Application of divided convective-dispersive transport model to simulate variability of conservative transport processes
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RESEARCH ARTICLE
Application of divided convective-dispersive transport model to simulate variability of conservative transport processes inside a planted horizontal subsurface flow constructed wetland Ernő Dittrich 1
&
Mihály Klincsik 2 & Dávid Somfai 1 & Anita Dolgos-Kovács 1 & Tibor Kiss 1 & Anett Szekeres 3
Received: 3 April 2020 / Accepted: 21 September 2020 # The Author(s) 2020
Abstract This paper offers a novel application of our model worked out in Maple environment to help understand the very complex transport processes in horizontal subsurface flow constructed wetland with coarse gravel (HSFCW-C). We made tracer measurements: Inside a constructed wetland, we had 9 sample points, and samples were taken from each point at two depths. Our model is a divided convective-dispersive transport (D-CDT) model which makes a fitted response curve from the sum of two separate CDT curves showing the contributions of the main and side streams. Analytical solutions of CDT curves are inverse Gaussian distribution functions. This model was fitted onto inner points of the measurements to demonstrate that the model gives better fitting to the inner points than the commonly used convective-dispersive transport model. The importance of this new application of the model is that it can resemble transport processes in these constructed wetlands more precisely than the regularly used convective-dispersive transport (CDT) model. The model allows for calculations of velocity and dispersion coefficients. The results showed that this model gave differences of 4–99% (of velocity) and 2–474% (of dispersion coefficient) compared with the CDT model and values were closer to actual hydraulic behavior. The results also demonstrated the main flow path in the system. Keywords Divided convective-dispersive transport (D-CDT) model . Fréchet distribution . Inverse Gaussian distribution . Subsurface flow constructed wetlands . Transport processes . Tracer test . Hydraulic variability inside the constructed wetland
Nomenclature CW FSCW SFCW
VSFCW Constructed wetland Free-surface flow constructed wetland Subsurface flow constructed wetland
Responsible editor: Marcus Schulz * Ernő Dittrich [email protected] 1
Faculty of Engineering and Informatics, Department of Environmental Engineering, University of Pécs, Boszorkány u. 2, Pécs H-7624, Hungary
2
Faculty of Engineering and Informatics, Department of Mathematical Sciences, University of Pécs, Boszorkány u. 2, Pécs H-7624, Hungary
3
Hidro-consulting Ltd., Budai Nagy Antal u. 1, Pécs H-7624, Hungary
HSFCW-C
HRT D [m2/h] Dx [m2/h] q [1/h] x [m] CDT CSTR LiCl C [mg/l] vx [m/h] L [m] R [-] a, b, c
Subsurface flow constructed wetland with vertical flow direction Horizontal subsurface flow constructed wetland using coarse gravel filter media Hydraulic retention time Dispersion coefficient Longitudinal dispersion coefficient Specific loading rate Longitudinal coordinate Convection-dispersion tank Continuous stirred-tank reactor Lithium-chloride Concentration Longitudinal velocity in poro
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