California State University FresnoCE 142L Environmental Qual.docx

California State University Fresno
CE 142L Environmental Quality Laboratory
Laboratory Manual
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California State University, Fresno
Department of Civil & Geomatics Engineering
CE 142L: Environmental Quality Laboratory Manual
2
PRELUDE: WHAT IS ENVIRONMENTAL CHEMISTRY

INTRODUCTION:
What is environmental chemistry? This question is a little
difficult to answer because environmental
chemistry encompasses many different topics. Some define it as
follows:
“Environmental chemistry is the study of the sources, reactions,
transport, effects, and fates of
chemical species in water, soil, and air environments." (Stanley
E. Manahan. 1991.
Environmental Chemistry, 5th ed.).
"(The) central position of aquatic chemistry in the natural
sciences gives it an increasing
popularity in science and engineering curricula; it also makes it
a difficult topic to teach for it
requires exploring some aspects of almost all sciences."
(Francois M. M. Morel. 1983. Preface to
Principles of Aquatic Chemistry).
Basically, Environmental Chemistry is the use of chemistry to
understand the interactions of
environmental systems. Water chemistry is an important aspect
of Environmental Chemistry.
A fundamental tool in analyzing water chemistry is total
dissolved solids (TDS). The TDS in water
consists of dissolved inorganic salts and organic materials. In
natural waters, salts are chemical
compounds comprised of anions (-) such as carbonates,
chlorides, sulfates, and nitrates (primarily in
ground water), and cations (+) such as potassium (K),
magnesium (Mg), calcium (Ca), and sodium (Na)
(EPA, 1986). In ambient conditions, these compounds are
present in proportions that create a charge-
balanced solution. If there are additional inputs of dissolved

solids to the system, the balance is altered
and the solution will adjust to achieve charge balance.
This lab manual includes exercises in water chemistry
calculations in order to better understand chemical
reactions within the aquatic environment. A fundamental
understanding of water chemistry is necessary
for the remaining laboratory experiments and, later on, for
professional practice in civil engineering.
PREPARATION BEFORE ARRIVING AT LAB:
1. The knowledge provided in high school chemistry courses
and in CHEM 1A and 3A, while
important, is not adequate for this course or for CE 142 lecture.
In view of this, all students in both
courses are expected to devote a considerable amount of time
outside of class expanding their
knowledge of the chemical concepts contained in the lab manual
for this course and in the textbook
adopted for CE 142.
2. Students are expected to arrive to lab with a complete
understanding of the topic assigned for the
week. Therefore, students are to (a) study in advance of the lab
all relevant material in the lab manual
pertaining to the topics and (b) conduct additional reading on
the topics from the recommended
textbook and other sources (books, Web, etc..). An excellent
source of knowledge can be found in
YouTube videos.
3. Students are expected to print and bring to class hard copies
of each lab exercise, or to have ready
access to the material on their laptop.

3
Contents
LAB 1: WATER CHEMISTRY CALCULATIONS
....................................................... 4
LAB 2: GAS TRANSFER
..............................................................................................
5
LAB 3: BIOCHEMICAL OXYGEN DEMAND
.......................................................... 12
LAB 4:
ADSORPTION........................................................................
........................ 21
LAB 5: SOLIDS IN WATER
....................................................................................... 24
LAB 6: CHEMICAL COAGULATION JAR TESTING
.............................................. 30
LAB 7: CHEMICAL EQUILIBRIUM, BUFFERING, AND
ALKALINITY ............... 36
LAB 8: HARDNESS
...............................................................................................
..... 44
LAB 9: CADILLAC DESERT: WATER &
TRANSFORMATION OF NATURE ...... 48

4
LAB 1: WATER CHEMISTRY CALCULATIONS
Instructions: Do your calculations on engineering paper and
then transfer the answers to the spaces
indicated near the problem statement. Attach your calculations
to the lab sheets when you are finished.
Your calculations should be presented in a professional manner
-- legible, organized, and complete so that
someone else can understand them.
Recommended reading from your course textbook (Sawyer,
C.N., P.L. McCarty, and G.F. Perkin,
Chemistry for Environmental Engineering, 4th ed., McGraw
Hill, New York, 1994.): Chapter 2
1. (15 pts.) Molecular weights -- Calculate molecular weights
of the compounds:
a. Sodium bicarbonate (baking soda) -- NaHCO3 Answer:
b. Ferric Chloride -- FeCl3 Answer:
c. Ammonium sulfate -- (NH4)2SO4 Answer:
2. Molar and mass concentrations
a. (10 pts.) If the molar concentration of sodium bicarbonate
(NaHCO3) is 2.00 mM (millimolar),
what is the mass concentration of NaHCO3 (in mg/L)? For the
same molar concentration, what is
the mass concentration of Na+?
Answer: Answer:
b. (15 pts.) What are the molar concentrations of iron (Fe3+)
and chloride (Cl-) in a solution with a
mass concentration of 40.7 mg/L FeCl3?

Answer:
3. Mass loading and concentration calculations
a. (10 pts.) What mass of ammonium sulfate (NH4)2SO4 must
you add to water to make a 1.50 L
solution that is 0.045 M?
Answer:
b. (10 pts.) Suppose 1.50 L of a solution with a mass
concentration of 45 mg/L of some salt is left
uncovered in a warm dry room. If, after a week, the volume has
dropped to 0.45 L due to
evaporation, what is the final concentration?
Answer:
c. (10 pts.) A treatment plant discharges a wastewater flow to a
lake. If the flow is 3.550 million
gallons per day and the concentration is 25.00 mg/L of Nitrate
(NO3), what is the annual mass
loading of total Nitrogen (N) (in lb/yr).
Answer:
4. Ideal Gas Law (15 pts): How many pounds of Argon are
there in a 3.880 cubic foot tank if the
pressure is 18.00 atm, the temperature is 20.00 �C, and the
Argon purity is 99.0%?
Answer:
5. Adsorption (15 pts): In an adsorption batch test, substance Y
is dissolved in the solution with an initial
concentration of 370 mg/L. 0.450 gram of granulate activated
carbon (GAC) was added to 100 mL of
such solution and had sufficient contact time with the solution.
The substance Y solution now has a

concentration of 12.0 mg/L. What is the mass of substance Y
that is adsorbed to the GAC? What is
mass to mass ratio of the adsorbed substance Y to GAC in
mg/kg at this equilibrium concentration?
Answer:
5
LAB 2: GAS TRANSFER
INTRODUCTION
Gas transfer is defined as the process of allowing any gas to
dissolve into a fluid, or, the process of
promoting the release of a dissolved gas from a fluid. For our
purposes the gas of interest is oxygen. Gas
transfer of oxygen to water plays an important role in water and
wastewater treatment through a process
known as aeration. In wastewater treatment, aeration has
several functions, which are as follows:
· Prevents the formation of hydrogen sulfide, an odor causing
substance.
· Stripping of volatile organics and inorganics from the water.
· Oxygen supply for aerobic biological treatment of activated
sludge. This is also needed for a
process known as nitrification in which bacteria convert
ammonia nitrogen into Nitrate NO3-

(Vesilind 1997).
· Raising the dissolved oxygen (D.O.) levels in treated effluent
to waterways to protect aquatic life.
· Increasing oxygen concentration in receiving waterways for
emergency situations, to restore
aquatic life in waterways that have been contaminated.
In water treatment, Aeration also aids in the following:
· Remove taste and odor causing hydrogen sulfide.
· Removal of excess carbon dioxide in groundwater.
· Oxidizing ions such as iron and manganese (Schroeder 1987).
Diffusers and mixers, large scale versions of those used in this
lab, are often utilized in the Aeration
process.
The objective of this lab is to observe and measure gas transfer
rates in three different types of systems
with the aid of a Dissolved Oxygen meter. The three systems
observed are a control system, where the
water is not disturbed, a system involving mixing, and a final
system utilizing a fine bubble diffuser.
BACKGROUND:
Dissolved oxygen (DO) is the measure of the concentration of
free (i.e. not chemically bonded) molecular
oxygen, usually measured in mg/L or percent saturation.
Considered the most important and commonly
employed measure of water quality, DO is primarily used to
assess a body of water’s ability to support
aquatic life. Adequate concentrations of DO are necessary for
aerobic respiration as well as the
prevention of offensive odors.

The presence of DO is a result of a continuous circulation of
oxygen within the environment, commonly
called the oxygen cycle. This process has two primary phases,
one where oxygen is produced and one
where it is consumed. Oxygen is produced during
photosynthesis, a process that converts carbon dioxide
(CO2) to oxygen and sugar using energy from the sun.
Respiration and decomposition consume oxygen
in highly complex processes that covert organic matter into
usable energy.
This cycle of production and consumption, for the most part,
maintains DO levels throughout the
environment at a constant level. On a daily basis, however,
noticeable differences can occur. Because
photosynthesis is dependent upon sunlight, levels of oxygen
production decline during the night. While
6
production declines, consumption, from respiration and
decomposition, continue at a steady pace. The
net result is a decline in DO levels, usually most noticeable
during early twilight.
The amount of dissolved oxygen within water is controlled
primarily by the concentrations of DO both
within the water and within the surrounding air. Oxygen

concentrations within air are usually around
21% while those in water are about 10 ppm. This differential in
concentrations causes oxygen molecules
at the waters surface to dissolve into the water, a result of
partial pressures between the two substances.
Because this process is directly proportional to the area of air in
contact with the water, movement of the
water greatly affects the amount of DO present. Movement of
the water creates waves on the waters
surface. These waves produce a net increase in the available
surface area that, in turn, allows for more
diffusion of oxygen into the water. The more turbulent the
flow, the more surface area and the greater the
concentration of DO within the water.
The amount of DO within the water may be described using
Henry’s Law.
))(( CCak
dt
dC
SL -=
where:
C = the concentration of dissolved gas (mg/L or mole/L)
CS = the concentration of gas under saturated conditions
kL = gas transfer coefficient (cm/s or m/s)
a = ratio of gas/liquid interfacial area to liquid volume (cm-1 or
m-1)
t = time
CS describes the saturation concentration which is the
concentration predicted by Henry’s Law. By
integrating this equation and applying the necessary boundary

conditions
(at t = 0 and C = C0) we are left with the exponential decay
function;
)(
0 )(
atk
SS
LeCCCC --=-
(CS –C), often called the “deficit” shows how the relationship
between the initial concentration and the
saturated concentration effects the decay function. Notice that
when C is farthest away from CS, the slope
of the decay curve is greatest. This implies that as the
concentration increases towards saturation, the
amount of dissolving decreases. Also note how the decay
function is related to “a,” the ratio of surface
area to volume. This relationship shows how the creation of
waves affects the amount of dissolving.
Another physical attribute of water that greatly affects DO
concentrations is that of temperature.
Saturation, the point at which a substance has the maximum
amount of another substance within in it, is
greatly affected by temperature. Colder water, for instance, is
capable of holding more oxygen than
warmer water (i.e. warmer water becomes saturated more easily
than cold water). If a body of water, say

7
a lake, is warm it will be capable of holding less oxygen than if
it were cold. Even if the water is 100%
saturated, it will still have less DO than an equivalent lake at a
lower temperature.
This affect of temperature on the levels of DO can lead to
stratification of the body of water. Thermal
stratification can lead to layers within the water body that are
completely devoid of DO while other layers
may have too much. This can be of great concern to aquatic life
that may be dependent upon specific
levels of DO. Too much or too little DO may result in death.
CONCLUSION
Gas transfer is defined as the process of allowing any gas to
dissolve into a fluid, or, the process of
promoting the release of a dissolved gas from a fluid. Gas
transfer of oxygen to water plays an important
role in water and wastewater treatment through a process known
as aeration. Therefore, the objective of
this lab is to observe and measure the gas transfer rates in three
different types of systems with the aid of
a Dissolved Oxygen meter. The three systems observed are a
control system, where the water is not
disturbed, a system involving mixing, and a final system
utilizing a fine bubble diffuser.

8
LAB 2: PROCEDURES (Gas Transfer)
Objective: To observe and measure gas transfer rates in several
systems.
Equipment and Materials:
· Dissolved oxygen meter
· Deoxygenated water (provided by instructor)
· 1,000 mL beaker (1)
· Watch with second hand
Procedures
Your instructor will brief you on the use of the dissolved
oxygen (DO) meter. Before lab, your instructor
de-oxygenated several beakers of tap water by storing them
under a vacuum and/or reacting them with
sodium sulfite (Na2SO3) and/or bubbling nitrogen gas in the
water.
1. Gently pour approximately 400 mL of deoxygenated water in
the beaker with the beaker at a 45
degree slope and the pour spout of the carboy resting on the
inner wall of the beaker. Try not to
disturb the water excessively while doing so. (Do you know
why?)
2. Set up the beaker either on the counter (control), on a mixer,
or on a bubbler as directed by your
instructor. Assign at least two people to each beaker -- one to
measure the DO and one to keep track

of the time. Either person (or a third) can record the data.
3. Before starting any testing set the meter measurement mode
to “Continuous.” Then measure the
initial DO and the temperature using the DO meter. Wait for the
reading to stabilize. Once the reading
has stabilized and you have an initial DO measurement, you can
start the experiment and the timer.
4. The control beaker should be started first because it takes the
most time. You can run the mixed
beaker test in parallel with the control, except, start it 30
minutes later. When the mixed beaker
measurements are complete you can start the bubbler beaker
test. When moving the probe from the
mixed beaker or bubbled beaker back to the control it will take
time for the probe to adjust to the
lower DO condition, so you must wait for the reading to
stabilize before taking/ recording the first
reading.
5. At the beginning, take time and concentration readings every
1 to 5 minutes in the systems with
slower transfer (i.e., the control) and every 1 to 10 seconds in
the systems that you expect will have a
lot of gas transfer (mixed, bubbled). After you see how fast the
concentration is changing, you can
adjust the time interval. The goals are to make a minimum of
15 to 20 measurements spread out over
the test period for each beaker and to have each test period be
long enough for the DO to approach
saturation (you will not achieve this for the control, so measure
that one for only 1.5 to 2 hours).
Data Analysis
1. Using the temperature read in the lab, find and record the

saturation concentration from an
environmental textbook or from the Internet.
2. Record the data for all of the water samples.
Continued
9
3. Use a spreadsheet program and create a table with time in the
first column and corresponding values
of raw DO concentration in the second column. Create a plot of
DO concentration against time.
4. Add a column to the spreadsheet containing deficit values (D
= CS - C).
· Note that the saturation concentration value (CS) is obtained
from a reference book and the
value will depend only on the water temperature.
· For the control beaker, omit deficit data collected in the early
time period when DO values
were constant (before they began increasing).
5. Add another column containing the quantity -ln(D/D0). The
initial deficit (D0) is the first value of
deficit in the table.
Plot -ln(D/D0) against time (in minutes). Show your plot on a
separate worksheet.

Determine the transfer coefficient for each test using the slopes
of your plots (See the gas transfer
notes.) You can use the linear trend line function to get the
best-fit regression line. Be sure to force
the regression through zero. Format your graph so that the lab
data are displayed as points only (no
connecting line) and the linear trend line.
6. To check the reasonableness of your calculated transfer
coefficient, prepare a plot with your original
data points (plotted as points only) and a line (only) generated
from the integrated gas transfer
equation* using your calculated transfer coefficient.
7. Exchange results with the other groups. Why are the transfer
rates different? Are the differences what
you would expect? Explain.
* C = CS - (CS - C0)e
-(KLa)t
10
LAB 2: NOTES ON GAS TRANSFER KINETICS
Henry's Law describes an equilibrium situation -- the rate of gas
dissolving into the liquid from the
atmosphere (rd) equals the rate at which the gas volatilizes from
the liquid (rv). Under equilibrium, rd = rv.
But what if we are not in equilibrium? Suppose, for instance, a

jar of water with little or no oxygen in it is
opened to the atmosphere and left on a countertop. If we were to
monitor the concentration of oxygen in
the water over time, the results might look like:
Figure 1. Variation of DO Level v.s. the Saturated DO
Concentration
As can be seen, the concentration approaches some maximum
concentration (CS) asymptotically.
Experiments of this kind have shown that the rate of change of
dissolved gas concentration can be
expressed mathematically by:
where
C = the concentration of dissolved gas (mg/L or mole/L)
CS = the concentration of gas under saturated conditions (called
Cequil in your text, p 267)
kL = gas transfer coefficient (cm/s or m/s)
(kL*a) = overall gas transfer coefficient (1/s)
a = ratio of gas/liquid interfacial area to liquid volume (cm-1 or
m-1)
t = time
CS is called the saturation concentration. It is the concentration
when the system is at equilibrium. In other
words, it is the concentration predicted by Henry's Law. Let's
see if this equation makes sense. If C < CS,
then dC/dt > 0, and the concentration rises, indicating that the
net movement is from the air into the water
(rd>rv). If C > CS, then dC/dt < 0, and the concentration drops,
indicating that the net movement is from
the water into the air (rd<rv).
If we integrate this equation and apply the appropriate boundary
condition (at t=0, C=C0), the resulting
equation is:(Do you remember how to do this?)

)(
0 )(
atk
ss
LeCCCC --=- C0: Dissolved Oxygen Concentration at t = 0 sec
In the environment, C is usually less than CS, so the term (CS-
C) is often called the "deficit", D. Rewriting
the integrated equation in terms of the deficit yields:
D = D0e-(kLa)t D0: Deficit of Dissolved Oxygen at t = 0 sec
0
1
2
3
4
5
6
7
8
9
10
0 5 10 15
Time (min)
C
on
ce
nt

ra
tio
n
of
di
ss
ol
ve
d
O
2
(m
g/
L)
Cs = 9 mg/L
))(( CCak
dt
dC
SL -=

11
Notice that this is an exponential decay function. Can you see it
in the graph of experimental results
shown above?
It is helpful to think of the deficit (or CS-C) as a "driving
force" for net gas transfer. Looking at the
differential equation dC/dt = kLa(CS-C), the slope of the C
curve is steepest when C is farthest from CS
(i.e., when the deficit is largest). As C approaches CS, the slope
gets smaller and smaller. In other words,
the driving force for net gas transfer diminishes as the system
approaches equilibrium. This is another
example of Le Chatelier's Principle. When the system's
equilibrium is disturbed, it attempts to re-establish
that equilibrium. The larger the disturbance, the "harder" the
system works to re-establish the equilibrium.
Besides the deficit, what other factors do you think might affect
the rate of gas transfer? Recall our
hypothetical experiment. We left the jar sitting quietly on a
countertop and watched the oxygen climb to
the saturation value. What if we mixed the jar? What if we
bubbled air through the jar? Would the degree
of mixing or the size and number of the bubbles affect the
results? Yes they would.
Physical factors like mixing and bubbles change the gas transfer
rate by their effects on the overall gas
transfer coefficient, kLa. Identifying and measuring the many
factors that affect kLa is usually so difficult
that it is easier to measure k directly by experiment. We can do
this by linearizing the integrated deficit
equation as shown below:
D = D0e-(kLat) D/D0 = e-(kLa)t ln(D/D0) = -(kL a) t (or, y =
mx)

If we run the hypothetical experiment and graph the results
according to the linearized equation, we
should get a plot that looks like:
The slope of a regression line forced through the origin will be
kLa. Measuring the kLa values for several
gas transfer systems is the goal of our lab exercise this week.
Figure 2. Linear Regression of the –Ln (D/D0) Time Sequence
Data
12
LAB 3: BIOCHEMICAL OXYGEN DEMAND
OBJECTIVES
The objectives of this lab are to measure the seven-day
Biochemical Oxygen Demand (BOD7) of a dairy
wastewater sample, to learn how BOD is related to the amount
of organic substances present the
wastewater, and to learn the importance of dilution.
INTRODUCTION1
Biochemical Oxygen Demand (BOD) is the amount of oxygen
used in the metabolism of biodegradable
organics. Typically, BOD tests are conducted over a five day
period. However, for convenience, this
experiment will be conducted over a seven day period. To
understand how BOD is related to organic
substances in water, it is necessary to know about the

degradation of these substances. Bacteria and other
forms of microbes feed on organic waste. These microbes, like
most life forms, consume oxygen while
metabolizing food, causing a demand for oxygen, or BOD. In
water, there is only a limited amount of
oxygen, dissolved oxygen (D.O.), present for consumption. If
all the available oxygen is consumed by
microbes, it can be catastrophic to the aquatic life in the water
that also depend on the D.O. for survival.
In wastewater treatment, these same microbes are used to aid in
the removal of organic substances from
the water. This is done through aeration, by transfer of oxygen
to the water through diffusers or mixers,
to keep the D.O. constant until the microbes consume all the
organic matter present. For these reasons it
is important for engineers to be able to determine the BOD of
waters as an indirect measure of the organic
substances in the water.
BACKGROUND
Biochemical Oxygen Demand
BOD measures the amount of oxygen required by aerobic
bacteria and other microorganisms which
decompose organic matter. Microorganisms use oxygen directly
proportional to the amount of organic
matter oxidized in biochemical oxidations. BOD determination
is used in studies to measure the
purification capacity of streams. It also serves regulatory
authorities as a means of checking the quality of
effluents discharged into such waters. The BOD test is the only
test that can measure the amount of
biologically oxidizable organic matter present. It determines
the rates at which oxidation will occur or
BOD exertion in the receiving bodies of water. This is the
reason why BOD is a major criterion used in

stream pollution control where organic loading must be
restricted to maintain desired dissolved-oxygen
levels.
BODt is the amount of BOD exerted during the duration of a
test, while the BODu is proportional to the
total biodegradable organic content of the water. The BODu is
the ultimate or limiting BOD, meaning the
DO reaches a point where it stops dropping and remains
constant. The total DO drop at this point
represents the ultimate BOD. This means that the bacteria
consumed all of the organic material or that
there was not a sufficient supply of oxygen for decomposition.
Dissolved Oxygen (DO)
DO is a major determinant of water quality in streams, lakes,
and other water courses such as
groundwater. The saturation of oxygen in water is a function of
temperature and pressure. Also, the
concentration of dissolved solids in the water affects the
saturation levels of oxygen in water. For
1
Adapted from the Technical Information Series—Booklet No. 7
by Clifford C. Hach, Robert L. Klein, Jr., Charles R. Gibbs
13
example, the solubility is less in saline waters. Also, solubility
of oxygen varies greatly with the

temperature. DO will be measured using an oxygen probe and
meter for this experiment. For a successful
experiment, two factors must be taken into consideration.
Since the rate of oxygen consumption is
temperature dependent, temperature must remain constant, ± 2
�C for an accurate analysis of BOD.
Also the reaction needs to take place in the dark. This is very
important because the presence of algae
will produce an error in the BOD measurements. Algae
photosynthesizes in the light, producing oxygen
in the testing bottles, creating an error in the end results.
Dilution
The size of the sample volume plays an important factor in the
success of a BOD measurement. If the
sample volume is too large, oxygen supply will be diminished
before the five day mark yielding an
inaccurate BOD analysis. Bacteria will be overwhelmed by the
massive amount of organic material
available and will quickly deplete the oxygen supply since
decomposition of organic material is
proportional to oxygen consumption. In the other case, if the
sample volume is too small, the change in
DO will be too small to give reliable results. The change in DO
will be minimal. Therefore, the dilution
is crucial to ascertain reliable results. The following table
shows the standard DO thresholds, which will
be used to discredit sample volumes falling into the two DO
concentrations conditions:
Threshold Test Problem
Final DO < 1 mg/L Sample volume too large
DOo – DOt < 2 mg/L Sample volume too small
Any test that falls in either of the conditions listed above is
considered invalid.

The effect of sample volume on the D.O. in the bottle during a
BOD test is shown in the Figure 1.
Figure 1. Effect of Sample Volume on Dissolved Oxygen
During a BOD Test
For any chosen dilution, you can calculate the range of BOD
values that give valid tests. The upper BOD
value can be calculated from assuming the starting D.O. to be a
typical saturation value at room
temperature (say, 8 mg/L) and setting the final D.O. equal to 1
mg/L. The lower BOD value can be
calculated by setting the �D.O. value to be 2 mg/L. A table of
BOD ranges for different dilution factors
is shown below in Table 1. (Can you duplicate these
calculations?)
0
2
4
6
8
10
0 1 2 3 4 5 6 7 8
time (day)
D
O

(m
g/
L)
Too much organic mat'l
Not enough organic mat'l
14
Table 1 BOD Measurable with Different Sample Dilutions
(Adapted from Sawyer, et. al.)
Volume of Sample in a 300-mL Bottle
(mL)
Range of BOD Measurable
(mg/L)
0.02 30,000 - 105,000
0.05 12,000 - 42,000
0.1 6,000 - 21,000
0.2 3,000 - 10,500
0.5 1,200 - 4,200
0.7 857 - 3,000
0.8 750 - 2,625
1 600 - 2,100
1.25 480 - 1,680

1.5 400 - 1,400
1.75 343 - 1,200
2 300 - 1,050
5 120 - 420
10 60 - 210
50 12 - 42
100 6 - 21
300 2 - 7
Based on past experience, we've chosen sample volumes for the
wastewater to be tested. To cover
possible fluctuations from past experience, we will choose
several dilutions to cover a wide range of
possible BOD5 values. Some bottles will exceed the threshold
values discussed above, but if we've
chosen wisely, at least one bottle will result in a valid test.
Length of Test
The standard BOD test is read after 5 days. For the sake of
convenience, we'll read ours after 7 days
during the normal lab period.
15
BOD Equations
Expressing the word definition of BOD in the form of an
equation yields:

VolumeSample
VolumeBottleSampleConc.)DOFinal-Conc.DO(Initial
SampleofVolume
usedDOofMass
BOD
´
==
The shorted version is:
P
DO-DO
BOD t0t =
where: BODt = Biochemical oxygen demand at time t, mg/L
DO0 = Initial dissolved oxygen concentration in the BOD
bottle, mg/L
DOt = Final dissolved oxygen concentration in the BOD bottle,
mg/L
P = Ratio of the sample volume to the bottle volume
(Vsample/Vbottle)
Vbottle = 300 mL for standard bottle
CONCLUSION
Biochemical Oxygen Demand (BOD) is the amount of oxygen
used in the metabolism of biodegradable
organics. The design of treatment facilities relies on the
information concerning the BOD of wastes. It
factors into the choice of treatment methods and is used to
determine the size of treatment units,
particularly trickling filters and activated-sludge units. The
BOD test is used to evaluate the efficiency of

various processes during operation at treatment plants.
Typically, BOD tests are conducted over a five day period.
However, for convenience, this experiment
will be conducted over a seven day period. The objectives of
this lab is to measure the seven-day
Biochemical Oxygen Demand (BOD7) of a dairy wastewater
sample and to learn the importance of
dilution.
Second Week of BOD Pre-Lab, Final Report & Presentation
The material below applies to (1) the pre-lab for the second
week of the BOD lab, (2) the final report and
(3) the presentation. Define and discuss the terms and topics
listed below in your own words (paraphrase
the works of others). CITE YOUR SOURCES (provide
references).
1. A. Ultimate BOD (BODU)
B. Carbonaceous BOD (CBOD)
C. Nitrogenous BOD (NBOD)
D. Addition of nutrients
E. Addition of seed microorganisms.
F. Modeling BOD Remaining (BODR(t)) and BOD Exerted
(BOD(t))*.
2. Theoretical Oxygen Demand (ThOD)
3. Chemical Oxygen Demand (COD)
* See additional notes (located after the procedures below).

16
LAB 3: PROCEDURES
Objective: The objectives of this lab are to measure the seven-
day Biochemical Oxygen Demand (BOD7)
of a dairy wastewater sample, to learn how BOD is related to
the amount of organic
substances present the wastewater, and to learn the importance
of dilution.
Bottle Set-up and Incubation
1. Each group will be given a water sample to test. The
instructor will brief you on the source of the
sample to be tested.
2. We don't know in advance the BOD values of the different
waters. Consequently, we will need to
make several dilutions so that the change in dissolved oxygen
(DO) is neither too great nor too small.
Each group will set up several BOD bottles, but because some
tests are likely to fail, we'll combine
everyone's data at the end.
3. Your instructor will direct you on how many bottles to set up,
and what volumes of sample to test.
Use a pipet for volumes less than 50 mL, and a graduated
cylinder for larger volumes.
4. Without excessive agitation fill the remaining volume of each
BOD bottle with dilution water
provided by your instructor.
5. Measure the dissolved oxygen concentration using a DO

meter and probe. Be very careful that there
are no air bubbles in the bottle when you do this measurement.
a. Remove the probe shield (remove it carefully to avoid
damaging the plastic probe cap).
b. When the probe shield is off, be careful to protect the probe
tip from being scraped.
c. Record the bottle numbers, their contents, and the DO
concentrations (after dilution).
6. Seal each bottle with a glass plug. Be very careful that there
are no air bubbles in the bottle. After
sealing, make sure that there is water in the "wet well" at the
top of the bottle. If not, remove the glass
stopper, add more dilution water, and reseal. Finally, place a
plastic cap over the "wet well" to
prevent the seal from evaporating.
7. Place all of the bottles in the constant temperature room as
directed by your instructor.
Dissolved Oxygen Measurement
8. After seven days (i.e., the next lab period), take your samples
from the constant temperature room.
Before opening each bottle, note (and record) if the water seal
in the wet well is not intact and if any
bubbles are visible in the bottle. (Bubbles may be CO2, but
they may also indicate a malfunctioning
seal.)
9. Measure the DO concentrations and record your data.
10. Rinse the DO probe with DI water; carefully replace the
probe shield (CAUTION – do not tighten
shield while it is resting on the plastic probe cap; move it back
before tightening.)
11. Wash the glassware, caps, etc…. and set them to dry on the

glassware rack.
Data Analysis
1. Check your data against the threshold values (i.e., the
minimum allowable DO after seven days and
the minimum allowable change in DO). Throw out any invalid
test results.
2. Calculate the BOD7 values associated with your valid test
data and record those values. (Don't forget
to provide sample calculations.)
3. Collect and record the valid BOD7 values from the other
groups.
4. Summarize all of the valid test results (BOD values from the
entire class) the data statistically by
reporting the range, mean and standard deviation values.
17
LAB 3: ADDITIONAL NOTES ON BOD
Let's think about how one might measure organic material. If
the material was a single substance, such as
sucrose (table sugar), it would be possible to employ one of
several chemical techniques to isolate and
measure the amount of sucrose. But suppose you wanted to
measure a mixture of organics. It might be
possible to isolate each and measure it through chemical means,

but this wouldn't be practical or useful. In
wastewater or even natural waters like rivers and lakes, there
may be hundreds of organic substances.
Analyzing for all of these compounds would be a huge task, and
wouldn't tell us what we really want to
know anyway. We could use a "lumped" parameter like Total
Organic Carbon (TOC), but this doesn't tell
us anything about the biodegradability of the organic substances
or the rates of conversion.
Biodegradability is a key issue.
All natural environments teem with microbial life (e.g., a
typical agricultural soil can contain as many as a
million bacteria per gram!). For these microorganisms, organic
waste is a source of food. Like virtually
all higher forms of life (i.e., you and me), many of these
microbes use oxygen to metabolize their food.
As microbes degrade organic substances, they pull oxygen from
the local environment in direct
proportion to the amount of organic material metabolized.
There's lots of oxygen in the air, but the
amount dissolved in water is limited (recall the gas transfer
lab). If enough organics are present, microbes
will use up all of the available oxygen and fish will die. This is
the reason engineers are interested in
measuring organic materials.
The Biochemical Oxygen Demand (BOD) test was developed in
Britain in the early part of this century.
It is a simplified physical model of what would happen if an
organic waste is added to a stream. In the
test, a liquid containing organic wastes (either full strength or
diluted) is placed in a bottle. The DO is
measured and the bottle is sealed. After some incubation time
(usually 5 days), the DO of the sample is
measured again. Because the bottle is sealed, the difference in

the DO values represents the oxygen used
by microbes in degrading the waste. The change in DO is an
indirect measure of the organic substances
in the bottle. Through this process we see that biodegradable
organic materials have associated with them
a potential demand for oxygen when they are degraded (hence
the name biochemical oxygen "demand").
The calculation of the BOD uses the following equation:
Where
DO0, DOt = dissolved oxygen concentrations at t=0 and t=t
P = dilution factor = Volume of sample � Volume of the BOD
bottle (300 mL)
If the waste is strong, the oxygen in the bottle will run out
before the end of the incubation period. This is
why we dilute the waste. If we over-dilute it, the change of DO
will be too small to be statistically
reliable.
P
DODO
BOD t
-
= 0

18
A typical graph of DO in the BOD bottle as a function of time
might look like Figure 1 below:
Figure 1. Decay of the DO in the BOD Bottle
As shown in the graph, if we wait a long time, the bacteria
consume all of the organic material, and the
DO stops dropping. The total DO drop at this point represents
the "ultimate BOD" (also called BODu or
sometimes BODL for "limiting BOD"). Twenty to thirty days is
a long time to wait, so usually the bottles
are opened and measured after 5 days, and the test results are
reported as the "5-day BOD" or BOD5.
Originally, 5 days was chosen as the incubation time because
that is the longest travel time of any river in
Britain. We continue to use this value today, although the
choice of incubation time is really arbitrary.
To convert between BOD5 and BODu, we need to know
something about the kinetics of the BOD test.
Suppose we set up 7 BOD bottles on day 0. Periodically over
the next month, we open a bottle and
measure the DO. If we use these DO values in the BOD
equation shown above, we would see an
increasing BOD result. In other words, BOD1 > BOD2 > BOD3
… because DO1 < DO2 < DO3 …. If we
plot the BOD values against time, we get a curve like that
shown in Figure 2.
Figure 2 Increase of BOD values with time

19
Notice that the measured values of BOD start at 0 and end up at
the ultimate value. When you compare
Figure 2 with Figure 1, you see that Figure 2 is actually Figure
1 flipped over. While it is not always true,
very often we can fit a first order exponential model to these
data. The equation of the model is:
BODt = BODu (1 - e-kt)
If you plug "5" in for "t", you can convert between BOD5 and
BODu using this equation.
It is important that you understand the difference between
BODu and BODt.
BODu is proportional to the total biodegradable organic content
of the water. If you add more
biodegradable organic material to water, BODu will increase.
BOD5 is the amount of BOD exerted in the 5-day test and is
proportional to the amount of organic
material degraded in 5 days. It is normally assumed that BOD5
is proportional to the BODu but this may
not always be true. In Figure 3 for instance, three samples all
exerted about the same BOD5, yet they all
had different BODu's. How might this happen? Different
organic substances degrade at different rates.
Most waters contain a mixture of organic substances. In two
samples, if the amounts of organic
substances degradable in 5 days are equal, then the BOD5
values will be equal. The two samples could
have different amounts of organics that degrade more slowly, so
the BOD u values will be different.

Figure 3. Measured BOD variation over time for different
organic substances
Please note that the first order model does not always fit BOD
data. Don't be surprised if in real life, you
get data that doesn't plot out in such neat curves. Like any
mathematical model, use the first order
equation with care.
Finally, there is one more kinetic issue to consider. Suppose we
put a water sample with biodegradable
organics into a batch reactor and supply it with oxygen in the
form of air bubbles. Now suppose we take
a sample out each day and test the sample in a BOD5 test. We
would see that the BOD5 of the original
water decline over time as shown below:
20
Figure 4 BOD decay over time
What we see here is that the BOD5 of the water declines over
time. If the k value is constant, then the
relationship between BOD5 and BODu will be constant. So if
the measured BOD5 declines over time, the
BODu, representing the organic material in the water, also
declines over time. In other words, the organic
material remaining in the water is being converted to something

else -- CO2 and other nondegradable
substances -- by the bacteria. Often, a first order decay reaction
can be fit to these data. If the organic
material in the water (expressed in BOD units) is called "L" (as
it is in your book), then
L = L0 e-kt
Usually L is measured as BODu. We will see this relationship
often in solving mass balance problems for
the degradation of organic materials in streams, lakes, or
treatment plants. Be warned, however, that not
all organics decay according to a first order model. Don't be
surprised by real-life data following a
different pattern.
21
LAB 4: ADSORPTION
Objectives
The purpose of this exercise is to demonstrate the phenomenon
of adsorption and compare the adsorptive
behaviors of different materials. Batch adsorption tests will be
conducted using methylene blue (MB), a
cationic organic dye, and several different adsorbents (activated
carbon, clay, and sand).
Background
Adsorption of solutes originating from the bulk of one phase on
to the surface of an adjacent phase occurs

throughout nature. This mass transfer process is used to remove
contaminants in water treatment
operations. The Freundlich and Langmuir isotherms are two
mathematical models commonly used to
describe adsorption phenomenon. The isotherm is an empirical
relation between the concentration of a
solute on the surface of an adsorbent (mass/mass) to the
concentration of the solute in the liquid with
which it is in contact (mass/volume or mass/mass). Another
model is the B.E.T. The Freundlich
isotherm equation is as follows:
q = x/m = KCe
1/n
where: K and n are empirical coefficients;
K represents adsorption capacity at unit concentration
1/n represents strength of adsorption.
x = mass of MB adsorbed (mg)
= (mass of MB in the liquid at the start) - (mass of MB in the
liquid at the end)
= (Ci*VMB)start - (Ce*VMB)end = (Ci - Ce)VMB
Ci = initial concentration of MB in the solution (mg/L)
Ce = final concentration of MB in the solution when at
equilibrium (mg/L)
VMB = volume of MB solution (L)
m = mass of adsorbent (the material that adsorbs MB) (mg)
Procedures
Calculating the methylene blue concentration
Methylene blue can be measured using a spectrophotometer.
The intensity of a ray of monochromatic
light decreases exponentially as the concentration of light-
absorbing material in the medium (water in our
case) increases (Beer's Law). A spectrophotometer can sense the

absorbance of light at specified
wavelengths.
Absorbance = log(I0/I) = proportional to concentration
where I0 and I are the intensities of the light entering and
leaving the test sample, respectively. Light
absorbance at a wavelength of 655 nm has been found to work
well for detecting methylene blue. The
absorbance can be related to the concentration of the light-
absorbing substance through use of a linear
calibration curve.
1. Your instructor will provide a series of dilutions of a stock
methylene blue solution. Use a pipet to
remove about 10 mL of the solution and place it into a small
test cell designed for the
spectrophotometer (we will use the square 10 mL sample cells).
2. Zero the spectrophotometer unit using deionized water, then
measure absorbance values of the
standards your instructor gives you and report those values to
the class to be recorded in your lab
notebook.
22
3. Plot concentration of standard (y-axis) against absorbance (x-
axis) and use the trendline function on
the computer (in Excel) or on your calculator to fit a linear

curve through the data. Be sure to include
the equation for the curve on your plot. What we want is a
calibration curve equation that yields
concentration values when experimentally-found values of
absorbance are plugged in to it.
4. Use this equation to calculate methylene blue concentrations
from absorbance values in the rest of the
lab.
Adsorption Test
1. Place 50 ml of methylene blue solution into four100-ml
beakers.
2. Weigh out the adsorbent material assigned to your group and
prepare to add it to the beakers with the
dye in the next step. It's OK if you don't hit the specified
amount exactly; just record the mass you
use.
Mass of Adsorbent: 0.01, 0.05, 0.10, & 0.50 grams
3. When your instructor gives the signal, add all of your
adsorbent masses to the flasks containing MB
and swirl or stir the beakers for 15 minutes.
4. Transfer approximately 15 mL of solution from the top of
your beaker (avoid the solids) into
centrifuge tubes and give it to your instructor for centrifugation.
5. After centrifugation, remove your tube. Use a pipet to
remove about 10 mL of the supernatant, and
place it into a small test cell. Do this step very carefully.
Suspended solid material will cause you to
get an inaccurate absorbance reading.

6. Put the test tube into the spectrophotometer and read the
absorbance.
Data Analysis
1. Calculate the mass of MB adsorbed per mass of adsorbent, q
= x/m
2. Using your data, plot either:
a. log(x/m) as a function of log(Ce) on arithmetic scales. A
linear trend line is used to obtain the
Freundlich coefficients as follows: K = 10y-Intercept and 1/n =
the slope.
b. x/m as a function of Ce on log-log scales (as shown in Figure
1 below). A power function trend
line yields the Freundlich equation directly.
3. Exchange data with your classmates; Compare the results; In
the final report explain why the
adsorption capacities of the materials are different.
4. For the best adsorbent use the Freundlich isotherm equation
to generate a smooth plot and plot values
of x/m as a function of Ce on arithmetic scales.
23
Figure 1. Example of Freundlich Isotherm-generated data
plotted on log-log scales. When plotted in this

manner a power function trend line yields the Freundlich
equation directly.
[Note: When plotting Log(q) vs Log(Ce) on arithmetic scales a
linear trend line is used to obtain the
Freundlich coefficients as follows: K = 10y-Intercept and 1/n =
the slope.]
24
LAB 5: SOLIDS IN WATER
BACKGROUND
Tests will be performed to measure solid materials present in
wastewater. These tests are of great use in
assessing the reuse potential of a wastewater and in determining
which types of treatment processes are
best for the wastewater. Four types of tests will be performed
to determine total solids (TS), total
suspended solids (TSS), volatile suspended solids (VSS), and
turbidity. The measure of solid materials
within water supplies is of particular importance to engineering
practice. While the effects of such
measures are of primary concern to environmental and
biological engineers, they are not independent of
other engineering applications. Water’s abundance and its
significant role in life processes has made it
into one of the many commonalties shared by all engineering
disciplines. As such, the effects that solid

materials have on water’s chemical and physical properties are
of considerable importance to the
practicing engineer. With this in mind, this lab was developed
to familiarize one with four different
measures of solid materials in water and to provide a means to
obtain such measures.
TOTAL SOLIDS
The first measure, total solids (TS) deals with both undissolved
and dissolved solids. Undissolved solids
are usually referred to as suspended solids (discussed further
below). Total solids, as the name implies, is
a measure of all residue left after evaporation of the water
phase, usually at around 103�C. This test
consists of placing a known volume of a sample in a pre-
weighed evaporating dish, allowing all water to
evaporate, and then determining the mass of dried solids as the
difference between the dish plus dried
solids and the dish alone. Total solids is calculated as mass of
dried solids divided by the sample volume
as follows:
Note: A & B are defined differently here than in the eqn.’s that
follow.
where: TS = Total Solids (mg/L)
A = Final mass of container with sample after dry (mg)
B = Initial mass of empty container (mg)
V = Sample volume (mL)
There are many reasons for determining the total amount of
solids present in water. One reason is for
determining if water is suitable for domestic use, such as for
drinking water. Water that contains more
than 500 mg/L of solids often has a laxative effect on humans,

especially those who are not accustomed to
it (Schroeder 1987). It is also extremely valuable in analyzing
raw and digested sludges, which is
important when designing and operating sludge-digesters,
vacuum-filters, and incinerators for wastewater
treatment facilities. Another use of the total solids test is in
detecting changes in the water density of
waterways to determine if there is possible contamination from
wastewater.
TOTAL SUSPENDED SOLIDS
The second measure concerns total suspended solids (TSS).
Suspended solids are the undissolved solids
present in water. Analysis of suspended solids is useful when
the turbidity measurements do not provide
adequate information and is very valuable in analyzing polluted
waters. Measurement of suspended
solids aids in evaluating the strength of wastewaters and helps
when evaluating the efficiency of treatment
facilities. While total solids measured all solid material, total
suspended solids is a measure of only those
solids that are larger than approximately 1.2 µm in size and
typically held in suspension within the
sample. In other words, total suspended solids are those that
are “undissolved”. The measurement of
TSS is accomplished by means of a filter that removes all
suspended solids within a given sample. Total
suspended solids can be classified into two main categories,
those that are volatile and those that are not.
V
1000 xB)-(A
TS =

25
Note: A & B are defined differently here than in the other
equations.
where: TSS = Total Suspended Solids (mg/L)
A = Final mass of container with filter and sample after dry
(mg)
B = Initial mass of container with filter (mg)
VOLATILE SUSPENDED SOLIDS
Volatile suspended solids (VSS), also called organic solids, are
solids that are combustible at 550�C.
The volatile solids test is often used in estimating the organic
characteristics of solids present in a
wastewater and thus is an indirect measurement of the organic
matter present. VSS is measured by
igniting the total suspended solids and measuring whatever is
left. The mass that is left behind after
combustion is a measure of the non-volatile solids while the
mass lost during incineration comprises the
amount of volatile solids.
V
1000 xB)-(A
VSS = Note: A & B are defined differently here than in the

other equations.
where: VSS = Volatile Suspended Solids (mg/L)
A = Mass of container with filter and sample after drying and
before ignition (mg)
B = Mass of container with filter and sample after ignition (mg)
TURBIDITY
The final measure of solid material within water is called
turbidity. The turbidity test is useful in water
treatment for determining the quality of drinking water. When
colloidal (clay-size) particles are present
in the water (mud puddle water for our purposes), they cause
incoming light to become scattered, thus
causing the water to appear cloudy or turbid. The portion of
light that scatters at an angle of 90 degrees
from the direction of the source light is measured using photo-
sensitive cells. A turbidimeter is an
instrument capable of measuring turbidity. Turbidity is often
measured using a special the unit NTU.
CONCLUSION
The measure of solid materials within water supplies is of
particular importance to engineering practice.
While the effects of such measures are of primary concern to
environmental and biological engineers,
they are not independent of other engineering applications.
Water’s abundance and its significant role in
life processes has made it into one of the many commonalties
shared by all engineering disciplines. As
such, the effects that solid materials have on water’s chemical
and physical properties are of considerable
importance to the practicing engineer. In this Lab, tests will be

performed to measure solid materials
present in wastewater. Four types of tests will be performed to
determine total solids (TS), total
suspended solids (TSS), volatile suspended solids (VSS), and
turbidity.
V
1000 xB)-(A
TSS =
26
LAB 5: PROCEDURES (Measuring solids in water)
Purpose of Lab
The purpose of this lab exercise is for the student to become
familiar with four different measures of solid
materials in water: (1) total solids (TS), (2) total suspended
solids (TSS), (3) volatile suspended solids
(VSS), and (4) turbidity.
Procedures
Total Solids
1. Weigh two (2)* clean evaporating dishes on the precision
balance (the one with a glass enclosure
with sliding sides). Record those values.
2. Add a known volume of representative sample (about 10 ml)
to the dish and place it in the drying

oven (at 105 � C) until the water is completely evaporated
away.
3. Weigh the evaporating dish plus sample. Record that value.
4. Remove the dish from the oven and cool in a dessicator.
5. Reweigh the dish (with solids) and record the mass.
* Normally three or more samples would be analyzed. Do you
know why? We are using less due to the
limited time available during the lab period.
Total and Volatile Suspended Solids (TSS and VSS)
1. Obtain two (2) filters and aluminum boats from your
instructor. These filters will have been
previously washed and dried. Because you are weighing things
on an analytical balance, which can
read 1/10,000 gram, you want to be careful to avoid
contaminating the sample with dust or dirt from
the bench top, oils from your fingers, etc. So, handle the filters
and boats with tongs or tweezers at all
times, and rest them only on clean surfaces. One suggestion is
keep the boats on a designated clean
piece of paper.
2. Identify the boat with a physical mark (indentation). This is
your identification mark, so take care that
each filter stays with the same boat.
3. Weigh the aluminum boats with the filters in them on the
analytical balance. Record those masses.
4. Using tweezers, place a filter on the suction apparatus as
directed by the instructor. Be sure the filter
flask is clean.
5. Filter 25 to 50 mL of representative sample (or another
volume as directed by the instructor). You

want to put as much sample through the filter as you can
without causing it to clog. Stop adding
sample when the flow rate through the filter slows noticeably.
Approximately 15 ml of filtrate will be
needed for turbidity measurement.** Record the amount of
sample filtered, and take care that your
sample is well-mixed at all times.
** Dilution, while not desirable, may be necessary for water
containing significant amounts of particulate
matter in order to obtain 15 ml of filtrate. If done, the resulting
TSS and VSS values must be multiplied by
the appropriate dilution factor and diluted sample must be used
for the initial turbidity reading.
6. Turn off the vacuum, and without disassembling the filter
holder and funnel, remove them from the
filter flask. Pour the filtrate into a labeled beaker for later
turbidity analysis. Replace the filter holder
and funnel and restart the vacuum.
27
7. Wash the filter with three successive washings of deionized
water (about 10 mL each) while
continuing suction. Wait 3 minutes between washings. If some
solids have been caught in your
glassware (graduated cylinder, funnel), rinse them out with

these washings.
8. Turn off the suction and, using tweezers, place the filter in
its boat.
9. Repeat steps 4-8 for each sample as directed by your
instructor.
10. Place the all the aluminum boats and filters in the drying
oven (at 105 � C) for at least one hour.
11. Remove the aluminum boats and filters from the oven and
place in the desiccator for at least 15
minutes or until they are at room temperature.
12. Weigh the aluminum boats and filters. Record those values.
13. Place the filters and boats into the muffle furnace (at 550 �
C) for 20 to 30 minutes. The muffle
furnace is hot, so be careful!
14. Remove the filters from the muffle furnace and place them
into the desiccator for at least 15 minutes
or until they are at room temperature.
15. Weigh the filters and record the masses again. Look again at
the filters. How do their appearances
compare with their appearances before combustion at 550 � C?
Turbidity
1. Turbidity is measured on an instrument. Your instructor will
describe how to use the instrument.
2. Measure and record the turbidities of the available water
samples as directed by your instructor.
3. Measure and record the turbidities of the filtrates for those
samples you used in the TSS test.
Data Analysis
Calculate the TS values for the samples you analyzed. TS is the

mass of dry solids on the dish (after
drying at 105 �C) divided by the volume of sample passed
through the filter. Express your results in
mg/L (milligrams of dry particles per liter of suspension). Show
all your work in your lab notebook.
Calculate the TSS values for the samples you filtered. TSS is
the mass of dry solids on the filter (after
drying at 105 �C) divided by the volume of sample passed
through the filter. Express your results in
mg/L. Show all your work in your lab notebook.
For the samples you combusted at 550 � C, calculate the VSS.
VSS is the mass of dry solids that
volatilized (left) the filter after combustion at 550 �C divided
by the volume of sample passed through
the filter. Express the VSS in mg/L and as a percentage of the
TSS.
For the samples you filtered, calculate the percentage of solids
captured on the filter based on the
percentage change in the turbidity. How does this value
compare with the ratio of TSS to TS based on
mass measurements? If there is a difference, explain why.
28
Discussion Questions
1. Calculate the total volume of the samples used in the TS test
based on a calculation of the sample
mass from measurements made on the analytical balance and on

an assumption that sample density is
1.00 kg/Liter. Compare the gravimetric-based calculated volume
with the volumetric measurement.
Which method is more accurate? Why? Under what
circumstances would you use one method rather
than the other?
2. Knowing what you do about the source of the water sample
tested, and the nature of the particles in
the sample, do your lab results make sense? Explain why or why
not. (For instance, are the relative
TSS and VSS values what you expected, or were there any
surprises?)
3. What fraction of the turbidity was removed on the glass fiber
filter? If that fraction is less than 100%,
discuss why all the turbidity wasn't removed. (Hint: What was
in the filtrate?)
4. Do the TSS and turbidity tests measure the same thing? When
would you use one type of
measurement and when the other? (Second hint: Think about
mass vs. number.)
5. Would you expect the analytical results to be higher than,
lower than, or the same as the true value
under following conditions, and why?
a. Weighing a warm crucible?
b. Estimate the organic content by volatile-solids analysis of a
sample containing a large
quantity of organic materials having high vapor pressure.
c. Estimate the organic content of a sample by combustion at
800oC

Lab Write-up
1. Report your data and the results of your calculations in your
lab notebook.
1. Provide sample calculations for every different kind of
calculation done. Be sure to check for
appropriate significant figures.
29
Example data table format:
Water Sample Identification Table
Sample ID Description of Sample
Total Solids (TS) data and calculated results.
Sample
No.
Mass
boat (g)
Mass boat + sample
before drying (g)
Mass boat + solids
after drying (g)
Vol. of

sample (mL)
Mass of
sample (b)
Total Solids
(mg/L)
Total Suspended Solids (TSS) and Volatile Suspended Solids
(VSS) data 1
Sample
No.
ID Number
on Boat
Mass of clean
filter and boat (g)
Mass of filter, boat, and
solids after drying (g)
Mass of filter, boat, and
solids after combustion (g)
Total Susp. Solids (TSS) and Volatile Susp. Solids (VSS) data 2
and calculated results.
Sample
No.
Volume of sample
filtered (mL)
Total Suspended
Solids (mg/L)

Volatile Suspended
Solids (mg/L)
VSS/TSS ratio
(expressed as %)
Turbidity data and calculated results
Sample
No.
Turbidity
of sample
(NTU)
Turbidity
of filtrate
(NTU)
Percent of turbidity
removed by filtering (%)
30
LAB 6: CHEMICAL COAGULATION JAR TESTING
INTRODUCTION
Coagulation is accomplished through neutralization of

negatively charged colloidal (clay size) particles.
This is necessary since the repelling forces between the
particles, due to their negative surface charge, is
greater than the attractive body forces when the particles are
separated. For this reason, without the
neutralization process, particles do not collide, stick together
and grow into larger particles that would
settle to the bottom, thus, the small particles remain in
suspension.
The purpose of chemical coagulation is to condition the water
such that small particle growth is
promoted, thus increasing particle size and density. The
physical process in which the particles actually
group together forming “flocs”, is known as flocculation. This
increase in size and density of the
particles facilitates removal in gravity sedimentation and water
filtration processes. Coagulation and
flocculation are two separate stages. They play a vital role in
improving the aesthetics of drinking water
and also remove microorganisms and other contaminants that
can be harmful to our health.
BACKGROUND
Coagulation refers to the chemical alteration of the suspended
particles that allows the particles stick
together in larger clumps called flocs. Flocculation refers to
the physical process that collects these flocs
into even larger clumps that easily settle out by means of
gravity. Particles in water can be classified into
two different size groups: colloidal and suspended solids.
Colloidal particles, also referred to as colloids
range in size from 1 micrometer to 5 nanometers while
suspended solids generally consist of particles
larger than 0.5 micrometers. These particles can also be

differentiated by the nature of how they react
with water molecules. Hydrophobic particles are defined by
having a low attraction to water and are
generally inorganic in origin. Hydrophilic particles react more
readily with water and often consist of
organisms both living and dead such as bacteria, algae and
viruses. Regardless of which group these
particles may fit into it is their chemical properties and not their
size that dictates the way in which they
will react during the coagulation and flocculation processes.
Almost all colloidal particles have a negative charge, meaning
that they will be attracted to particles
holding a positive charge and repel other particles that are also
negative. This tendency to repel other
negatively charged ions slows the process of gravity induced
settling considerably. Due to this slow rate
of settling it is necessary to artificially expedite the rate at
which the particles can be separated.
When a coagulant such as alum is put into solution in water it is
rapidly dissolved into aluminum ions and
sulfate ions. These molecules carry a positive charge and
combine with the negatively charged colloids to
form various ions of aluminum oxides and hydroxides. The ions
that are produced depend on many
variables such as temperature, pH and the speed and method of
mixture. Two types of reactions then
occur between the ions and the colloids, both of which result in
coagulation. One of these types is known
as charge neutralization and occurs when the positive charges
from the aluminum ions counteract the
negative charges of the colloids. The other type is called
bridging and occurs when aluminum hydroxide
ions stick together several negative colloid particles, acting as a
sort of chemical glue between like

charges.
31
Coagulants, in our case aluminum sulfate, are used to neutralize
the charges. When the aluminum sulfate
is added to water it dissolves and forms aluminum ions and
sulfate ions. The aluminum ions are of
particular importance in this process since they are unstable and
form stringy charged species of
aluminum oxides and hydroxides that adsorb to particles,
thereby neutralizing the particles which creates
conditions where they can form flocs.
Water treatment is a process used to remove impurities within
domestic water supplies for their use within
domestic, commercial, and industrial applications. These
processes have become particularly important
within the last 100 years with the growth of both urban and
industrial development. As demands for
water purification have increased, so to has the responsibility of
engineers to develop more efficient and
cost effective applications to water treatment. Conventional
water treatment usually involves two
processes: clarification and disinfection. Clarification removes
most of the turbidity within the water
sample while disinfection destroys any pathogenic microbes that
might be present. In addition to
clarification and disinfection, processes of softening, aeration,

and fluoridation are often used in public
water sources.
Figure 1 Process Diagram of a Typical Water Treatment Plant
The process of clarification is shown above and is most often
comprised of four distinct stages:
coagulation, flocculation sedimentation, and filtration.
1. Coagulation is a chemical process used to destabilize
colloidal-sized particles.
2. Flocculation is a physical process that increases particle-
particle collision frequency and thereby
causes growth of particles into larger sizes. Through the
addition of coagulants and subsequent
flocculation step, non-settling particles are brought together to
form larger, heavier particles
called floc.
3. Sedimentation is then used to allow the floc to settle to the
bottom of large storage tanks where it
is then removed.
4. The water is then passed through several layers of filters to
remove any of the remaining
suspended solids.
flocculation

32
Aluminum sulfate, or alum, is the most common coagulant used.
When added to water, aluminum sulfate
initially dissolves into aluminum cations and sulfate anions.
Some of these aluminum ions then form
various types of stringy aluminum oxides and hydroxides that
adsorb to particles. This accomplishes one
of two things. First, it reduces the effective charge of the
suspended solids within the water sample
thereby allowing the particles to collide and stick together.
Second, the aluminum oxides and hydroxides
bond to the negatively charged solid particles, thereby
increasing their effective mass and size.
The net effect of this ion and molecular compound formation is
the development of large, massive
particles. This process, called flocculation, is enhanced through
the use of large paddles that continuously
mix the water. Mixing is necessary so that the velocities of the
individual water (and solid) molecules are
kept in continuous fluctuation, thereby allowing the particles to
collide and stick together. As the
particles become more and more massive, their density
increases. Eventually the density of the floc
becomes greater than the surrounding water and particles begin
to settle to the bottom. This last process,
known as settling, occurs only when the velocity of the water is
kept to a minimum. In water treatment
plants this is usually accomplished through the use of large
storage tanks where the movement of the
water can be closely monitored. After the floc has settled to the
bottom of the tank, it can be removed by
means of large scrapers. These scrapers funnel the “sludge” to
the bottom of the tank where it is siphoned

out.
CONCLUSION
Coagulation is accomplished through neutralization of
negatively charged colloidal (clay size) particles.
The purpose of chemical coagulation and physical flocculation
is to promote the growth of small particles
into larger particles called flocs, thus increasing particle size
and density. The physical process in which
the particles actually group together forming “flocs”, is known
as flocculation. Coagulation and
flocculation are two separate stages in the process of separating
and removing suspended particulate
matter from water. They play a vital role in improving the
aesthetics of drinking water and also remove
microorganisms and other contaminants that can be harmful to
our health.
33
LAB 6 PROCEDURES (Coagulation)
Objectives
The objective of this lab is to become familiar with the
procedures that are to be followed while
conducting jar tests using a chemical coagulant. We will
determine the optimum amount of alum and the
mixing speed that produces the best flocculation in a water

sample.
Approach
Laboratory jar testing will be used to determine the optimum
dosage of alum and optimum degree of
mixing for coagulating and flocculating a water sample supplied
by the instructor.
Materials
Phipps and Bird multiple stirring apparatus
4, 1.5-L square Plexiglas “beakers”
4, 50-mL glass beakers (one per large beaker)
Graduated pipets
Graduated cylinders (various sizes)
Hach nephelometric turbidimeter
Stock solution of alum: 2,000 mg/L of Al2(SO4)3�14H2O for
doses > 10 mg/L
200 mg/L of Al2(SO4)3�14H2O for doses � 10 mg/L
Procedures
A. Jar test to determine optimum dosage at a single mixing
speed
1. Measure and record the mixer paddle diameter and the
temperature of the test water prepared by
your instructor.
2. Be sure the water in the carboy is well-mixed. Measure out 4
samples in the 1.5-L square beakers
and a small sample (20 – 30 mL) for measuring initial turbidity.
The samples should be between
700 and 800 mL each. (The exact volume is not important as
long as the same volumes are used
in all four beakers and you record what the volume is.).

3. Measure the initial turbidity of the test water, using the
turbidimeter, as per your instructor's
direction.
4. Locate the beakers at the center of the mixer shaft on the
multiple-paddle mixer. (Running the
mixer at a very slow speed will help you do this.)
5. Calculate the volumes of stock solution needed to achieve the
target dosages (Cjar). Based on
conservation of mass:
CstockVstock = CjarVjar ; Vstock = (CjarVjar)/Cstock
The target alum concentrations are as follows: Groups1 & 3: 0,
5, 20, & 40 mg/L
Groups 2 & 4: 0, 10, 30, & 50 mg/L
6. Measure out the appropriate volumes of alum stock solution
into small beakers but do not add
them to the water samples yet.
7. Turn the mixer light on. Start the mixers on the highest
possible speed. When you are ready to
start timing, add the pre-measured alum stock to all the jars
simultaneously. After 10 seconds,
34

reduce the mixer's speed to 30 rpm and flocculate for 15
minutes. Observe and record the time
required for flocs to form in each sample.
8. After flocculating for 15 minutes, turn off the mixer.
Immediately, observe and record the
relative average floc sizes for the samples, using a 1 to 4 scale
(1 = smallest; 4 = largest).
9. Allow the samples to settle for 20 minutes.
10. Decant or pipette about 50 mL of supernatant from each
beaker, taking care not to disturb the
settled material, or catch any fine particles floating on the
surface. Measure the turbidities of
these samples, then discard the contents of all of the beakers.
11. Select the two "best" flocculation dosages based upon the
first appearance of floc, floc size, final
turbidity (most significant factor), and coagulant dose.
12. Share the resulting data from Part A with the other groups.
Side note: The turbidity standard for drinking water is 0.5 NTU.
Is it necessary to achieve this after
settling? No. In a conventional treatment plant, settling is
followed by filtration. Conventional filters
are capable of removing up to 10 NTU of turbidity reliably.
Therefore, your goal in flocculation is to
produce water that can be treated by sand filtration at the lowest
cost. Discuss your choices with your
instructor before proceeding.
B. Jar test to determine optimal speed
In Part B, take your two water samples from the same carboy
that you obtained samples from in Part

A. Be sure the water in the carboy is well-mixed. If you have
any doubt, measure the starting
turbidity again. If it is higher, dilute the sample with tap water
until you get the same turbidity as in
Part A.
1. Repeat the test at a higher speed (60 rpm) using the two
"best" alum dosages as determined in the
30 rpm test. It isn't necessary to record the time to first floc
formation, or the relative floc sizes,
but do record the final turbidities. Recommendations:
a) While the beakers are undergoing slow mix (i.e.,
flocculation), have group members measure
out water samples and coagulant doses for the next part of the
lab (15 rpm).
b) Remove the 60 rpm samples from the mixer at the end of the
flocculation period and set them
aside for the 20-minute settling period.. This lets you begin the
next part of the procedure and
save time.
2. Repeat the test as described above at a lower speed (15 rpm).
Data Analysis
Create a spreadsheet to accomplish the following computations,
and then answer the questions:
1. Plot the data from the 30 rpm test using coagulant dosage as
the abscissa (x) and final turbidity as the
ordinate (y). Include Part A data obtained from other groups so
that the data series contains seven
data points. Be sure your graph is properly labeled. What
flocculation mechanism(s) are evident?
What were the two best doses? Why?

2. Calculate the velocity gradients at the three mixing speeds.
Show a sample hand calculation (see the
equations provided below). For each of your best two doses,
plot (x-y scatter) the data from all three
tests using velocity gradient (G) as the abscissa (x) and final
turbidity as the ordinate (y). Use only the
data that your group collected. You will have two data series
on the graph, one for each of your best
two doses. Each series will consist of three data points -- a final
turbidity value for each G value. Use
straight or curved lines to connect data markers. Based on your
results, what value of mean velocity
gradient is optimal for flocculation? Why? Include in your
answer a discussion how floc growth rate
(or size) is impacted when G (mixing speed) is increased from
a value of zero to a very large value.
35
Velocity gradient and power equations
G = (P/��)1/2 where: G = velocity gradient (s-1)
P = power dissipated in the water (W or ft-lb/s)
� = viscosity (N-s/m2 or lb-s/ft2)
� = volume (m3 or ft3)
If turbulent conditions are assumed (a good assumption in our

case):
P = (KT n3 D5 � ) / g where: P = power (ft-lb/s)
n = rotational speed (rev/s)
D = diameter of paddle (ft)
� = specific weight of water (lb/ft3)
g = acceleration due to gravity (32.17 ft/s2)
KT = empirical constant = 2.4 for Phipps & Bird mixer
(calculated from data provided by Phipps and Bird.)
Works Cited
1. Culp, Gordon L., Russell L. Culp. New Concepts in Water
Purification; Litton Educational
Publishing Inc., 1974
2. Hudson, Herbert E. Water Clarification Processes, Practical
Design and Evaluation; Litton
Educational Publishing Inc., 1981
3. Sawyer, Clair M., Perry L. McCarty, Gene F. Parkin.
Chemistry for Environmental Engineering;
McGraw-hill, 1994
References for G calculations:
1. McCabe, W. L., J. C. Smith, and P. Harriott, Unit Operations
of Chemical Engineering, 5th ed.,
McGraw-Hill, 1993.
2. Rushton, J. H., "Mixing of Liquids in Chemical Processing",
Industrial and Engineering
Chemistry, American Chemical Society, v 44, n 2, p 2931, Dec
1952.

3. Rushton, J. H. and J.Y. Oldshue, "Mixing -- Present Theory
and Practice", Chemical Engineering
Progress, v 46, n 4, p 161, April 1953.
4. Reynolds, T. D. and P.A. Richards, Unit Operations and
Processes in Environmental
Engineering, PWS Publishing Company, 1996.
5. Wagner, E.G., "Jar Test Instructions, Conduct of Jar Tests
and the Important Information
Obtained", booklet from Phipps and Bird, 8741 Landmark Rd.,
Richmond, VA 23228, July 1993.
36
LAB 7: CHEMICAL EQUILIBRIUM, BUFFERING, AND
ALKALINITY
INTRODUCTION
Natural bodies of water are an important part of a carbon cycle.
Carbon moves from the atmosphere into
the tissues of plants and animals and into water bodies.
Inorganic carbon complexes contained within
water bodies affect numerous important aquatic chemistries,
including alkalinity, acidity, CO2, pH, total
inorganic carbon, and hardness. For example the amount of CO2
affects pH and photosynthesis.
Alkalinity, acidity, and pH are explored in this lab. Water

hardness will be explored in a subsequent lab.
pH
The pH of water is critical to the survival of most aquatic plants
and animals. It is a chemical parameter
that increases our understanding of the water’s health. pH may
vary during the day or season, so it is
important to take many pH readings throughout the day to
obtain diurnal variations, and take many
readings throughout the year at the same time of day in order to
get an accurate long-term representation.
pH measurement is quick and easy and establishes a baseline so
that unexpected water quality changes
can be understood. Some basic characteristics of pH are as
follows:
· pH is a measure of how acidic or basic (alkaline) a solution is.
pH < 7 is acidic; pH > 7 is basic;
and pH = 7 is neutral.
· pH measures the hydrogen ion (H+) activity in a solution, and
is expressed as a negative
logarithm. pH = -Log{H+} where { } denotes activity. For fresh
waters, { } � [ ] where [ ]
denotes molar concentration.
· pH measurements are typically given on a scale of 0.0-14.0
(www.epa.gov), but values outside of
this range can exist.
· For each 1 unit change in pH, the alkalinity or acidity changes
by a factor of 10 (i.e., pH of 5 is 10
times more acidic than 6)

Many species of life have trouble surviving if the pH is lower
than 5 or higher than 9. Small shifts in the
pH of water can affect the solubility of certain metals such as
iron and copper, which indirectly affects the
aquatic organisms by releasing metals that were present in the
lake’s sediments. Acids, such as from acid
rain can diminish the survival of fish eggs.
Some other factors that can change the pH in a body of water as
follows:
· Sewage Overflows
· Chemicals in runoff
· Bacterial Activity
· Acid drainage from coal mines, accidental spills, and acid
rain.
· Water turbulence (mixing chemicals from the sediment into
the water column)
· Photosynthesis by aquatic plants.
· Algal blooms caused by an overload of nutrients
The objectives of this experiment are to:
1) determine the strength of an acid by a "conservation of
equivalents" method,
2) measure the alkalinities of several water samples and to see
how they vary, and
3) develop the titration curves for several water samples to
examine the buffering characteristics of these
waters and see the relationship between buffering and
alkalinity.
http://www.epa.gov/

37
Chemical Equilibrium, Carbonate System, and Alkalinity
Chemical equilibrium is the condition within the course of a
reversible reaction whereupon there is no net
change in the amounts of reactants or products. Reversible
reactions are reactions where the products, as
soon as they have formed, react to produce the original
reactants. Therefore, in chemical equilibrium two
opposing reactions occur at equal rates. Such equilibrium may
be represented by the qualitative
formulation,
DCBA +Û+
While the reaction rates between A+B and C+D are equal during
chemical equilibrium, the concentrations
may or may not be. This concentration differential may be
accounted for by a coefficient called the
equilibrium constant (Ke). Consider the following reaction,
iA + jB � mC + nD
where the differential concentrations of each reactant are
represented by the superscripts i, j, m and n.
The reaction constant may be determined by the following
relationship,
eji
nm

K
BA
DC
=
This implies that for a given reaction, the equilibrium constant
is proportional to the amount of products
and reactants present at equilibrium. This constant, however, is
not the same for all reactions and is
dependent upon the pressure and temperature according to
LeChatelier’s principle. LeChatelier’s
principle states that if a system in a balanced, or equilibrium,
state is disturbed, the system will readjust
itself so as to neutralize the disturbance and restore equilibrium.
Consider the reaction in which the
stoichiometric coefficients are all equal to 1 and the chemical
system has reached equilibrium,
A + B � C + D
If more of the reactant C is added to the balanced system, the
opportunity for the reaction of C and D
increases. As the reaction between C and D increases, the more
of A and B that is produced. This
increase in the reaction of C and D offsets the original condition
that disturbed the equilibrium by
removing the additional C and producing more of A and B. In
order that Ke remain constant, D must
decline while A and B increase. This process continues until
equilibrium in the system is reached.
Closely related to chemical equilibrium is the process of
buffering. Buffering describes the process by
which pH changes very little when an acid or base is added to

water. Despite the addition of more H+
(acid) the concentration of acid in the sample remains constant.
This process is accomplished by the
addition of a chemical agent known as a buffer. A solution of
acetic acid (CH3COOH) and sodium
acetate is a commonly used buffering agent.
In natural waters, the reaction responsible for buffering is,
-+ += 332 HCOHCOH
38
The bicarbonate ion can further dissociate into a carbonate and
hydrogen ion,
-+- += 233 COHHCO
When acid is added to the water most of the H+ reacts with
HCO3- to make H2CO3. If the concentration of
CO32- remains high in comparison to added H+, the pH will
remain nearly constant.
The amount of acid that may be added to a solution without the
pH value dropping below 4.5 is known as
the alkalinity. Alkalinity is most often referred to as the ability
of solution to neutralize acid and may be
determined by summing the molar concentrations of the agents
that react with the H+. For the example

reaction above,
Alkalinity = (1)[HCO3-] + (2)[CO32-] + (1)[OH-] – (1)[H+]
where the numbers in () are the numbers of H+ that can be
reacted with each ion and the numbers in [ ] are
the molar concentrations. Using the units only,
Alkalinity = (1 or 2 eq/mole) x [mole/L] = eq/L = N (normality)
Alkalinity is often expressed in the units of meq/L
(milliequivalents per liter) or mg/L as CaCO3.
Alkalinity as CaCO3 = (Alkalinity in meq/L) x (50 mg as
CaCO3 / meq )
The calculation of alkalinity in the lab may be accomplished by
using an equivalents balance,
(Nalkalinity)(Vwater) = (Nacid)(Vacid added)
CONCLUSION
The pH of water is critical to the survival of most aquatic plants
and animals. It is a chemical parameter
that increases our understanding of the water’s health. It is
quick and easy and establishes a baseline so
that unexpected water quality changes can be understood.
The amount of acid that may be added to a solution without the
pH dropping below 4.5 is known as the
alkalinity. Alkalinity is most often referred to as the ability of
solution to neutralize acid and may be
determined by summing the molar concentrations of the agents
that react with the H+. Alkalinity is
expressed in the units of meq/L (milliequivalents per liter) or
mg/L of CaCO3. The calculation of
alkalinity in the lab may be accomplished by using an

equivalents balance.
The objective of this experiment is to (1) determine the strength
of an acid by a "conservation of
equivalents" method, (2) measure the alkalinities of several
water samples and to see how they vary, and
(3) develop the titration curves for several water samples to
examine the buffering characteristics of these
waters and see the relationship between buffering and
alkalinity.
39
LAB 7: PROCEDURES (Alkalinity and Buffering)
Objectives
1. To determine the strength of an acid by a "conservation of
equivalents" method.
2. To measure the alkalinities of several water samples and to
see how they vary.
3. To develop the titration curves for several water samples to
examine the buffering characteristics of
these waters and see the relationship between buffering and
alkalinity.
Procedures
Part A: Determining the Strength of an Acid
Equipment and Materials:

q Primary standard solution (provided by the instructor)
q Sulfuric acid solution (made by instructor)
q Buret and stand (Please be careful with these; they are
expensive.)
q 250-mL beaker or Erlenmeyer flask
q Methyl orange indicator
q 50-mL graduated cylinder
q 25-mL volumetric pipet
1. Obtain from your instructor 20 mL of a base solution made
with sodium carbonate (Na2CO3). This is
called a "primary standard".
2. Place 2 drops of Methyl-Orange indicator (pH 4.5) solution
into the sample.
3. Fill your buret with the acid (titrant) using a small beaker.
(You don't have to fill the buret to any
particular mark.)
4. Note the beginning mark on the buret. (Remember to read
the bottom of the meniscus.)
5. Carefully, add titrant to the sample while continuously
swirling. When the color shifts from a light
yellow to a light orangish-pink, the endpoint has been reached.
Stop adding acid at that point.
6. Note the ending mark on the buret. Calculate the volume of
titrant used.
7. Calculate the normality of your acid from: (NV)standard =
(NV)acid. Include this in your sample
calculations.
8. Collect the Nacid values from each lab group. Calculate the
average and use that value for the
alkalinity testing.

Sample format for recording primary standard data in your lab
notebook:
Normality of the primary
standard solution (meq/L)
Titration Data for Your Group:
Volume of
Primary Standard
solution (mL)
Initial Buret
Marking (mL)
Final Buret
Marking (mL)
Titrant Volume
(mL)
Normality of
acid (meq/L)
40
Class Data (cross out any values not used in the calculation of
the average):

Group Acid Normality (meq/L)
1
2
3
4
5
Average
Part B: Measuring Total Alkalinity
1. Measure the pH's of the water samples provided by the
instructor.
2. Put 20 or 25 mL of sample into a beaker or Erlenmeyer flask.
(Measure this volume carefully.)
3. Place two drops of Methyl-Orange indicator (pH 4.5) solution
into the sample.
4. Titrate with your standardized acid (in the buret) until the
methyl orange changes color.
5. Note the ending mark on the buret. Calculate the volume of
titrant used.
6. Calculate the total alkalinity of each sample from:
(NV)Titrant = (alk)(VSample). Express your answer in
both meq/L and mg/L as CaCO3. Include one of these
calculations in your sample calculations.
Sample format for recording data in your lab notebook:
Water Samples
Label Description
DI Deionized water

SW Surface water
GW Groundwater
DI + BS Deionized water + baking soda (NaHCO3). Amount of
NaHCO3 added/ L: g/L
SP Soda pop
Titration Data
Sample Initial pH
Sample
Volume (mL)
Initial Titrant
Buret Mark
(mL)
Final Titrant
Buret Mark
(mL)
Titrant
Volume (mL)
DI
SW
GW
DI + BS
SP

41
Alkalinity Calculations
Sample
Sample
Volume (mL)
Titrant
Volume (mL)
Titrant
Normality
(meq/L)
Total
Alkalinity
(meq/L)
Total Alkalinity
(mg/L as CaCO3)
DI
SW
GW
DI + BS
SP
Part C: Titration Curves
1. Your instructor will set up a pH meter, buret and water
sample.
2. Add acid to 100 mL of sample in very small increments,
recording the pH and the amount of titrant

added until the pH is less than 4.5.
3. Repeat with other water samples as directed by the instructor.
4. Return unused titrant in the buret to the container that it
came from.
Data Analysis
Part B: Calculate the alkalinities of the water samples tested
and express your answers in both meq/L and
mg/L as CaCO3 units. Summarize these in a table. Discuss the
meaning of the results; are they
what one would expect? Why?
Part C: Using a spreadsheet, graph pH on the y-axis vs.
cumulative meq. of acid added per liter of water
sample on the x-axis. Plot all titration curves on the same
graph. Properly title and label your
graphs. Discuss the meaning of the results; are they what one
would expect? Why? Make sure that
you include a discussion of each water’s buffering capacity.
Discussion Questions (20% of the report total score)
1. (2.5%) Why didn't the soda pop have any alkalinity?
(Consider the form of the carbonate species at
this pH.)
2. (2.5%) Why did adding baking soda to the deionized water
increase its alkalinity?
3. (7.5%) Was the resulting alkalinity of the DI+BS sample
about what you expected? Show
calculations for what you expected.
4. (7.5%) A factory wishes to discharge an acidic waste to a
local stream. State regulators want to assure
that the local fish population is not harmed by too drastic a

change in pH. Your job is to estimate how
much wastewater can be discharged (in Liters/min) so that the
pH of the stream downstream doesn't
change by more than 1.0 pH units. The proposed discharge has a
concentration of 5.50 N. The stream
has a flow rate of 30 cfs and a titration curve like that found in
the groundwater.
Lab Write-up
Report your alkalinity data and the results of your calculations
in your lab notebook. Provide sample
calculations for every different kind of calculation done. Be
sure to check for appropriate significant
figures. Present your titration curve data and graphs on print-
outs from a spreadsheet program. Provide
sample calculations for the calculations done on spreadsheets
also. Show the calculations. Answer the
discussion questions.
42
LAB 7: NOTES ON CHEMICAL EQUILIBRIUM,
BUFFERING, AND ALKALINITY
Chemical reactions often go in two directions (reversible
reactions):
A + B à C + D (forward), or
A + B ß C + D (backward)

We express this on paper as: A + B Û C + D, or in shorthand: A
+ B = C + D.
For example, 2SO2(g) + O2(g) à 2SO3(g). But some SO3(g)
breaks down, so we have at the same time
2SO2(g) + O2(g) ß 2SO3(g)
When the rate of the forward reaction equals the rate of the
reverse reaction, the system is in "dynamic
equilibrium". The word "equilibrium" means the relative
concentrations of reactants and products do not
change with time. "Dynamic" reminds us that the reactions are
still going on.
Equilibrium Constants
Just because the reaction rates are equal, doesn't mean the
concentrations are equal. In the example above,
the equilibrium concentrations are:
[SO2] = 1.65 M (M = molarity = moles/L)
[SO3] = 12.43 M
In general, for the reaction:
iA + jB = mC + nD
it has been empirically determined that the equilibrium
concentrations are related by the following
relationship:
eqji
nm
K
BA

DC
=
][][
][][
(Remember: "products over reactants")
Note that Keq is usually determined by experiment, and is
affected by various environmental factors, most
notably, temperature.
LeChatelier's Principle or the Law of Mass Action
If a chemical reaction at equilibrium is subjected to a change in
conditions that moves it away from
equilibrium, then the reaction rates adjust so that a new
equilibrium state is reached. In other words, the
system adjusts in a way that, at least partially, offsets the
condition that disrupted the equilibrium. This
adjustment continues until a new equilibrium is established.
For example, suppose a system is described by the following
equilibrium equation:
A + B = C + D
Now, suppose we add more "C" from some outside source (say,
from a salt that contains C). The
increased concentration of C increases the opportunities for C
and D to react. The additional C will
increase the rate of the reverse reaction and some of the
additional C will be converted to A and B. (This
is the action that offsets the condition that disturbed the original
equilibrium. The increased rate of

43
disappearance of C counters our action of adding C to the
solution.) If more C and D react, the
concentration of C and D decline and the concentrations of A
and B increase. This process continues until
the equilibrium equation is satisfied again. Mathematically, if
we artificially increase C, then for the Keq
equation to hold true, D must decline and A and B must
increase. This coincides with the chemical
changes that occur.
Buffering
"Buffering" describes that phenomenon in which pH changes
only a little when an acid or base is added to
a water. In other words, despite adding H+ in the form of an
acid, the concentration of acid in the water
(measured by pH) doesn't change accordingly. It stays relatively
constant. In most natural waters, the
reaction responsible for this phenomenon is:
H2CO3 = H+ + HCO3- (where H2CO3 = carbonic acid and
HCO3- = bicarbonate ion)
The bicarbonate ion can further dissociate into carbonate ion
and H+ as follows:
HCO3- = H+ + CO32-
So, when acid is added, most of the H+ added reacts with
HCO3- to make H2CO3. (The H+ would react

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