ABSTRACT
Although aluminium is a significant component of most rock types, it is only under certain environmental conditions that concentrations of the element become elevated in natural waters. Such conditions have been detected in the uplands of Wales, and result from acid deposition from industrial emissions falling on an area where the rocks and soils afford minimal buffering. Adverse ecological effects have been noted in streams and lakes with low pH and high aluminium concentrations. Some private water supplies in upland areas may contain elevated aluminium levels deriving from natural sources where no pH correction is carried out. However the most likely reason for the presence of aluminium in public supplies is the use of aluminium sulphate as a coagulating agent in the water treatment process. The maximum admissable concentration (MAC) for aluminium in the EC Drinking Water Directive (80/778/EEC) is 0.2 mg/L, applying to water at the consumer's tap.
