PROCEEDINGS of the FOURTH INTERNATIONAL CONFERENCE ON “SMALL AND DECENTRALIZED WATER AND WASTEWATER TREATMENT PLANTS” Organized by: Department of Planning and Regional Development, University of Thessaly Department of Chemistry, Aristotle University of Thessaloniki Food Technology Department, TEI of Thessaloniki Hellenic Union of Municipal Enterprises for Water Supply and Sewerage EDITORS: A. ZOUBOULIS A. KUNGOLOS P. SAMARAS Volos, October 25-27, 2013