Comparative life cycle assessment of water treatment plants Alexandre Bonton a, ⁎, Christian Bouchard a , Benoit Barbeau b , Stéphane Jedrzejak a a Département de génie civil et de génie des eaux, Université Laval, Québec, Canada G1K 7P4 b Département des génies civil, géologique et des mines, École Polytechnique de Montréal, Montréal, Canada H3T 1J4 abstract article info Article history: Received 11 May 2011 Received in revised form 28 July 2011 Accepted 19 August 2011 Available online 9 September 2011 Keywords: Life cycle assessment Drinking water Nanofiltration Conventional water treatment Energy The production of drinking water from fresh surface water involves several processes, energy consumption and chemical dosing, all having global environmental impacts. These should be considered in the choice of water treatment processes. The objective of the present study was to conduct a comparative life cycle assessment of two water treatment plants: one enhanced conventional plant and one nanofiltration plant. One existing nanofiltration plant was chosen and investigated in great detail, including its operation and construction phases. This plant is located in the northern part of the Province of Quebec and has been in operation for over 10 years. A virtual conven- tional plant was designed for comparative purposes. The comparative life cycle assessment was performed using SimaPro software for inventory and impact assessment phases. The study revealed very different im- pacts for the two plants, drawing attention to the importance of the choice of water treatment chemicals and energy source. © 2011 Elsevier B.V. All rights reserved. 1. Introduction The main objective of water treatment is to deliver good quality drinking water to consumers. Treatment involves protection against microorganisms, removal of natural organic matter, removal of toxic substances, aesthetic quality, and protection of the distribution net- work against corrosion and recontamination. Traditional water treat- ment systems consist primarily of physical–chemical and chemical processes such as coagulation–flocculation, settling, granular filtra- tion and chemical disinfection. More recently, pressure-driven mem- branes and UV disinfection have been used increasingly in the water industry [43]. Membrane processes offer an attractive alternative to traditional processes as they mainly require energy for water filtra- tion through the membranes. Generally, the choice of the “best” water treatment system is based first and foremost on economic and technical constraints. How- ever, the water treatment industry may be responsible for significant global environmental impacts, the most common amongst which are the depletion of natural resources and indirect release of pollutants into the water, land and air through chemicals and energy consump- tion. To date, little information on those impacts is available, especial- ly in the North American context and for new water treatment processes such as membranes. Life cycle assessment (LCA) is a tool that could be used to generate information on the environmental impacts of water treatment sys- tems. LCA serves to assess the global environmental damages poten- tially caused by a product, a process or a service in a “cradle to grave” approach [20]. Four stages are necessary to conduct an LCA [16]: goal, scope and functional unit definitions, life cycle inventory (LCI), life cycle impact assessment (LCIA), and Life cycle interpreta- tion. LCA can be used to analyse and compare several processes or systems through their contribution to global environmental impacts. The definition of the functional unit is an important issue that allows fair comparison of different systems through LCA. Adopting a unique functional unit for all the studied water treatment systems (for exam- ple delivering 1 m 3 of water at a specified quality) guarantees that the impacts of these systems may be compared to each other. The LCI is a flow tree of all relevant processes used to produce, transport, use and dispose of the selected product. Inflows (raw material, energy, other processes, etc.) and outflows (emissions, wastewater, etc.) are listed for all relevant processes. The LCIA transforms inflows and outflows into a number of environmental impacts (climate change, resource depletion, etc.). Conducting an LCA requires the use of a software such as SimaPro [33] or GaBi [32]. These software products usually in- clude several inventory databases (European reference Life Cycle Data system, U.S. Life-Cycle Inventory database, Ecoinvent, etc.) and im- pact assessment methods (Impact2002+, Traci, Ecoindicator, etc.). Since the databases were developed primarily in the European con- text, they usually have to be adapted when applied to other locations. Another important challenge is that several processes used for water treatment are not included in existing databases. This may limit the achievement of robust water treatment LCA. Desalination 284 (2012) 42–54 ⁎ Corresponding author at: École supérieure d'aménagement du territoire et du développement régional, Université Laval, Pavillon Félix-Antoine-Savard, local 1718, Québec, Canada G1K 7P4. Tel.: +1 418 656 2131x4788. E-mail address: alexandre.bonton.1@ulaval.ca (A. Bonton). 0011-9164/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.desal.2011.08.035 Contents lists available at SciVerse ScienceDirect Desalination journal homepage: www.elsevier.com/locate/desal