Keywords
integrated modelling, urban wastewater system, operational strategies, optimisation, monte carlo simulation, global sensitivity analysis
Start Date
1-7-2012 12:00 AM
Abstract
In some regions, like in the Mediterranean area, streams are characterized by harsh hydrological fluctuations, with very low flow rates in summer and high in autumn. During low river flow conditions, wastewater treatment plant (WWTP) discharges contribute significantly to the total river flow and hence their impact is higher. The objective of this paper is to find solutions to confront this typical problematic situation by means of integrated modelling. The benefits of modelling the whole urban wastewater system (UWS) to evaluate multiple operational strategies are shown. The model includes two sewer systems, two WWTPs, a connection channel between the two WWTPs, storage tanks and a river stretch. The methodology is based on Monte Carlo simulations, used to conduct a Sensitivity Analysis to identify the most important operational settings and to perform a screening of the best combinations of settings with respect to immission-based criteria. The results show that properly using the storage tanks before the two WWTPs and the connection between them, as well as setting adequate aeration and recycle flow rates, allow to reduce the ammonia peak concentrations in the river by almost 30% and to increase the DO concentration in the river by about 10%, with a negligible increase in the operational costs.
Use of integrated models to minimize the impact of urban wastewater systems on a Mediterranean stream
In some regions, like in the Mediterranean area, streams are characterized by harsh hydrological fluctuations, with very low flow rates in summer and high in autumn. During low river flow conditions, wastewater treatment plant (WWTP) discharges contribute significantly to the total river flow and hence their impact is higher. The objective of this paper is to find solutions to confront this typical problematic situation by means of integrated modelling. The benefits of modelling the whole urban wastewater system (UWS) to evaluate multiple operational strategies are shown. The model includes two sewer systems, two WWTPs, a connection channel between the two WWTPs, storage tanks and a river stretch. The methodology is based on Monte Carlo simulations, used to conduct a Sensitivity Analysis to identify the most important operational settings and to perform a screening of the best combinations of settings with respect to immission-based criteria. The results show that properly using the storage tanks before the two WWTPs and the connection between them, as well as setting adequate aeration and recycle flow rates, allow to reduce the ammonia peak concentrations in the river by almost 30% and to increase the DO concentration in the river by about 10%, with a negligible increase in the operational costs.
