The use of Vertical Flow Constructed Wetlands in Wastewater Treatment Vassilios A. Tsihrintzis 1 Received: 1 March 2017 /Accepted: 11 May 2017 # Springer Science+Business Media Dordrecht 2017 Abstract Alternative to conventional (i.e., the commonly used biological plants) wastewater treatment systems are presented which are appropriate for small communities and settlements. These systems are the natural treatment systems. The emphasis here is given on vertical downflow flow constructed wetlands (VF CWs). First, advantages and disadvantages of these systems are presented compared to conventional systems. Applications in treating different types of wastewaters and various pollutants are summarized. Components, treatment processes and performance are also presented. General description of facility compartments, layout and operation is given. Design guidelines on recommended unit areas, organic loading rates and hydraulic loading rates from various EU countries for VF CW systems used in municipal wastewater treatment, and data on the efficiency of such systems are also presented. Maintenance and operation issues are discussed. Finally, investment and operation and maintenance costs are addressed based on data from full-scale facilities. Keywords Constructed wetlands . Wastewater treatment . Horizontal subsurface flow . Vertical flow systems . Design issues 1 Introduction The science and engineering of wastewater (WW) treatment has significantly progressed from the mid-years of the past century until today; proposed technologies in developed countries mostly use mechanized (herein referred to as ‘conventional’) treatment systems. The technol- ogy progress has been outstanding, and today we can treat wastewater to produce high quality effluents, even reaching drinking water standards. However, to achieve high treatment goals, Water Resour Manage DOI 10.1007/s11269-017-1710-x * Vassilios A. Tsihrintzis tsihrin@survey.ntua.gr; tsihrin@central.ntua.gr; tsihrin@otenet.gr 1 Centre for the Assessment of Natural Hazards and Proactive Planning & Laboratory of Reclamation Works and Water Resources Management, Department of Infrastructure and Rural Development, School of Rural and Surveying Engineering, National Technical University of Athens, 9 Iroon Polytechniou St., Zografou, 157 80 Athens, Greece