Development of prediction model for incoming sewage disturbance and assessment of its effects on activated sludge process

Abstract

Various external and internal disturbances were known as the most difficult factors in operating the wastewater treatment plants (WWTPs) in good condition. In Korea, lack of reliable information about the behaviors of WWTPs under various disturbances left field operators with little choice but to operate plants mainly with their own experience. This research was aimed to investigate the dynamic behaviors of an activated sludge process under various conditions. Firstly, sewage disturbance caused by flow rates and total suspended solid (TSS) concentration was studied. Effects of sewage flow, rainfall, and seasonal variations were investigated by measuring the flow rates and sewage components at every single hour. And their model equations were developed under the several assumptions including defined profiles of diurnal variances of sewage production and consideration of the infiltration without the exfiltration. Calibrated with measurement, those models could give reasonable implications for estimation of measured data with 7.8% and 22.9% error for flow rate and TSS concentration, respectively. And standard input files were made for dry and wet weather scenarios, which would be used for the simulation of the plants. Secondly, the combination of ultraviolet (UV) absorbance and neural network was suggested for an effective on-line measurement technology, which could provide reliable results for the total nitrogen (TN) and total phosphorus (TP) concentrations as well as TSS and total chemical oxygen demand concentrations. The prediction accuracies were always higher than those of a linear regression which was widely used by previous researches and the RMSE (root mean square error) of results were 12.8, 23.0, 4.1 and 0.4 for TSS, TCOD, TN and TP, respectively. From a result, more efficient operation, qualified effluent and cost reduction could be expected. However, the soluble nitrogen such as ammonia, which could not be determined using UV absorbance due to t...