Comparing Tertiary Wastewater Treatment to Seawater Desalination Using Life Cycle Assessment

Abstract

The Gulf Corporation Council (GCC) countries consume approximately half of their oil production for water and energy cogeneration. This intricate situation of increasing water consumption and freshwater scarcity paradox have made wastewater treatment and reuse indispensable. Reuse of treated wastewater contributes to savings fossil fuels and entailed environmental impacts. The objective of this chapter is to demonstrate the application of life cycle assessment (LCA) to evaluate the environmental impact and missed opportunity of treating municipal wastewater to tertiary quality compared to conventional water production. The conventional method compared is the dominant seawater desalination using multistage flash distillation (MSF). The study follows the ISO 14040/44 standards and uses a functional unit of 1 M m3 of tertiary treated effluent (TTE). The modeling concept adopts the cradle-to-gate consequential modeling paradigm. The life cycle inventory is based on filed data collection, reports, literature, and Ecoinvent database processes. The inventories include: infrastructure, grid, materials, energy requirements, chemical additives, and sludge disposal; for primary, secondary, and tertiary treatment. The life cycle impact assessment is applied on both the characterized and normalized level using the ReCiPe method. The normalized results indicate that MSF has over 70 times the impact on fossil depletion and over 8 times the impact on particulate matter formation, human toxicity, and climate change for water production compared to the effects of TTE. The TTE effluent is best for agricultural use.