Unit operations and processes occur in a variety of combinations in treatment flow diagrams The rate at which reactions and conversions occur and the degree of their completion, is generally a function of the constituents invol ved, the temperature, and the type of reactor (i.e. container or tank in which the reactions take place) The fundamental basis for the analysis of the physical chemical, and biological unit operations and processes used for wastewater treatment is the materials mass balance principle in which an accounting of mass is made before and after reactions and conversions have taken placeUnit operations and processes occur in a variety of combinations in treatment flow diagrams. The rate at which reactions and conversions occur, and the degree of their completion, is generally a function of the constituents involved, the temperature, and the type of reactor (i.e., container or tank in which the reactions take place). The fundamental basis for the analysis of the physical, chemical, and biological unit operations and processes used for wastewater treatment is the materials mass balance principle in which an accounting of mass is made before and after reactions and conversions have taken place