Acta Universitatis Sapientiae Agriculture and Environment, 1 (2009) 57-64 57 On-site wastewater treatment systems and legal regulations in the European Union and Hungary Viola SOMOGYI 1 , Viktória PITÁS 2 , Endre DOMOKOS 3 , Bence FAZEKAS 4 1 University of Pannonia, Institute of Environmental Engineering, Veszprém, Hungary, e-mail: somogyiv@uni-pannon.hu 2 UP, Institute of Environmental Engineering, Veszprém, Hungary, pitasv@almos.vein.hu 3 UP, Institute of Environmental Engineering, Veszprém, Hungary, domokose@ uni-pannon.hu 4 UP, Institute of Environmental Engineering, Veszprém, Hungary, e-mail: fazekasb@almos.uni-pannon.hu Manuscript received 28.07. 2009; revised 15.09. 2009, accepted; 20.09.2009 Abstract: The on-site wastewater treatment systems (WWTS) provide an alternative to regional wastewater treatment plants. Their application can be limited by the options for the disposal of treated water. The Hungarian settlement structure underpins the importance of on-site WWTSs. It would be essential to apply wastewater treatment methods that are economical and environmentally reliable contributing to meet the requirements raised by the EU. The aim of the research was to examine the regulations and practice of different European countries and to develop recommendations for further use of treated water originating from on-site WWTSs considering the Hungarian circumstances illustrated with an example. Key-words: decentralised systems, legislation, water reuse, sewage disposal 1. Introduction An alternative to the centralized way of wastewater treatment has begun to evolve nowadays: the application of on-site WWTSs as a decentralized way of sewage treatment. These small-scale units have high priority in low population density areas, where the discharge of sewage to a central WWTP through a drainage system is not profitable. Constructing too long drainage conduits is not rational for two reasons: high costs and stagnant wastewater. The latter can cause rotting and/or