detention time of the reactor being measured. The measured output is as described on Fig. 4-3(a-I and b-D) In the second method, a continuous step input of dye is introduced until the effluent concentration matches the influent concentration. The measured response is as shown on Fig. 4-3(a-2 and b-2). Another response curve can be measured after the dye injection has ceased and the dye in the reactor is flushed out Analysis of Tracer esponse Curves 10=48.7 min types are used Tracers of var 8000m3d 4000m3d commonly to assess the hydraulic performance of reactors used for Typical examples of tracer response curves are shown on Fig 4-8 ime, min Fig. 4-8 Typical tracer response curves: two different types of circular clarifiers and open channel Uv disinfection systen Tracer response curves, measured using a short-term and continuous injection of tracer, are known as C (concentration versus time)and F(fraction of tracer remaining in the reactor versus time)curves, respectively. The fraction remaining is based on the volume of water displaced from the reactor by the step Input of tracer. 4-4 Reactions, Reaction Rates, and Reaction Rate Coefficients From the standpoint of process selection and design, the controlling stoichiometry and the rate of the reaction are of principal concern. The number of moles of a substance entering into a reaction and the number of moles of the substances produced are defined by the stoichiometry of a reaction. The stoichiometry of reaction refers to the definition of the quantities of chemical compounds involved in a reaction. The rate at which a substance disappears or is formed in any given stoichiometry reaction is defined as the rate of reaction. The rate expressions discussed in this section will be integrated with the hydraulic characteristics of the reactors. discussed previously. to define treatment kinetics. Types of Reactions The two principal types of reactions that occur in wastewater treatment are classified as homogeneous and Homogeneous Reactions. In homogeneous reactions, the reactants are distributed uniformly throughout the fluid so that the potential for reaction at any point within the fluid is the same, Homogeneous reactions are usually carried out in the batch, complete-mix, and plug-flow reactors(see Figs. 4-2a, b, c, and d) Homogeneous reactions may be either irreversible or reversible Simple reactions b. Parallel reactions A+E c Conse reactions D Examples of reversible reactions are As will be discussed subsequently, for both irreversible and reversible reactions, the rate of reaction will 4-84-8 detention time of the reactor being measured. The measured output is as described on Fig. 4-3(a-1 and b-l). In the second method, a continuous step input of dye is introduced until the effluent concentration matches the influent concentration. The measured response is as shown on Fig. 4-3(a-2 and b-2). Another response curve can be measured after the dye injection has ceased and the dye in the reactor is flushed out. Analysis of Tracer Response Curves Tracers of various types are used commonly to assess the hydraulic performance of reactors used for wastewater treatment. Typical examples of tracer response curves are shown on Fig. 4-8. Fig. 4-8 Typical tracer response curves: two different types of circular clarifiers and open channel UV disinfection system Tracer response curves, measured using a short-term and continuous injection of tracer, are known as C (concentration versus time) and F (fraction of tracer remaining in the reactor versus time) curves, respectively. The fraction remaining is based on the volume of water displaced from the reactor by the step input of tracer. 4-4 Reactions, Reaction Rates, and Reaction Rate Coefficients From the standpoint of process selection and design, the controlling stoichiometry and the rate of the reaction are of principal concern. The number of moles of a substance entering into a reaction and the number of moles of the substances produced are defined by the stoichiometry of a reaction. The stoichiometry of reaction refers to the definition of the quantities of chemical compounds involved in a reaction. The rate at which a substance disappears or is formed in any given stoichiometry reaction is defined as the rate of reaction. The rate expressions discussed in this section will be integrated with the hydraulic characteristics of the reactors, discussed previously, to define treatment kinetics. Types of Reactions The two principal types of reactions that occur in wastewater treatment are classified as homogeneous and heterogeneous (non-homogeneous). Homogeneous Reactions. In homogeneous reactions, the reactants are distributed uniformly throughout the fluid so that the potential for reaction at any point within the fluid is the same, Homogeneous reactions are usually carried out in the batch, complete-mix, and plug-flow reactors (see Figs. 4-2a, b, c, and d). Homogeneous reactions may be either irreversible or reversible. Examples of irreversible reactions are a. Simple reactions A——>B A + A——> C aA + bB ——> C b. Parallel reactions A + B ——> C A + B ——>D c. Consecutive reactions A + B ——> C A + C——> D Examples of reversible reactions are A <——> B A + B <——> C + D As will be discussed subsequently, for both irreversible and reversible reactions, the rate of reaction will