Proposal of a standard experimental model to determine the contaminant removal rate constants in subsurface flow constructed wetlands
The objective of this study was to establish a standard experimental model to determine the removal rate constants of wastewater pollutants in subsurface flow–constructed wetlands. Such the rate constants of removal processes of removal processes of COD, BOD, NH4+, total nitrogen (TN), etc., are important parameters for calculating the size of wetlands, yet the data published in the international textbooks and research articles fluctuate in very wide ranges, that make it challenging to design constructed wetland accurately. By evaluating influencing factors and referencing available models, we proposed the experimental wetland model of cylindrical shape (Ø18cm and 30cm height), with the type of material and plant, which must be specified for each experiment determining the rate constants. The experimental procedure has been given, including setting up the system, running experiments to collect data, and processing data to calculate the rate constant. The initial experiments with small gravel and common reed plant, determining the removal rate constants of COD, NH4+ and TN, provided good repeatability results, and the values are within a reasonable range with the published values in the world. This result shows the applicability of the proposed experimental model and procedure to determine the contaminant removal rate constants in constructed wetlands uniformly. Eventually, a complete set of more converging rate constants data can be obtained, which improves the accuracy of the constructed wetlands setup.