Life cycle assessment of wastewater treatment options for small and decentralized communities : energy-saving systems versus activated sludge

There are several methodologies that enable direct comparison of centralized and decentralized sewage treatment systems, both in economical and ecological view. One of the latter is the so-called Life-Cycle Analysis (LCA), which accounts for the environmental impacts of a product, service, or process over the course of its life cycle. Assessed environmental impacts generally include consumption of land, energy, water, and other resources as well as the release of substances (harmful and beneficial) into air, water, and soil. LCA is largely quantitative in nature and thus can help in selecting strategies that solve environmental problems rather than merely shifting them back and forth. In the present study, an LCA comparison of several treatment processes for small and decentralized communities is made. The LCA focused on the construction, operation and disassembling phases of two energy-saving or natural systems (constructed wetland and slow rate infiltration) and a conventional one (activated sludge). The lower environmental impact of natural wastewaters treatment plants was clearly demonstrated using several ecologic indicators (e.g.: Global warming), confirming that decentralized technologies are advantageous, mainly because they require less resources