AERATION BOD DISSOLVED OXYGEN ENVIRONMENT FOOD AND BEVERAGE REGULATIONS TSS WASTEWATER

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Abstract

Faced with increasing nutrient regulations and expanding plant production, a large food plant that cans vegetables (mostly sweet potatoes and green beans) embarked on an innovative pretreatment project. The facility’s wastewater contained high biological oxygen demand (BOD), with concentrations regularly reaching 5,000-milligrams per liter (mg/L). In the past, the facility used a facultative lagoon to provide treatment before land applying the effluent on nearby property.

However, because of increased production, the facility commonly exceeded its allowable land application rate. Plant production slowed because of high precipitation, which prevented the effluent from being dispersed throughout the irrigation fields. Furthermore, increased nutrient regulations threatened the facility’s ability to land apply because of phosphorus concentrations. 

Ultimately, plant officials opted into a pretreatment agreement with the local municipality. However, the existing process was unable to reduce influent BOD to 350-mg/L, as required by the municipality’s contract. Design engineers developed a plan to convert the lagoon into an aerobic treatment process. The project introduced new influent screening, oxygenation technologies for aeration, a dissolved air flotation system for removing solids, effluent tanks for storage, as well as a pump station and force main to the municipality. 

The project was completed in the fall of 2014; however, start-up and optimization continued for several months. pH levels in the facultative lagoon dropped significantly because anaerobic conditions, and chemicals were implemented to raise pH values within the neutral range. Once pH levels were stable, the lagoon was seeded with microbes to quickly establish aerobic treatment. Entering 2015, the facility’s monthly surcharges decreased from approximately $450,000 to $19,000, resulting in an estimated annual savings of approximately $5 million. This article will review a treatment technology that helped in creating the aerobic conditions.

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