Following the adoption of the new regulations for wastewater treatment in rural areas, the Danish Ministry of Environment has developed official guidelines for various treatment options for systems up to 30 person equivalents (PE). Soakaways are the preferred solution because of simplicity and because of the low costs, but at many locations soil infiltration is not possible due to clayish soil conditions, high ground water tables or because of proximity to drinking water wells. At such sites, other treatment options must be used. These include on-site systems, such as biological sand filters, different types of constructed wetlands, willow systems, collecting tanks, technical systems (mini treatment systems) as well as the connection to a centralised large-scale sewage treatment system.