Emissions of organic matter

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Since the 1940s, in most European countries, the increase of industrial and agricultural production and connection to sewerage has resulted in an increase of discharge to water of organic waste. Over the last twenty years, marked changes have occurred in the proportion of the population connected to waste water treatment as well as in the waste water treatment technology involved (see factsheet WEU16 Urban waste water treatment). In many major European rivers, oxygen levels decreased and the ecological quality was heavily affected. During the 1990s, the BOD levels improved by 20 to 30 % in the rivers of both the EU and Accession Countries (see factsheet WEU2 Nutrients, BOD and ammonium in rivers). More recently, improvements have been made in rural (autonomous) waste water treatment in the EU. Data availability is very heterogeneous, depending on the number of Member States who reported data for the year concerned. Based on available data, mean BOD emissions have decreased in the past ten years in the EEA area. The slight upward trend in Nordic countries is due to transfers from diffuse sources (not taken into account in the indicator) to point sources. This trend suggests that urban domestic pressure, as for organic water pollution, is lessening (or decreasing) but the situation in the EEA area is mixed. The trend observed is in accordance with the last SoE report of the EEA (§ 3.5 Water Stress, p168) assessing that the reduction of urban organic water pollution is to be linked to the improvement of sewage treatment technology. The decrease in the emission of organic pollution is mainly due to improvements in the level of treatment, which leads in turn to an increase in the quantities of sludge produced. The sludge has to be disposed of, mainly through spreading on soils, deposits in landfills or incineration that can result in pollution transfers from water to soil or air.