Key Parameters

The 10 Key Drinking Water Quality Standards in Scotland are:

Parameter	Significance
Total Coliforms	The coliform group of organisms is present in large numbers in the gut of all warm-blooded animals but are also widely distributed in the environment. While their presence in water supplies indicates a breach in the integrity of the water supply system, it may not be presumed that faecal pollution has occurred.
Faecal Coliforms	Faecal coliforms are present in large numbers in the gut of all warm-blooded animals. Their presence in water supplies indicates a breach in the integrity of the water supply system and that faecal pollution may have occurred
Colour	Colour is derived from humic substances which occur naturally, particularly in acidic water sources derived from moorland catchment areas. High colour may be unacceptable to consumers on aesthetic grounds and the humic substances responsible for colour are precursors of disinfection by-products. Colour may be removed by coagulation/sedimentation/filtration.
Turbidity	Naturally turbidity is caused by suspension of finely divided or colloidal matter of predominantly inorganic origin. Turbidity may also be caused by the breakthrough of coagulant floc from overloaded or badly maintained filters. High turbidity is unacceptable to consumers on aesthetic grounds and may also compromise disinfection. Turbidity levels are controlled by effective operation of treatment processes.
Hydrogen Ion (pH)	Most surface waters and many groundwaters are slightly corrosive towards the materials used in water treatment systems and consumers installations. This effect persists even when the pH exceeds the neutral point (pH7) and is countered by adding an alkali during treatment to raise the pH. As chlorine disinfection is more effective at low pH addition of Alkali is normally made after the disinfection stage. Extreme pH values may present a risk to the health of consumers.
Aluminium	Aluminium occurs in acidic waters derived from moorland catchments and is removed in water treatment by coagulation and filtration. High concentrations are unacceptable to consumers on aesthetic grounds. Aluminium sulphate is used as a coagulant in water treatment. Claims of a weak association between low concentrations of aluminium in water supplies and the incidence of Alzheimer·s disease have not been substantiated.
Iron	Iron is present naturally in many water sources and is removed by conventional water treatment processes. Iron in water supplies may also be derived from corrosion of iron mains and inadequate filtration of the residues of iron based coagulants used in water treatment. High iron concentrations are unacceptable to consumers on aesthetic grounds.
Manganese	Manganese occurs naturally in many water sources and particularly high concentrations are encountered in anaerobic groundwaters. Conventional water treatment processes remove manganese. Elevated manganese concentrations are unacceptable to consumers on aesthetic grounds.
Lead	Lead is not normally present in water sources but significant concentrations may be present at consumers· taps if lead pipes are present and the water supply is plumbo-solvent.
Trihalomethanes	Trihalomethanes occur in drinking water principally as products of the reaction of chlorine with naturally occurring organic materials and with bromide, which may also be present in the water. In controlling trihalomethanes, a multi-step treatment system should be used to reduce organic trihalomethane precursors, and primary consideration should be given to ensuring that disinfection is never compromised.