Abstract :
Eutrophication is the enrichment of water bodies with plant nutrients and precursors, typically nitrogen, phosphorus, and organic matter. There exists a “natural” and slow eutrophication, which, over geological times, turns a lake into a marsh and then dries it entirely. Today, however, eutrophication is mostly referred to the human process that “results in the stimulation of an array of symptomatic changes, among which increased production of algae and macrophytes, deterioration of water quality and other symptomatic changes are found to be undesirable and interfere with water uses” as defined by the OECD in 1982. This undesirable process is observed mostly in enclosed water bodies, such as lakes, but also in some rivers, some estuaries, and some coastal zones. In most freshwater systems, phosphorus has been identified as the “limiting nutrient” to phytoplankton development. This nutrient is brought to aquatic environments from rock weathering, soil leaching, and rain (natural sources), but also and mostly from agricultural runoff and domestic sewage. Some food processing industries (meat, vegetables, cheese processing) also contribute significantly to the phosphorus budget, even though the pollution may be due to floor and utensil cleaning rather than to direct food wastes.
