Development of the integrated fuzzy analytical hierarchy process with multidimensional scaling in selection of natural wastewater treatment alternatives Xiaoguag Ouyang a, b, *, Fen Guo c , Dan Shan d , Huanyun Yu e , Jian Wang f a Australian Rivers Institute and School of Environment, Griffith University Gold Coast Campus, Southport, Qld 4222, Australia b Beijing Zhongqi Anxin Environmental Science & Technology Co., Ltd., Beijing 100053, China c State Key Laboratory of Environmental Criteria and Risk Assessment, Chinese Research Academy of Environmental Sciences, 8 Dayangfang, Beiyuan, Anwai, Beijing 100012, PR China d Development Centre of Ministry of Environmental Protection, Beijing 100001, PR China e State Key Laboratory of Organic Geochemistry, Guangdong Institute of Eco-Environmental and Soil Sciences, Chinese Academy of Science, P.O. Box 1131, Wushan, Guangzhou 510640, PR China f Department of Environment and Energy Engineering, Anhui Jianzhu University, Hefei, Anhui 230001, PR China A R T I C L E I N F O Article history: Received 17 August 2014 Received in revised form 18 October 2014 Accepted 9 November 2014 Available online xxx Keywords: Analytical hierarchy process Fuzzy matter-element Multidimensional scaling Wastewater treatment alternative Sensitivity analysis A B S T R A C T Multi-criteria decision-making in selection of wastewater treatment alternatives has been explored widely, while few past studies comprehensively addressed the integration of various aspects (e.g., environmental, economical, ecological and management, and technical factors), which is a priority for decision-makers. This paper develops the integrated fuzzy analytical hierarchy process (AHP) with multidimensional scaling (MDS) approach to improve current methods for determining the optimal alternative. The integrated method incorporates the weights computed by AHP into the fuzzy matter- element, and allows evaluators to understand the relative importance of each index or criterion at a high level. This is followed by the MDS method to determine the optimal alternative directly through the coordinates associated with each alternative in a two-dimensional configuration. The method was evaluated via specific programming language software packages, and was applied to select natural wastewater treatment alternatives in a case study. Results indicate the stabilization pond was the optimal alternative among five natural wastewater treatment systems. Sensitivity analysis was conducted and reflects the importance of weighing on alternative selection. ã 2014 Elsevier B.V. All rights reserved. 1. Introduction The high costs of the most conventional wastewater treatment processes have generated economic stress on societies even in the developed world. Creative, cost effective and environmental friendly ways are therefore required to explore approaches to manipulating water pollution (Tsaur et al., 2002). Stabilization pond, constructed wetland and other ecological land treatment systems are the centralized sewage treatment options, and ecological engineering that are employed to reduce water pollution and developed as sustainable ecosystems that have both human and ecological values (Mitsch, 2012). They have been used in both developed and developing countries, due to the general good performance in maintenance, minimal fossil fuel consump- tion (Crites et al., 2014; Kivaisi, 2001) as useful options for climate change adaptation. These natural wastewater treatment processes have been continuously recognized as significant alternatives for mechanical treatment systems and attracted considerable atten- tion from ecological and engineering communities. For example, the rank of key words “constructed wetlands” has ascended from 59th in 1991 to 4th in 2008 in wetland research (Zhang et al., 2010) and pollution control is the most ubiquitous topic in the research of this field (Mander and Mitsch, 2009). In order to determine the best wastewater treatment alter- natives, three main analyses should be conducted (Tsagarakis et al., 2001). First, the required effluent quality should be taken into account. Second, numerous factors that would limit the manage- ment and applicability of some processes should be considered such as economic, climatic, environmental, land availability, operational simplicity (Marcos et al., 2005). Last but not least, a cost effectiveness analysis should be carried out, as one of the selection criteria, to determine the optimal economically feasible solution. * Corresponding author. Tel.: +61 7 55528983. E-mail address: xiaoguang.ouyang@griffithuni.edu.au (X. Ouyang). http://dx.doi.org/10.1016/j.ecoleng.2014.11.006 0925-8574/ ã 2014 Elsevier B.V. All rights reserved. Ecological Engineering 74 (2015) 438–447 Contents lists available at ScienceDirect Ecological Engineering journal homepage: www.elsevier.com/locate/ecoleng