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Water Quality (CIVL 7062) > Week 3&4: Chemical Characteristics of Water > Flashcards

Week 3&4: Chemical Characteristics of Water Flashcards

1
Q

What is the purpose of using chemical indicators in water?

A

To determine the presence of organics/ non-organics and their impact on water quality

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2
Q

List some typical cations

A

Ca2+, Mg2+, Na+, K+

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3
Q

List some typical anions

A

CO3 2-, HCO3-, SO4 2-, Cl-, NO3-

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4
Q

Describe Arsenic and its risk in water

A

Occurs naturally in geologic formations. Used in timber treatment and pesticides. Been linked to lung and bladder cancer

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5
Q

Describe Chloride and its effect in water

A

Its presence in water from leaching of sedimentary deposits, brine, or industrial/domestic wastes. Causes noticeable taste in water.

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6
Q

Describe iron and its effect in water

A

Its presence in water from iron in geologic material. Causes reddish colour in water and affects taste

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7
Q

Describe lead and its risk in water

A

Primarily from corrosion of pipes. Interferes with red blood cell formation, kidney damage, impacts cognition

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8
Q

Describe Manganese and its effect in water

A

Naturally occuring or from discarded batteries, steel production, agricultural products. Stains water and causes medicinal taste

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9
Q

Describe Sodium and its risk in water

A

Often comes from home water softeners. Can affect people suffering from heart, kidney or circulatory ailments

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10
Q

Describe Sulfate and its effect in water

A

Come from leaching of natural deposits. May cause laxative effects

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11
Q

Describe Zinc and its effect in water

A

May come from ore deposits. Can cause undesirable taste in water

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12
Q

Describe Nitrates/Cyanides and their risk in water

A

Nitrate can cause infant cyanosis or “blue baby syndrome. Cyanides tie up hemoglobin sites resulting in oxygen deprivation - cyanosis.

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13
Q

Describe toxic heavy metals and their risk in water

A

Arsenic, barium, cadmium, lead, mercury, etc. May be acute poisons or cause chronic disease

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14
Q

What happens to inorganic compounds when placed in water?

A

They dissociate into ions

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15
Q

What is valence?

A

The combining power of an element based on that of a hydrogen value (e.g. Na+ =1 and Cl- = -1)

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16
Q

What is the relationship for meq/L?

A

meq/L = mg/L * valence/atomic weight

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17
Q

What is the formula and units for Equivalent Weight (EW)?

A

EW = atomic weight/valence OR atomic weight/e-charge. The units are g/eq

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18
Q

When doing a graphical representation of water analysis, what is the typical order of cations?

A

Ca2+, Mg2+, Na+, K+, etc.

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19
Q

When doing a graphical representation of water analysis, what is the typical order of anions?

A

HCO3-, SO4 2-, Cl-, etc.

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20
Q

Sum of Cations = ?

A

Sum of Anions

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21
Q

What are three major inorganic constituent indicators?

A
  • pH
  • Alkalinity
  • Hardness
22
Q

Define pH

A

A measurement of the acid-base properties of a solution. pH<7 = acid. pH>7 = base

pH = -log[H+]

23
Q

Define Alkalinity and what it’s important for

A

A measure of the water’s capacity to neutralize acids

  • ability to absorb H+ without significant pH change
  • important for chemical and biological processes
24
Q

What are the major acids of alkalinity?

A

Bicarbonate (HCO3-), Carbonate (CO3 2-), Hydroxide (OH-)

25
Q

Define equation for Total Alkalinity (meq/L)

A

TA = (HCO3-) + (CO3 2-) + (OH-) - (H+)

26
Q

How do you convert meq/L of substance to mg/L as CaCO3?

A

meq/L * 50 mg/meq = mg/L CaCO3

27
Q

How do you convert concentration of species from mg/L to meq/L?

A
  • Find MW of species
  • Divide MW by valence to get EW
  • Divide concentration of species by EW to get meq/L
28
Q

How can alkalinity be determined experimentally?

A

Using a titration with H2SO4

29
Q

Describe the two stages of a titration

A

If pH is > 8.3, then two stages carried out

Stage 1:
- titration is carried out until pH = 8.3 with phenophthalein as indicator (pink to colourless)
- known as P-alkalinity where carbonate converted to bicarbonate, but bicarbonate not converted to carbonic acid

Stage 2:
- titration is carried out to pH = 4.5 with BCG as indicator (green to pink)
- known as T-alkalinity where bicarbonate converted to carbonic acid

30
Q

What is included in T-alkalinity?

A

Means total alkalinity, so includes the p-alkalinity. Equals volume of acid added for both stages of titration.

31
Q

What is Hardness?

A

It is caused by multivalent cations (so 2+ or more), and causes a reduction in the cleaning action of soap as well as scaling in pipes, boilers, etc.

32
Q

What are the most abundant cations that contribute to hardness?

A

Calcium and Magnesium

33
Q

Does total hardness include cations such as Na+?

A

No, total hardness is a combination of Ca2+ and Mg2+ since Na+ is not a multivalent cation.

34
Q

What is the most abundant form of hardness and how does it occur?

A

Calcium Bicarbonate. It is picked up by rainwater containing carbonic acid which passes through limestone. It reacts with Calcium Carbonate in the soil to produce Calcium Bicarbonate.

35
Q

What are the the two types of hardness?

A
  • Carbonate (Temporary) Hardness
  • Non-carbonate (Permanent) Hardness
36
Q

What is Carbonate Hardness (CH)?

A

It’s associated with HCO3- and CO3 2-. It can easily be removed by heating.

37
Q

What is Non-Carbonate Hardness (NCH)?

A

Associated with other anions. It is not easily removed by heating.

38
Q

What happens if alkalinity is greater than total hardness?

A

NCH = 0

39
Q

What does TOC stand for?

A

Total Organic Carbon

40
Q

What are the major sources of TOC in raw water?

A
  • Natural organic material (NOM)
  • synthetic organic compounds (SOC)
41
Q

How are Synthetic organic compounds produced?

A
  • chemical reaction during treatment
  • originating from human activities
42
Q

What is NOM?

A
  • proteins, carbs, lipids etc.
  • originates from degredation of plant/animal material
43
Q

How does NOM affect Disinfection as a water treatment process?

A

It reacts with and consumes disinfectants which requires an increase in dosage

44
Q

How does NOM affect Coagulation as a water treatment process?

A

It reacts with and consumes coagulants which requires an increase in dosage

45
Q

How does NOM affect Adsorption in water treatment?

A

It adsorbs to activated carbon, depleting capacity of the carbon

46
Q

How does NOM affect Membranes in water treatment?

A

It clogs membranes leading to a decline in water passability

47
Q

How does NOM affect Distribution systems in water treatment?

A

Leads to corrosion and slime growth in the system

48
Q

What are DBP’s when discussing synthetic organic compounds?

A

Disinfection byproducts

49
Q

What are the two most common DBP classes?

A

THM’s and HAA’s

50
Q

What are four ways NOM is removed in water?

A
  • coagulation
  • filtration
  • dissolved air flotation
  • adsorption, oxidation, ion exchange

Water Quality (CIVL 7062) (6 decks)

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