Lesson 2

Water Quality Certain substances, such as ion, can affect the taste or color of water but are harmless unless present at very high levels. Other substances, such as certain chemicals and microorganisms can be harmful to your health. In the U.S. the _________________________________ is responsible for developing water-quality standards.

Acidity The pH level of water also affects its quality. The pH of water is a measurements of how __________________ or ___________ the water is on a scale of ______________ has a pH of 7, it is neutral, meaning it neither an acid or nor a base. The _______________ the pH, the more basic the water. The _______________ the pH, the more acidic the water.

Hardness The combines level of two minerals ________________ and _________________, in a sample of water is referred to as the hardness of that sample of water. Hard water does not form suds easily.

Disease-Causing Organisms The presence of disease-causing organisms affects water quality. Such organisms can be detected in water by conducting a __________________, which measure the number of Escherichia coli bacteria. A high coliform count is a sign that the water may also contain other disease-causing organisms.

Treating Drinking Water Water from both public and private supplies often needs some treatment to ensure that it is clean and safe to drink.

Filtration and Coagulation The first step in treating water from a lake or river is usually _________________. In the second step, a chemical is added to cause sticky globs, called ______________, to form. Other particles stick to this substance. This process is known as _____________________.

Chlorination and Aeration The next step is to chlorinate your water. Chlorine is added to drinking water for the same reason it is added to swimming pools: to kills disease- causing microorganisms. After chlorination, ______________ is then forced through the purified water. The process reduces unpleasant odors and tastes from your water.

Testing Samples __________________________ regularly test samples of water from treatment plants to assess water quality. They test for the substances covered by the drinking- water standards, including chemicals, dissolved solids, pH, hardness, and disease-causing microorganisms.

Treating Wastewater Two ways communities deal with sewage are wastewater treatment plants and septic systems. _____________________ sewers carry sewage away to wastewater treatment plants. Sewage flows into a _________________, where bacteria breakdown the waste material into simpler chemicals. Cleaner water leaves the tank and flows into a ____________________.

Questions for Thought What is a leach field? What is the goal of drinking-water treatment? What two minerals affect a water sample’s hardness?