Ecological Engineering 44 (2012) 249–258 Contents lists available at SciVerse ScienceDirect Ecological Engineering j ourna l ho me page: www.elsevier.com/locate/ecoleng Economic and environmental analysis of using constructed riparian wetlands to support urbanized municipal wastewater treatment Chia-Ji Teng a , Shao-Yuan Leu b,∗ , Chun-Han Ko c,∗∗ , Chihhao Fan d , Yiong-Shing Sheu e , Hui-Yu Hu f a Department of Safety, Health and Environmental Engineering, Tungnan University, New Taipei City 22202, Taiwan b Department of Civil and Environmental Engineering, University of California, Los Angeles, CA 90095, USA c School of Forest and Resources Conservation, National Taiwan University, Taipei 10617, Taiwan d Department of Safety, Health and Environmental Engineering, Mingchi University of Technology, New Taipei City 24301, Taiwan e Department of Water Quality Protection, Environmental Protection Administration, Executive Yuan, Taipei 10042, Taiwan f MWH Americas Inc. Taiwan Branch Office, Taipei 10695, Taiwan a r t i c l e i n f o Article history: Received 16 November 2011 Received in revised form 7 March 2012 Accepted 26 March 2012 Available online 2 May 2012 Keywords: Wetland Wastewater Economic Reaction kinetics Modeling a b s t r a c t This paper evaluated the economic and environmental benefits of using riparian constructed wetlands (CWs) for municipal wastewater treatment in an urban watershed. The monitoring data were collected from seven CWs in Tan-Shui River basin of the metropolitan Taipei, and were compared with a centralized wastewater treatment plant in the same watershed. Operation parameters such as site conditions, effluent quality, construction and operation/maintenance (O&M) costs were analyzed and used to calculate the first order reaction kinetics (k v20 ) of three pollutants, i.e. TSS, BOD, and NH 4 –N. The reaction kinetics and costs vary significantly among the CWs and treatment plant. The overall treatment performances of BOD and NH 4 –N generally confirmed with the references, with variation only among the different sites, but the removal of TSS was less desirable for all CWs. The total costs of the CWs were between 0.425 and 3.621 USD per kg total BOD removed, and the costs of the centralized wastewater treatment plant was approximately 1.186 USD per kg total BOD removed. The wetlands provide reasonable pollutants removal and show additional benefits on education and recreation while the sanitary sewer system and new treatment plants are under construction. The experiment results confirmed with the references and the methodology can be used to developing water quality management plans for urbanized watersheds in subtropical areas. © 2012 Elsevier B.V. All rights reserved. 1. Introduction Constructed wetlands (CWs) are an economic and ecological alternative for wastewater treatment. This on-site wastewater treatment process has been used to treat different types of wastewaters, i.e. domestic wastewaters (Brix et al., 2007; Öövel et al., 2007), animals or agriculture wastewaters (Cronk, 1996; Harrington and McInnes, 2009), urban runoffs (Scholz, 2006; Kao et al., 2001), and industrial wastewaters (Chen et al., 2006; Di Luca et al., 2011), and can effectively remove many contaminants, i.e. nutrients (Kadlec and Knight, 1996; Lin et al., 2009; Kadlec, 2009), organic chemicals (Larue et al., 2010), and metals (Scholz, 2006; Maine et al., 2007). In addition, some CWs are habitats of many ∗ Corresponding author. Tel.: +1 310 526 1534; fax: +1 310 206 2222. ∗∗ Corresponding author. Tel.: +886 2 3366 4615; fax: +886 2 2365 4520. E-mail addresses: syleu@ucla.edu (S.-Y. Leu), chunhank@ntu.edu.tw (C.-H. Ko). wild lives and can provide additional benefits on research, restora- tion, and recreation (Knight, 1992; Zedler and Leach, 1998). U.S. EPA (2000) suggests that CWs are more suitable than activated sludge processes (ASPs) for wastewater treatment in small communities with wastewater flow less than 3800 m 3 /day and when the land is available. The key challenges of the CWs are the treatment efficiencies and operation stability. The treatment performances of the CWs are affected by many factors, i.e. hydraulic loading rates (HRL) and ambient temperature (Kadlec and Knight, 1996), vegetation species and properties (Vymazal, 2011), and weather or damages caused by nature disasters (Fan et al., 2009; Ko et al., 2010). It is essential to obtain complete understandings of the benefits and limitations of the CWs before incorporating these processes in a municipal wastewater treatment system. The goals of this paper were to develop a methodology to quantify the economic and environmental benefits of the CWs for municipal wastewater treatment. The experimental results were 0925-8574/$ – see front matter © 2012 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.ecoleng.2012.03.009