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Tom's Foods Inc. operates a corn and potato chip processing plant outside of Dallas, Texas. In order to meet pretreatment limitations, they operate an aerated stabilization basin (ASB) with preliminary treatment of food solids using vibratory screening and oil and grease (O&G) using a gravity separator. Recently, after increases in production, the ASB has had instances of elevated fixed suspended solids (FSS) and soluble biochemical oxygen demand (sBOD).With these elevated effluent conditions, the municipality is evaluating the current pretreatment limits for suspended solids.

A performance evaluation of the system was conducted to determine the root cause of the elevated discharge parameters. A microscopic examination revealed a filamentous bulking sludge, due primarily to oxygen deficiency with some nutrient deficiencies. Nitrogen, phosphorus, and chemical oxygen demand (COD) analyses as part of the evaluation confirmed the cause of the filamentous bulking sludge. Further evaluation of the COD and O&G data indicated the majority of the substrate was insoluble. Particulate COD constitutes over 60 percent of the COD loading, which averages 4,400 pounds per day. Nitrogen and phosphorus analyses revealed that the nutrient deficiencies were only transient.

An approach to upgrade the ASB was developed that considered preliminary treatment first followed by ASB upgrades. The focus was therefore on enhancing solids and O&G removal followed by adding aeration capacity and nutrient addition equipment. These upgrades were implemented in a stepwise fashion. All have been completed with the exception of the nutrients upgrades. The results have included detection of only a few filaments, elevated ASB dissolved oxygen (DO) concentrations, reduced influent particulate COD, and reduced effluent sBOD and FSS. The nutrient addition system is currently on hold pending the municipality's plan to change the pretreatment limitation for FSS. New limitations may require conversion of the ASB to an activated sludge unit.

Document Type: Research Article


Publication date: 2003-01-01

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