Stormwater quantity and quality for sustainable management of runoff in an industrial district. Preliminary analysis and modelling of first foul flush effect

When water flows on impervious surfaces, a huge amount of various pollutants is dragged away throughout the drainage system; stormwater management is essential because it is an applied discipline whose practical applications deal with quality and quantity characteristics of water coming from rain. The main deal is to understand how to manage and treat stormwater according to the land use and the hydrologichydraulic performance of the basin. The present study reports the numerical model of the first foul flush phenomenon in an industrial district by using EPA SWMM 5.0. The paper was written considering numerical methods and inspections on the field, focusing attention on grits and sediments transported thru the outlet: they are a serious problem for the primary unit of the treatment plant and for the receiving systems in case of overflowing. This numerical approach was applied on a case study in the CIPAF Industrial District of Friulian Region (North-Eastern Italy) where mainly stainless steel and woody industries are located. The first flush phenomenon is very significant because of the presence of large and uncovered working areas: polluted scraps coming from ordinary activities settle down on the ground so they are available for washoff processes. This work looks forward to obtain basic elements to evaluate toxicity charge coming from the stormwater, in order to set a quality-quantity integrated environmental protection model.