ENVI Chapter 2

8/14/2019 ENVI Chapter 2

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U n i v e r s i t y o f S a

n C a r l o s - D e p a r t m

e n t o f C h e m i c a l E n

g i n e e r i n g






g i n e e r i n g

Mid 19th

century: the relationship between waste,drinking water and disease was documented

1954: Dr. John Snow noted a high correlation

between cholera cases and consumption of water

form a well on Broad Street

Late 19th century: Pasteur made advances in thegerm theory of disease






g i n e e r i n g

The Hydrologic Cycle and Water Quality

Water

Table 1. World Water Distribution

Location

Volume, 1012 m3 % of total

Land Areas

Freshwater lakes 125 0.009

Saline lakes and inland seas 104 0.008Rivers (average instantaneous volume) 1.25 0.0001

Soil moisture 67 0.005

Groundwater (above depth of 4000m) 8 350 0.61

Ice caps and glaciers 29 200 2.14

Total land area (rounded) 37 800 2.8

Atmosphere (water vapor) 13 0.001

Oceans 1 320 000 97.3

Total all locations (rounded) 1 360 000 100

Source: Adapted from The Water Encyclopedia.

- one of the most abundant compounds found in nature






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Figure 1. Hydrologic cycle.






g i n e e r i n g Classification of Solids in Water

Suspended or Nonfilterable Material

- consists of particles larger than molecular size that are

supported by buoyant and viscous forces within the water

Dissolved Materials

- consists of molecules or ions that are held by the molecular

structure of water

Colloids

- very small particles that technically are suspended but often

exhibit many of the characteristics of dissolved substances






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Water Pollution – the presence in water of impurities in such quality and of such nature as to

impair the use of water for a stated purpose

Standard Methods for the Examination of Water

and Wastewater – the authoritative standard for test

procedures for many years






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Physical Water – Quality Parameters

Physical Parameters – those characteristics of water that respond

to the senses of sight, touch, taste and smell

Suspended Solids

Sources Impacts Measurements Uses

inorganic or organic

particles

immiscible liquids

aesthetically

displeasing

provides adsorption

site for chemical

and biological

agents

may include

disease-causing

organisms

Total Solids Test - quantifies all the

solids in the water,

suspended and

dissolved, organic

and inorganic

Suspended Solids

Test

- removed from

water by filtration

to measure the

quality of the

wastewater influent

to monitor several

treatment processes

to measure the

quality of the

effluent

Environmental Protection Agency (EAP) – Maximum suspended-solids standard of 30 mg/L






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Turbidity


Erosion of colloidal

material

Vegetable fibers and

microorganisms

Soaps, detergents

and emulsifying

agents

aesthetically

displeasing

provides adsorption

site for harmful

chemicals

cause undesirable

tastes and odors

May interfere withlight penetration and

photosynthetic

reactions

Photometric Method

Adsorption Mode- measures light intensity

on the side of the vial

opposite form the light

source

Scattering Mode-Measures light intensity

at a 90o

angle form thelight source

Readings expressed as:

ormazin turbidity units

(FTUs) and nephelometry

turbidity units (NTU)

ormally made

on clean waters

EPA drinking

water standards:

maximum of 1

FTU

American Water

Works

Association: has

set 0.1 FTU

- a measure of the extent to which light is either absorbed or scattered

by suspended material in water

- not a direct quantitative measurement of suspended solids






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Color


Organic debris –

yellowish brown

Iron oxides – reddish water

Manganese oxides –

brown or blackish

water

Industrial wastes

aesthetically

displeasing

Unsuitable for someindustries like

laundering, dyeing,

papermaking etc.

Reduce the

effectiveness of

chlorine as

disinfectant

Comparison with

Standardized Colored

aterials

- Results are expressed intrue color units (TCUs)where 1 unit is equivalent to the

color produced by 1 mg/L of

platinum in the form of

chlorplatinate

Spectrophotometer Techniques

Indirect

measurement

of humic

substances inthe water

Apparent Color – partly due to suspended matter

True Color - contributed by dissolved solids that remain after removal

of suspended matter






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Taste and Odor


Inorganic

substances

Organic Material

aesthetically

displeasing

Health threat

cause undesirable

tastes and odors

Gas or Liquid

Chromatography

Quantitative Test

- Employ the human

senses of taste and smell

ormally made

on potable

waters

EPA standards: no

recommendation

Public Health

Service: maximumof 3 TON

Substances that produce an odor in water will almost invariably

impart a taste as well






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Temperature

Sources Impacts

Ambient temperature

Use of water for dissipation and discharge

Removal of forest canopies

Affects the reaction rates and solubility

levels of chemicals

Affects other physical properties

- one of the most important parameters in natural surface-water systems

- has an effect on most chemical reactions that occur innatural water systems






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Chemical Water – Quality Parameters

Chemical Parameters – related to the solvent capabilities of water

Total Dissolved Solids


Inorganic- Metals and gases

Organic- Decay of

vegetation, organic

chemicals andorganic gases

aesthetically

displeasing color,

tastes and odor

Toxic and

carcinogenic

Total Dissolved Solids

(TDS)- expressed as

milligrams per liter on

a dry-mass basis

Specific Conductance- ability of water to

conduct electricity

Gross measurement

of the dissolved

material

Material remaining in the water after filtration for

the suspended-solid analysis






g i n e e r i n g Ion Balance

Table 2. Common Ions in Natural Waters

Major constituents,

1.0-1000 mg/L

Secondary Constituents,

0.01-10 mg/L

Sodium Iron

Calcium Strontium

Magnesium PotassiumBicarbonate Carbonate

Sulfate Nitrate

Chloride Fluoride

Boron

Silica

Source: Adapted from The Water Encyclopedia.






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Alkalinity


CO32-, HCO3

-, OH-,

HSiO3-, H2BO3

-,

HPO4-, H2PO4

-, HS-

and NH30

bitter taste

Reactions withcations can foul

pipes

Titration with an Acid - Expressed as mg/L of

CaCO3

Buffering

capacity

determination

- the quantity of ions in water that will react to neutralize hydrogen ions






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Hardness

- The concentration of multivalent metallic cations in solutions

Carbonate Hardness – due to the presence of bicarbonates of Ca and Mg

Noncarbonate Hardness – due to the sulfates and chlorides of Ca and Mg

O H COCaCO HCOCa 22323 )( ++ → ∆

2223 2)()( COOH Mg HCOMg + → ∆

Carbonate Hardness






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Calcium and

Magnesium

Iron, manganese,

strontium and

aluminum

High soap

consumption

Boiler Scale

Laxative effect on

unaccustomed

persons

Spectrophotometer

Techniques

Titration with EDTA

For natural

waters and on

waters

intended for

drinking

EPA standards: no

recommendation

Public Health

Service: maximum

of 500 mg/L

Hardness

Table 3. General Accepted Classification of Hardness

Soft < 50 mg/L as CaCO3

Moderately Hard 50 – 150 mg/L as CaCO3

Hard 150 – 300 mg/L as CaCO3

Very Hard > 300 mg/L as CaCO3






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Fluoride

- associated in nature with a few types of sedimentary or igneous rocks- toxic to humans and other animals in large quantities- help prevent dental cavities in children (1.0 mg/L)- Mottling is relatively common when concentration exceed 2.0 mg/L

Hardness Calculation

+

+=

2

2

3

50*)/(

/

M of wt eq Lmg inM

CaCOas Lmg in Hardness

50*)/(

/

2

3

LmeqinM

CaCOas Lmg in Hardness

+=






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Metals

- Are soluble to some extent in water

Nontoxic Metals

Sodium – most common nontoxic metal

– corrosive to metal surfaces

– toxic to plants

– health hazard to cardiac and kidney patient

Iron and Manganese – may cause color problems

(Fe – 0.3 mg/L and Mg – 0.05 mg/L)

– used by some bacteria

Toxic Metals

- Include arsenic, barium, cadmium, chromium, lead, mercury and silver






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Organics

Natural Organics – consist of the decay products of organic solids

Synthetic Organics – the results of wastewater discharges or agricultural

practices

Two Broad Categories of Dissolved Organics

Biodegradable Organics

Nonbiodegradable Organics






g i n e e r i n g Biodegradable Organics

– consist of organics that can be utilized for food by microorganisms

– consist of starches, fats, proteins, alcohols, acids, aldehydes and esters – end products of the initial decomposition of plant or animal tissue

Biochemical Oxygen Demand (BOD) – amount of oxygen consumed

during microbial utilization of organics

Aerobic Anaerobic

Utilization of Dissolved Organics

(microorganisms)






g i n e e r i n g Nonbiodegradable Organics

– organic materials that are resistant to biological degradation

– examples are alkyl benzene sulfonate (ABS), organic pesticides,industrial chemicals and hydrocarbon compounds combined

with chlorine

Nutrients

Nitrogen

Phosphorous

– elements essential to the growth and reproduction of plants and animals

– constituent of proteins, chlorophyll and many other biological compounds

Methemoglobinemia – nitrate poisoning has been referred toas the “blue baby” syndrome

– constituent of soils and animal waste

– appears exclusively as phosphate in aquatic environment






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Biological Water – Quality Parameters

Pathogens

Bacteria

Viruses

Protozoa

Helminths

– those organisms capable of infecting or of transmitting diseases to humans

– lowest form of life capable of synthesizing protoplasm from the

surrounding environment

– smallest biological structures that contain all the genetic information

necessary for their own reproduction

– complete, self-contained organisms that can be free-living or parasitic,

pathogenic or nonpathogenic, microscopic or macroscopic

– their life cycles often involve two or more animal hosts



U n i v e r s i t y o f S a n C a r l o s - D e p a r t m


g i n e e r i n g

Determine the total hardness of the following water sample

2.429.3Mg2+

360Ca2+

Concentration

(meq/L)

Concentration

(mg/L)

Constituent

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ENVI Chapter 2