Envi Chapter 2

University of San Carlos - Department of Chemical Engineering

University of San Carlos - Department of Chemical Engineering

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 the germ theory of disease

University of San Carlos - Department of Chemical Engineering

The Hydrologic Cycle and Water Quality Water

- one of the most abundant compounds found in nature

Table 1. World Water Distribution

Volume, 1012 m3

% of total

Freshwater lakes

125

0.009

Saline lakes and inland seas

104

0.008

Rivers (average instantaneous volume)

1.25

0.0001

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

Location Land Areas

Soil moisture

Source: Adapted from The Water Encyclopedia.

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Figure 1. Hydrologic cycle.

University of San Carlos - Department of Chemical Engineering

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

University of San Carlos - Department of Chemical Engineering

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

inorganic or organic particles

aesthetically displeasing

immiscible liquids

provides adsorption site for chemical and biological agents may include disease-causing organisms

Measurements

Uses

Total Solids Test - quantifies all the solids in the water, suspended and dissolved, organic and inorganic

to measure the quality of the wastewater influent to monitor several treatment processes

Suspended Solids to measure Test quality of - removed from effluent water by filtration

the the

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

University of San Carlos - Department of Chemical Engineering

Turbidity - 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 Sources Erosion of colloidal material

Impacts aesthetically displeasing

Vegetable fibers and provides adsorption microorganisms site for harmful chemicals Soaps, detergents and emulsifying agents

cause undesirable tastes and odors

Measurements Photometric Method

Uses Normally made on clean waters

Adsorption Mode drinking - measures light intensity EPA on the side of the vial water standards: opposite form the light maximum of 1 FTU source American

Water

Scattering Mode Works -Measures light intensity Association: has May interfere with at a 90o angle form the set 0.1 FTU light penetration and light source photosynthetic Readings expressed as: reactions formazin turbidity units (FTUs) and nephelometry turbidity units (NTU)

University of San Carlos - Department of Chemical Engineering

Color Apparent Color – partly due to suspended matter True Color - contributed by dissolved solids that remain after removal of suspended matter Sources

Impacts

Organic debris – yellowish brown

aesthetically displeasing

Iron oxides – reddish water

Unsuitable for some industries like laundering, dyeing, papermaking etc.

Manganese oxides – brown or blackish water Industrial wastes

Reduce the effectiveness of chlorine as disinfectant

Measurements

Uses

Comparison with Standardized Colored Materials - Results are expressed in true color units (TCUs)

Indirect measurement of humic substances in the water

where 1 unit is equivalent to the color produced by 1 mg/L of platinum in the form of chlorplatinate

Spectrophotometer Techniques

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Taste and Odor Substances that produce an odor in water will almost invariably impart a taste as well

Sources

Impacts

Inorganic substances

aesthetically displeasing

Organic Material

Health threat cause undesirable tastes and odors

Measurements

Uses

Gas or Liquid Normally made Chromatography on potable waters Quantitative Test - Employ the human EPA standards: no senses of taste and smell recommendation Public

Health

Service: maximum of 3 TON

University of San Carlos - Department of Chemical Engineering

Temperature - one of the most important parameters in natural surface-water systems - has an effect on most chemical reactions that occur in natural water systems Sources Ambient temperature

Impacts Affects the reaction rates and solubility levels of chemicals

Use of water for dissipation and discharge Affects other physical properties Removal of forest canopies

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Chemical Water – Quality Parameters Chemical Parameters – related to the solvent capabilities of water

Total Dissolved Solids Material remaining in the water after filtration for the suspended-solid analysis Sources Inorganic - Metals and gases Organic - Decay of vegetation, organic chemicals and organic gases

Impacts aesthetically displeasing color, tastes and odor Toxic and carcinogenic

Measurements

Uses

Total Dissolved Solids Gross measurement (TDS) of the dissolved expressed as material milligrams per liter on a dry-mass basis Specific Conductance - ability of water to conduct electricity

University of San Carlos - Department of Chemical Engineering

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

Potassium

Bicarbonate

Carbonate

Sulfate

Nitrate

Chloride

Fluoride Boron Silica

Source: Adapted from The Water Encyclopedia.

University of San Carlos - Department of Chemical Engineering

Alkalinity - the quantity of ions in water that will react to neutralize hydrogen ions Sources CO32-, HCO3-, OH-, HSiO3-, H2BO3-, HPO4-, H2PO4-, HSand NH30

Impacts bitter taste Reactions with cations can foul pipes

Measurements

Uses

Titration with an Acid Buffering - Expressed as mg/L of capacity CaCO3 determination

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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

Carbonate Hardness ∆ Ca ( HCO3 ) 2   →CaCO3 + CO2 + H 2 O ∆ Mg ( HCO3 ) 2   →Mg (OH ) 2 + 2CO2

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Hardness Sources

Impacts

Calcium and Magnesium

High soap consumption

Iron, manganese, strontium and aluminum

Boiler Scale Laxative effect on unaccustomed persons

Measurements Spectrophotometer Techniques

Uses For natural waters and on waters intended for drinking

Titration with EDTA EPA standards: no recommendation Public

Health

Service: maximum of 500 mg/L

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

University of San Carlos - Department of Chemical Engineering

Hardness Calculation

Hardness in mg / L as CaCO3 =M

2+

(in mg / L) *

50 eq wt of M 2 +

Hardness in mg / L as CaCO3 = M 2 + (in meq / L) * 50

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

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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

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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

Utilization of Dissolved Organics (microorganisms)

Aerobic

Anaerobic

Biochemical Oxygen Demand (BOD) – amount of oxygen consumed during microbial utilization of organics

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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 – elements essential to the growth and reproduction of plants and animals Nitrogen – constituent of proteins, chlorophyll and many other biological compounds Methemoglobinemia – nitrate poisoning has been referred to as the “blue baby” syndrome Phosphorous – constituent of soils and animal waste – appears exclusively as phosphate in aquatic environment

University of San Carlos - Department of Chemical Engineering

Biological Water – Quality Parameters Pathogens – those organisms capable of infecting or of transmitting diseases to humans Bacteria – lowest form of life capable of synthesizing protoplasm from the surrounding environment Viruses – smallest biological structures that contain all the genetic information necessary for their own reproduction Protozoa – complete, self-contained organisms that can be free-living or parasitic, pathogenic or nonpathogenic, microscopic or macroscopic Helminths – their life cycles often involve two or more animal hosts

University of San Carlos - Department of Chemical Engineering

Determine the total hardness of the following water sample

Constituent Concentration Concentration (mg/L) (meq/L) Ca2+ Mg2+

60 29.3

3 2.4