Organic Compounds in Water and Wastewater PCBs: Introduction and - - PowerPoint PPT Presentation

CEE 697z

Organic Compounds in Water and Wastewater

PCBs: Introduction and Properties

CEE 697z - Lecture #34

Print version

Lecture #34

PCBs in the Lake Superior

 Reference: Jeremiason, Hornbuckle and Eisenreich, Environmental Science and

T echnology, 28:903 (1994)

CEE 697z - Lecture #34

• St. Mary’s

River

Empirical Models

 Data tell us that about 26,500 kg has been lost from

the water column between 1980 and 1992

CEE 697z - Lecture #34

( )

PCB PCB e

• t

= ∑

∑

− 25 0 20 25 .

( )

PCB PCB e

• t

= ∑

∑

− 82 0 22 82 .

Loss rates depend on specific congener

• 0.6
• 0.5
• 0.4
• 0.3
• 0.2
• 0.1

4.5 5 5.5 6 6.5 7 7.5 Log Kow k (/yr) k (yr-1) k-regr.

CEE 697z - Lecture #34

Good correlation with Kow

Sorption

 Definitions  dissolved to particulate

equilibrium

CEE 697z - Lecture #34

p d

c c → ←

'

Particle

m ku K

cd

' ≡ dissolved toxicant

c p ≡ particulate toxicant

and: c

c

d d

= φ

'

so: c

c c

T p d

= +

Langmuir Isotherm

 At Equilibrium

 Rate of adsorption = rate of desorption

 So, solving for the sorbed concentration (ν)

CEE 697z - Lecture #34

( )

ν ν ν

s de m d s ad de ad

M k c M k R R = − =

d k k d m

c c

ad de +

= ν ν

Limiting Cases

 When Cd is small, and there are lots of surface sites

 Common situation for trace “toxics” like PCBs  So the bulk particulate concentration is:  And the total toxicant is:

CEE 697z - Lecture #34

d de ad m k k d m d k k d m

c k k c c c

ad de ad de

ν ν ν ν = ≈ + =

d dc

K = ν

d d p

c mK m c = = ν

d d d p d T

c mK c c c c + = + =

Toxics: Linear sorption modeling

 Now define  adsorption model

CEE 697z - Lecture #34

T d d

c f c =

T p p

c f c =

m K f

d d

+ = 1 1

m K m K f

d d p

+ = 1

1 = +

p d

f f

d d d d T d d

c mK c c c c f + = ≡

Estimation of partition coefficients

 Relationship to organic fraction  and properties of organic fraction  combining, we get:

CEE 697z - Lecture #34

• c
• c

d

K f K =

• w
• c

K x K

7

10 17 . 6

−

=

Octanol:water partition coefficient

• w
• c

d

K f x K

7

10 17 . 6

−

=

Karickhoff et al., 1979; Wat. Res. 13:241

        −           − − − C g m

• r

m tox mg C g tox mg

3 3

. .             − − − − O H m tox mg Oct m tox mg

2 3 3

. . .

m K f

d d

+ = 1 1

Octanol:water partitioning

 2 liquid phases in a separatory funnel

that don’t mix

 octanol  water

 Add contaminant to flask  Shake and allow contaminant to reach

equilibrium between the two

 Measure concentration in each (Kow is

the ratio)

CEE 697z - Lecture #34

Observations

 Summary of Kow and

TSS effects

 From Chapra, pg. 722

CEE 697z - Lecture #34

Box and Whisker Plots

 Useful for summarizing non-ideal data distributions

CEE 697z - Lecture #34

x Thickness is proportional to the square root of the number of

• bservations

Median Lower data range Upper data range

• utlier

Upper quartile Lower quartile

CEE 697z - Lecture #34

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