Sustainable water management for macroscopic systems Fabricio Nápoles-Rivera a, * , Medardo Serna-González a , Mahmoud M. El-Halwagi b, c , José María Ponce-Ortega a a Chemical Engineering Department, Universidad Michoacana de San Nicolás de Hidalgo, Morelia, Mich. 58060, Mexico b Chemical Engineering Department, Texas A&M University, College Station, TX 77843, USA c Adjunct Faculty at the Chemical and Materials Engineering Department, Facultyof Engineering, King Abdulaziz University, Jeddah 21589, P. O. Box 80204, Saudi Arabia article info Article history: Received 18 September 2012 Received in revised form 22 November 2012 Accepted 24 January 2013 Available online 15 February 2013 Keywords: Water management Optimal water distribution and storage Sustainable systems Optimization Macroscopic systems abstract This paper proposes a mathematical programming model for sustainable water management in macroscopic systems. To meet the system demands for water, the model considers the possibility of using alternative water sources such as rainwater and reclaimed water to enhance the sustainability of natural water bodies. The model is a multi-period problem for which harvested rainwater can be stored and used as necessary even during months with low precipitation. The problem consists of finding an optimal schedule for the distribution and storage of natural and alternative water sources to satisfy the demands of the different users in a macroscopic system (i.e., domestic and agricultural users) while maintaining sustainable levels of water in the natural water bodies. The objective is to maximize the total profit, which is given by the revenues of water sales less the operational and capital costs for imple- menting the optimized solution. This approach is applied to a case study from Mexico for the city of Morelia. The results show that implementing strategies that include alternative water sources might reduce fresh sources consumption and waste generation and still be economically attractive. Ó 2013 Elsevier Ltd. All rights reserved. 1. Introduction Water scarcity is one of the main concerns in most countries of the world. According to projection studies, by 2025 1.8 billion people will live in countries or regions with absolute water scarcity, and two-thirds of the world population could be under conditions of water stress (UN-Water, 2007). Therefore, it is necessary to launch initiatives aimed at alleviating this situation. Different optimization approaches have been proposed to deal with the management of industrial and macroscopic water systems. Recent reviews can be found in literature (e.g., Foo, 2009; Foo et al., 2011; El-Halwagi, 2012). The following discussion highlights sample contributions in the field. Material flow analysis (MFA) has been used in conjunction with systems integration models to account for physical, chemical, and biological activities taking place within watersheds (e.g., El-Baz et al., 2005a,b; Lovelady et al., 2009; Lira- Barragán et al., 2011a,b; 2013; Burgara-Montero et al., 2012). Dvarioniene and Stasiskiene (2007) presented a model for water integration in industrial processes using a water pinch-based method. Dakwala et al. (2009) applied a water pinch-based method to a multi-contaminant case in a starch industry. They found that using process integration may reduce up to 64% of the fresh water consumption in the process. Later, Nápoles-Rivera et al. (2010) proposed a mathematical programming model for the global optimization of mass and property integration networks. This model involves the reduction of fresh-water consumption by implementing decentralized treatment units. Spriggs et al. (2004), Chew et al. (2008), Lovelady and El-Halwagi, 2009, and Rubio- Castro et al. (2010) presented several approaches for water inte- gration in eco-industrial parks, where the wastewater can be reused in different industries reducing the overall waste generated and, at the same time, the fresh water consumption. Sotelo- Pichardo et al. (2011) proposed an approach for the optimal retrofit of water conservation networks, in which existing pro- cesses were adapted to satisfy new process conditions and/or environmental constraints, while minimizing the fresh water con- sumption and the waste generation. Different approaches for water conservation considering the use of alternative sources of water such as desalinated water, rainwater harvesting and wastewater reuse have been proposed. In this context, Muginstein et al. (2003) studied the possibility of imple- menting power/desalination plants in Israel to satisfy the increasing energetic (approximately 7.2% annually) and water * Corresponding author. E-mail addresses: fnapoles@umich.mx, fabricio_napoles@yahoo.com.mx (F. Nápoles-Rivera). Contents lists available at SciVerse ScienceDirect Journal of Cleaner Production journal homepage: www.elsevier.com/locate/jclepro 0959-6526/$ e see front matter Ó 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.jclepro.2013.01.038 Journal of Cleaner Production 47 (2013) 102e117