Life cycle assessment of upflow anaerobic sludge blanket sludge management and activated sludge systems aiming energy use in the municipality of Itajuba, Minas Gerais, Brazil

This study aimed to carry out the Life Cycle Analysis (LCA) targeting to decide the better management system for sludge from both Activated Sludge Process (ASP) and from Upflow Anaerobic Sludge Blanket (UASB). Using the SimaPro(R) software, three post-use scenarios were applied to this process for each type of sludge: Scenario A, which consisted of the option of disposing of UASB sludge in a sanitary landfill; Scenario B, in anaerobic digestion (AD) with the generation of biogas and electricity and use of digested sludge; and Scenario C, the use of UASB sludge as an agricultural fertilizer. Besides, we carried out the analysis of heavy metals in the sludge before and after the AD using the Scanning Electron Microscopy. The elements found with a marked presence in the treatment of UASB and ASP sludge samples, before and after AD, were, among others: Oxygen, Carbon, Aluminum, Silicon, and Iron. The energy avoided for UASB sludge is 0.0502 MJ. For activated sludge, it is 0.00173 MJ. The use of activated sludge as an agricultural fertilizer (Scenario C) presented the best performance in eight of the eleven categories due to the presence of products avoided in the process.