pH of Ground Water and City Water

Abby Sherman and Kate Miller

Abstract

 Ground water and city water were tested in various locations throughout Milwaukee, Waukesha and Dodge counties in Wisconsin to determination their pH. The water samples were tested using an electronic pH meter to determine if there was a difference in their buffering capacity. Results indicated there was not a significant difference between the pH of ground water and city water (P = 0.7243).

Keywords: pH, city water, ground water

Introduction

The purpose of this research was to identify and quantitatively analyze the pH levels in both treated city water and in untreated groundwater from a well or aquifer. Our hypothesis was that city water tested has a lower pH than ground water tested. City water is closely managed and quantitatively measured by municipalities. Municipalities use pH as an indicator of potential growth of harmful biological organisms. In a test of water quality conducted by the United States Geological Survey for the Department of Homeland Security, a significant correlation was discovered, p £ .01, between organism recovery in water and pH level (Francy et. al, 2009). This finding demonstrates pH monitoring as a useful tool in discovering biological organisms in drinking water. The municipal water sources tested in our research were located throughout Wisconsin including, City of Milwaukee, Oconomowoc, Ironridge, Hustisford, and Eagle (Tables 1 & 2).  Each public water system is routinely monitored for the purpose of identifying and informing the public about potential safety concerns. The data collected through routine water analysis is compared against federal and state guidelines and can be used to identify or rule out a public safety concern. In Wisconsin, water from municipal sources is monitored to ensure quality, but the monitoring of well or ground water is up to each individual homeowner. 

Information gained through the Milwaukee Department of Public Works 2009 Annual Water Quality Report was used to facilitate research of various water measures in our project, including pH. The average measured pH in Milwaukee drinking water was 7.57 (Milwaukee Public Works, 2010).  To gain perspective of the obtained values, the scientific measure of neutral pH is 7. Normal rainfall has a pH of about 5.6 due to carbon dioxide gained from the atmosphere, which causes the water to become acidic (USGS 2010). Drinking water that is found to have a pH greater than 7 requires additional chlorine to be added because the higher pH interferes with the effectiveness of using chlorine as a disinfectant to purify drinking water (Park, et.al, 2004).

Materials and Methods

Water samples were collected and pH was tested between October 16, 2010-November 7, 2010 at various sites in Milwaukee County, Waukesha County and Dodge County all located in Wisconsin (Tables 1 and 2).

A Hanna Checker® Pocket-Sized pH Meter with Replaceable Electrode Model #MHA-52301 was used to determine the pH of each of the samples. Before each sampling the pH meter was calibrated according to the instructions, using pH 4 and pH 7 buffers. 150 mL of cold water was dispensed into a 200 mL plastic container and the pH was immediately tested on site. The same plastic container was used to test all the samples; in between samplings container rinsed with de-ionized water. The pH of the samples were tested in triplicate and the results were averaged. The data was analyzed using a type 2, T-test with 1 tail in Microsoft Excel.

 

Results

Results indicated there was not a significant difference between the pH of ground water and city water (P = 0.7243). The ground water had a pH of (M= 7.9, STDEV= 0.412). The city water had a pH of (M= 7.8, STDEV=.563).

Table 1. Data for ground water

Ground Water

Sampling Date

Site Type

Address

pH

10/16/2010

Park

County Hwy ZZ Eagle, WI 53119

7.5

10/16/2010

Park

County Hwy ZZ, Eagle, WI 53120

7.7

10/18/2010

Residential

W2907 Lehman Rd., Neosho, WI

8.2

10/18/2010

Residential

W267 N4782 Kate’s Bridge Dr., Sussex WI 53089

8.1

11/1/2010

Residential

W329 N3711 Timberwood Ct., Nashotah WI 53058

7.8

11/1/2010

Residential

312 S. Dylan Dr., Wales WI 53183

8.3

11/1/2010

Residential

725 W. Main St. Wales, WI 53186

8.6

11/2/2010

Residential

W329 N3619 Timberwood Ct., Nashotah WI 53059

7.6

11/7/2010

Residential

W425 N3652 N. Garfield Rd., Iron Ridge WI 53183

7.3

11/7/2010

Residential

W274 N3587 S. Cove Dr., Iron Ridge WI 53184

7.7

Table 2. Data for city water

City Water

Sampling Date

Site Type

Address

pH

10/13/2010

Park

3400 South 43rd St., Milwaukee, WI 53234

7.7

10/17/2010

Park

 9274 S. Main St., Ironridge, WI 53035

6.7

11/1/2010

Residential

343 W. South St., Oconomowoc, WI 53066

8.1

11/1/2010

Residential

343 Bolivar Ave., Milwaukee, WI 53221

8

11/2/2010

Residential

145 S. Highland St., Hustiford WI 53034

8

11/7/2010

Residential

119 S. Highland St., Hustiford WI 53034

8.2

11/7/2010

Residential

101 N. Lake St., Hustiford WI 53034

8.1

11/7/2010

Residential

118 E Wisconsin Ave., Oconomowoc, WI 53066

7.8

11/7/2010

Residential

W227 N752 Westmound Dr., Waukesha, WI 53186

6.9

11/7/2010

Residential

312 E. Main St., Waukesha, WI 53186

8.4


Figure 1. Average pH of ground water vs. city water

Discussion

pH is a logarithmic measure of the acidity or basicity of water, it can be used to determine water quality issues, such as contamination. Ideally water would have a pH of 7, but natural and artificial additives affect pH, so it is uncommon to find water with a natural pH 7.

In repeating the experiment, emphasis would be placed on controlling water temperature. Controlling the water temperature is important because the Kw, a measure of the equilibrium constant of water, changes with temperature variation. In pure water, water that the amount of hydrogen ions equals the amount of hydroxide ions, the pH is 7. This value is found when water is at room temperature. At room temperature hydrogen and hydroxide ions are equal, but as temperature increases the reaction is driven to favor the formation of hydrogen ions. The formation of more hydrogen ions causes the pH to drop (Piver, et. al, 1997). In our findings, the ground water samples were colder due to being in a non-temperature controlled environment and we found that these samples were higher in pH. A follow-up study that included a variable of temperature control could determine if temperature played a major role in the findings.

References

Francy, D., Bushon, R., Brady, A., Bertke, E., Kephart, C., Likirdopulos, C., Mailot, B., Schaefer, F., III, and Lindquist, H. 2009, Performance of traditional and molecular methods for detecting biological agents in drinking water: U.S. Geological Survey Scientific Investigations Report 2009, 17

 

Milwaukee Water Works. 2010. 2009 Annual Water Quality Report. Milwaukee Public Works. Retrieved on December 8, 2010 from: http://city.milwaukee.gov/ImageLibrary/Groups/WaterWorks/files/FinishedWaterQualityfrTreatmentPlants09.pdf

 

 

Park, H., Hung, Y., and C. Donghwan. 2004. Effects of chlorine and pH on efficacy of electrolyzed water for inactivating Escherichia coli O157:H7 and Listeria monocytogenes. International Journal of Food Microbiology 91: 13– 18

 

Piver, W., Jacobs, T., Medina Jr., M. 1997. Evaluation of health risks for contaminated aquifers. Environmental Health Perspectives. 105: 127-143

 

United States Geological Survey 2010. Water Properties pH. Retrieved September 20, 2010 from: http://ga.water.usgs.gov/edu/phdiagram.html