Efficiency evaluation and dynamic modeling of intermittently aerated horizontal subsurface-flow constructed wetlands

Abstract

Introduction: Constructed wetland (CW) is an efficient system for the treatment of domestic wastewater. The use of intermittent aeration in CW allows nitrification and denitrification to occur simultaneously, increasing the efficiency of total nitrogen removal. Since this is a dynamic system, the characteristics of the treated effluent vary greatly. Dynamic models would allow the evaluation of the behavior of CW over time. Objective: Develop and evaluate the efficiency of artificially aerated CWs, evaluate the performance of hydraulic models and develop a model using the System Dynamics methodology to evaluate and simulate the behavior of constructed wetland components and their specific interrelationships over time. Material and methods: Five horizontal subsurface-flow CWs with different aeration intervals (0, 3, 6, 12 and 24 h d-1) will be evaluated. The behavior of the CWs will also be evaluated using different oxygen application rates (0, 3, 6, 12 and 20 L min-1). Each CW will receive a daily flow of 10 L of synthetic domestic wastewater, resulting in a hydraulic retention time of 4.5 days. The following parameters will be evaluated in each CW: biochemical oxygen demand, chemical oxygen demand, suspended solids, turbidity, dissolved oxygen, redox potential, pH, total nitrogen, nitrate, nitrite, total phosphorus, potassium, electrical conductivity, temperature and flow. The chemical oxygen demand and total nitrogen data determined throughout the five CWs will be compared in terms of the coefficient of determination (R2) with estimated values provided by hydraulic models. Additionally, will be developed a dynamic model in the SIMILE software which will allow to simulate the behavior of aerated CWs over time.