[PDF] - Nitrogen (Chapra L23) Nitrification/Denitrification nitrification: PDF Document

SLIDE 1

CEE 577 Lecture #18 10/30/2017 1

Lecture #18 Streeter‐Phelps: Distributed Sources & Nitrogen

(Chapra, L22 & L23)

David Reckhow CEE 577 #18 1

Print version

Updated: 30 October 2017

Nitrogen (Chapra L23)

 Nitrification/Denitrification

 nitrification: oxygen consuming  denitrification: anaerobic, form N2

 Eutrophication

 stimulates plant growth

 Nitrate pollution

 from fertilizers and nitrification

 Ammonia toxicity (NH3 form)

David Reckhow CEE 577 #18 2

SLIDE 2

CEE 577 Lecture #18 10/30/2017 2

Nitrogen Cycle

David Reckhow CEE 577 #18 3

Atmospheric N Organic N (plants) Organic N (animals) N in sediments

r soils

Aqueous N Decomposition

Nitrification/Denitrification

David Reckhow CEE 577 #18 4

Nitrification: will satisfy NBOD and NH3 toxicity

NH O NO H O H

Nitrosomonas 4 3 2 2 2 2

2

  

      

NO O NO

Nitrobacter 2 1 2 2 3  

    

Can be combined with traditional activated sludge so that NBOD is removed along with CBOD; occurs naturally in surface waters

Denitrification: will remove nitrate, nutrient control

NO N CO H O

3 2 2 2  

   

rganic

Requires an anaerobic environment

SLIDE 3

CEE 577 Lecture #18 10/30/2017 3

Modeling Nitrification

David Reckhow CEE 577 #18 5

 

L L e S k e

N N o k t D n k t

n n

  

 

1

Point Distributed

LN = 4.57*TKN

In‐class problem I

 A poorly treated municipal wastewater is discharged into

Evergreen Brook at milepoint zero. In addition there is a continuous discharge of soluble BOD from a series of hog farms extending from milepoint zero to mile 25.

 The WWTP discharges sufficient BOD such that there is 12

mg/L BOD at the point of mixing, 30% of which is particulate

 The hog farms release 5 g‐BOD/d for every foot of stream

length

 The stream can be considered to have a uniform depth of 4 ft,

a width of 22 ft and a rocky bottom. Velocity is 3 mi/d.

 Assume a BOD settling rate of 1.2 d‐1

 What is the BOD concentration 10 miles downstream and

how much originates from each source (WWTP vs hog farm)?

David Reckhow CEE 577 #18 6

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CEE 577 Lecture #18 10/30/2017 4

In‐class problem II

 First determine distributed loading term  Next estimate deoxygenation rate  Then formulate BOD model

David Reckhow CEE 577 #18 7

 



d L mg ft ft H S A S S

L ft d ft g d c d d

    



. 2 22 4 5

3 . 28 1 ' ' '

3 1 434 . 434 .

405 . 8 4 3 . 8

  

               d H C kd

 

U x U x U x r r

e e e e k S e L L

t k r D t k

405

. 405 . 605 . 1

1 405 . 2 ) 7 . ( 12 ) 3 . ( 12 1

    

      

deoxygenation only, no settling

In‐class problem II

David Reckhow CEE 577 #18 8

Distance Downstream (miles)

5 10 15 20 25

BOD (mg/L)

2 4 6 8 10 12 14 Dissolved Point Source Dissolved Distributed Source Particulate

 5.86 mg/L @10 mi

 2.19 mg/L from WWTP  3.67 mg/L from hog farms  Essentially all is dissolved

SLIDE 5

CEE 577 Lecture #18 10/30/2017 5

Full Equation

David Reckhow CEE 577 #18 9

       

 

  

 



t k t k n a n Nd n t k a n Nd n t k t k r a r d d t k a r d d t k a B t k t k n a No n t k t k r a

d

t k

a

n a a r a a a n a r a

e e k k k S k e k k S k e e k k k S k e k k S k e k H S R P e e k k L k e e k k L k e D D

           

                            1 1 1

'

Point NBOD Distributed NBOD

Sample Problem (T&M, pg.309)

 Problem

 Determine the maximum allowable ultimate oxygen

demand (UOD) in the effluent entering the stream if the DO concentration is to equal or exceed 5 mg/L. Assume the effluent DO is equal to the stream’s DO saturation concentration.

David Reckhow CEE 577 #18 10

Qe = 4 MGD CBOD5 = 30 mg/L, f=2.0 NH3-N = 10 mg/L Qu = 20 cfs cu = cs Lu = Nu = 0 ka = 0.80/d @ 20oC kr=kd= 0.40/d @ 28oC kN = 0.40/d @ 28oC

SLIDE 6

CEE 577 Lecture #18 10/30/2017 6

Problem (cont.)

 Analysis of existing conditions

 Loading

 BOD and NBOD may be treated as one UOD load since the

decay rates are the same in the stream. Assume only the ammonia is significant in the NBOD.

David Reckhow CEE 577 #18 11

 

L mg x x N NH x fxCBOD L mg UOD / 7 . 105 10 57 . 4 30 . 2 57 . 4 ) / (

3 5

     

d lb x MGDx UOD W

L mg

/ 3530 34 . 8 7 . 105 4 ) (      

L mg e u

cfs

cfs d lb Q Q UOD W L . 25 4 . 5 548 . 1 4 20 / 3530 ) (     

Problem (cont.)

 Adjust Reaction rates to ambient temp.  Determine tcrit

David Reckhow CEE 577 #18 12

 

C d x C k k

T
a

a

28 @ 97 . 024 . 1 8 . ) 20 (

1 ) 20 28 ( 20   

   

 

d

1

L k k k D k k k

k

1 = t

d

r a

r

a r a crit

55 . 1 . 25 40 . 40 . 97 . ( 1 40 . 97 . ln 40 . 97 . ( 1 ln                                  

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CEE 577 Lecture #18 10/30/2017 7

Problem (cont.)

 Then get xcrit  And cs is:

 accounting for temp. & altitude

 Finally the cmin is:

David Reckhow CEE 577 #18 13

 

mi d fps Ut x

fps mpd

7 . 12 55 . 1 5 .

4 . 16

  

L mg t k a d

s

e e k k L c c

crit r

64 . 97 . 40 . . 25 19 . 6

) 55 . 1 ( 40 . min

    

 

L mg s

c 19 . 6 

Problem (end)

 Determine allowable load, if WQC require 5.0

mg/L minimum D.O.

 Recognize that the loading:deficit relationship is

linear

 so determine allowable L

David Reckhow CEE 577 #18 14 crit rt

k a d

s

crit

e k k L c c D



  

min

Also, tcrit is independent of L when Do=0

L mg crit

allowable

crit allowable

allowable
allowable

crit

crit

D L D L L D L D 23 55 . 5 ) 7 . 105 ( 19 . 1

) ( ) ( ) ( ) (

   

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CEE 577 Lecture #18 10/30/2017 8

Additional notes on WLA

 Selecting a model

 number of dimensions

 usually 1, major gradients are longitudinal, very minor

gradients in lateral and vertical directions

 sometimes 2, deep rivers or river‐run impoundments; use

should be justified

 never 3, except research and a few extraordinary cases

David Reckhow CEE 577 #18 15

Not from Chapra

Additional notes on WLA (cont.)

 Loads, sources & sinks

 Categorize

 category I ‐ major sources controlling water quality

 thorough data collection ‐ temporal variation

 category II ‐ background sources

 small to moderate data collection

 necessary data

 long‐term BOD,with nitrification inhibition  analysis of all forms of nitrogen

 org‐N, NH3, NO2, NO3 David Reckhow CEE 577 #18 16

SLIDE 9

CEE 577 Lecture #18 10/30/2017 9

Additional notes on WLA (cont.)

 Time scale

 steady state  quasi‐steady state

 const. loads, constant Q, diurnal DO variations due to

photosynthesis

 const. loads, variable Q  variable loads, constant

Q

 others

 Fully time‐variable analysis

David Reckhow CEE 577 #18 17

Additional notes on WLA (cont.)

 Design Conditions

 7Q10 ‐ summer

 generally endorsed by USEPA

 Spring Floods ‐ large event

 storm intensity, sequences, recessional hydrograph

 Ice cover ‐ winter

 Spatial Extent

 well into the zone of recovery

David Reckhow CEE 577 #18 18

SLIDE 10

CEE 577 Lecture #18 10/30/2017 10

Additional notes on WLA (cont.)

 Dispersion (is it significant?)

 calculate E

 from slope  from dye studies

 calculate dimensionless estuary #  use Chapra’s criteria

 n<0.1, advection predominates  n>10, diffusion predominates

 or calculate reaeration/deoxygenation ratio & use

O’Connor figure

David Reckhow CEE 577 #18 19

E x UB HU 



3 4 10 5

2

.

*

U gHS

* 

mi2/d ft ft/s ft

n k E U

d



2

  k k

a d

 Figure prepared by O’Connor  From: Technical Guidance Manual for Performing Waste Load Allocations: Book II, Chapter 1

David Reckhow CEE 577 #18 20

SLIDE 11

CEE 577 Lecture #18 10/30/2017 11

Full Equation

David Reckhow CEE 577 #18 21

       

 

  

 



t k t k n a n Nd n t k a n Nd n t k t k r a r d d t k a r d d t k a B t k t k n a No n t k t k r a

d

t k

a

n a a r a a a n a r a

e e k k k S k e k k S k e e k k k S k e k k S k e k H S R P e e k k L k e e k k L k e D D

           

                            1 1 1

'

Point NBOD Distributed NBOD

Additional notes on WLA (cont.)

 Nitrogen modeling

 NBOD

 measure and model TKN only

 all 4 major species

 org‐N, NH3, NO2, and NO3  requires separate analysis of loadings, rate coefficients, etc.

David Reckhow CEE 577 #18 22

SLIDE 12

CEE 577 Lecture #18 10/30/2017 12

General Model Kinetics

David Reckhow CEE 577 #18 23

Dissolved Oxygen CBOD CBOD

K1 K3

Atmosphere

K2

NBOD

KN1

SOD

K4

General Model Kinetics with N species

David Reckhow CEE 577 #18 24

Dissolved Oxygen CBOD CBOD

K1 K3

Atmosphere

K2

Organic N

3

SOD

K4

NH3 NO2 NO3



1

2  

5 1

4 3  

6 2

 

6 2

SLIDE 13

CEE 577 Lecture #18 10/30/2017 13

Additional notes on WLA (cont.)

 Algal modeling

 Level I

 measure P‐R: diurnal swings in D.O.

 Level II

 measure chlorophyll a, light, light extinction, nutrients

“in‐situ”

 calculate P‐R

 Level III

 assess nutrient loadings, light extinction  model nutrient conc., chlorophyll a, P‐R

David Reckhow CEE 577 #18 25

General Model Kinetics with algae

David Reckhow CEE 577 #21 26

Dissolved Oxygen CBOD CBOD

K1 K3

Atmosphere

K2

Organic N

3

SOD

K4

NH3 NO2 NO3



1

2  

5 1

4 3

(Ks) (Ka) (Kd) Chlorophyll a

(Algae)

Org-P Diss-P

 

1 F

 

1

1 ( )  F

 

1

 

1

 

2

 

2

 

3

 

4

4

5 2

1

2 6



SLIDE 14

CEE 577 Lecture #18 10/30/2017 14  To next lecture

David Reckhow CEE 577 #18 27