A Pilot Scale-Study at the Nine Springs Wastewater Treatment Plant: Seasonal Cod and F/M Ratio Trends and Their Application To Modeling Treatment Processes

Wastewater treatment is a complex process that involves the simultaneous application of diverse sciences such as chemistry, biology, and engineering. Chemistry allows to describe the composition of wastewater through the Total Chemical Oxygen Demand (TCOD), which is an essential parameter in wastewater treatment. TCOD influences sludge production, oxygen demand, anoxic denitrification, phosphorus removal, and effluent quality. Typically, the TCOD concentration in domestic wastewater fluctuates within the range of 250 to 800 mgCOD/L. TCOD value is dependent of the day and the time when the measurement is done, as well as on the influent wastewater flowrate, which changes the Hydraulic Retention Time (HRT). Greater flowrates decrease HRT, increasing the dilution of the wastewater. Decreasing HRT consequently increases the oxygen required to treat the wastewater due to more remaining COD and ammonia loads in the process. As a result of that, COD has become an interesting parameter to study in wastewater treatment. The characterization of COD into different components has become an essential set of data to model different treatment systems. Activated sludge modeling has grown to be an important part of the wastewater treatment industry. Software developers have built powerful tools to predict and understand current and future plant facilities. Two Biowin 6.0 models were built in this study, using the Influent Specifier tool and the Biowin Controller tool, seeking to increase the models’ accuracy in predictions related to treatment plant configurations. In this project, 11 variables were analyzed with Biowin models. The successful calibration of 7 out of 11 of the analyzed variables was possible. More work on the calibration should be done to identify possible sources of error and identify the most sensitive parameters that influence the calibration of these models. The results allowed the identification of HRT as a parameter that influences oxygen demand and the Solids Retention Time (SRT) as a parameter that influences nutrient removal and microbial concentration