Water and Wastewater Properties and Characteristics

Abstract

Abstract Water in nature is most nearly pure in its evaporative state. Because the very act of condensation usually requires a surface, or nuclei, water may acquire impurities at the very moment of condensation. Additional impurities are added as the liquid travels through the remainder of the hydrologic cycle and comes into contact with materials in the air and on or beneath the surface of the earth. Human activities contribute further impurities in the form of industrial and domestic wastes, agricultural chemicals, and other less obvious contaminants. Ultimately, these impure waters complete the hydrologic cycle and return to the atmosphere as relatively pure water molecules. However, the water quality in the intermediate stage is of greatest concern because the quality at this stage affects human use of water. The impurities accumulated by water throughout the hydrologic cycle and from human activities may be in both suspended and dissolved form. Suspended material consists of particles larger than molecular size that are supported by buoyant and viscous forces within the water. Dissolved material consists of molecules and ions that are held by the molecular structure of water. Colloids are very small particles that technically are suspended but often exhibit many of the characteristics of dissolved substances. Water pollution is the presence of impurities in water in such quantity and of such nature as to impair the use of the water for a stated purpose. Many parameters and characteristics have evolved that qualitatively reflect the impact that various impurities have on selected water uses. Knowledge of properties/characteristics/parameters of water and wastewater treatment processes is essential for environmental scientists and engineers.