S. Environmental Protection Agency, Washington, D.C., EPA/600/2-78/117 (NTIS PB285682), 1978.
Description:
A three-year pilot-scale research investigation at the EPA Lebanon Pilot Plant was conducted to evaluate the feasibility of a unique biological secondary treatment process, designated the Expanded Bed Biological Treatment Process (EBBT). The EBBT process is a three-phase (oxygen/wastewater/sand media) fluidized bed contacting system in which settled wastewater is passed upwards through a series of two to eight columnar reactors partially filled with fine sand particles. The velocity of the wastewater flow is sufficient to keep the sand particles in suspension. The result is a fluidized bed of sand which provides a large surface area upon which bacteria can grow. These bacteria remove contaminants from the wastewater as it passes by. An aerobic environment is provided by concurrently feeding high-purity oxygen gas into the base of each reactor or preferably by diffusing it into the wastewater before it enters each reactor. The performance of this three-phase fluidized bed biological contacting system for secondary treatment of settled wastewater was investigated in a 37.9 l/min. pilot plant. The process achieved an average TCOD removal efficiency of 75 percent and an effluent TCOD of 48.8 mg/l (13 mg/l TBOD5) at an empty bed retention time of 44 minutes and a TCOD loading rate of 6.4 kg/cu m/day. Secondary effluent guideline quality was possible at a retention time as short as 25 minutes. System MLVSS concentrations ranged from 14,000 to 16,000 mg/l, with net waste solids production ranging from 0.26 to 0.57 kg VSS/kg TCOD removed at solids retention times of 8.7 days and 5.2 days respectfully. System performance was found to be directly proportional to the ability to control excess biological growth on the sand and prevent sand particles from washing out of the system.