Water Quality and Contamination: Lab Analysis of Tap vs. Bottled Water

Introduction

Often, human activities introduce contaminants into our drinking water. The dumping of household products percolates into groundwater, necessitating treatment before public consumption. Water treatment plants filter contaminants from drinking water before releasing it into the public supply to ensure safety.

Texas has implemented several programs to reduce water pollution, including Clean Texas Marinas, the Water Pollution Abatement Plan (Edwards Aquifer), the Texas Clean Rivers Program, and "Don't Mess with Texas Water: A Way to Report Illegal Dumping" at selected surface-water and groundwater sites. The United States Geological Survey (USGS) maintains instruments that continuously record physical and chemical characteristics of water, including pH, specific conductance, temperature, dissolved oxygen, and percent dissolved-oxygen saturation.

Waste Reduction and Research Goals

Before Texas transitioned to more efficient filtration methods, incidents like the one affecting a small northeastern Texas town were rare. A chemical used to treat wastewater, sodium hydroxide, was accidentally released into the public water supply. When contaminants reach high concentrations, human exposure can cause severe illness. In this incident, 248 persons exposed to highly alkaline water with a pH of 12.0 suffered skin rashes, first-degree burns, nausea, vomiting, and diarrhea (Brender, Harris, Samples-Riuz, Weidman, & Schwarz, 1998, p. 21).

The goal of these tests is to identify certain chemicals present in tap water and compare them to those in store-bought bottled water. The results will clarify whether spending extra money on bottled water is justified. Because common household items such as vegetable oil, vinegar, and laundry detergents are disposed of and poured onto the ground by humans, it is significant to understand how soil behaves when introduced to these contents. Observing how quickly these contents filter through soil to reach groundwater, or whether soil absorbs and retains them, blocking their flow to groundwater, is essential.

This investigation addresses three key questions: (1) Is additional testing needed? (2) How does tap water quality compare to tap water in other cities? (3) Are the chemical levels in tap water acceptable, and can they be reduced?

The experiments test whether household products (vegetable oil, vinegar, and laundry detergents) reaching groundwater are retained in soil or pass through to contaminate it. Groundwater contamination occurs when substances are not retained by soil layers.

The filtration experiment tests whether a multi-layer filtering method can successfully remove contaminants from water. If the filtering method is successful, the water will be filtered clean and uncontaminated for drinking.

Materials and Methods

The final experiment compares tap water with Dasani and Fiji bottled water by testing for ammonia, chloride, phosphate, iron, alkalinity, chlorine, hardness, and pH levels. The hypothesis is that if tap water travels through unknown pipe and faucet conditions while bottled water is produced in a controlled environment, then bottled water will contain fewer contaminants and taste purer.

This experiment tested soil's ability to filter water contaminants. Materials included eight 250 mL beakers, three wooden stir sticks, a 100 mL graduated cylinder, 10 mL of vegetable oil, 10 mL of vinegar, 10 mL of liquid laundry detergent, a 100 mL beaker, 240 mL of soil, a funnel, cheesecloth, and water.

Beakers were numbered one through eight. Beaker one contained 100 mL water; beaker two contained 100 mL water and 10 mL vegetable oil; beaker three contained 100 mL water and 10 mL vinegar; and beaker four contained 100 mL water and 10 mL liquid laundry detergent. After stirring each mixture, observations were recorded. In phase two, beakers five through eight were used. Cheesecloth was cut into five pieces and folded in half twice to create four layers. Each layer was used to line the funnel. Sixty milliliters of soil was placed in the cheesecloth-lined funnel. The contents of beaker one were poured through the lined soil funnel for one minute into beaker five. Observations of filtration were recorded. The cheesecloth and soil were discarded, and the procedure was repeated for beakers two through four, with contents filtering into beakers six, seven, and eight respectively.

This experiment tested the ability to purify contaminated water using a filtering system. Materials included 100 mL potting soil, two 250 mL beakers, two 100 mL beakers, a 100 mL graduated cylinder, 40 mL sand, 20 mL activated charcoal, 60 mL gravel, a wooden stick, alum, a funnel, cheesecloth, bleach, a stopwatch, and water.

One hundred milliliters of soil was poured into a 250 mL beaker and filled with water. The soil and water were mixed to create contaminated water. Ten milliliters of the contaminated water mixture was poured into a clean 100 mL beaker and set aside for later comparison. The remaining contaminated water was treated with 10 grams of alum and stirred together. A funnel was placed in a rinsed 250 mL beaker, lined with four-layer cheesecloth. Forty milliliters of sand was poured into the cheesecloth-lined funnel, followed by 20 mL of activated charcoal, and then 40 mL of gravel. Clean tap water was repeatedly poured through the funnel and allowed to drain for five minutes. The contaminated water was then poured into the funnel and allowed to filter for five minutes. A few drops of bleach solution were added to the filtered water and stirred. The treated water was compared to the initial 10 mL sample of contaminated water.

This experiment tested chemical components in bottled and tap water. Materials included Dasani bottled water, Fiji bottled water, ammonia test strips, chloride test strips, 4-in-1 test strips, phosphate test strips, iron test strips, three 250 mL beakers, a stopwatch, parafilm, pipettes, three foil packets of reducing powder, and tap water.