NYC: Cannonsville Case Study CEE 577 #41 2 1 CEE 577 Lecture - - PDF document

CEE 577 Lecture #41 4/17/2013 1 Lecture #41 TOC & THMFP Models II

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CEE 577 #41 1

Updated: 17 April 2013

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NYC: Cannonsville Case Study

CEE 577 #41 2

CEE 577 Lecture #41 4/17/2013 2

 Algal & THM Precursor Models

 Doerr, Stepczuk and others

 Cannonsville Reservoir

 Part of Catskill‐Delaware Supply for NYC  Dimictic; Eutrophic (impounded in 1965)

 Pavg = 30 µg/L

 Characteristics for 1995

 Hydraulics

 Hmean= 19 m  V = 373 x106 m3  mean = 4.7 months  SA = 19.3 x106 m2  DA = 1160 x106 m2

 Loading

 TOC = ? x 102 kg/yr  P = ? x 103 kg/yr CEE 577 #41 3

For more, see the literature at:

https://www.ecs.umass.edu/eve/research/nyc_chloramines/literature.html

Cannonsville Reservoir Study

 Inflow

 West Branch of

Delaware River (WBDR) ~80%  Three outflows

 Over spillway  Withdrawal to aqueduct

 10, 20** or 37 m below

spillway  Release at base of dam

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 Individual models

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 Lower flows in 1995,

resulted in lower loadings

Forcing Functions

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PAR

 Photosynthetically‐

active radiation

 Often defined as the

light between 400 and 700 nm

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SOD

 For

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SOD continued

 In‐situ device

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 Weekly measurement in

water column

 Objective: monthly

average within 2 standard deviations

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Model Performance

Performance II

 Systematic depletions of:

 Epilimnetic NOx  Hypolimnetic DO

 Over‐prediction of

ammonia?

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Performance: DO

 Progressive

depletion of DO in hypolimnion

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Verification

 Problem with limited

data in 1994

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Verification

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Verification

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Performance: Withdrawal

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Cannonsville THMs: General Info

 Major Papers

 Stepczuk, Martin, Longabucco, Bloomfield & Effler, 1998

 “Allochthonous Contributions of THM Precursors in a Eutrophic

Reservoir”, J. Lake & Res. Mgmt., 14(2/3)344‐355  Stepczuk, Martin, Effler, Bloomfield & Auer, 1998

 “Spatial and Temporal Patterns of THM Precursors in a Eutrophic

Reservoir”, J. Lake & Res. Mgmt., 14(2/3)356‐366  Stepczuk, Owens, Effler, Bloomfield & Auer, 1998

 “A Modeling Analysis of THM Precursors for a Eutrophic Reservoir,

• J. Lake & Res. Mgmt., 14(2/3)367‐378

 THMFP Method

 Method 5710B of Standard Methods

 pH 7.0, 7 days, 25 C, dosed to get >1.0 mg/L residual  Average CV was 4% for field replicates CEE 577 #41 19

1995 Data

 Severe Drought  Net production of

precursors in Epilimnion is evident from THMFP data

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Stepczuk et al., 1998, J. Lake & Res. Mgmt., 14(2/3)367-378

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 Terms

 W = allochthonous mass loading



From tributaries  E = mass export by outflow



Spill + release + water supply withdrawal  S = net autochthonous production



Gross production ‐ decay

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Stepczuk et al., 1998, J. Lake & Res. Mgmt., 14(2/3)367-378

S E W M   



E W M S   

• us

allochthon

• us

autochthon

Mass Balance Model: THMFP

Mass Balance Model: DOC

 Mid‐summer drop in S

 Not seen with THMFP

 Lower average S:W ratio

 1.7 for THMFP  0.7 for TOC

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Stepczuk et al., 1998, J. Lake & Res. Mgmt., 14(2/3)367-378

• us

allochthon

• us

autochthon

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Mass Balance Model: S

 Monthly changes in S

 Incremental not cumulative

 No apparent correlation

between net production of THMFP and DOC

 Raises questions about use of

TOC as a surrogate for THMFP

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Stepczuk et al., 1998, J. Lake & Res. Mgmt., 14(2/3)367-378

2‐Layer model

 Spatial resolution

 Epilimnion

 Designated “1” or “E”

 Hypolimnion

 Designated “2” or “H”

 Loading (W)

 Measured stream data

for epilimnion  Outflow (Q)

 Separated based on

withdrawal location  Mixing (E)

 From temperature data

 Net production (S)

 Not directly observed

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Stepczuk et al., 1998, J. Lake & Res. Mgmt., 14(2/3)367-378 2 2 2 1 12 2 2 2 1 2 1 1 1 2 12 1 1 1 1 1

) ( ) ( S V c c E c Q W dt dc V S V c c E c Q W dt dc V            

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Estimation of vertical Dispersion Coefficient

 Use analogous 2‐layer

temperature model

 Apply measured

temperature profiles to get E

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   

V T t E A z T T E T T V z T T tA

t t 2 2 12 12 12 1 2 12 2 1 2 2 12 1 2 12

             

 ( ) ( )

Owens, 1998, J. Lake & Res. Mgmt., 14(2/3)152-161

Fitting S to Data

 Adjust S to match model

predictions to data

 Keep S at zero

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S1 & S2 determined by fitting curves to data S1 & S2 equal to 0

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Select of S (cont.)

 Intermediate option

 Fit S1 to data  Set S2 to zero

 Justification for S2 =0

 No algal growth in

hypolimnion

 Allochthonous THMFP

• riginally trapped in

hypolimnion is recalcitrant

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Stepczuk et al., 1998, J. Lake & Res. Mgmt., 14(2/3)367-378

Mechanistic Model for S

 Sub‐model for algal FP production  Depends on:

 Algal concentration (A)

 from measured Chl (CT)

 Light Function

 From Microcosm studies  Data fit data to Steele’s Equation

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         

L z L z z

K I K I FL 1 exp

 

A FL FN A dt THMFP d

z TTHMFP TTHMFP

) )( (

max

     

Stepczuk et al., 1998, J. Lake & Res. Mgmt., 14(2/3)356-368

day Chl g THMPF g

R





max

5 

 s m E L

K

2

150  

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Mechanistic Model for S

 Sub‐model for degradation of THMFP

 Independent 1st order loss terms for autochthonous and

allochthonous forms

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 

• us

autochthon au L

• us

autochthon

THMFP k dt THMFP d

) (

 

 

• us

allochthon al L

• us

allochthon

THMFP k dt THMFP d

) (

 

Mechanistic Model

 Results based on:

 Two Scenarios

 No decay of any

THMFP in hypolimnion

 No decay of

allochthonous THMFP  Fitted KL values

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Stepczuk et al., 1998, J. Lake &

• Res. Mgmt., 14(2/3)367-378

Epilimnion: kL(al)=kL(au)=0.08d-1 Hypolimnion: kL(al)=kL(au)=0.00d-1 Epilimnion: kL(al)=0.00; kL(au)=0.15d-1 Hypolimnion: kL(al)=0.00; kL(au)=0.15d-1

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2‐Layer model

 Spatial resolution

 Epilimnion

 Designated “1” or “E”

 Hypolimnion

 Designated “2” or “H”

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Stepczuk et al., 1998, J. Lake & Res. Mgmt., 14(2/3)367-378 2 2 2 1 12 2 2 2 1 2 1 1 1 2 12 1 1 1 1 1

) ( ) ( S V c c E c Q W dt dc V S V c c E c Q W dt dc V            

S1 & S2 determined by fitting curves to data

 To next lecture

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