http://web.deu.edu.tr/atiksu/ana52/ani404.html
[Accessed: 09.03.2010]
Different material on biological wastewater treatment (biofilm processes, trickling filters, Rotating Biological Contactors, Stabilization Ponds, Lagoon Systems, Oxidation Ditch, Advanced Treatment, Intermittent Sand Filters", Chemical Treatment and Imhoff Tank) available on the Tropak Homepage hosted by the Turkish Dokuz Eylul University in Izmir.