Research Project

pH differences in Tap Water vs. Retention Pond Water

Krista Russell

Abstract

I tested whether the pH in tap water would be different than retention pond water. I hypothesized that the pH of pond water would be lower (more acidic) than tap water due to the vegetation around. 10 samples of both the pH of both tap and pond water in Menomonee Falls, Wisconsin, was tested and analyzed. The results showed that the pH level in retention pond water were more acidic than tap water. The average pH of retention pond water was 5.2 and the average pH of tap water was 6.65. The p-value was 0.000396 which is significant enough and supports my hypothesis.

Keywords: retention pond, tap water, pH

Introduction

The development of new subdivisions in Menomonee Falls has resulted in an increase to improve waterproofing conditions. In an effort to reform, retention ponds were created to control the flow of precipitation and to trap runoff water from flooding streets (Le et al. 1997). Retention ponds are expected to contain medals such as zinc and lead from car debris on the road (Le et al.1997). The biochemical composition of wastewater ponds are influenced by factors such as sunlight and wind energy, precipitation, and evaporation (Tadesse et al. 2003). I hypothesized that the pH in pond water would be lower because the amount of vegetation around pond areas. The pH of pond waters containing vegetation such as algae, increase due to the rate of photosynthesis. Because of the variation of water temperatures, the diffusion rate of atmospheric CO₂ is very small. As algae consumes more carbon dioxide then can be produced, the water’s concentration of hydroxyl ions increases thus making the water more alkaline (Tadesse et al. 2003).

Methods and Materials

On Saturday October 24, 2009, I visited a series of 10 Retention Ponds located in Menomonee Falls, Wisconsin. Both pond site 1 and 2 were located on Crestwood Drive, site 3 on Marach, site 4 on Lily Road, site 5 on Asper Drive, site 6 on Brookside Drive, site 7 on Millcreek Court, site 8 and 9 on Ash Drive, and site 10 on Terrance Drive. A pH test strip was inserted into each sample of pond water and the color was compared to the picture samples given on the pH strip container. The procedure was then repeated using tap water from 10 local households located near the sites of the retention ponds in Menomonee Falls WI. With a sample size of 20, the data was analyzed on Microsoft Excel 2007.

Results

The results showed that the pH level in pond water was lower than tap water. My hypothesis was supported. The average pH of retention pond water was 5.2 and the average for pH of tap water was 6.65. The p-value was 0.000396 which is significant. At site 7 both the pH levels in pond and tap were relatively the same. At site 6 the pH level of the pond water was 4. This was probably due to the fact that it was surrounded by a lot of vegetation which contains acidity.

Figure1. The average pH levels in the retention pond waters are more acidic than the tap waters.

Discussion

Retention ponds are the run off wastewaters of a given area (Le et al. 1997). Factor such as acid rain and soil can affect the composition. Retention ponds are expected to contain medals such as zinc and lead from car debris on the road (Le et al. 1997). The results showed that the pH level in pond water was lower than pond water. There were possible factors that were not accounted for that could have affected my results. Some of the faucets had water filters and some did not. The tap waters that were filtered could have filtered out the acidic material although it was still coming through the pipeline. Others that did not have filters were getting materials from the pipeline. Water samples that were not filtered gave a more accurate result accounting of medals such as cadmium, lead and zinc. When concentrations of such elements are high enough they may be harmful to health (Durand et al. 2004). Also sample sites were from newly constructed neighborhoods built in the past 10 years. This could have affected the pH of both pond and tap water because the trees were landscaped and did not naturally grow there.

If I were to conduct this experiment again I would pick areas that were not newly built which might potentially affect the pH of the pond water. Also I would also pick tap waters that were not filtered to get an accurate account for the tap water directly from the pipeline. I would also test for the presence of medals such as lead and zinc to see how much actually gets into the tap water system.

Literature Cited

Durand, C., Ruban, V., Amblès, A., and Oudot, J.2004.Characterization of the organic matter of sludge: determination of lipids, hydrocarbons and PAHs from road retention/infiltration ponds in France. Environmental Pollution, 132,3:375-384

Le, P. K .,Touray J.C, Baillif, P., Ildefonse, J.P.1997 Heavy metal contamination of settling particles in a retention pond along the A-71 motorway in Sologne, France. Science of the Total Environment, 201,1:1-15

Tadesse I., Green, F.B.,Puhakka, J.A.2003. Seasonal and diurnal variations of temperature, pH and dissolved oxygen in advanced integrated wastewater pond systems treating tannery effluent. Water Research, 38,3: 645-654