Subsurface Flow Constructed Wetlands Performance Evaluation Using Area-Based First-Order Kinetics

This paper discusses the effectiveness of commonly used area-based first-order reduction models in predicting the performance of constructed wetland (CW) system. A subsurface flow CW systems in a small community near Lincoln, Nebraska, has been studied as a natural treatment system to evaluate several design approaches used in sizing and predicting the performance of CW systems. Extensive monitoring has been conducted biweekly since June 1996. The water quality parameters included in this evaluation are soluble CBOD5, NH3-N and total P. Generally, the first-order kinetics can be used to predict the level of CW treatment with respect to carbonaceous and nitrogenous materials in wastewater. But, there is a lack of a good agreement between the removal of phosphorous in CW with the predictions of the first-order kinetics. The comparison of the effluent concentrations with the performance predictions from the models revealed that the equations tended to overestimate the performance of CW systems. Thus, the reduction rates derived from the wetlands are generally lower than the reduction rates recommended by the prediction models.