Transcript Monitoring and Assessing Water Quality

Water Quality
Chapter 6 Water Sources
WQT 121
Lecture 1
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Objectives
Reading assignment:
Handout: Chapter 6 Water Quality
1. Review Principle Water Quality Characteristics
2. Understand common secondary MCLS.
3. Effect of pH, Taste, Odor, Corrosion on water quality
3. Review of MCLS & key contaminants in water
4. Hard verse soft water
Mineralogical Analysis of Water
• Concentration (Mg/L) Quantity of a constituent in a
standard volume (1 liter) is measured by its weight (in
milligrams). 1 ppm (old school) = 1mg/L (correct)
• General Mineral Content Ca, Na, Mg, Fe, Mn, HCO3, CO3,
SO4 and Cl2.
– Rivers < 500 mg/L to 2,000 mg/L
– Groundwater 100-10,000 mg/L
In the water treatment field, mg/L
and ppm are considered to be
equivalent units.
100%
Fa
ls
e
0%
Tr
ue
1. True
2. False
3.5% salinity or 35,000 TDS (mg/L),
10,5000 mg/L Na, 19,700 mg/L Cl2, 2,650
mg/L SO4, 1,310 mg/L Mg, Ca 410 mg/L,
Br 65 mg/L, Bicarbonate 152 mg/L, pH 8.1
Rainwater
Seawater
Lake Water
Groundwater
85%
at
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w
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aw
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Se
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5%
r
5%
r
5%
R
1.
2.
3.
4.
Groundwater in comparison to
surface water is generally:
95%
5%
an
d
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.
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ep
1. Lower in turbidity and
higher in mineral content
2. Higher in turbidity and lower
in mineral content
3. More susceptible to
seasonal changes
4. More susceptible to algal
blooms
5. Warmer and is quite soft
7.1 TDS mg/l, 7 mg/L Na, 1 mg/L Cl2, 2
mg/L SO4, 0.74 mg/L Mg, Ca 5.5 mg/L, pH
6.9
Rainwater
Seawater
Lake Water
Groundwater
53%
35%
12%
r
at
e
er
nd
w
ro
u
G
La
ke
W
at
er
aw
at
Se
ai
nw
at
e
r
0%
R
1.
2.
3.
4.
180 TDS mg/l, 7 mg/L Na, 23 mg/L Cl2, 40
mg/L SO4, 8.6 mg/L Mg, Ca 53 mg/L, pH
6.0-8.5
Rainwater
Seawater
Lake Water
Groundwater
52%
48%
at
e
er
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w
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G
La
ke
W
at
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aw
at
Se
at
e
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nw
r
0%
r
0%
R
1.
2.
3.
4.
Key Words
• Dissolved Solids very stable inorganic or organic
substances that remain in suspension.
• Colloidal Solids Tiny clay and organic materials that float
in water and repel each other.
• Suspended Solids Large particles of silt and sand that
settle out in a sedimentation basin or clarifier.
• National Secondary Drinking Water Regulations
(NSDWRs): are non-enforceable guidelines regulating
contaminants that may cause cosmetic effects (such as
skin or tooth discoloration) or aesthetic effects (such as
taste, odor, or color) in drinking water
Turbidity and Corrosion
• Turbidity: A measure of the light scattering property
of water
• The unit of measure is the NEPHELOMETRIC
TURBIDITY UNIT, or NTU.
• Corrosion: The destruction of metal by electrochemical processes.
• Corrosion is simply natures way to return metals
back to their natural state: OXIDES
Corrosion Factors
1. Low pH, which is often associated with
EXCESS CARBON DIOXIDE in water
2. High oxygen
3. High total dissolved solids (salts) in the form
of chlorides or sulfates
4. Soft water, or low hardness water
5. High temperature often exaggerates corrosion
problems
6. Low alkalinity
Corrosion Controls
Aggressive soil and water
1. Protective coatings inside and outside of pipe
(cement lining is very effective for ductile iron
pipe plastic wrap can effectively protect ductile
iron pipe from soil corrosion)
2.Cathodic protection, using zinc or magnesium
sacrificial anodes to coat
3.Adjust water chemistry by increasing the pH,
adding alkalinity, or adding hardness ions
4. Galvanic corrosion
Electro-chemical process similar to a battery
that occurs when dissimilar metals are joined.
What does TDS stand for?
96%
4%
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To
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To
0%
To
1. Total dissolved solids
2. Temporarily dissolved
solids
3. Total disaggregated
solids
4. Total dissolved salts
The total solids in water would
be a combination of:
88%
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Su
1. Fixed solids and
settleable solids
2. Dissolved solids and
volatile solids
3. Dissolved solids and
suspended solids
4. Suspended solids and
fixed solids
5. Fixed solids and
dissolved solids
Total Dissolved Solids are
dried at this temperature
38%
103oC
105oC
180oC
550oC
27%
23%
C
55
0o
C
18
0o
C
5o
10
3o
C
12%
10
1.
2.
3.
4.
The secondary MCL for TDS in
drinking water is?
47%
10 mg/L
500 mg/L
1,000 mg/L
1 mg/L
26%
16%
m
g/
L
1
m
g/
L
0
00
1,
50
0
m
g/
L
m
g/
L
11%
10
1.
2.
3.
4.
Key Words
• Turbidity A measure of the light scattering property of water
(cloudiness)
• The unit of measure is the NEPHELOMETRIC TURBIDITY UNIT, or NTU.
• Corrosion The destruction of metal by electro-chemical processes.
• Corrosion is simply natures way to return metals back to their natural
state: OXIDES
NTU stands for?
1. Nephelometric turbidity
unit
2. Nephelometric total
solids utilization
3. Nepelometric turbidity
utilization
4. Nominal Turbidity Unit
5. Nominal Tubidity
Utilization
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0% 0% 0% 0% 0%
Turbidity is caused by?
Dissolved solids
Suspended particles
Dissolved gases
Dissolved colored
solids
..
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.
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D
1.
2.
3.
4.
Which of the following is a major
part of a turbidimeter?
light
aspirator
Reference electrode
Objective nosepiece
...
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1.
2.
3.
4.
Turbidimeters must be
calibrated:
1. Monthly
2. Quarterly
3. If factory calibrated,
never
4. Daily
5. Weekly
ee
k
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Which of the following
parameters is used to indicate
the clarity of water?
pH
Chlorine residual
Turbidity
Bacteriological
a.
..
0%
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0%
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0%
id
...
0%
C
1.
2.
3.
4.
Which of the following
substances will reduce the
effectiveness of chlorine
disinfection?
color
radon
Turbidity
Carbon dioxide
0%
di
ox
rb
id
i
id
e
ty
0%
C
ar
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Tu
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0%
ra
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0%
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1.
2.
3.
4.
According to the Interim Enhanced Surface Water Treatment Rule, a
public water system serving a population of 10,000 or more must
maintain the combined effluent turbidity of direct or conventional
filtration 95% of all measurements taken each month at :
1.
2.
3.
4.
≤0.3 ntu
≤0.5 ntu
≤1.0 ntu
≤5.0 ntu
The conductivity of the source
water indicates the quantity of
dissolved material present
1. True
2. False
ls
e
0%
Fa
Tr
ue
0%
In general for every 10 units of
Electrical Conductance reported
represents 6 to 7 mg/L increases
of dissolved solids
1. True
2. False
ls
e
0%
Fa
Tr
ue
0%
Electrical Conductance is
reported in mmhos/cm at 25oC.
1. True
2. False
ls
e
0%
Fa
Tr
ue
0%
Color
•
•
•
Apparent color: from light that is reflecting off the
particles (giving it a yellow or straw color)
True color: tea color that remains after filtering (organic
acids from vegetation)
Units are CU or color units
What is apparent color?
C
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sa
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C
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sa
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C
0%
...
0%
...
0%
C
1. Color in a sample after
it is filtered
2. Color in a sample
before it is filtered
3. Color in a sample after
it is disinfected
4. Color in a sample
before it is disinfected
__________ can interfere with a
turbidity meter measurement.
SS concentration
pH
Color
Temperature
0%
ra
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0%
m
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C
pH
0%
Te
co
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tr
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0%
SS
1.
2.
3.
4.
Sludge accumulations in settling
basins over a period of time
usually:
...
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In
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0%
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0%
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R
1. Add hardness to the
water
2. Increase the algae
growth
3. Result in taste and odor
problems
4. Result in the growth of
pathogenic organisms
As water temperatures decrease,
the disinfecting action of
chlorine:
0%
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..
...
0%
en
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Decreases
Increases
Remains the same
Depends on the altitude
s
1.
2.
3.
4.
As temperatures increase chemical reactions speed up
Arrhenius equation: reaction rate doubles every 10 degree
celsius
Lake Stratification
• Epilimnion- top of the lake
• Thermocline- middle layer that may change depth
throughout the day
• Hypolimnion- bottom layer
• Temperature change- from season create a cyclic
pattern that is repeated from year to year.
The formation of layers of
different temperature in a body
of water is called what?
1.
2.
3.
4.
Thermal stratification
Thermal justification
Limnoptic layering
Limnoptic stratification
0%
Th
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..
L
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0%
ra
st
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Reservoir turnover is?
1. Related to the pH of
water
2. Caused by denser
water at the surface
sinking toward the
bottom
3. Caused by wind
cracking ice on the
surface
4. Needed to control algae
growth
87%
13%
0%
R
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0%
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..
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N
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.
Hard vs Soft Water
Hardness:
Ca+2 &
Mg+2
250 mg/L
*poor suds / soap ring
*mineral buildup (scale)
*fixture staining (white chalky)
*Ion exchange softening
*Lime - soda softening
*sequestering agents
1. Hard Water
Hard water is any water containing an appreciable
quantity of dissolved minerals. > 250 mg/L (mostly
Ca+2 and Mg+2).
Precipitates on pipes, Soap hard to lather because it
reacts with Ca and Mg salts in hard water. Need to use
ion exchange or treat with lime
2. Soft Water
Soft water is treated water in which the only cation
(positively charged ion) is sodium.
Hardness #2340
What are typical values in nature?
Classification
mg/L
Soft
Slightly hard
Moderately hard
Hard
Very Hard
0 - 17.10
17.1 - 60
60 - 120
120 – 180
180 & over
Drinking water average is about 250 mg/L as calcium
carbonate hardness
Hardness #2340
How is it done?
Before w/
indicator
After EDTA titration
To endpoint
Hardness #2340
What are the units and conversions?
•hardness in mg/l as CaCO3
Calculations and Formulas?
Hardness as CaCO3 mg/L=
(ml of EDTA (sample) – ml of EDTA (blank))(0.01 M EDTA)(100 mg=CaCO3 milliMole)(1000 ml/L)
ml of sample volume titrated
Hard Waters in the USA
Alkalinity and hardness are both analyzed by
adding a known reagent to the sample. This
process results in a ______ change.
1.
2.
3.
4.
93%
Color
Temperature
Time
Ionic strength
0%
C
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0%
Ti
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c
ni
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ng
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s
th
This is the titrant used for the
Hardness analysis.
100%
1. EDTA - A Chelating
Agent
2. 0.03 N Sulfuric acid
3. 0.125 N Hydrochloric
acid
4. Sodium hydroxide
0%
ED
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0.
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0%
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Hardness is defined as the sum of the
_____ and ____ ions, although any
divalent metal ion can contribute to
hardness.
100%
1. Calcium and
Magnesium
2. Magnesium and
Sodium
3. Calcium and Sulfate
4. Struvite
C
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0%
0%
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pH
• Definition: The potential of hydrogen. Negative log of the
hydrogen ion activity/concentration.
• Formula pH= -log10(αH+)
• The pH scale:
• -?.................................. 7 ....................................14
•
Acid
Neutral
Basic
• The pH range for drinking water is 6.5 to 8.5
Some characteristics of water, such as
pH and dissolved oxygen, change so
quickly that they need to be measured
immediately.
73%
Fa
ls
e
27%
Tr
ue
1. True
2. False
Acid-Base pH Balance
Figure 2.7
Which of the following pH
readings indicates an acidic
source water?
1.
2.
3.
4.
3
7
9
12
94%
0%
3
7
0%
9
6%
12
A water with a pH value of 7.00 is
considered to be:
1.
2.
3.
4.
5.
Basic
Acidic
Hot
Neutral
Cold
92%
8%
0%
B
as
ic
A
di
ci
c
0%
H
0%
ot
N
l
tra
u
e
C
d
ol
When operating a surface water treatment
plant, which of the following laboratory tests is
of most significance for establishing chemical
dosages for coagulating water?:
47%
1.
2.
3.
4.
pH and alkalinity
Sulfates
Chlorides
Calcium and
magnesium
5. Total hardness
33%
13%
7%
0%
pH
a
nd
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m
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ta
To
h
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dn
r
a
s
The pH is a measure of the
concentration of _____ ____ in a
solution
1.
2.
3.
4.
100%
Hydrogen ions
Hydrozide ions
Acid equivalents
Base equivalents
0%
H
y
en
og
r
d
ns
io
H
y
e
id
z
o
dr
ns
io
A
d
ci
a
iv
u
eq
0%
n.
le
..
B
as
e
v
ui
q
e
0%
en
al
...
Which one of the following
statements is true in regard to
the concept of pH?
1.
2.
3.
4.
5.
pH indicates the amount of
total alkalinity available.
A raw water sample with a pH
of 6.5 is slightly basic.
The range of pH is between 0
and 14
A pH meter gives the percent
hydrogen ion concentration as
its direct readout value.
Accurate pH measurements on
raw water require that a 24-hour
flow-proporational sample be
collected.
92%
8%
0%
pH
di
in
t
ca
es
A
.
t..
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0%
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Th
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0%
..
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pH
et
m
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.
iv
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r
A
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at
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pH
e.
m
..
pH sensors consist of
1. A glass electrode and
reference electrode
2. A pH electrode and
temperature electrode
3. A junction electrode
and null electrode
62%
31%
8%
A
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A
pH
ec
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.
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el
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The range of a pH analyzer is
1.
2.
3.
4.
100%
2 to 14 pH units
4 to 14 pH units
0 to 14 pH units
1 to 14 pH units
0%
2
to
14
pH
.
i..
n
u
4
to
14
0%
pH
.
i..
n
u
0
to
14
0%
pH
.
i..
n
u
1
to
14
pH
.
i..
n
u
pH sensors measure the activity
of which ion?
1.
2.
3.
4.
100%
Sodium
Hydrogen
Chlorine
Caustic
0%
S
0%
m
iu
d
o
H
y
en
g
o
dr
C
e
in
r
o
hl
0%
C
s
au
tic
What is the maximum recommended
holding time for a sample that is to
be analyzed for pH?
93%
1. None; it must be
analyzed immediately
2. 48 hours
3. 7 days
4. 14 days
7%
N
o
;i
ne
tm
t
us
...
48
u
ho
0%
rs
7
ys
da
0%
14
y
da
s
What is the minimum number of
pH standards needed for
calibration of a pH meter?
1.
2.
3.
4.
1
2
3
4
44%
25%
25%
6%
1
2
3
4
Temperature does not affect pH
measurement.
1. True
2. False
100%
ls
e
Fa
Tr
ue
0%
Water Properties
• Dipolar Molecule
• High surface tension= hydrogen bonding
• Expands upon freezing (10%)-more dense as liquid
– Freezing point 0oC boiling point 100oC.
•
•
•
•
•
•
•
Most abundant liquid on surface of earth
Exist in 3 phases on earth (Triple point)
Universal solvent
High heat capacity
High heat of fusion
High heat of evaporation
High heat of vaporization
+
+
104.5°
-
Water Impurities
• Dissolved, Colloidal, and Suspended solids- (acid, base,
sand, clay, organics)
• Inorganic acids: sulfuric, nitric, hydrochloric, carbonic
• Bases: caustic soda, soda ash, hydrated lime
• Salts: ferric chloride, aluminum sulfate, sodium chloride
• Organics: volatile organic compounds (VOCs), synthetic
organic compound
SMCL
Water Quality Problem
Treatment Methods
Iron
0.3 mg/L
*red water complaints
*taste and odor
*staining of clothing and fixtures
(red -brown)
*chlorine + filtration
*aeration + filtration
*manganese green sand +
permanganate
*sequestering agents
Manganese
0.05 mg/L
*staining of clothing and fixtures
(black or dark purple)
*chlorine + filtration
*aeration + filtration
*manganese green sand +
permanganate
*sequestering agents
Hardness:
Ca+2 & Mg+2
250 mg/L
*poor suds / soap ring
*mineral buildup (scale)
*fixture staining (white chalky)
*Ion exchange softening
*Lime - soda softening
*sequestering agents
Sulfate
250 mg/L
* salty off taste
*temporary diarrhea
*reverse osmosis / ion exchange
TDS
500 mg/L
*high mineral content (salts) does
not quench thirst, leaves mineral
deposit
*reverse osmosis / ion exchange
Chloride
250 mg/L
*salty taste
*contributes to corrosion
*reverse osmosis / ion exchange
Hydrogen
Sulfide
0.1 mg/L
*rotten egg odor
*oxidize with chlorine, chlorine
dioxide or permanganate
Odor
3 T.O.N.
*makes water un-palatable
*permanganate
*activated carbon (PAC, GAC)
*flushing programs
Color
15 colorunits
*makes water un-palatable
*effective coagulation
pH Effect Water Quality
• Disinfection with Chlorine:
– Water pH has a big impact on chlorine effectiveness.
Chlorines effectiveness is reduced at pH values above
pH 7.
• Corrosion: Lead and Copper.
– Low pH tends to make water more corrosive. A basic
treatment technique to control lead and copper
corrosion is to increase the pH.
• Coagulation of Turbidity
– Alum, the most popular coagulant if very sensitive to
pH. Alum works best at a pH range of 6.5 - 7.5.
pH Adjusters
Raise pH
Soda ash
Caustic soda
Lime
X
X
X
Sodium
bicarbonate
Carbon dioxide
X
Sulfuric acid
Lower pH
X
X
Taste
4 tastes
Sweet
Salty
Bitter
Sour
4 taste sensations
hot
cool
astringent
acrid
ODOR
• Treated or finished water is diluted with odor free
water until there is no perceptible odor. The dilution
factor needed to achieve no odor is the ODOR
THRESHOLD NUMBER. Odor free water is produced
by treating tap water with activated carbon.
Causes of Bad Taste and Odor
•Plankton: various species of algae, especially blue
green algae
•Decayed vegetation-Decaying leaves are
especially important in the late summer, early fall.
•Dissolved minerals/gasses: sulfates, chlorides,
iron, etc.
•Industrial chemicals: phenolic compounds are
especially a problem in very small concentrations,
VOC, SOC,
MCL Inorganics Review
Nitrate and Nitrite
MCL are: nitrate = 10 mg/L, nitrite = 1 mg/L, nitrate + nitrate = 10 mg/L
Blue baby syndrome or methemeglobinemia, results in loss of oxygen to the brain, with
possible brain damage. Infants 0 - 6 months most at risk.
Sources include fertilizer, animal manure, and septic tank leachate
Lead and Copper
Action Levels for lead and copper (When the Action Levels are exceeded, corrosion
control is required), lead = 0.015 mg/L, copper = 1.3 mg/L
The health effect of lead is damage to the nervous system and lowered intellectual
development, especially in developing children.
The health effect of copper is minor, but can cause severe reaction in some individuals
who are allergic to copper.
Lead and copper are regulated in a Treatment Technique which requires systems to take
tap water samples at sites with lead pipes or copper pipes that have lead solder and/or are
served by lead service lines. The action level, which triggers water systems into taking
treatment steps if exceeded in more than 10% of tap water samples, for copper is 1.3 mg/L,
and for lead is 0.015mg/L.
Fluoride
Fluoride MCL = 4 mg/L
Causes mottling of teeth and may cause bone deformation or fluorosis
Fluoride is a naturally occurring mineral that is normally present in groundwater.
MCL IOC and SOC
IOCs
Certain inorganic chemicals can be toxic when found in drinking water.
Health effects include nervous system damage and cancer.
Some of the regulated IOCs:
arsenic, antimony, asbestos, barium, beryllium, cadmium, chromium, copper,
cyanide, fluoride 4 mg/L,
lead regulated by action levels as part of the lead/copper rule
mercury
nitrate, nitrite 10, 1 mg/L (nitrate + nitrite must not exceed 10)
selenium
Thallium
SOCs
MCL, Health Effects, Sources, Sampling
Synthetic Organic Chemicals make up most of the regulated contaminants in
drinking water! These chemicals are typically carcinogens. Examples of SOCs
include
Pesticides like 2-4,D, methoxychlor, chlordane, di-methly bromide, dioxin
Solvents like TCE, carbon tetrachloride, benzene
Industrial chemicals like styrene, PCBs
MCLs DPB, Radionuclides, VOC
THMs and other Disinfection By-Products (DBPs)
Tri Halo Methane, or THM is the original regulated disinfection by-product. Most familiar is chloroform.
THM MCL = 0.1 mg/L Considered a carcinogen
THMs form as the result of chlorine reacting with organic material in water, especially humus-like
substances.
Sampling required for chlorinated systems greater than 10,000 pop., once each quarter. A running
average is calculated.
Halogenated Acetic Acid, or HAA6 is an important new disinfection by-product
MCLs for disinfectants:
*free chlorine
4 mg/L
*chloramine
4 mg/L
*chlorine dioxide
4 mg/L
*ozone
0
Radionuclides
Radionuclides emit alpha, beta and gamma radiation that can result in an increased risk of cancer from
exposure. Contamination of water is the result of natural radioactive minerals in geologic strata.
VOCs
Volative Organic Compounds that are readily lost from water if it is exposed to air. They are a problem in
groundwater not surface water. VOCs are chemicals used as solvents, cleaning agents, and gasoline
additives
VOCs are suspected carcinogens; examples are the gasoline additives called BTEX
*benzene
*toluene
*ethylbenzene
*xylene
MCL Microbiological & Turbidity
Coliform Bacteria and Turbidity
Coliform bacteria are generally harmless indicator bacteria. They indicate possible fecal
contamination and the potential for waterborne pathogens to be present.
No more than 5.0% samples total coliform-positive in a month.
(For water systems that collect fewer than 40 routine samples per month, no more than one sample
can be total coliform-positive).
Every sample that has total coliforms must be analyzed for fecal coliforms.
There cannot be any fecal coliforms.
Fecal coliform and E. coli are bacteria whose presence indicates that the water may be
contaminated with human animal wastes. Microbes in these wastes can cause diarrhea,
cramps, nausea, headaches, or other symptoms.
Turbidity does not have a health effect. Turbidity is regulated for the following reasons:
*it may interfere with the disinfection process
*it may hide or protect microorganisms from the action of disinfectants
At no time can turbidity (cloudiness of water) go above 5 nephelolometric
turbidity units (NTU); systems that filter must ensure that the turbidity go no higher than 1
NTU (0.5 NTU for conventional or direct filtration) in at least 95% of the daily samples
in any month.
Breakpoint Chlorination
Zone I: Chlorine is destroyed by reducing agents such as
iron, manganese, clay and silt. Chlorine reduced to
chloride
Zone II: Chlorine comes into contact with organics and
ammonia. Chloroorganics and chloramines are formed.
Zone III: Chloroorganics and chloramines are partially
destroyed. Chloramines are broken down and converted to
nitrogen gas which leaves the system
Zone IV: Breakpoint. Beyond this point, free available
residual is formed. Some chloroorganics still remain as
combined residual.
Chlorine demand is difference between applied chlorine and the free chlorine
residual at any two points on the breakpoint curve.
The objectives for this week to become
familiar with basic characteristics of
drinking water quality has been met
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