Water quality refers to such things as the temperature of the water, the amount of dissolved solids, and lack of toxic and biological pollutants. Water that contains a high amount of dissolved material through the action of chemical weathering can have a bitter taste, and is commonly referred to as hard water. While the level of salinity is the most common concern, other dissolved solids present in groundwater can cause problems. Hard water causes scaly deposits to form in water heaters and pipes, and makes soap difficult to lather. High levels of iron are present in some groundwater. Iron can discolor water and stain clothing; it is undesirable for many manufacturing processes as well. Sulphates in water can leave a bitter taste, and can also have a laxative effect.
A research developed by EEA in 1999 aimed to provide an overview of the status of Europe’s groundwater through the distribution of selected quality indicators: nitrates, pesticids, chloride, alkalinity, pH-values, electrical conductivity, with special emphasis on nitrates and pesticids. EU countries were requested to submit the most recent available data at national level, together with that for at least three important groundwater areas. Sampling sites were then classified according to their annual mean values using the threshold values and ranges given in the following table. For every indicator EEA identified a critical value basing on experience and the levels given in Drinking Water Directive (80/778/EC) and in World Health Organization (WHO) report .
For more information check the following pages: groundwater contamination, source of groundwater pollution, contaminants (seawater intrusions, nitrates, arsenic, iron), reducing groundwater contamination.