Abstract
In urban centres, the degree of pollution from combined sewer overflows and stormwater runoff is becoming ever more noticeable and critical. Among the many stormwater management alternatives for combined sewer overflow abatement, remote monitoring/real-time control is emerging as a cost-effective method in large urban centres. Its advantage is that it does not require additional facilities, but uses the existing system more effectively.
A general computer model is needed in the planning stage, which can estimate the overall performance of real-time control and other stormwater management alternatives, without employing expensive, single-event models like WREM. The well-established and most widely used initial planning model STORM is unable to provide an overall system description. Therefore, a new programme, named RAFFI, was devised which can be combined with STORM. The RAFFI is a simple model which provides hourly information on flows and pollutants (BOD and SS) diverted into receiving waters from various overflow points and treatment and by-pass operations at the plant.
The model can simulate the overall behaviour of existing and proposed systems in multi-basin urban areas for single storms, or for many storms over a long period, such as one year. In-system storage can be simulated by assuming that the interceptor acts as a common reservoir which can store flows from all watersheds, while each trunk can store flows only from the watershed that it serves. Dynamic regulators can be simulated according to a built-in control strategy, which changes the flow capacity of diversion pipes and outfalls, based on plant, trunk and interceptor flow and storage values at each hour. Capacities for primary, secondary or by-pass operations at the plant can be varied during storms. Treatment of overflows at each outfall can also be simulated. The model is equally applicable to separate storm sewer systems.
The objective was not to produce yet another new model, but to integrate programme RAFFI with STORM, in order to increase its capabilities in the initial planning stage. By using STORM-RAFFI, a decision-maker can estimate the overall performance of an existing system during wet
Predictive Real-Time Control Optimization of a Stormwater Management System*