When selecting the type of sewage treatment plant for a particular plot of land, several factors need to be taken into account. These include the size of the plot of land, groundwater level, and soil permeability. A drainage treatment plant works well when there is a relatively large area of land and groundwater conditions are favourable (low groundwater level and good soil permeability). Biological wastewater treatment plants are a more modern solution, complying with European standards (they can be used in agglomerations). However, their disadvantage is that they require a power supply. For more information on the selection of treatment plants, see the guide.