The Use of Rainwater as Process Water in a Factory : Software Aided Evaluation Methodology and Case Studies

Factories often have large roof and/or paved surface areas which drain off large amounts of rainwater without collecting, storing and using it as process water. Storing such rainwater in tanks for later use as process water however can save money and/or comply with environmental legislation on saving water. Simulation software can be used for an efficient and reliable comparison between several rainwater storage and usage scenarios. Moreover, buffering tanks with a delayed discharge facility which level out disposal peaks of excess rainwater from heavy rainfall can also be introduced. As a result, the simulation software RAINBOW was developed at VITO in order to model rainwater networks at factories. The program runs under Matlab-Simulink and allows to simulate different rainwater network configurations and to determine optimal volumes of rainwater storage tanks. For delayed rainwater discharge during heavy rainfall peaks, the software also allows to design adequate buffering tanks with a controlled discharge flow. A broadly applied strategy of delayed rainwater discharge in sewer systems during heavy rainfall can prevent flooding in residential areas. The software approach is illustrated in two case-studies.