Chapter 2 Environmental slide

8/13/2019 Chapter 2 Environmental slide

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WATER & WASTEWASTER QUALITYMANAGEMENT


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Water and Wastewater Quality

Parameters Physical parameters

Chemical parameters

Biological parameters


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Water Quality Parameters

Physical Chemical Biological

Suspendedsolid

Temperature

Turbidity

Odor and taste

TDS

Alkalinity

HardnessOrganiccompounds

Inorganiccompounds Nutrient

Nitrogen Phosphorus

PathogenOrganisms

IndicatorOrganisms


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PHYSICAL PARAMETERS1 - Total Suspended Solids (TSS)

Consists of inorganic or organic particles or immiscibleliquids. Inorganic clay, silt, soil Organic plant fibers, biological solids (bacteria, etc)

Immiscible liquids oils and greases

Impact: unpleasant smell & may cause disease


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Total Suspended Solids (TSS)

Measurement:

By filtration Water sample is filtered

through a glass fiber filter.

The filtrate is dried usingtemperature at 180OC(TDS) filterable residues.

The residue on the filter isdried at 103 105OC (TSS)nonfilterable residues


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ExampleDetermining the concentration of suspended solid:

A filterable residue analysis is run on a sample of

water as follows. Prior to filtering, the crucible andfilter pad are kept overnight in the drying oven,cooled, and the dry mass (tare mass) of the pairdetermined to be 54.352 g. 250 mL of the sample is

drawn through a filter pad contained in the porous-bottom crucible. The crucible and filter pad are thenplaced in a drying oven at 104C and dried until aconstant mass of 54.389 g is reached. Determine the

suspended solids concentration of the sample.


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Solution1.Mass of solids removed

2.Concentration of the solidsgsolidsofmass

gmassTare

gsolidsmassTare

037.0

352.54

389.54

Lmg

LmginconcsampleofmL

LmLsolidsmg

/148250100037

//1000


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2-Turbidity For potable water supplies measurement Is caused by suspended substances in the water such as

clay, silt, fine organic materials, planktons etc Turbidity is a measure of the extent to which light is

either absorbed or scattered by suspended material inwater.

Impact-Give unpleasant apparent, interfere lightpenetration

Turbidity measurement is an optical measurement -suspended matter disperse light.

Unit NTU (nephelometry turbidity units)


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BKC 3543 ENVIRONMENTAL ENGINEERING


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water quality samples ranging from 25 NTU on the leftthrough 2000 NTU on the far right.


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3. Color

Pure water is colorless

However, dissolved solids will affect the color truecolor

Yellowish-brown : leaves, weeds, wood; reddish : iron;

Not aesthetically acceptable

Measurement: by spectrophotometer


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4. Taste and Odor

Many mineral substances that produce taste but no

odor Inorganic: taste (no odor)

Organic : taste + odor

Minerals, metals, salts, biological reactions and

constituents of wastewaterAesthetically displeasing


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5. Temperature

Temperature of surface waters governs to a large extent

the biological species present and their rates of activity Effect chemical reaction

At lower temp the rate of biological activity is slower,temp increased, biological activity increases


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CHEMICAL PARAMETERS1. Total Dissolved Solids (TDS)

Dissolved substance may be organic or inorganic(minerals, metals and gases)

Produce aesthetically displeasing color, taste, odorand might be carcinogenic

Ions balance common ions (summed in equivalentbasis) to represents approximateTDS

Anions = cations


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Example 2-5: Tests for common ions are run on a sample of water and the resultsare shown below. If a 10% error in the balance is acceptable, should the analysisbe considered complete?

LmgClLmgNa

LmgSOLmgMg

LmgHCOLmgCa

tsConstituen

/89/98

/60/18

/250/55

2

2

4

2

3

2


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Solution:

valence

gmassmolecularoratomicmassequivalentwhere

massequivalentLmgionionconcentrat

Lmeq

:

1

Component Mg/L Equivalent mass Meq/L

Ca2+ 55 20.0 2.75

Mg2+ 18 12.2 1.48

Na+ 98 23.0 4.26

Total cations 8.49

HCO3- 250 61.0 4.10

SO42- 60 48.0 1.25

Cl- 89 35.5 2.51

Total anions 7.86


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Calculate percent of error

2.

analysisaccept

%10%8

%810086.7

86.749.8

Ca2+ Mg2+ Na+

HCO3

- SO4

2- Cl-

Meq/L

Meq/L 0

0 2.75

4.10

4.23

5.23 7.86

8.49


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2. Alkalinity Defined as the quantity of ions in water that will react to

neutralize hydrogen ions (neutralize acids) CO

3

2- (carbonate), HCO3

-(bicarbonate), OH-(hydroxide), HS-.

Resultant from dissolution of mineral substances in soil andatmosphere

Originate from CO2, a constituent of the atmosphere and aproduct of microbial decomposition of organic material

hydroxideOHHCOOHCO

carbonateCOHHCO

ebicarbonatHCOHCOH

acidcarbonicandCOdissolvedCOHOHCO

32

2

3

2

33

332

23222


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Utilization of the bicarbonate ion as a carbon source byalgae can drive the reaction to the right (carbonate) andresult in substantial of OH-

Heavy algal growths often has high pH values (9 to 10) Imparts a bitter taste

Reaction between alkaline constituent and cation (+veion) produces precipitation in pipe


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Measure by titrating water with an acid and

determining the hydrogen equivalentAlkalinity expressed as mg/L of CaCO3.

Eg : 0.02 N H2SO4is used, 1mL of acid will

neutralize 1 mg of alkalinity as CaCO3 H+from the acid react with the alkalinity

according equations

323

3

2

3

2

COHHHCO

HCOHCO

OHOHH


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3. Hardness Concentration of multivalent metallic cations in

solution

Cations + anions = solid precipitate Classified as carbonate hardness and noncarbonate

hardness Calcium, magnesium, iron, manganese Hard water used in soap consumption will bring

economic loss to the water user Precipitate form on hardware Precipitate in pipe temp and pH increased


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Soft 50 mg/L as CaCO3

Moderately hard 50-150 mg/L as CaCO3

Hard 150-300 mg/L as CaCO3Very hard 300 mg/L as CaCO3


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Hardness and alkalinity measurement unit (mg/L as

CaCO3)

33 CaCOformassequivalentL

meqCaCOas

Lmg

meqmgCaCOformassequivalent

COofmassequivalent

COofmassequivalentCaofmassequivalentCaCOformassequivalent

/503020

30

2

60

3

2

3

2

3

2

3


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Ca2+ Mg2+ Na+

HCO3- SO4

2- Cl-

Meq/L

Meq/L 0

0 2.75

4.10

4.23

5.23 7.86

8.49

Hardness (Ca2++ Mg2+) = 4.23 meq/L

Mass balance for CaCO3= 50.0

Hardness = 4.23 x 50.0 = 211.5 mg/L CaCO3


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4. Fluoride In groundwater (few regions) Toxic to human and animal in large quantity

5. MetalsNontoxic metals Ions, calcium, magnesium, sodium, aluminum Sodium: excessive conc. may cause bitter taste and hazard to

cardiac and kidney patientsToxic metals Arsenic, mercury, silver, barium, lead Harmful to humans and animals


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6. Organics

Biodegradable organics

Consists of organics that can be utilized for food bynaturally occurring microorganisms within a reasonablelength of time

Dissolved form: consists of starches, fats, proteins, alcohol

etc May cause color, taste, odor problems- main problem is

action of microorganisms

Microbial utilization can be oxidation/reduction

Aerobic env, the end products are stable and acceptable Anaerobic env, unstable product. When oxygen present,

anaerob products will be oxidized to aerob end products


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The amount of oxygen consumed during microbialutilization of organic is called the biochemical oxygendemand (BOD)

Measured by determining the oxygen consumed from asample placed in an air-tight container and kept in acontrolled env for preselected period of time. (stand :300mL BOD bottle, incubated at 20OC for 5 days, light isexcluded to prevent algal growth that may produce oxygen)

Dissolved oxygen (DO) = oxygen solubility in water, depends on

temp, TDS and atmospheric pressure

mLbottleofsizemLusedsamplep

PDOBOD F

,,,DO I


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BOD5represent oxygen consumed in 5 days

To calculate BOD for any period

tt kL

dtdL

kt

ot

eLL


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047.1,2020

T

T kk

)1( kt

ot

tot

eLy

exertedBODLLy

Value ytapproaches Lo, indicating that the total/ultimate BOD (yu)

yu= initial oxygen equivalent of the water Lo

Value of k for any given organic compound is temperature-dependent

k value increase with increasing temp (microb more active)

Typical values of k are shown in Table 2.6 or can be determine using

vant Hoff-Arrhenius model

ktu eyy t

1


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Example 2-9

BOD conversionsThe BOD5of a wastewater is determined to be 150 mg/L at20C. The k value is known to be 0.23 per day. What would the BOD8be ifthe test were run at 15C?

Solution:

1. Ultimate BOD (yu)

Lmg

e

e

yy

ktu

/220

1

150

1

523.0

5


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2. k value for 15C

3. y8

18.0

047.123.0 5

20

20

TT kk

Lmg

eyeyy

kt

ut

/168

)1(2201

818.0

8


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The BOD of a wastewater sample is estimated tobe 180 mg/L. What volume of undiluted sampleshould be added to be a 300 mL bottle? Also,

what are the sample size and dilution factor usingthis volume? Assume that 4 mg/L BOD cam beconsumed in the BOD bottle.

Example


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Nonbiodegradable organics

Resistant to biological degradation

tannic &lignic acid, cellulose, phenols biodegrade so slowly

Molecules with strong bond (polysacch) and ringed structure(benzene) are nonbiodegrade

Some organics nonbiodegrade because they are toxic toorganism (eg: pesticides; hydrocarbon compound combined

with chlorine) Measurement : Chemical oxygen demand (COD) test or Total

organic carbon (TOC)

To quantify nonbiodeg must subtract BOD


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7. Nutrients Elements essential to the growth and reproduction of organisms Limiting factor nutrient: nitrogen and phosphorus

Nitrogen Constituents of proteins, chlorophyll and biological compound Upon death of plants or animals, complex organic matter is

broken down to simple forms by bacterial decomposition(eg:proteinous matter)

Proteins converted to amino acid and finally reduced toammonia (NH3)

If oxygen present, NH3oxidized to nitrite (NO2-) and then to

nitrate (NO3-)


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Nitrification

Depending on the pH of water, the dissolved ammonium gas andammonia ions will exist as

)(21

)(22

3

322

2224

rnitrobacteNOONO

asnitrosomonOHHNOONH

OHNHOHNH 234


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At pH 7 or below, most of the ammonia will be ionized (NH4+). At

higher pH, the proportions of deionized ammonia will increase(NH3)

Nitrate may also cause additional BOD

NH3is toxic to fish and NH4+is a nutrient to algae and aquaticplants (also exerts DO demand) NO3- poisoning in human and animal babies (human babies below

than 6 month old) blue baby syndrome NO3-NO2- (in acidic condition)-will substitute O2 in blood

vessel Baby will breathe less oxygen and eventually die


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Phosphorus

Appears as phosphate (PO43-) in aquatic environments. Also as

orthophosphate, condensed phosphates or organic phosphates

Main sources : domestic sewage, animal feedlots, surface runofffrom agricultural areas

Not toxic, do not have direct health effect to organism- indirectthreat to water quality

Phosphate and nitrogen is the limiting nutrient N:P ratio in surface water is set at 10:1. Therefore, if N:P in the

water 10, then P isthe limiting nutrient


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BIOLOGICAL PARAMETERS Biological species their present or absence may indicate in general

terms the characteristics of a given water body

Pathogens

capable of infecting, transmitting diseases to humansBacteriasingle cell microb Organism that derive both energy and material from inorganic

source autotrophs Bacteria that obtain both energy and material from from organic

compound heterotrophs Aerobic heterotrophs require oxygen and anearobic heterotrophs

utilize organics in the absence of oxygen Utilize sunlight for an energy source and inorganic substance for a

material source


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Viruses

the smallest biological structures

Parasites - requires host to live Cause diseases polio, hepatitis

Protozoa

lowest form of animal life, unicellular organisms

Highly adaptable in natural waters

Helminths

also known as parasitic worms


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Pathogen indicator

Be applicable to all types of water

Always be present when pathogens are present

Always be absent when pathogens are absent Lend itself to routine quantitative testing

procedures without interference from orconfusion of results because of extraneous

organisms

Safety


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Indicators organisms their presence shows thatpollution has occurred and suggests the TYPE andLevel of pollution

Typical indicators used are coliform groups

Coliforms groups : Fecal coliforms (E. Coli) andTotal coliforms (FC, Soil C. and any others)

Determination experimental methods : MembraneFiltration Method and multiple-tube fermentationmethod most probable number (MPN)



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Parameter measure : Total Coliform (TC)

1. Using membrane filter technique (pore do not exceed 0.45m)

To determine the number of coliform organisms that are present inwater

Advantage : faster than MPN procedure and gives a direct count of thenumber

Can be determine by passing a known volume of water sample througha membrane filter that has a very small pore size. The bacteria areretained on the filter then contacted with an agar that containsnutrients necessary for the growth of the bacteria. After incubation, thecoliform colonies can be counted and the conc. in the original watersample determined

General formula

sampleofvolume

countedcoloniesNo

mL

colonies 100.

100


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Plate culture method (pour

plate)



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Plate culture methods (spread

plate)


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2. Multiple-tube fermentation test

Use lactose and other substances broth

3 set of 5 test tubes, consider positive with air bubble Incubate 24 2 hours, 35 0.5OC

The dilution of the water sample is in sequence. 10 mL,1 mL and 0.1 mL to use Most Probable number (MPN)

index.


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Example of a result

If the dilution for the above results is 10mL, 1mL and

0.1mL, Index MPN gives the results as 27 MPN/100mL If the dilution is at 1mL, 0.1mL and 0.01mL, the result

should be 270MPN/100mL

Thomas formula is used if the number combination is

not in the MPN index

03

4

)()(

100

100 tubesallformLinsampletotaltubesnegativeinmLinsampletotal

tubespositiveofno

mL

MPN


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Example 1A sample of combined sewer overflow is tested for

coliform by MPN method with the following results.Determine the coliform density;

Size of portion, mL No. positive No. negative

0.0010.0001

0.000010.000001

55

53

00

02


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Example 2An analysis for BOD5 is to be run on a sample of wastewater. The BOD is expectedto range from 50 to 350, and the dilution are prepared accordingly. In each case,a standard 300 mL BOD bottle is used. The data are recorded below.

Determine the BOD5 of the wastewater

Bottle no Wastewater,

mL

DOi DO5

1 20 8.9 1.5

2 10 9.1 2.5

3 5 9.2 5.8

4 2 9.2 7.5


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Bottle no Wastewater, mL

DOi DO5 O2 used

mg/L

P BOD 5

mg/L

1 20 8.9 1.5 7.4 0.067 110.45

2 10 9.1 2.5 6.6 0.033 200

3 5 9.2 5.8 3.4 0.017 200

4 2 9.2 7.5 1.7 0.007 242.86


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Example 3Determine the 1- day BOD and the ultimate first stageBOD for a wastewater 5 days, 20 oC BOD is 200 mg/L.the reaction constant k=0.23d-1. What would have been

the 5- day BOD if the test had been conducted at 25 C.


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Example 4 Express the following concentration of elements and

compounds as milligrams per liter of CaCO3

95 mg/L Ca2+ 420 mg/L MgSO4

87 mg/L Mg2+ 189 mg/L NaHCO3

125 mg/L Na+ 221 mg/L Ca(HCO3)2

Chapter 2 Environmental slide

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