quality of water

• Groundwater is very high quality. Water passes through rocks dissolving minerals from them.
• Fluoride ions - reduces tooth decay 
• Calcium and magnesium - hard water, harmless but leaves limescale. 
• Arsenic - toxic, found in water in India. 
• Younger water - from recharge zones is categorised by formation of hydrogen carbonate ions. It becomes older and more sulphate ions become present. 
• Natural filtration - water passes through the natural sieve of grains in aquifers that filter impurities, lack of oxygen prevents growth of bacteria. Once cleaned the water remains clean. 
• Groundwater does not always need to be treated like chlorination to kill bacteria.