Modeling of an IFAS Process with Fungal Biomass Treating Pharmaceutical Wastewater
The project involved the dynamic modeling of a wastewater treatment plant (WWTP) treating pharmaceutical wastewater. The WWTP uses an integrated fixed-film activated sludge (IFAS) process with suspended carriers for biological treatment. The plant is unique in that it uses both fungal and bacterial IFAS reactors. The fungal biomass has been shown in laboratory testing to degrade a portion of the waste not degraded by bacterial biomass alone. The GPS-X simulator was used to model the plant. The mantis model, which is a modified version of ASM1, was used for the biological processes. Modifications were made to mantis to model the adsorption of inert soluble COD onto particulate matter and the uptake of phosphorus for biomass growth. The GPS-X model was calibrated to the first 90 days of data from 2004 and verified using data from the remainder of 2004. Calibration involved characterizing the influent waste streams, specifying operational variables, and adjusting certain key model parameters to minimize the error between the measured and predicted data. Minimal adjustments to the model parameters were required to calibrate the model. The model was found to be applicable to simulation of plant performance over the entire year. This suggests that the International Water Association (IWA) activated sludge models (ASM) with some modifications are applicable to the modeling of fungal biomass. For demonstration purposes, a number of simulations were conducted to study the sensitivity of the plant performance. It was found that taking a train out of service increased the effluent soluble COD while lowering the temperature or using less air had little impact on the effluent soluble COD.