Environmental Evaluation of Different Treatment Processes for Sludge from Urban Wastewater Treatments: Anaerobic Digestion versus Thermal Processes (10 pp)

摘要: Huge amounts of sewage sludge, that need to be handled, are generated all around the world from wastewater treatment plants and its management in an economically environmentally acceptable way has become a matter increasing importance during last few years. In this paper, we make use Life Cycle Assessment (LCA) compare biological thermal processes, is say, anaerobic digestion versus pyrolysis incineration. This paper will complete analysis performed plant, where sludge post-treatment was identified as one main contributors environmental impact on global system. LCA tool for evaluating performance goods well processes or services (collectively termed products). ISO 14040 defines compilation evaluation inputs, outputs potential impacts system throughout life cycle: production raw materials disposal waste generated. In study, data relating actual scenario existent plant were considered. Both bibliographical real existing facilities used proposed. The Centre Environmental Science (CML) Leiden University's methodology chosen quantify associated with different scenarios under study. The software SimaPro 5.1 CML factors (updated 2002) characterisation normalisation stages. In previous found critical point so alternatives have been tackled here. Anaerobic followed by land application pasty comprises both energy recovery nutrient recovery. Other such incineration pyrolysis, allow (both electrical thermal) and, although nutrients lost, new co-products produced (tar char at pyrolysis). Here, most adverse case (that total amount heavy metals supposed released reach environment) applied consider negative due spreading agricultural soils; more research required order establish precise effectively uptaken crops transferred another phase leachate. Thermal presented here good option recover sludge; value lost. Tar char, examples evaluated here, recycling bottom ashes manufacture ceramic other options studied near future. During years, several opinions declared favour application, but many voices also spoken out against each one. To obtain general conclusions overall comparison urban not easy there contradictory aspects. effective utilisation implies material re-use, always possible. Nevertheless, think digested option, probably best least one, long efforts focused minimisation metal content final cake.