Çeçen, F., Semerci, N., Geyik, A. G., “Inhibitory Effects and Speciation of the Heavy Metals Ni, Cu, Zn, Co in a Nitrifying Activated Sludge”, Micropol & Ecohazard 2009- 6th IWA/GRA Specialised Conference on Assessment and Control of Micropollutants/Hazardous Substances in Water, San Francisco, USA, 2009.