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Chris Castello

Professor Kney

CE 321

11/18/13

Homework #10

1. If the BOD of a municipal wastewater at the end of 7 days is 60 m!" and the

ultimate BOD is $.0 m!"% what is the rate constant&

Known: BOD7= 60 !/" BOD#=8$ !/"

60 !/" = 8$ !/"%1&e'&()7*ays+ k' 0.17$ day(1

). *ssumin that the data in +ro,lem 1 were taken at )$o-% compute the rate constantat 16o-.

Known: ,=16oC ( 2$=0-17$ *ays&1

0-17$ *ays&1= ( 20)1-0$6'%2$&20+ ( 20=0-133 *ay&1

( 16=0-133)1-13$'%16&20+ k 16'0.001 day(1

. * sample of municipal sewae is diluted to 1/ ,y olume prior to runnin a BOD$ 

analysis. *fter $ days the oyen consumption is determined to ,e ).00 m!".2hat is the BOD$ of the sewae&

Known: O.y!en onstion=$ !/" ale *ilte* to 1 4ole

2 !/" / -01 = )00 m!"

3. If the BOD$ alues for two liestock wastes hain k  alues of 0.00 day(1 and 0.)30

day(1 are 16)0.0 m!"% what would ,e the ultimate BOD for each&

Known: ( 1=0-38 *ay1 ( 2=0-250 *ay

1 BOD$=16230 !/"

"i4esto( 1= 16230 !/"= "0)%1&e'%&0-38*ay&1)$ *ays+ "0'BOD41'1503.3 m!"

"i4esto( 2= 16230 !/"= "0)%1&e'%&0-25 *ay&1)$ *ays+ "0'BOD4)')))$. m!"

$. * wastewater has a fie(day BOD eual to )10 m!" test performed at )0o-8 and an

ultimate BOD of $0 m!". 9ind the fie(day BOD at )$o-.

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Known: BOD$= 210 !/l at 20 C "0=3$0 !/" at 2$ C

210 !/" = 3$0 !/" ) %1&e'%&( )$+ ( 20= 0-183 *ay&1

( 2$=-183)1-0$6'%2$&20+=-250 *ay&1

BOD$ at 2$ *e!rees C= 3$0 !/" )%1&e'&-25 ) $+= )33.$ m!"

6. In a standard fie(day BOD test%

a. 2hy is the BOD ,ottle stoppered&

,he BOD test ottle is stoere* to ensre that the syste is lose*-

,. 2hy is the test run in the dark or in a ,lack ,ottle8&

,he test rn is *one in the *ar( or in a la( ottle to ensre there is no snli!ht

!ettin! into the ottle- ,his is to a(e sre or!ani aterials ant !row-

c. 2hy is it usually necessary to dilute the sample&

,he o.y!en *ean*e* fro the or!aniss is in the *issol4e* water- ,he

a.i o.y!en that an *issol4e is !/"- ,his eans BOD sales nee* to

 e *ilte* to 2&7 !/"-

d. 2hy is it sometimes necessary to seed the sample&9t is neessary to ro4i*e iro&or!aniss to o.i*ie or!ani atter-

e. 2hy isn:t ultimate BOD measured&

;easrin! ltiate BOD wol* ta(e too h tie as the r4e e!ins to flatten

ot shortly after $ *ays-

f. 2hat concentration of DO would you suest as a startin concentration&

!/" is the s!!este* initial *issol4e* o.y!en-

7. *ssumin 0.1 m; of lutamic acid -$H5O3

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BOD$= % !/" @ 6 !/"+/ %10"/300"+= 0 !/"

"0= % !/" @ 3 !/"+ / %10" /300"+ = 180 !/"

0 !/"= 180 !/" ) %1&e'&( )$ *ays+ (=-13 *ay &1

BOD10= 180 !/" ) %1&e'&-13 *ay&1 ) 10 *ays+ = 1$.17 m!"

5. =he followin fiure shows a plot of BOD remainin ersus time for a sample of theeffluent taken from a wastewater treatment plant.

a. 2hat is the ultimate BOD "o8&

"0=30 m!" - 2hat is the fie(day BOD&

BOD$= 50 ( 1$ !/" = )$ m!"2hat is "t for 7 days& 

10 m!"

10. If the BOD$ for some wastewater is )00

m!" and the ultimate BOD is 00 m!"%find the reaction rate constant k ,ase e8 and > ,ase 108.

Known: BOD$= 200 !/" "0= 300 !/"

200 !/" = 300 !/" ) %1&e'%&( ) $ *ays+ k' 0.)) day(1

200 /" = 300 !/" ) %1&10'%&K ) $ *ays+ >' 0.05$ day(1

11. ?uppose a wastewater has a BOD$ eual to 10 m!" and a reaction rate k8 eual to

0.))!day.

a 9ind the ultimate car,onaceous oyen demand -BOD8.

180 !/"= "0 %1&e'%&0-22 *ay&1

 ) $ *ays++ "0')65. m!", 9ind the remainin BOD after fie days hae elapsed.

26-8 !/" @ 180 !/" = 5. m!"

1). @lutamic acid -$H5O3

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14!.9 mg/L + !5.32 mg/L 212.12 mg/L O2= THOD

13. 10.0 ml sample of wastewater with enouh water to fill a 00 ml ,ottle has an

initial DO of 5.0 m!". =o help assure an accurate test% it is desira,le to hae at leasta ).0 m!" drop in DO durin the fie day run% and the final DO should ,e at least )

m!". 9or what rane of BOD$ would this dilution produce the desired results.

*ssume this test to ,e a fie(day% unseeded BOD test.

Known: 10" saleA 300 " ottleA DO i= !/" DOf = 2A7 !/"

BOD$= % !/" @ 2 !/"+ / %10"/300"+= 210 !/"BOD$= % !/" @ 7 !/"+ / %10"/300"+= 60 !/"

ane' 60 m!" to )10 m!"

14. A water sample is diluted by a factr f 1! usi"g seededdilution water . Dissl#ed $yge" c"ce"trati" is measured at1%d i"ter#als& a"d t'e results are listed belw. (si"g t'esedata& determi"e t'e )OD as a fu"cti" f time& i.e.& calculatet'e )OD fr eac' day.

"#o$#% &ilutio# 'acto !.1um, 300 mL ottl, 30 mL aml,

f= see* in *ilte* sale/ see* water in ontrol sale= 0 / 100 = 0.5Day 1= %8-$$&5-3$+&f %8-7$&8-70+ / -1 = 55-$$ !/"

Day 2=%8-$$&5-0$+&f %8-7$&8-66+ / -1= 55-1 !/"Day 3=%8-$$&3-3$+&f %8-7$&8-61+ / -1= $0-75 !/"

Day 5=%8-$$&2-7$+&f %8-7$&8-$7+ / -1= $6-38 !/"

Day $=%8-$$&2-50+&f %8-7$&8-$3+ / -1=$-$2 !/"Day 6=%8-$$&2-10+&f %8-7$&8-5+ / -1= 62-16 !/"

Day 7=%8-$$&1-8$+&f %8-7$&8-56+ / -1= 65-3 !/"