ARTICLE Statistical Modeling of Batch Versus Continuous Feeding Strategies for Pollutant Removal by Tropical Subsurface Flow Constructed Wetlands Wang Dong Ni & Dong Qing Zhang & Richard M. Gersberg & Jianhao Hong & K. B. S. N. Jinadasa & Wun Jern Ng & Soon Keat Tan Received: 27 May 2012 / Accepted: 29 January 2013 / Published online: 16 February 2013 # Society of Wetland Scientists 2013 Abstract In this study, six mesocosms, including three subsurface flow constructed wetlands (SSF CWs) and three sand filters (without plants) were set up at the campus of Nanyang Technological University, Singapore. The objec- tive of this study was to compare the removal efficiencies of chemical oxygen demand (COD), nitrogen (N) and total phosphorus (TP) under batch and continuous operational modes. Three factors, namely, with/without the presence of vegetation, operational modes (batch and continuous) and hydraulic residence time were investigated by two statistical models including factorial design and its rationale analysis and a quadratic polynomial regression model with ANOVA, to find the relationships between the contaminant removal efficiencies and the affecting factors, as well as to determine the dominant variables and how each of them interact for each parameter. Keywords Batch (drain and fill) . Continuous flow . COD . Nitrogen . Phosphorus . Statistical model . Subsurface flow constructed wetland Introduction Constructed wetlands (CWs) have been demonstrated to be a cost-effective and environmentally friendly technology for the efficient removal of contaminant from wastewater efflu- ents at relatively high application rate (Gersberg et al. 1983; Greenway and Woolley 1999; Kayranli et al. 2010). Wetlands remove aquatic pollutants through a complex va- riety of biological, physical and chemical processes (Gersberg et al. 1986). However, the availability of oxygen for the oxidation of carbon and nitrogen is a limiting factor in the effectiveness of subsurface flow constructed wetlands (SSF CWs) for wastewater treatment (Reed and Brown 1992). Batch-fed CWs with alternate draining and flooding has been shown to result in entrainment of air within micro- pores of the soil/gravel matrix, which leads to the augmen- tation of both carbon and nitrogen oxidation (Burgoon 1989; Brix and Schierup 1990). Indeed, several studies have demonstrated that operating of a SSF CW in batch mode may enhance both nitrogen and phosphorus removal W. D. Ni : D. Q. Zhang (*) : J. Hong DHI-NTU Centre, Nanyang Environment & Water Research Institute, Nanyang Technological University, N1.2-B1-02, 50 Nanyang Avenue, Singapore 639798, Singapore e-mail: dqzhang@ntu.edu.sg W. D. Ni e-mail: WDNI@ntu.edu.sg R. M. Gersberg Graduate School of Public Health, San Diego State University, Hardy Tower 119, 5500 Campanile, San Diego, CA 92182-4162, USA J. Hong Taiwan Typhoon and Flood Research Institute, Taichung 40763, Taiwan e-mail: dinohong@narl.ttfri.org.tw K. B. S. N. Jinadasa Department of Civil Engineering, University of Peradeniya, Peradeniya 20400, Sri Lanka W. J. Ng Nanyang Environment and Water Research Institute, Nanyang Technological University, N1-B3b-29, 50 Nanyang Avenue, Singapore 639798, Singapore S. K. Tan Maritime Research Centre and School of Civil and Environmental Engineering, Nanyang Technological University, N1.2-B1-02, 50 Nanyang Avenue, Singapore 639798, Singapore e-mail: ctansk@ntu.edu.sg Wetlands (2013) 33:335–344 DOI 10.1007/s13157-013-0389-x