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Glossary of terms related to Urban Waste Water

Agglomeration An area where the population and/or economic activities are sufficiently concentrated for urban waste water to be collected and conducted to an urban waste water treatment plant or to a final discharge point
Appropriate treatment Treatment of urban waste water by any process and/or disposal system which after discharge allows the receiving waters to meet the relevant quality objectives and the relevant provisions of this and other Community Directives
Coastal waters The waters outside the low-water line or the outer limit of an estuary
Collecting system A system of conduits which collects and conducts urban waste water
Domestic waste water Waste water from residential settlements and services which originates predominantly from the human metabolism and from household activities
Estuary The transitional area at the mouth of a river between fresh-water and coastal waters.
Eutrophication The enrichment of water by nutrients, especially compounds of nitrogen and/or phosphorus, causing an accelerated growth of algae and higher forms of plant life to produce an undesirable disturbance to the balance of organisms present in the water and to the quality of the water concerned.
Industrial sectors subject to specific controls See Annex III of the Directive (pdf)
Industrial waste water Any waste water which is discharged from premises used for carrying on any trade or industry, other than domestic waste water and run-off rain water
Less sensitive areas

Marine water bodies or areas where the discharge of waste water does not adversely affect the environment as a result of morphology, hydrology or specific hydraulic conditions which exist in that area. When identifying less sensitive areas, Member States shall take into account the risk that the discharged load may be transferred to adjacent areas where it can cause detrimental environmental effects. Member States shall recognise the presence of sensitive areas outside their national jurisdiction. The following elements shall be taken into consideration when identifying less sensitive areas:

  • open bays, estuaries and other coastal waters with a good water exchange and not subject to eutrophication or oxygen depletion or which are considered unlikely to become eutrophic or to develop oxygen depletion due to the discharge of urban waste water.
Population equivalent (1 p.e.) The organic biodegradable load having a five-day biochemical oxygen demand (BOD5) of 60 g of oxygen per day
Primary treatment Treatment of urban waste water by a physical and/or chemical process involving settlement of suspended solids, or other process in which the BOD5 of the incoming waste water is reduced by at least 20% before discharge and the total suspended solids of the incoming waste water are reduced by at least 50%
Secondary treatment Treatment of urban waste water by a process generally involving biological treatment with a secondary settlement or other process in which the requirements established in Table 1 of Annex I of the Directive are respected
Sensitive areas
  • Freshwater bodies, estuaries and coastal waters which are eutrophic or which may become eutrophic if protective action is not taken;
  • Surface freshwaters intended for the abstraction of drinking water which contain or are likely to contain more than 50 mg/l of nitrates;
  • Areas where further treatment is necessary to comply with other Council Directives such as the Directives on fish waters, on bathing waters, on shellfish waters, on the conservation of wild birds and natural habitats, etc.
Sludge Residual sludge, whether treated or untreated, from urban waste water treatment plants
Urban waste water Domestic waste water or the mixture of domestic waste water with industrial waste water and/or run-off rain water