In recent years, the amount of waste water treated by processes of secondary or tertiary treatment increased, while the amount with primary treatment decreased. The amount of wastewater that was treated with secondary treatment processes, has, since 2003, increased by 211% or 38 million m3(in 2003) to 81 million m3(in 2012). Tertiary wastewater treatment was almost nonexistent in Slovenia in 2003, while in 2012 37% of all treated wastewater, or 48 million m3 wastewater was treated by tertiary processes.