1. Minnesota State University
Measuring Alkalinity, Acidity, and
Hardness to determine Water Quality
Fall
13
Written by: Raquel Collison
ABSTRACT – Alkalinity, acidity, and hardness have been classified as three important factors affecting
Minnesota State University’s tap water quality. The various experiments conducted to test the stated factors were
performed using a burette and cold tap water and three trials were noted to represent each qualification standard.
The results revealed that the water properties (in respective order) stated that the water had a high alkalinity
(29.33 ppm of CaCO3), lower acidity (8 ppm of CaCO3), and was classified to have a hardness value of 210
(ppm of CaCO3). From this information conclusions were made regarding the low sensitivity of the sample
water supply towards additional acid (such as polluted rain), representing its fertility in a natural system, as well
as be classified with a hardness rating of “hard,” which signifies a greater dissolved metal content than other
chemically treated waters. This information then can be better understood as means of classification of
Mankato’s water supply and as a basis for any treatment options that may be required.

2. Water quality control measures have been taken across the United States for
concerns relative to both the natural environment and human use. These concerns
are almost always symbiotic, representative of the need for consistent monitoring of
the three largest factors that contribute to water quality: alkalinity, acidity, and
hardness. In this experiment, we will investigate the three factors and determine an
average for each, so that we can better understand the makeup and chemical
balance of Mankato State University’s tap water system in order to make valid
conclusions relative to quality as dictated by the various ranking systems proposed.
The classification guidelines are defined as follows:
Alkalinity represents the ability of water molecules to accept H+ protons. In
short, it signifies the capacity of water to neutralize acids that may stem from acid
rain, for example. A high alkalinity means that a lake is fertile and buffered, in other
words, its pH does change enough to affect the aquatic animals, and so life thrives in
such a water body with a high alkalinity.
Acidity represents the ability of water molecules to neutralize OH- molecules,
the exact opposite of alkalinity. Acidic water typically has a high CO2 concentration,
which in usually high levels can lead to eutrophication of a water body.
Eutrophication is the resulting death of a lake caused by the oxygen – depleting
process of dead algae breakdown by microbes (“The Carbon Dioxide Greenhouse
Effect,” 2013).
Water hardness is computed by analyzing the concentration of dissolved
metals found in a water body – specifically calcium and magnesium – which can
Introduction

3. affect the efficiency of societal processes. For example, heavy metal machinery that
work with vast amounts of water perform more economically when the water is soft
(containing very little dissolved metal compounds) because there is less corrosion
and thus, less money is spent in costly maintenance (“Water Hardness and
Alkalinity,” n.d.).
In this report, we will be analyzing three separate experiments in order to
determine the general water quality of Mankato’s tap water system. The results will
allow us to make valid conclusions based upon the chemical makeup of the water,
which will furthermore allow us to better understand the effects that alkalinity,
acidity, and hardness have on our changing world.

4. Alkalinity. Observations relative to the amount of sulfuric acid needed to put cold
tap water at a pH of 4.5 appeared consistent within our group’s data. After the addition of
the acid to each 25 mL water sample, we noted the amount lost from the burette in order
to calculate the volume required to change the water with the added buffer (bromocresol
green – methyl indicator) into a yellow hue. Our findings can be expressed in Table 1.
Titration trial run 1 2 3
Volume of water
sample (mL)
25 25 25
Initial burette
reading of acidic
solution (mL)
5.0 3.5 4.3
Final burette reading
of EDTA solution
(mL)
5.7 4.3 5.0
Amount of acid
added to water (mL)
0.7 0.8 0.7
Ppm of CaCO3 28 32 28
Methods
Results
Table 1. Calculations relative to finding alkalinity of tap water through the
addition of an acid.
Average alkalinity = 29.33
Standard Deviation = 2.31
Please refer to the three attached handouts in regards to the materials and methods used in in the
alkalinity, acidity, and hardness labs respectively

5. According to the results, the average amount of sulfuric acid required to bring the
solution to a yellow hue (which represents the pH change of the water to 4.5) is around
0.7 mL. The alkalinity was calculated as follows:
CaCO3 = [(0.02)(mL of acid)(50,000)] / 25
Where: CaCO3 represents alkalinity in mg/L
0.02 represents the normality of the acid
25 represents the water sample volume in mL
Table 2 refers to relative alkaline levels in mg/L and their effect on a water body.
According to the results from the experiment, our resulting average alkalinity
level fell into the “not sensitive” level, which will be mentioned to a greater extent in the
Discussion.
United States EPA Category Concentration of CaCO3 (in mg/L)
Acidified < 1
Critical < 2
Endangered 2 - 5
Highly Sensitive 5 - 10
Sensitive 10 - 20
Not Sensitive > 20
Table 2. Distribution of the concentration of CaCO3 as dictated by the EPA1.

6. Acidity. Observations relative to the amount of base required to bring the cold tap
water solution to a pH of 8.3 were as follows in Table 3.
According to the results, the average amount of basic solution needed to put the
water at a pH of 8.3, was 0.2 mL (which turned the solution [with the added
phenothaliene indicator] pink). The acidity was calculated as follows:
CaCO3 = [(0.02)(mL of base)(50,000)] / 25
Where: CaCO3 represents the acidity of the solution in mg/L
0.02 represents the normality of the base
25 represents the water sample volume in mL
Titration trial run 1 2 3
Volume of water
sample (mL)
25 25 25
Initial burette
reading of basic
solution (mL)
11.4 11.6 11.7
Final burette
reading of basic
solution (mL)
11.6 11.7 12
Amount of basic
solution added (mL)
0.2 0.1 0.3
Ppm of CaCO3
8 4 12
Table 3. Calculations relative to finding acidity of tap water through the addition of a
base.
Average Acidity = 8
Standard Deviation = 4

7. Due to the waters calculated higher number (8), we can now determine that that
the solution is more likely to neutralize H+ protons (alkaline), then to neutralize OH- ions
(acid).
Hardness. Observations relative to the amount of ethylenediaminetetraacetate
(EDTA) required to determine the hardness of the water is listed in Table 4.
According to the results, the average amount of EDTA solution needed to
determine water hardness (which turned the solution blue) was 10.5 mL. It was calculated
as follows:
Titration trial run 1 2 3
Volume of water
sample (mL)
50 50 50
Initial burette
reading of EDTA
solution (mL)
0 10.3 20.6
Final burette
reading of EDTA
solution (mL)
10.3 20.6 31.5
Amount of EDTA
solution added (mL)
10.3 10.3 10.9
Ppm of CaCO3
206 206 218
Table 4. Calculations relative to finding the hardness of tap water through the addition
of an EDTA solution
Average ppm of CaCO3 = 210
Standard Deviation = 6.93

8. CaCO3 = [(0.02)(mL of EDTA)(50,000)] / 50
Where: CaCO3 represents water hardness
0.02 represents the normality of the EDTA solution
50 represents the water sample volume in mL
From the equation and additional statistics from the experiment (Table 4), we
have determined the average hardness level to equal 210. Utilizing Table 5, we can define
the metal content as follows:
According to the chart, our average number of 210 falls into the “Hard” water
quality guideline, where there is a greater amount of dissolved ions, such as Na+, K+,
Ca2+, Mg2+, Cl-, and HCO3-, among others, in our tap water supply.
Hardness Level Water Class
0 - 75 Soft
75 - 150 Moderately Hard
150 - 300 Hard
Over 300 Very Hard
Table 5. Distribution of the amount of dissolved ions in water and their relative
hardness concentration classifications

9. The results we received from the alkalinity, acidity, and hardness labs
respectively play an important role in the understanding of the chemical properties of our
local water supply.
To begin, alkalinity represents the capacity of a water body to neutralize H+
protons; in other words, it is a buffer that prevents a lake or stream from becoming too
acidic for life to flourish. From the results of our alkalinity experiment, we have
determined the average water alkalinity level at 29.33 for Mankato’s tap water system.
According to Table 2 from the Results, our local water supply is not sensitive to possible
additions of acid, as alkalinity acts as a buffer.
In a natural environment, alkalinity plays a role in the fertility of a specific water
supply. In aquatic settings, a high alkalinity represents the water’s ability to neutralize
acid rain (additional H+ protons), for example, and maintain the pH of the system at a
relatively neutral 7 – 8 range. In these regards, animal life is able to flourish in an
environment that maintains a relatively constant pH. If a body of water has a low
alkalinity, the pH drops below seven and becomes acidic because there is little to no
buffer to neutralize the acid rain and so life becomes sparse or perishes. In general,
alkalinity represents the capacity of the water to accept H+ protons, while pH represents
the intensity relative to the quantity of H+ suspended in the water body. Most alkalinity
that is found naturally in water bodies comes from calcium carbonate (CaCO3).
Alkalinity is also important in agriculture – for the levels of both the soil and added water
must remain relatively equal.
Discussion

10. Acidity is the ability of water to neutralize OH- ions. In our lab experiment, we
concluded that the average acidity of the water tested was 8 mg/L. Because of eight’s
location on the pH scale (as shown in Figure 1), we can determine, and furthermore
support from the alkalinity test, that the water is more alkaline than acidic.
This means that our example water supply has a greater ability to neutralize H+ p
We calculated water hardness through finding the average amount of calcium
carbonate (CaCO3) in the sample, which resulted in 210 parts per million (ppm).
According to Table 5 from the Results section, our water sample had received a water
hardness classification of “hard” which represents that a greater amount of dissolved ions
were contained within the examples we used for each trial. In a human society, a water
body which is classified as “soft” has many important benefits. For example, household
detergents are more efficient when utilized with soft water, and factories that operate with
heavy machinery prefer soft water so that their machines run more efficiently and with
less corrosion over their lifetime. Relative to drinking water however, hard water can
actually be beneficial, for it contains many of the minerals we need that are not consumed
from our solid food diets.
Figure 1.
Retrieved from: http://www.abundanthealthcenter.com/blog/the-acid-alkaline-ph-scale

11. In conclusion, water quality is determined by symbiotic factors that can be
classified in order to make appropriate chemical treatment decisions that will better our
water supply for both human and animal abundance. Water is a very important resource,
and so it is with great importance that it is cared for and utilized in the most efficient way
possible.

12. 1Godfrey, P.J., Mattson M.D. , Walk, M.F. , Kerr P.A. , Zajicek, O.T., and Ruby, A.
(1996). “The Massachusetts Acid Rain Monitoring Project: Ten Years of
Monitoring Massachusetts Lakes and Streams with Volunteers.” University of
Massachusetts Water Resources Research Center. Received from
http://www.uri.edu/ce/wq/ww/Publications/pH&alkalinity.pdf.
2013, February). “The Carbon Dioxide Greenhouse Effect.” The Discovery of Global
Warming. Retrieved from http://www.aip.org/history/climate/co2.htm.
(n.d.). “Water Hardness and Alkalinity.” USGS – Water Quality Information.
Retrieved from http://water.usgs.gov/owq/hardness-alkalinity.html.
Please refer to the attached packets for more information.
References
Appendix