Wetland model is the most popular method from the ′80s to calculate the wetland area designing of subsurface flow constructed wetlands. This is a statistical first-order plug flow model that is used widely in environmental and chemical engineering sciences. In case of Hungarian application of this model is necessary to know the K (m/d) values (area removal rate constant). However, this value depends on many factors especially local weather conditions and wastewater quality can varies within a wide range. The operational characteristics of the subsurface flow constructed wetlands depend very much on this parameter. Because of that it is very important to calculate this designing parameter for Hungarian circumstances. In spite of this model is used in many countries in the world this parameter values have not been calculated to Hungarian experiences before.There are 8 subsurface flow wetlands in Hungary that have enough detailed data to analysis. From these constructed wetlands the K-values were calculated for biochemical oxygen demand, chemical oxygen demand, total suspended solids, ammonium-nitrogen, total phosphorus. The Hungarian values are compared with the international ones, and the uncertainties of the results are analyzed too.
In this article new result of international researches focused on the hydraulic behavior of the subsurface-flow constructed wetlands (SF-CW-s) for wastewater treatment are shown. The results presented below are focused on the tracer experiments to simulate transport processes, the effect of Total Suspended Solids (TSS) and organic substances loads, and the effect of macrophytes, meteorological conditions. The Hungarian experiences of constructed wetlands are compared to that of international ones and the main differences are discussed. The main considerations of comparison are: specific load of organic substances, specific load of TSS, specific hydraulic load, the type of soil, the pre-treatment systems, etc. The conclusion of this comparison is the main directions of development of the subsurface-flow constructed wetlands in Hungary.