Lifecycle Assessment of Two Urban Water Treatment Plants of Pakistan

Abstract

Water treatment technologies are striving to retain their ecological and economic viability despite the rising demand, conventional infrastructure, financial constraints, fluctuating climatic patterns, and highly stringent regulations. This study evaluates the lifecycle environmental impact of urban water treatment systems within the two densely populated South Asian municipalities of Islamabad and Rawalpindi, Pakistan. The scope of this study includes a process-based Life Cycle Assessment (LCA) of the entire water treatment system, particularly the resources and materials consumed during the operation of the treatment plant. The individual and cumulative environmental impact was assessed based on the treatment system data and an in-depth lifecycle inventory analysis. Other than the direct emissions to the environment, the electricity used for service and distribution pumping, coagulant use for floc formation, chlorine gas used for disinfection, and caustic soda used for pH stabilization were the processes identified as the most significant sources of emissions to air and water. The water distribution consumed up to 98% of energy resources. The highest global warming impacts (from 0.3 to 0.6 kg CO2 eq./m3) were assessed as being from the coagulation and distribution processes due to extensive electricity consumption. Direct discharge of the wash and wastewater to the open environment contributed approximately 0.08% of kg-N and 0.002% of kg-P to the eutrophication potential. The outcome of this study resulted in a thorough lifecycle inventory development, including possible alternatives to enhance system sustainability. A definite gap was identified in intermittent sampling at the treatment systems. However, more stringent sampling including the emissions to air can provide a better sustainability score for each unit process.