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Sewege sludge is domestic and sometimes industrial waste which goes into a public sewerage system. If there is no public sewage collecting system, no sewage sludge is recorded - thus Africa, much of Asia and South America are small on this map. The United Nations Environment Programme (2005) notes that whilst sewage sludge can be a useful fertiliser, its environmental dangers include possible presence of heavy metals, organic compounds and pathogens. The most sewage sludge produced per person is in Luxembourg, mainly because this city state has no room for cesspits. |