21 water quality & water pollution

7/30/2019 21 Water Quality & Water Pollution

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WATER QUALITY AND

WATER POLLUTION


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IMPURITIES IN HYDROLOGIC CYCLE

Natural Impurities:Dissolved Solids: TDS:Ca, Mg, HCO3, Fe, Mn,F, SO4, Cl, K, Mn,

Salt Water IntrusionTDS:NaCl

Detergents-P

Human Waste: Organics,

N,P& Pathogens

Eutrophication

Stream Pollution

Industries:heavy Metals.

Cr, Cd, Pb, Hg

SS, Pesticides, NOM

Bioaccumulation &Biomagnification

Salinity


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Size Classification of Impurities

10-3 10-2 1.0 10 102 103

Aqueous Salts Virus Protozoa Silt Sand

10-4

Metal Ions

Trihalomethanes

Bacteria (Coliform)

Clay Cryptosporidium

Pesticides Humic Acid

10-1

Micrometer Scale

Precipitation

Oxidation

ReverseOsmosis

Coagulation & Flocculation

Ultrafiltration &Nanofiltration

Slow Sand Filtration

Ultrafiltration, MicrofiltrationSand Filtration

Dissolved Suspended SubstancesColloids


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Presence of impurities in such

quantity and of such nature

as to impair the use of waterfordesignated purpose

WATER POLLUTION

How Much ?? (mg/L) Organic, Inorganic, Color, Odor

Drinking, Bathing, Industrial use,

Fishing, Recreation


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Water

Sectors ofusage

Pollutantsbeing contributed

Agriculture Pesticides, fertilizers, salts

Municipal Human waste

Power Plant Elevated temperature

Industry Variety of chemicals

Unsuitable for drinking, recreation, agriculture, industry

Diminishes aesthetic quality

Destruction of aquatic life

Eventually affect human health too/ Nobody escapes

Major categories of Water Pollutants

Pathogens Heat (Thermal Pollution)

O2 Demanding Wastes Heavy Metals

Nutrients Pesticides

Salts Volatile Organic Compounds


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Impurities/pollutants in water

Physical : Physical water qualityparameters

Chemical : Chemical water qualityparameters

Bacteriological: Bacteriological waterquality parameters

Biological : Biological water qualityparameters


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Physical Water Quality Parameters

Parameters responding to the senses of

Sight: Suspended Solids (SS/TSS),Turbidity and Color

Touch: Temperature (no source of cold wateremission)

Taste : Taste

Smell : Odor


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Suspended Solids

Organic and inorganic particles suspended in water. Settleable or non-settleable (Colloids) Organic : Algal cell, bacteria, protozoa, plant fibers etc., Inorganic: Clay, Silt etc., Sources

storm water wastes dumping erosion

Measured by filtering a water sample,

drying (104o

C,24 h) and weighing the filter, reportedin mg/l


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Suspended Solids

Range: 0: Clear groundwater

300 mg/l sewage1000 mg/l Monsoon rivers100,000 mg/l Food industry

Problems: aestheticssedimentationmay exert oxygen demandadditional filtration/pre-treatment


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Turbidity

Turbidity is the cloudiness or haziness ofa fluid caused by individual particles(suspended solids) that are generallyinvisible to the naked eye, similar tosmoke in air. The measurement ofturbidity is a key test of water quality.


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Turbidity

Normally used for drinking water.Imparts opaqueness & color

It is the measure of the extent to which light is absorbed orscattered by suspended material in water.

Measured in NTU

Removed by Coagulation-Flocculation-Sedimentation and/orSand Filtration

Drinking water: less than 1 NTU

NTU: Nephelometric Turbidity Units

Equipment used : Nephelometer


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Turbidity

Photomultiplier

Light Source

Sample Cell


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Color

By organic debris, leaves, tannins (polyphenols),humic acids: Natural color

Iron and Manganese: Brown & Blackish Color

Different types of industries impart different colors

Pulp & paper industry; sugar industry; textile industry

Aesthetic problem, color causing substances react

with chlorine and form Trihalomethanes (THM).

Can be removed by Coagulation-Flocculation,Activated Carbon Adsorption & Ozonation

Measured by Spectrophotometer


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Taste & Odor

Alkaline material : Bitter taste

Metallic Salts : Salty taste

Organic Material : Reduced Products ofSulphur (Rotten Eggs)

Aesthetically displeasing for consumers

Removed by Activated Carbon Adsorption,Ozonation, RO


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Thermal Pollution

A typical nuclear Plant- Warms 150,000m3/ h coolingwater by 10 degree C

Life threatening: Trout & Salmon (omega 3 fatty acids)

Beneficial: for some fishes

Within certain limits- promotes fish growth, fishingmay improve

Sudden change in temperatureundesirable

With increase in temperature:

Metabolic rate increases by a factor of 2 for each10 degree C rise in temp.

DO requirement increases &

Available DO reduces


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Chemical Water Quality Parameters Total Dissolved Solids:

Major Ions (Na+, K+, Ca2+, Mg2+, SO42-, Cl-, HCO3

- and CO32- )

Hardness

Fluorides

Metals:

Non Toxic: Ca, Mg,Fe, Mn, Al, Cu, Zn Toxic: Cr, Cd, Pb, Hg

Organics

Biodegradable

Non-Biodegradable

Nutrients: Nitrogen

Phosphorus


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Nutrients

P, C, S, Ca, N, K, Fe, Mn, B, CO: Essential for growth

Considered Pollutants: These support the excessive

growth of aquatic life

Nutrient Enrichment: Blooms of algae/ die,

decompose / remove DO/water can not support

normal life forms/ add color turbidity, odour, tastes/

reduced acceptability for water supply

Aquatic Species- Three important : C,N,P

Limiting nutrients- Seawater-N

Fresh Water-P


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Total Dissolved Solids (TDS) or

Salts Dissolved solids, or salts, may be present as any

number of ions

cations: Na+, K+, Mg2+, Ca2+

anions: Cl-, SO42-, HCO3-

Typically measured as total dissolved solids (TDS)

Water classification

freshwater 5000 mg/l

sea water 30,000-34,000 mg/l


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Salts

Drinking Water - TDS


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Effects of TDS

Interfere with wastewater reuse

Crop damage/soil poisoning


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Ion Balance (meq/L)

Na+, K+, Ca2+, Mg2+

SO42-, Cl-, HCO

3- and CO

32-

% IB = + meq of Cations meq of Anions * 100 meq of Cations + meq of Anions


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Samples with pH = 100 ueq/l

|IB| = 100 ueq/l

IB < -20% Invalid 478 or 278

-20%


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Hardness

cause soap scum

Ca2+ + (Soap)- Ca(Soap)2 (s)

increase the amount of soap neededcause scaling on pipes

cause valves to stick due to the formation ofcalcium carbonate crystals

leave stains on plumbing fixtures

A term often used to characterize the ability of a water to:


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Formation of Hardness

CO2 + H2O H2CO3

Subsoil

Limestone CaCO3(s) + H2CO3 Ca(HCO3)2MgCO3(s) + H2CO3 Mg(HCO3)2

Precipitation

Topsoil


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Fluorides

Occurs in few types of sedimentary or igneous

rocks

Toxic to humans in large quantities:

discoloration of teeth if fluoride> 2mg/l

> 5 mg/l causes bone fluorosis or other

abnormalities.

Can be removed by alum and ion exchange

methods


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Metals

Na (non toxic): Bitter taste and health hazard

to cardiac and kidney patients.

Iron & Manganese (non toxic): Impart color

Arsenic, barium, cadmium, chromium, lead

mercury: Hazardous: concentrated by food

chains and greatest danger to the top of food

chain organisms


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Heavy MetalsImportant ones- Hg, Pb, Cd, As

Toxic Non-degradable

Essential nutrients-Cr, Fe

Cr, Fe in higher doses nervous system / kidney damage,creation of mutation , induction of tumors

Inhaled / Ingested: Absorption depends on particular

metal and form .Ex. Liquid Hg- not very toxic

Hg Vapor- Highly Toxic/ enters lungs./ diffused in toblood stream/ can pass in to the brain / damage thecentral nervous system

Kidney/complex filter/ eliminate toxic substance frombody.

Kidney- Contain millions of excretory units-nephronschemical toxic to kidney- nephrotoxins

Ex. Of nephrotoxic metals-Cd, Pb, Hg

P ti id


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Pesticides

Volatile Organic CompoundsMost commonly found in contaminated GW

Suspected carcinogens/ MutagensCan be removed by aeration

Kill undesirable organisms

Insecticides , herbicides, Rodenticides,

Fungicides


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Characteristics Standard Remarks

Color Colorless Generally cause by decaying vegetation or industries

Odor Unobjectionable (a) Test cold when heated

(b) Test at several dilutions

Caused by biological reactions and sewage

Turbidity 5 NTU

Dissolved solids mg/L,

Max

500 Beyond this palatability decreases and may cause gastro

intestinal irritation From minerals, metals

pH 6.5-8.5 Beyond this range, the water will affect the mucous

membrane and/or water supply system

Total Alkalinity 200 mg/L

Total hardness (as

CaCO3) mg/L, Max

300 Encrustation in water supply structure and adverse effects

on domestic use

DRINKING WATER QUALITY STANDARDS


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Characteristics Standard Remarks

Chlorides (as Cl) mg/L,

max

250 Beyond this limit, taste, corrosion and palatability are

affected

Fluoride (as F) mg/L,

Max

1.0 Fluoride may be kept as low as possible. High chloride

may cause fluorosis, Less than 1 mg/L help to prevent

dental activities in children.

Sulphate (as SO4) mg/L,

Max

200 Beyond this limit, taste/appearance are affected, has

adverse effect on domestic uses and water supply

structures

Nitrate (as NO3-N

) mg/L,

Max

45 as NO3-N

10 mg/L as

NO3

Beyond this methaemoglobinemia takes place.

(bluish discoloration)

Bacterial Counts: Nil


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Biodegradable organics

Oxygen-Demanding Material Measured in Terms of BOD

BOD (Biochemical Oxygen Demand): amount ofoxygen (DO, Dissolved Oxygen) required for thebiological decomposition of organic matter. Theoxygen consumed is related to the amount ofbiodegradable organics.

When organic substances are broken downinto CO2 and water, oxygen is consumed

organic C + O2 CO2

Organic C : protein, Carbohydrates, Fatsetc., in Human Waste

Measure of BOD =

Initial oxygen- Final

Oxygen after 5 days


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Biochemical Oxygen

Demand Measurement Take sample of waste; dilute with

oxygen saturated water; add nutrients

and microorganisms (seed) Measure dissolved oxygen (DO) levels over 5

days

Temperature 20

C

In dark (prevents algae from growing)

Final DO concentration must be > 2 mg/L

Need at least 2 mg/L change in DO over 5 days


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Example 1: Raw Data

Time(days)

Dilutedsample

DO (mg/L)

Blank SeededSample DO

(mg/L)

0 7.95 8.151 3.75 8.10

2 3.45 8.05

3 2.75 8.00

4 2.15 7.95

5 1.80 7.90


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Example 1: Calculations

What is the BOD5 of the sample?

Plot the BOD with respect to time.

sampledilutedtheofionsconcentratDOfinalandinitialDO,DO

(blank)waterdilutedseeded

theofionsconcentratDOfinalandinitialB,Bvolumetotalsample/volumefactordilutionP

P

P)])(1B(B-)DO[(DOBOD

fi

fi

fifim


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Example 1: Time Concentration

Plot

0

100

200

300

400

500

600

700

0 1 2 3 4 5 6

time (days)

BOD(mg/L)


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Modeling BOD as a First-order Reaction

0

1

2

3

4

5

6

0 10 20 30

time (days)

Conc.(m

g/L)

Organic matter oxidized

Organic matter remaining


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Modeling BOD Reactions

Assume rate of decomposition of organic

waste is proportional to the waste that isleft in the flask.

demandoxygenuscarbonaceoultimatetheiswhere

:yieldsequationthisSolving

(timeconstantrateBODthe

ttimeafterleftdemandoxygenofamountwhere

1-

o

kt

ot

t

t

t

L

eLL

k

L

- kLdt

dL

)


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Ultimate BOD

0

1

2

3

45

6

0 10 20 30

time (days)

Con

c.(mg/L)

Lt

Lo

Lo- Lt BOD exerted

L remaining

BODt

Ulti t Bi h i l O


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Ultimate Biochemical Oxygen

Demand

Lt = amount of O2 demand left in sample at

time, t

Lo = amount of O2 demand left initially (at time 0,no DO demand has been exerted, so BOD = 0)

At any time, Lo = BODt + Lt (that is the amount

of DO demand used up and the amount

of DO that could be used up eventually)Assuming that DO depletion is first order

BODt = Lo(1 - e-kt)


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Example 2 If the BOD5 of a waste is 102 mg/L and the

BOD20 (corresponds to the ultimate BOD) is158 mg/L, what is k (base e)?

kteL

10tBOD

kte

L

0

1 tBOD

ktL

0

1ln tBOD


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Example 2 (cont)

t

Lk

01ln tBOD

day

mg/L

mg/L

5

158

1021ln

k

-1day21.0k


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Biological Oxygen Demand:

Temperature Dependence Temperature dependence of biochemical

oxygen demand

As temperature increases, metabolismincreases, utilization of DO also increases

kt = k20T-20

= 1.135 if T is between 4 - 20 oC

= 1.056 if T is between 20 - 30 oC


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Example 3

The BOD rate constant, k, was determined

empirically to be 0.20 days-1 at 20 oC.

What is k if the temperature of the water

increases to 25 oC?What is k if the temperature of the water

decreases to 10 oC?


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Example 3

2025

25 )056.1(20.0 -1dayk

-1

day26.025 k

2010

10 )135.1(20.0 -1dayk

-1day056.010 k


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Oxygen-Demanding Material

Increased Biochemical Oxygen Demand

(BOD) can result in

anaerobic conditions.

Anaerobic conditions lead to fish kills and bad

smell (H2S, NH3).

High oxygen levels necessary for healthy stream

ecology trout require 5-8 mg/L dissolved oxygen (DO)

carp require 3 mg/L DO

aesthetic problem


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Dissolved Oxygen Depletion

Waste


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Non-Biodegradable Organics

Molecules with exceptionally strong bonds (somepolysaccharides) and ringed structures (benzene)

Constituent of woody plants: tannic and lignin acids,cellulose, phenols,

Petroleum products, pesticides, industrial chemicals:Toxic to microorganism.

Total (Biodegradable+non Biodegradable) can be

measured in terms of Chemical Oxygen Demand(COD).

Individual Organics are Analyzed by GC &/or HPLCand other sophisticated methods


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Al & Al l Bl


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Algae & Algal Blooms

Ph h
http://ioc.unesco.org/hab/intro1.htm


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Phosphorus

Phosphorus is typically the limiting nutrient in lakes,

and algae growth is linked to phosphorus inputs. Problems

aesthetic

taste and odor in drinking water

can be toxic, especially to farm animals

fouling

diurnal DO cycles


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Phosphorus

P Sources

fertilizers

detergents

P can exist in a variety of chemical forms, so

total P in normally measured


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Nitrogen

Nitrogen is often the limiting nutrient in ocean

waters and some streams

Nitrogen can exist in numerous forms, but

nitrate (NO3-), nitrite (NO2

-), ammonia (NH3)

are most commonly measured

Sources are primarily from fertilizers and acid

deposition


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Biological Water Quality

Parameters

Aquatic Organisms. Single Cell Fish: Trout:

Higher Quality of Water than Carp

Water Body Hosting Large number of specieswith well balanced number of individuals :

Healthy System

For Human Use and Consumption: Pathogens:Capable of infecting or transmitting disease to

humans


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Pathogens

Not native to aquatic system: Usually require ananimal host for growth and reproduction.

Transported by natural water: temporary memberof aquatic community.

Able to survive in natural waters and maintaintheir infectious capabilities.

Include bacteria, viruses, protozoa, helminthes

(parasitic worms)


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Impacts on Human Health


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Pathogenic Organisms

Smallest biological structures: Nervous System

disorders: Immunization

Single cell: Rod or spherical in shape:

Gastrointestinal Infections

Salmonella

Typhi

Poliovirus
http://www.pbrc.hawaii.edu/~kunkel/gallery/viruses/page002/24314a.htmlhttp://www.pbrc.hawaii.edu/~kunkel/gallery/viruses/page002/24314a.html


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Pathogenic Organisms

Giardia Lambia

Lowest form animal life, unicellular, complexfunctional activity Milder Gastrointestinal Infections

Parasitic Worms


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Analysis of Pathogens

Analysis of known pathogens time consuming. Test

for specific microorganisms only when needed.

Generally purity of water is checked by using

indicator microorganisms. Indicator microorganism should be:

Always present when pathogens are present and always

absent when pathogens are absent

Applicable to all types of water.

Native to intestinal track of humans

For the safety of lab personnel's: not pathogen itself


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Indicator Organism

Fecal coliform groups, several strains principal

is E Coli.: Non pathogenic and longer survival

time outside the human body

Simple tests to determine the presence or

absence and enumeration

Membrane filer technique or multiple tube

tests


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River Bathing Standards

BOD - BIO-CHEMICAL OXYGEN DEMANDDO - DISSOLVED OXYGENMPN - MOST PROBABLE NUMBER

BOD 3 mg/L (MAXIMUM)

DO 5 mg/L (MINIMUM)

COLIFORM (FECAL) 500 (DESIRABLE)

2500 (MAX. PERMISSIBLE)

PERMISSIBLE LIMITPARAMETERS

MPN100 ml


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AVERAGE DENSITY OF FECAL COLIFORMSEXCRETED IN 24 HOURS

(million/100ml)Human 13.0

Duck 33.0

Sheep 16.0

Pig 3.3

Chicken 1.3

Cow 0.23

Turkey 0.29


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Treated Water Quality Standards

INTO WATER BODY ON LAND

BOD (mg/l)

T S S (mg/l)

FECAL (MPN/100 ml)

COLIFORMS

30

50

1000

10000

100

200

(Desirable)

(Maximum)

TSS : Indian Standards: 100 mg/L

NRCP: 50 mg/L

21 water quality & water pollution

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