Chp7 DO Sag Curves Streams

7/24/2019 Chp7 DO Sag Curves Streams

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Environmental Modeling

Chapter 7:Dissolved Oxygen Sag Curves in Streams

Copyright 2006 by DBS


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Quote[Mathematics] The handmaiden of the Sciences

-Eric Temple Bell


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Concepts

Introduction Input sources Mathematical Model

Sensitivity analysis Limitations


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Case Study: Any Stream Any!here

Every stream has inputs o"or#anic !aste $ Spreads disease

$ Consumes %& ondecomposition

Ancient communities 'uiltnear "lo!in# !ater

e(#( )* City London+( Europe


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Case Study: Any Stream Any!here

The ,ro'lem: %(&(

B&%Se!a#e treatment 'e#ins

Chemical process:

M&.s consume %&,hysical process:

/e-aeration 'yatmosphere

Meado!s et al ( 0112


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Introduction

Modelin# the e""ects o" release o" o3idi4a'le or#anic matter into a"lo!in# 'ody o" !ater $ %& 5 chemical measurement o" dissolved o3y#en 6m# L -7 8 $ B&% 5 total %& needed to o3idi4e or#anic matter in a !ater sample

5 chan#e "rom initial %& at saturation to amount a"ter 9 days

B&%

time


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Introduction

Standard o" livin# ade;uate !ater and!aste!ater treatment

Human Risks Challen#e o" preventin# rapid spead o" disease

e(#( typhoid "ever 6'acteria8 hepatitis 6viruses8cryptosporidosis 6proto4oa8

/emoved 'y sand "iltration andchlorination778


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The Streeter-,helps E;uation

!ithout trmt:

!ith trmt:

&r#anic matter is o3idi4ed stream re-aerates


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End

/evie!


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Basic Input Sources

,arameters "or S-, e;uation: $ +aste!ater: ?lo! rate temperature %& B&%

B&% measured in la' $ %& measured a"ter several days 6"lat portiono" curve8


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The "ollo!in# material and model iscovered in:

C@EM 911< 991


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Basic Input SourcesSe!a#e Treatment ,lants

/emove tur'idity o3idi4a'le or#anic matter and patho#ens $ Tur'idity $ settlin# tan s and "ilters $ &r#anic matter $ tric lin# "ilters activated slud#e $ ,atho#ens $ "iltration chloination o4onation

"tp:


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Basic Input SourcesSe!a#e Treatment ,lants

,relininary - screenin# o" lar#e materials

,rimary - sedimentation - settlin# tan s

Secondary - 'iolo#ical aeration $ tric lin#"ilters activated slud#e - meta'oli4es and"locculates dissolved or#anics

Tertiary $ e(#( , removal

http:
http://www.waterencyclopedia.com/Tw-Z/Wastewater-Treatment-and-Management.htmlhttp://www.waterencyclopedia.com/Tw-Z/Wastewater-Treatment-and-Management.htmlhttp://www.waterencyclopedia.com/Tw-Z/Wastewater-Treatment-and-Management.html


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Basic Input Sources

+aste!ater Treatment ,lantModel


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Movie

7( +aste!ater Treatment and %ischar#e 6011180( +aste!ater eneration and Collection 601118

( &ur Fr'an Environment: +ater Quality 601118


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End

/evie!


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Mathematical Model

Ta e a river: +hat parameters and processes !ould 'e important indevelopin# a model "or the o3idation o" or#anic !asteG

our model river: dra! in parameters

Fltimate B&% Lo" mi3

Stream %& de"icit

Consumption %& 'y M&.s

/e-aeration 'y atmosphere

Amount %& consumed


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D 5 k .B&%L He3p6-k .6 x


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%& at a #iven distance 'elo! the input:


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k 0. 5 "irst-order rate constant "or re-aeration Eact measurements are di""icult #et "rom ta'les:


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B&%L 5 ultimate B&% or ma3imum & 0 re;uired to o3i4e the!aste sample

%etermined "rom 9 day B&% test or usin# e;uation:

B&%L 5 B&% 97 $ e3p6- k .6 x


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Done o" Clean +ater 6Done 78Done o" %e#radation 6Done 08Done o" Active %ecomposition 6Done 8Done o" /ecovery 6Done 28Done o" Cleaner +ater 6Done 98

Al#ae "un#i proto4oa !ormslar#er planst die

ray


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t c 5 7 ln k 0. 7 $ D16k 0.-k .8

k 0. $ k . k . k . B&%L

and x c 5 vt c

Critical %& concentration Dc:

Dc 5 k . B&%L e3p6- k .6 x c


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,ro'lem

7( %etermine Dc and its location(

0( Estimate the 01 C B&% 9 o" a sample ta en at x c (

( ,lot the curve(

E3ample ,ro'lem: A city dischar#es 09 million #allons per day o" domesticse!a#e into a stream !hose typical rate o" "lo! is 091 cu'ic "eet per second(The velocity o" the stream is appo3imately miles per hour( The temperatureo" the se!a#e is 07 C !hile that o" the stream is 79 C( The 01 C B&% 9 o"the se!a#e is 7=1 m#


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7( %etermine %& in stream 'e"ore dischar#e 65upstream %&8:Saturation conc( at 79 C 5 71(0 m#1 saturated 5 71(0 m#1 5 >(0 m#


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Temperature of mixture: T 5 stream input J se!a#e input $ output e""ect

1 5 6stream "lo!86stream temp(8 J 6se!a#e "lo!86 se!a#e temp8 $ 6mi3 "lo!86mi3 temp81 5 6N70 3 71 N L2(= 3 71 N L


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BOD 5 of mixture:)et chan#e in B&% 9 5 B&%9 5 Stream input J Se!a#e output $ &utput1 5 6stream "lo!86stream B&% 9 8 J 6se!a#e "lo!86se!a#e B&% 9 8 $ 6mi3 "lo!86mi3 B&% 9 81 5 6N70 3 71 N L


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( Correct rate constants to 79(O C

k . 5 1( 267(7 98 79(O-01 5 1(7>O d -7

k 0. 5 1(N967(1028 79(O-01 5 1(9=O d -7

2( %etermine t c and x c:

D1 5 6initial stream & 0 - & 0 o" mi3ture85 6>(0 $ O(>O8 5 7(0 m# & 0 L-7


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2( %etermine t c and x c:

t c 5 7 ln k 0. 7 $ D16k 0.-k .8

k 0. $ k . k . k . B&%L

5 0(20 d

x c 5 vt c 5 mi


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9( %etermine Dc :

P 5 mi


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N( %etermine B&% 9 at critical point x c:

B&%9 5 B&% L e3p6- k .6 x O d -7867O2(0 mi8(1 m# L -7

01 C B&% 9 5 B&% 9 H7 $ e3p6-k .8698

5 7>(1 m# L -7 H7 $ e3p6-1( 2 d -7869 d8 5 79(9 m# L -7

Easier method


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Fse ?ate

Much easier than 'y hand


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End

/evie!


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Sensitivity Analysis


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Limitations

It uses avera#e re-aeration rates o" the stream 6pro'lem in alternatin#ri""le and pool areas8

Sedimentation is not allo!ed in the 'asic model 'ut can 'eincorporated !ith additional e3perimental data


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/emediation

,ro'lems are: -Eutrophication-&dors-Lo!


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End

/evie!


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?urther /eadin#Rournals and /eports +ipple (C( and +ipple M(C( 67>778 Solu'ility o" o3y#en in sea

!ater( Journal of the American Chemical Societ Pol( pp N0(


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Boo s

Craun ( 67>=N8 !ater"orne Diseases in the #nited States ( C/C ,ress Boca /aton ?L( Meado!s %( /anders R( and Meado!s %( 601128 $imits to %ro&th' The ()*+ear #,date (

Chelsea ren ,u'lishin# Compnay +hite /iver Runction PT( Metcal" and Eddy Inc( 67>>78 !aste&ater -n.ineerin. rd Ed( Mc ra!-@ill )e! *or ( Sa!yer C()( and McCarty ,(L( 67>O=8 Chemistr for -nvironmental -n.ineerin. ( Mc ra!-

@ill )e! *or ( Snoeyin P(L( and Ren ins %( 67>=18 !ater Chemistr ( Rohn +iley Sons )e! *or ( Standard Methods for the -xamination of !ater and !aste&ater 01th Ed( 67>>=8 American

+ater!or s Association +ashin#ton %(C( Streeter @(+( and ,helps E(B( 67>098 A Stud of the /ollution and natural /urification of

the 0hio 1iver ( Fnited States ,u'lic @ealth Service F(S( %epartment o" @ealth Educationand +el"are(

Tcho'ano#lous ( and Burton ?(L( 67>>78 !aste&ater -n.ineerin.' Treatment2 Dis,osal2and 1euse ( Mc ra!-@ill )e! *or (

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Chp7 DO Sag Curves Streams