Mathematical modelling of nitrogen removal in horizontal subsurface flow constructed wetland

Abstract

The research work presented herein makes a contribution to HSSF CW grey-
water treatment by developing a conceptual and numerical model to simulate the spatial
and temporal variations of nitrogen concentration. This paper presents the simulation of flow and nitrogen removal processes by using the advection-dispersion-
reaction modeling approach. The flow equation is solved by using the mixed finite ele-
ment method. The system of advection-dispersion-reaction is solved by using the technique of separation of the operators. The equation of advection is approximed by the
Characteristics-Galerkin Method. The dispersion-reaction equation was carried by using
the finite element method. The softwares freefem++ and matlab were used. This phenomenon was materialized by a horizontal subsurface Flow Constructed Wetland treating
greywater in a Moroccan primary school. The decay coefficient are been identified by
solving an inverse problem using observed data. The Particle Swarm Optimization and Gravitational Search Algorithm (PSOGSA) proposed by Mirjalili et al. is used to solve the inverse problem. Numerical simulation was validated
after calibration on the basis of obtained experimental data by controlling water quality parameters over a period of 100 days. Comparative analysis shows that the total predicted effluent of  nitrogen concentration obtained by the numerical simulation agrees
fully with the one obtained by experimental data.