ABSTRACT
From the development of the activated sludge process in 1914, the main focus in wastewater treatment has been devoted to improving effluent quality, which has evolved in parallel with increasingly strict discharge limits. The major differences found among the different Life Cycle Assessment reports on wastewater treatment systems are the selection of the functional unit (FU), the system boundaries, and the environmental indicators. Sewage sludge is an unavoidable waste product from the treatment of wastewater, and its final disposal plays a relevant role in the global impact of the Wastewater treatment plant. It has been estimated that around one percent of the average daily electricity consumption in Western Europe is due to municipal and industrial wastewater treatment. In the specific case of wastewater treatment, the system boundaries will typically include primary and secondary treatment as well as the production of energy and chemicals and the emissions associated with the process.
