LIFE CYCLE ASSESSMENT OF MEMBRANE BIOREACTOR VERSUS CAS WASTEWATER TREATMENT : MASDAR CITY AND BEYOND

Wastewater Treatment (WWT) has become compulsory by government regulations in most parts of the world due to the importance of maintaining the sanitation of fresh water and preserving the environment. The processes used to treat waste water generally include pre-treatment and either one or two decantation stages. One tool to assess environmental impacts resulting from shifting from one design choice for WWT to another is by conducting Life Cycle Analysis (LCA) of all considered designs/systems. An LCA study considers all the environmental impacts associated with a product or system throughout its life cycle (i.e., from cradle to grave). In this paper, an LCA study is conducted to compare between two wastewater treatment technologies, namely: Conventional Activated Sludge systems (CAS) and immersed Membrane Bioreactor (MBR) systems. In this effort, a full design of both systems was executed to account for relevant material and energy inventories and environmental impacts. The comparison starts at the level of a small community, considering the MBR plant in Masdar City (Abu Dhabi, United Arab Emirates) as an example, then scaling up the study to encompass the entire Abu Dhabi emirate. After the LCA, reflections based on the costs of the two wastewater treatment options are made. Moreover, in view of Abu Dhabi’s future sustainability targets, variables such as clean energy sources and carbon tax are also considered. The results of this study reveal that MBR treatment is more environmentally friendly than CAS treatment. However, when other parameters are taken into consideration, it is recommended that MBRs be used on a decentralized scale, whereas CAS plants should be used on a larger, more integrated scale.