Water, energy and food are the pillars upon which society can further advance. This note outlines some of the challenges and emerging solutions.

Water purity is a vague term often interpreted in a subjective manner. When applied to drinking water quality, the emphasis of "pure" can mean free from all types of bacteria and viruses when defined by EPA in the United States, or being wholesome as defined by drinking water legislation in the UK. These legal definitions have significant economic, practical and potential health implications that are of concern to the Water Science Forum (WSF) of the Royal Society of Chemistry. This brief outlines a UK-based perspective on the meaning of water purity based on relevant literature and consultation with our members. IntroductionWater is a simple compound made of hydrogen and oxygen, so "pure" water would be that which contains nothing but those elements. Pure water does not exist in nature because, even during its fall to earth as rain, water collects particles, minerals and gases from the air. Then, when the rain hits the ground creating surface water, it captures materials from soils and rocks. As it makes its way into groundwater, rivers and lakes, surface water can dissolve many different substances, envelop microorganisms and carry solid materials. Most water therefore will contain certain contaminants, bacteria, funguses and viruses; depending upon where the water falls and travels.

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