Abstract
In the history of Major Accident Hazard, but not only, many accidents causing a spill of pollutant in surface water are reported. Transport phenomena of pollutants in watercourses are widely discussed in scientific literature, however the available models are not always applicable to such industrial realities, both for the boundary conditions and for the required number of data, which is not always available.
This paper describes a model for the rapid assessment of the consequences of pollutants spill in a river and can be used as a predictive tool in the Risk Assessment. The aim of this model is to provide an estimate of the consequences of the accident using minimal and easily available input data. Indeed, the user can choose to insert required data, when known, or leave their estimation to the model, based on easily found information (river dimensions, environment, riverbed materials, etc.).
This one-dimensional model is applicable to instantaneous or short-term spills of partially or completely soluble substances in water, as well as insoluble and less dense substances, such as oils.
In the first case, the model calculates the maximum concentration reached along the axis of the watercourse considering the transverse and longitudinal diffusion, the removal of the substance by suspended solids and the volatility of the substance. In the second case, it estimates the evolution of the substance pool, evaluating the distance it can reach and considering its evaporation.
The calculation method is based on the theories of models proposed by official publications (ISPRA, EPA, etc.), providing a solution that gives satisfactory result when compared to other models, and is included in S.T.A.R. (Safety Techniques for Assessment of Risk). S.T.A.R. is a software provided by ARTES S.r.l. and acknowledged by OECD, used to estimate the consequences of accident scenarios, such as gas/liquid dispersion, fires and explosions. The model uses the database included in the software, that enlists more than 440 substances.
