1 IV. Wastewater Treatment Technologies Topic IV. 8. Biological Processes of Wastewater Treatment: Fazes, Kinetics - Monod’s Equations Basic Fazes of Biological Processes General mechanism of substances micro-biological transfer: §Extracellular substrate degradation by external enzymes §Substrate particles attachment at the cells walls §Substrate diffusion into the cells through the cells membranes §Cell metabolism (biochemical transformations) §Metabolism products diffusion out of the cells

2 Basic Fazes of Biological Processes General mechanism of substances micro-biological transfer: §Substrate necessary composition §Processes of substrate dissimilation (breathing) §Processes of substrate assimilation (cell growth) §Processes of the cells substances dissimilation (endogenous respiration) ;

3 Basic Fazes of Biological Processes Biological Processes Kinetics Biomass Growth Kinetics 1 - lag-faze; 2 - exponential growth faze; 3 - steady-state faze; 4 - endogenous respiration faze

4 Biological Processes Kinetics Equations of Monod §Rate of biomass growth X - biomass concentration, g/m 3  - coefficient of specific biomass growth rate, d -1 k d - coefficient of endogenous respiration, d -1  m - maximal value of the coefficient , d -1 S - substrate concentration, g/m 3 K s - half-saturation constant, g/m 3 §Rate of substrate utilisation Y - biomass yeld coefficient, gX/gS

5 Biological Processes Kinetics Transformations of Monod’s Equations §Substrate utilisation specific rate - U, gS/gX.d §Biomass age -  x, d §Biomass growth rate, d -1

6 Biological Processes Kinetics Kinetic Parameters Use in the Practice §In the bioreactors design t - necessary design hydraulic retention time to achieve S

7 Biological Processes Kinetics Kinetic Parameters Use in the Practice §In the real process regulation  - necessary degree of purification in respect to S S 0 - substrate concentration at the influent S - substrate concentration at the effluent and Then, or Therefore, the necessary effluent concentration S can be maintenance by maintenance of the relevant values of U and  x. The value of the later can be achieved by the excess biomass regulation.