Keywords: non–conservative pollutants, first order decay, hybrid cells modelling, hybrid model development, decaying pollutants, pollutant transport, streams, water pollution, simulation, advection, dispersion
Hybrid model development for the decaying pollutant transport in streams
A Hybrid Cells in Series (HCIS) model with decay (HCIS–D) has been conceptualised to simulate advection, dispersion, decay governed pollutant transport. The cells consist of a plug flow zone followed by two unequal size thoroughly mixed zones applied to steady flow and prismatic stream reaches. Compared to the analytical solution of the advection–dispersion–decay equation, the HCIS–D simulations were in good agreement when the size of the hybrid unit, Δx, satisfies the condition, Δx u/DL ≥ 4 or [(α + T1 + T2)u/Δx] ≈ 1, where u is the mean flow velocity, DL is the longitudinal dispersion co–efficient, α, T1 and T2 are residence times of plug flow zone, first and second mixed zones of hybrid unit respectively. The potential of the HCIS–D model has been demonstrated using synthetic and field data and the results of the HCIS–D model for non–conservative/decaying pollutant transport were in the expected lines.