Water chemistry

Abstract

Water chemistry is the branch of chemistry that concerns about water and its constituents, Such as salts, suspended solids, gases, and organic matter. Water chemistry is considered as the keystone that connects the principles of chemistry and other environmental sciences like atmospheric science, hydrogeochemistry, oceanography, biogeochemistry, soil chemistry, marine chemistry, limnological chemistry,… etc. The constituents of water and their exact concentrations are of great importance for the determination of water use. The increase or decrease in the concentration of any constituent in water is a matter of life or death for aquatic life, or it essential to determine the suitability of water for human beings. Also, the constituents determine the suitability of water for irrigation and cattle. A water chemist and a water engineer must have great knowledge about the reactions that take place in water bodies between water constituents, and their effect on water quality, before construction of various water and wastewater treatment plants. Water chemists have to know basic chemistry principles such as equilibrium, thermodynamics, acids and bases, bonding and oxidation-reduction reactions. Also knowledge about geological formations and minerals, their structures, physical and chemical properties, and waterrock interactions. Water chemistry concerns the interaction between geological formations and water. Modern computer programs are used for the interpretation of water samples and the constituents of water, these programs use mathematical model to give the relationship between cations and anions, for example, the relationship between total dissolved solids and electrical conductivity is given by the following formula: TDS(mg/L) = 0.65* EC (µS). Water types, which are indicators for water-rock interactions and gives an idea about the geneses of water, is predicted by Phreeqc, Hydrowin, and Aquachem computer software. In his book, “Water chemistry: an Introduction to the Chemistry of Natural and Engineered Aquatic Systems”, Patrick Resonik, brings a comprehensive information and basic tools on many topics concerning water chemistry, starting from fundamentals of inorganic and organic chemistry and units of measurement, through natural water chemistry and related subjects like acid-base equilibria, thermodynamics, chemical kinetics, solubility and redox reactions. The author also describes the physical and chemical properties of water and gives principles of water treatment like disinfection, metal ions removal, and organic matter treatment. In this exam, multiple-choice questions with their answers, are constructed in chapter 1 about the introduction matter, and in chapter 2 about the inorganic composition of natural waters.