[PDF] - CEE 697K ENVIRONMENTAL REACTION KINETICS Lecture #18 Chloramines PDF Document

SLIDE 1

11/13/2013 1

CEE 697K

ENVIRONMENTAL REACTION KINETICS

Introduction

David A. Reckhow

CEE 679 Kinetics Lecture #18 1

Updated: 13 November 2013

Print version

Lecture #18

Chloramines with Surface Reactions: Pipe walls & degradation in Distribution Systems Primary Literature

H2O H2O

NH3

NCl3 NH2Cl HOCl NOH NHCl2

H2O H2O 2H2O

1/2 NO3

2HCl + 1/2 H+

N2

H2O + HCl HOCl + HCl HCl 2HOCl + 3HCl

NH3

Breakpoint Reactions

Stable Oxidation Products FRC CRC

David A. Reckhow

CEE 679 Kinetics Lecture #18

2

SLIDE 2

11/13/2013 2

Statistics

David A. Reckhow

CEE 679 Kinetics Lecture #18

3

 Error types  Analytical measurements  Constant vs. proportional vs in-between  Experimental conditions  e.g., pH, temperature  Model error  Need for homoskedasticity  Use best transformation (or none at all)  Use log for data with errors directly proportional to concentration  No transform for data with constant error  Use data weighting for other error distributions  Plot residuals to determine heteroskedasticity

David A. Reckhow

CEE 679 Kinetics Lecture #18

4

SLIDE 3

11/13/2013 3

Kinetic Spectrum Analysis

David A. Reckhow

CEE 679 Kinetics Lecture #18

5

 For mixtures of many closely related compounds  A new continuum of rate constants  E.g., NOM

 Kinetic: Shuman model  Equilibria: Perdue model

 Very general, but highly subject to errors



 



n i t k i t

i

e C C

1

] [ ] [

Seasonal Variability & Biodegradation

6

 Chen & Weisel study  JAWWA, April 1998  Intensive study of Elizabethtown, NJ system  125 MGD conventional plant  4.9 mg/L DOC (raw water average)  pH 7.2

David A. Reckhow

CEE 679 Kinetics Lecture #18

SLIDE 4

11/13/2013 4

Elizabethtown, NJ: THMs

7

David A. Reckhow

CEE 679 Kinetics Lecture #18

Elizabethtown, NJ: TCAA

8

David A. Reckhow

CEE 679 Kinetics Lecture #18

SLIDE 5

11/13/2013 5

HAA Degradation

9

 Biodegradation:

dihaloacetic acids degrade more readily than

trihaloacetic acids

On BAC

 MHAA>DHAA>THAA  Wu & Xie, 2005 [JAWWA 97:11:94]

In distribution systems

 DHAA>MHAA>THAA  Many studies

David A. Reckhow

CEE 679 Kinetics Lecture #18

Degradation in Dist. Systems

10

Town Hall; Norwood, MA

Date

1 / 1 / 1 9 9 9 1 / 1 / 2 1 / 1 / 2 1 1 / 1 / 2 2 1 / 1 / 2 3 1 / 1 / 2 4 1 / 1 / 2 5 1 / 1 / 2 6

Concentration (g/L)

20 40 60 80 100 120 TTHM HAA5

Pier 1; Norwood, MA

Date

1 / 1 / 1 9 9 9 1 / 1 / 2 1 / 1 / 2 1 1 / 1 / 2 2 1 / 1 / 2 3 1 / 1 / 2 4 1 / 1 / 2 5 1 / 1 / 2 6

Concentration (g/L)

20 40 60 80 100 120 TTHM HAA5

Example: Norwood, MA

David A. Reckhow

CEE 679 Kinetics Lecture #18

SLIDE 6

11/13/2013 6

Degradation of HAAs

11

 Norwood, MA example

Percentile

20 40 60 80 100

HAA/THM Ratio (g/g)

0.0 0.2 0.4 0.6 0.8 1.0 1.2 Town Hall Pier 1 No Degradation Degradation David A. Reckhow

CEE 679 Kinetics Lecture #18

Why the loss of HAAs?

 Homogeneous Chemical Decomposition ?  Decarboxylation  What is half-life

 Is it too slow to be very important?

 Dehalogenation

 Probably too slow for chlorinated HAAs  Reaction with reduced pipe materials?

 Abiotic reductive dehalogenation not likely either,

especially for DCAA

 Biodegradation?

12

David A. Reckhow

CEE 679 Kinetics Lecture #18

SLIDE 7

11/13/2013 7

A few recent studies

David A. Reckhow

CEE 679 Kinetics Lecture #18

13

 Modeling HAA Biodegradation in Biofilters and

Distribution Systems

 Alina S. Grigorescu and Ray Hozalski, University of

Minnesota at Minneapolis

Journal AWWA, July 2010, 102(7)67-80

Background conclusion?

 “Thus aerobic biodegradation is believed to be the

dominant HAA degradation process in ….…..water distribution systems”

 Citing: Tung & Xie, 2009; Zhang et al., 2009a; 2009b;

Bayless & Andrews, 2008

David A. Reckhow

14

CEE 679 Kinetics Lecture #18

SLIDE 8

11/13/2013 8

Objective/hypothesis

 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

f physical parameters (e.g., fluid velocity) and biological

parameters (e.g., biodegradation kinetics, biomass density) on HAA removal”

David A. Reckhow

15

CEE 679 Kinetics Lecture #18

Transport Model

 Loss of HAAs in a pipe  One dimensional plug flow  Overall rate is a combination of rate of

biodegradation (kra) and mass transfer (kma)

 

U x

verall

k

e C C





ra ma

k k

verall

k

1 1

1  

David A. Reckhow

16

CEE 679 Kinetics Lecture #18

SLIDE 9

11/13/2013 9

Biodegradation model

 Monod model  Simplified for low C

C K kXC dt dC

M 

  XC k XC K k dt dC

r M

   

David A. Reckhow

17

CEE 679 Kinetics Lecture #18

Biodegradation model II

 Biodegradation rate (kra; in day-1) is the pseudo-

first order biodegradation rate constant (kr; in L/day/µg-protein) times the biofilm density (X; in µg-protein/cm2) and the specific surface area (a; in m-1)

   

L m cm r L m cm r ra

d X k Xa k k

2 2

10 10

4  

Where d is the pipe diameter in meters

David A. Reckhow

18

CEE 679 Kinetics Lecture #18

SLIDE 10

11/13/2013 10

David A. Reckhow

19

CEE 679 Kinetics Lecture #18

Mass Transfer Model I

 Mass transfer constant (kma) is the mass transfer velocity (km;

m/s) times the specific surface area; and km is related to the Sherwood number

 combining  Linton & Sherwood (1950) found the following correlation for

flow in pipes (fn(Reynolds and Schmidt numbers)):

2

4 d ShD a d ShD a k k

w w m ma

  

33 . 83 .

Re 023 . Sc Sh 

David A. Reckhow

20

CEE 679 Kinetics Lecture #18

d ShD k

w m 

a k k

m ma 

Compare to equ 7.126 in Clark Eq 7.164 in Clark

SLIDE 11

11/13/2013 11

Mass Transfer Model II

 The Schmidt number is the ratio of mass to viscous diffusion

timescales, and calculated from the viscosity, the density and the diffusion coefficient:

 And the Reynolds number can be calculated from the pipe

diameter, velocity, density and viscosity:

w w w

D Sc   

w w

du    Re

David A. Reckhow

21

CEE 679 Kinetics Lecture #18

Compare to equ 7.82 in Clark

Model Predictions

David A. Reckhow

 “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 > 105 cells/cm2 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

n pipe walls”

But this seems to contradict their introductory conclusion – how to reconcile?

David A. Reckhow

27

CEE 679 Kinetics Lecture #18 CEE 679 Kinetics Lecture #18

What could they have concluded?

 Variability vs diurnal demand

5 10 15 20 25 30 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 Q/Qavg u (ft/s) t (hr) C (ug/L) David A. Reckhow

28

SLIDE 15

11/13/2013 15

Objective/hypothesis

 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

f physical parameters (e.g., fluid velocity) and biological

parameters (e.g., biodegradation kinetics, biomass density) on HAA removal”

David A. Reckhow

29

CEE 679 Kinetics Lecture #18

What could they have said?

 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

f biodegradation in distribution systems

David A. Reckhow

30

CEE 679 Kinetics Lecture #18

SLIDE 16

11/13/2013 16

What could they have done?

 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?

David A. Reckhow

31

CEE 679 Kinetics Lecture #18

What else?

 Consider mass

transfer resistance within biofilm

David A. Reckhow

32

CEE 679 Kinetics Lecture #18

SLIDE 17

11/13/2013 17

What should be done next?

 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

David A. Reckhow

33

CEE 679 Kinetics Lecture #18

SANCHO Model

 B1: biologically fixed bacteria  B2: adsorbed bacteria 34

B1 B2 H1

H2

S CO2

Cl2 Mortality

B3

Cl2 Cl2

Mortality

BDOC

Fixed Bacteria

Free Bacteria

Input (H1, H2, B3) Output Internal Processes

David A. Reckhow

CEE 679 Kinetics Lecture #18

SLIDE 18

11/13/2013 18

David A. Reckhow

35

CEE 679 Kinetics Lecture #18

David A. Reckhow

36

CEE 679 Kinetics Lecture #18

SLIDE 19

11/13/2013 19

David A. Reckhow

37

CEE 679 Kinetics Lecture #18

Effect of Zn on HAAs

David A. Reckhow

CEE 679 Kinetics Lecture #18

38

 Effect of Zinc on the Transformation of HAAs in

Drinking Water

 Wei Wang and Lizhong Zhu  Journal of Hazardous Materials 174:40-46.

SLIDE 20

11/13/2013 20

David A. Reckhow

CEE 679 Kinetics Lecture #18

39

 To next lecture