ECOLOGICAL CHEMISTRY AND ENGINEERING S Vol. 16, No. S2 2009 Anna MUSZ 1* , Beata KOWALSKA 1 and Marcin K. WIDOMSKI 1 SOME ISSUES CONCERNING THE PROBLEMS OF WATER QUALITY MODELING IN DISTRIBUTION SYSTEMS WYBRANE PROBLEMY MODELOWANIA JAKOŚCI WODY W SIECIACH WODOCIĄGOWYCH Abstract: Some issues concerning the most popular practical problems encountered during modeling the water quality in water distribution systems were presented. The mathematical basis of water quality modeling, commonly understood as chlorine distribution modeling, covering the governing equations, initial and boundary conditions description as well as required and necessary simplifications, were discussed. Then, the most popular computer models of water quality in distribution systems used in environmental engineering practice, such as: input-output (I/O) model, inverse chlorine decay model and forward simulation, were introduced. The modeling assumptions, model structure and limitations, advantages and disadvantages of given models were also discussed. Keywords: water quality modeling, water distribution system, chlorine decay Introduction (Mathematical preliminaries) Water quality modeling in distributions systems concerns the prediction of water pollution with the use of mathematical simulation techniques. The formation of a water quality numerical model requires gathering of formulas and parameters determining the position and momentum of pollutants in the water body (ie of water supply systems) [1, 2]. But in practice, modeling of water quality encounters many practical problems caused by the complexity of the phenomenon, mutual interaction of considered effects and complication of their mathematical description. Thus, modeling of water quality may be considered a difficult task. The governing equations for the single-phase heterogeneous mixture covers widely presented laws of mass conservation, momentum conservation and conservation of energy. The movement equations (mass and momentum conservation) after assumption of fluid density, diffusion and viscosity coefficients constancy take the form of well known Navier-Stokes equations [3]. 1 Faculty of Environmental Engineering, Lublin University of Technology, ul. Nadbystrzycka 40B, 20-618 Lublin, tel. 081 538 43 22 * Corresponding author: email: A.Musz@wis.pol.lublin.pl