Do you want to know what’s in the water that you drink? This free course, What chemical compounds might be present in drinking water?, examines the chemical compounds that occur in drinking water. A high level of certain anions in water can cause environmental pollution and health problems. Cations are also important. For example, calcium salts contribute to the hardness of water and water treatment uses aluminium compounds. Additionally oxidising agents, such as ozone or chlorine, are vital in the disinfection of water. This OpenLearn course focuses on the chemistry of the p-block elements in Groups 13 to 18 of the Periodic Table.