Process Optimization of a Petroleum Refinery Wastewater Treatment Facility Using Process Modeling and Site Specific Biokinetic Constants

In this project, an old, out-of-service secondary clarifier was converted to a Complete Mix Batch Reactor (CMBR) and was designed to provide maximum deployment flexibility so that it could be operated in a number of modes. Simulation analysis with the MantisIW model in GPS-X™ was used to determine the optimal number of batch runs to treat a high strength COD and inhibitory waste stream to meet predefined effluent criteria for discharge to the Activated Sludge Unit (ASU). The CMBR was also deployed in another instance as an isolated sidestream chemostat reactor to treat a large quantity of floating free oil that was released to the wastewater treatment plant. Simulation analysis of the chemostat reactor was used to determine the optimal incubation period for the microbes to consume the free oil under aerobic conditions. A total of four CMBR batches were required to consume the high levels of free oil. After 24 hours immediately following the first CMBR effluent blend with the oxidation ditch influent, the clarifier effluent oil and grease levels were consistently below 15 mg/L. After an MCRT process control strategy had been effectively implemented at the WWTP, a full-scale Lawrence and McCarty (1970) model field biokinetic study was executed to determine the site-specific biokinetic constants of the existing wastewater treatment facility. The site-specific biokinetic constants were determined by fitting the operating data as a function of the microbial growth rate using statistical regression analysis. For the first time since it began operation, the true organic loading capacity of the existing facility was conclusively quantified. The calibrated GPS-X™ model utilizing the site-specific biokinetic constants is a fully predictive model that can be used to analyze and optimize the wastewater treatment facility operations and accurately predict the plant performance under hypothetical operating conditions.