A STELLA model for estimating phosphorus removal from wastewater in a vertical-flow constructed wetland system

Author(s): Ouyang, Y.

Elevated phosphorus (P) in surface waters can cause eutrophication of aquatic ecosystems and can impair water for drinking, industry, agriculture, and recreation. Vertical flow constructed wetland (VFCW) can purify P contaminated wastewaters before they discharge into streams and rivers. The goal of this study is to develop a model for predicting the fate, transport, and removal of P from wastewaters in a VFCW using the commercial available STELLA (Structural Thinking, Experiential Learning Laboratory with Animation) software. The VFCW used in this study consists of soil and plant species with variably saturation conditions such as wetting (ponding) and drying (draining) cycles. The water movement through the soil, xylem, and surrounding atmosphere in the VFCW system is calculated using water potential theory, whereas the fate and transport mechanisms of P used in this model include: (1) application of wastewater (containing P) to the VFCW; (2) adsorption of P in the soil; (3) uptake of P by plant roots, (4) mineralization of organic P; and (5) leaching of soluble P. Additionally, the surficial processes such as rainfall and evapotranspiration are included in the model. The resulted model is calibrated and validated with experimental data prior to its applications. A simulation scenario is then performed to estimate P removal from a domestic wastewater in the VFCW system under varying hydraulic retention times. Simulation results will be presented and discussed.

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