A hydrodynamic water quality model for propagation of pollutants in rivers

Abstract

Numerical modelling can be a useful tool to assess a receiving water body's quality state. Indeed, the use of mathematical models in river water quality management has become a common practice to show the cause-effect relationship between emissions and water body quality and to design as well as assess the effectiveness of mitigation measures. In the present study, a hydrodynamic river water quality model is presented. The model consists of a quantity and a quality sub-model. The quantity sub-model is based on the Saint Venant equations. The solution of the Saint Venant equations is obtained by means of an explicit scheme based on space-time conservation. The method considers the unification of space and time and the enforcement of flux conservation in both space and time. On the other hand, the quality sub-model is based on the advection dispersion equation. Particularly, the principle of upstream weighting applied to finite difference methods is employed. This method enable us to reduce the numerical dispersion avoiding oscillation phenomena. The optimal weighting coefficient was calculated on the basis of the mesh Peclet number. Regarding the quality processes, the model takes into account the main physical/chemical processes; these are degradation of dissolved carbonaceous substances, ammonium oxidation, algal uptake and denitrification, dissolved oxygen balance, including depletion by degradation processes and supply by physical reaeration and photosynthetic production. To properly simulate the river water quality, four state variables were considered: DO, BOD, NH4, and NO. The model was applied to the Savena River (Italy), which is the focus of a European-financed project for which quantity and quality data were gathered. A sensitivity analysis of the model output compared to the model input or parameters was carried out.

Modelagem hidrodinâmica e de qualidade da água como ferramenta para avaliação de enquadramento de corpos d'água

“…Os resultados de OD também exibiram diferença significativa entre as concentrações simuladas e observadas, comportamento que pode ser atribuído a sua complexidade de modelagem (Mannina & Viviani, 2010). Além de estar diretamente relacionado com as reações bioquímicas que o HEC-RAS simula, é possível que o sistema seja mais sensível a alguma dessas variáveis, de forma que os dados disponíveis e o método aplicado limitem os resultados gerados (Brunner, 2016).…”

Curvas de permanência de qualidade da água como subsídio para o enquadramento de corpos d'água a partir de modelagem matemática em regime não permanente

“…Esta foi a abordagem adotada neste trabalho, assim como em outros estudos semelhantes (MANNINA; VIVIANI, 2010;ROCHA;PITOMBEIRA, 2013). O método difusivo de Lax foi aplicado para a solução das equações de Saint-Venant, enquanto o módulo de transporte foi resolvido pelo método FTCS (ForwardTime/Centered-Space).…”

Research on the Optimal Regulation of Sudden Water Pollution

“…In recent years, the frequent occurrence of sudden water pollution events not only brings immeasurable impacts on the environment but also threatens social and economic development, causing people to worry about the water safety of the nullah water transfer project. Some scholars have conducted a series of studies on this issue [ 11 , 12 , 13 ]. Tang et al [ 14 ] studied the pollutant transport and diffusion rules under normal water transfer conditions of the middle route of the South-to-North Water Transfer Project.…”