Life Cycle Assessment of Wastewater Treatment Plant Varying Electricity Power Sources

Abstract

Wastewater treatment is an essential life process that enhances water quality as population and urbanization are increasing proportionally. The increase in population alongside the increase of wastewater treatment plants’ significance, lead to an increase in electricity demand to power the plants. All the mentioned factors together spell negative impacts on the environment that need to be mitigated urgently. Applying a life cycle assessment (LCA) for the process becomes essential. This study evaluates the LCA of a wastewater treatment plant in Nabatieh, South Lebanon. The studied treatment includes a preliminary stage, an oxidation ditch, and UV disinfection. The plant is powered by a source that is solely dependent on diesel combustion. The assessment is conducted using the software SimaPro 9.0 following ISO 14040 standards. Using CML-IA method several impact categories studied such as abiotic depletion of fossil fuels, global warming, and abiotic depletion of material in general. As a result, electricity showed the highest contributing factor on most of the impact categories. Moreover, the most affected category was the global warming. To reduce this impact, several scenarios were considered for powering the plant. The scenarios include alternative combinations of renewable (solar, wind, and hydroelectric energy) and non-renewable (natural gas, crude oil, and biomass) energy sources. Five different alternatives were compared. Result comparison showed that the scenario that depends on 53% fossil fuels, 45% several renewable energy sources, and 2% biomass, has the most enhancement on the most affected category which is the global warming and several others. However, due to renewable sources’ initial demand of material, it showed a deterioration in the effect of the abiotic depletion of material category. Also, other categories, such as freshwater ecotoxicity, were affected by the construction phase and wastes disposed during the transition to renewable energy sources. This interpretation is considering the environmental impact without the economic aspect. When introducing the economic aspect, the same scenario is the most expensive and costly one. This paper does not give a conclusive optimal solution, considering the Lebanese economic situation, yet it shows that it is possible to reach an improvement of 80% and more in certain sectors when introducing renewable energy sources.