Emergy evaluations for constructed wetland and conventional wastewater treatments J.B. Zhou a , M.M. Jiang a , B. Chen b , G.Q. Chen a, * a National Laboratory for Turbulence and Complex Systems, Department of Mechanics, Peking University, Beijing 100871, China b State Key Joint Laboratory of Environmental Science and Pollution Control, Faculty of Environment, Beijing Normal University, Beijing 100875, China Received 1 October 2006; received in revised form 20 June 2007; accepted 1 August 2007 Available online 14 September 2007 Abstract Based on emergy synthesis, this study presents a comparative study on constructed wetland (CW) and conventional wastewater treatments with three representative cases in Beijing. Accounting the environmental and economic inputs and treated wastewater output based on emergy, different characteristics of two kinds of wastewater treatments are revealed. The results show that CWs are environment-benign, less energy-intensive despite the relatively low ecological waste removal efficiency (EWRE), and less cost in construction, operation and maintenance compared with the conven- tional wastewater treatment plants. In addition, manifested by the emergy analysis, the cyclic activated sludge system (CASS) has the merit of higher ecological waste elimination efficiency. Ó 2007 Elsevier B.V. All rights reserved. PACS: 87.23.n; 89.60.k Keywords: Emergy; Constructed wetland; Wastewater treatment; Systems ecology 1. Introduction Constructed wetlands (CWs) are artificial wastewater treatment systems consisting of shallow ponds or channels which have been planted with aquatic plants, and which rely upon natural microbial, biological, physical and chemical processes to treat wastewater [1]. Due to its low cost and high efficiency, the ecological engineering of CW for wastewater treatment has been emerging nationwide in China including Beijing city located on the North China [2]. Using emergy, as a measure of the environmental and economic resource utilization, the wastewater recy- cling processes of the CWs have been evaluated in some researches [3–5]. Further, CW can be an advanced 1007-5704/$ - see front matter Ó 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.cnsns.2007.08.010 * Corresponding author. E-mail address: gqchen@pku.edu.cn (G.Q. Chen). Available online at www.sciencedirect.com Communications in Nonlinear Science and Numerical Simulation 14 (2009) 1781–1789 www.elsevier.com/locate/cnsns