CEE 697K ENVIRONMENTAL REACTION KINETICS

Transcription

1 Updated: 19 November Print version CEE 697K ENVIRONMENTAL REACTION KINETICS Lecture #19 Chloramines Cont: Primary Literature Enzyme Kinetics: basics Brezonik, pp Introduction

2 Conclusions 2 Overall the model calculations suggest that biodegradation is..not likely to play a major role in most water distribution systems the conditions needed for significant HAA removals in a distribution system (i.e., total biomass densities > 10 5 cells/cm 2 over long distances of pipe) are unlikely in the US water distribution systems where total chlorine residuals typically are high and thus inhibit the development of biofilm on pipe walls But this seems to contradict their introductory conclusion how to reconcile?

3 What could they have concluded? 3 Variability vs diurnal demand Q/Qavg u (ft/s) t (hr) C (ug/l)

4 Objective/hypothesis 4 Not really stated, but they did end the intro with: In this work, computer simulations were performed to predict the fate of three HAAs (MCAA, DCAA, and TCAA) along a distribution system and within a biologically active filter. Sensitivity analyses were performed to investigate the effects of physical parameters (e.g., fluid velocity) and biological parameters (e.g., biodegradation kinetics, biomass density) on HAA removal

5 What could they have said? 5 To determined if observed HAA loss could be attributed to biodegradation on pipe walls given known physical and microbial characteristics of distribution systems To estimate spatial and temporal variability of HAA concentrations based on a rational physical model of biodegradation in distribution systems

6 What could they have done? 6 Find some direct evidence for biodegradation of HAAs in distribution systems A product of the enzymatic reaction? Chlorohydroxyacetate? Evidence of abiotic reactions? Increase in MCAA?

7 What else? 7 Consider mass transfer resistance within biofilm

8 What should be done next? 8 Experimental Work In-situ controlled study of flow velocity vs DCAA loss in a pipe segment? Effect of biocide in above segment? Model Refinement Account for internal mass transfer resistance Combine with growth model for HAA degraders

9 B1: biologically fixed bacteria B2: adsorbed bacteria 9 SANCHO Model Input (H1, H2, B3) Internal Processes Output H2 H1 BDOC S CO 2 Cl 2 Free Bacteria B3 Cl 2 Mortality Cl 2 B2 Mortality B1 Fixed Bacteria

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13 Effect of Zn on HAAs 13 Effect of Zinc on the Transformation of HAAs in Drinking Water Wei Wang and Lizhong Zhu Journal of Hazardous Materials 174:40-46.

14 Enzymatic Reactions 14 Many ways of illustrating the steps Substrate(s) bond to active site Product(s) form via transition state Product(s) are released

15 Basic Enzyme Kinetics Note that some references use k 2 for k -1, and k 3 for k 2 15 Irreversible Single intermediate E + S k 1 k ES 2 E + P k- 1 The overall rate is determined by the RLS, k 2 d[ d[ P] r dt dt But we don t know [E, so we can get it by the SS mass balance d[ E dt 0 k [ ES 2 ] k1[ E][ k 1[ E k2[ E Again, we only know [E o ] or [E tot ], not free [E], so: ([ E ] [ E )[ k [ E k [ ] 0 k o ES

16 Reactants, products and Intermediates 16 Simple Progression of components for simple single intermediate enzyme reaction Shaded block shows steady state intermediates Assumes [>>[E] t From Segel, 1975; Enzyme Kinetics

17 Basic Enzyme Kinetics II 17 And solving for [E, k1[ E[ + k 1[ E + k2[ E k1[ Eo][ [ E k 1 k1[ Eo][ [ + k + k 1 2 [ Eo][ [ ES ] k 1 + k [ + k 1 2

18 Michaelis-Menten 18 Irreversible Single intermediate r d[ P] r dt d[ P] k2[ Eo][ rmax[ k 1 k2 dt + [ K + [ + k 1 E + S k 2 [ E k 1 k ES 2 E + P k- 1 s [ Eo][ [ ES ] k 1 + k [ + k 1 2

19 Michaelis Menten Kinetics 19 Classical substrate plot 100 rmax 80 Reaction Rate r max K s r d[ P] rmax[ dt K [ s Substrate Concentration

20 Substrate and growth 20 If we consider Y r d[ P] dt d[ dt 1 Y dx dt U We can define a microorganism-specific substrate utilization rate, U dx dt And the maximum rates are then 1 X d[ dt k[ K [ s + U and r X YX µ µ Y U max k µ Y max 1 d[ X ] µ max[ X dt K + s [

21 Linearizations 21 Lineweaver-Burke Double reciprocal plot Wikipedia version Voet & Voet version

22 22 das

23 3 types 23 Lineweaver Burk Hanes Eadie-Hofstee

24 Compare predictions 24 ad

25 Multi-step k 1 E + S k ES 2 EP 2 2E + P k- 2 1 P 1 k 3 25 Double intermediate Also gives: r d[ P] rmax[ dt K [ s + But now: r max k2k3[ E k + k 2 o 3 ] k K s + ( ) 3 k 1 + k2 ( k ) 2 k 3 k 1 Note what happens when: k 3 >> k 2

26 26 To next lecture

27 Enzymatic Reactions 27 Many ways of illustrating the steps Substrate(s) bond to active site Product(s) form via transition state Product(s) are released

28 Basic Enzyme Kinetics Note that some references use k 2 for k -1, and k 3 for k 2 28 Irreversible Single intermediate E + S k 1 k ES 2 E + P k- 1 The overall rate is determined by the RLS, k 2 d[ d[ P] r dt dt But we don t know [E, so we can get it by the SS mass balance d[ E dt 0 k [ ES 2 ] k1[ E][ k 1[ E k2[ E Again, we only know [E o ] or [E tot ], not free [E], so: ([ E ] [ E )[ k [ E k [ ] 0 k o ES

29 Reactants, products and Intermediates 29 Simple Progression of components for simple single intermediate enzyme reaction Shaded block shows steady state intermediates Assumes [>>[E] t From Segel, 1975; Enzyme Kinetics

30 Basic Enzyme Kinetics II 30 And solving for [E, k1[ E[ + k 1[ E + k2[ E k1[ Eo][ [ E k 1 k1[ Eo][ [ + k + k 1 2 [ Eo][ [ ES ] k 1 + k [ + k 1 2

31 Michaelis-Menten 31 Irreversible Single intermediate r d[ P] r dt d[ P] k2[ Eo][ rmax[ k 1 k2 dt + [ K + [ + k 1 E + S k 2 [ E k 1 k ES 2 E + P k- 1 s [ Eo][ [ ES ] k 1 + k [ + k 1 2

32 Michaelis Menten Kinetics 32 Classical substrate plot 100 rmax 80 Reaction Rate r max K s r d[ P] rmax[ dt K [ s Substrate Concentration

33 Substrate and growth 33 If we consider Y r d[ P] dt d[ dt 1 Y dx dt U We can define a microorganism-specific substrate utilization rate, U dx dt And the maximum rates are then 1 X d[ dt k[ K [ s + U and r X YX µ µ Y U max k µ Y max 1 d[ X ] µ max[ X dt K + s [

34 Linearizations 34 Lineweaver-Burke Double reciprocal plot Wikipedia version Voet & Voet version

35 35 das

36 3 types 36 Lineweaver Burk Hanes Eadie-Hofstee

37 Compare predictions 37 ad

38 Multi-step k 1 E + S k ES 2 EP 2 2E + P k- 2 1 P 1 k 3 38 Double intermediate Also gives: r d[ P] rmax[ dt K [ s + But now: r max k2k3[ E k + k 2 o 3 ] k K s + ( ) 3 k 1 + k2 ( k ) 2 k 3 k 1 Note what happens when: k 3 >> k 2

39 39 To next lecture