Chapter 11 Water Quality KEY QUESTION: What substances are in water, and where do they come from?

1. Chapter 11Water QualityKEY QUESTION: What substances are in water, andwhere do they come from? salinity concentration desalination contaminant fertilizer herbicide pesticide turbid thermal pollution watershed bioremediation sewer system blackwater greywater wastewater stormwater runoff Only a tiny fraction of the water on Earth is fresh water available for our use. Water can contain many different contaminants. The skills of scientific inquiry can be used to test water quality. Water must be used sustainably. Wastewater must be treated before being returned to the environment. Research skills can be used to learn more about water issues.

2. 11.1 Fresh Water and Salt Water • Most of the Earth’s water is in the oceans • Only 3% is fresh water (not salty) – most deep under the surface or frozen • ONLY 0.4% is fresh water at or near the surface • NOTE: Fresh does not always mean “suitable for drinking” salinity: a measure of the quantity of dissolved salt in water concentration: a measure of the quantity of dissolved substance contained per unit volume of solution The Dead Sea is a 30 % salt solution. (300 g/L) World’s oceans are only 3 to 4 % Any freshwater source (such as the Great Lakes) is less than 1 %. desalination: the technology of removing salt and other minerals from water Some desalination technologies involve evaporating and then condensing water to remove the salt. This process requires a lot of thermal energy, which makes it very expensive compared to using fresh surface water or groundwater directly.

3. 11.2 Contaminants in Water • Water is a very effective solvent; it can dissolve many substances. • Taking in water that contains contaminants can be hazardous to both plants and animals. contaminant: an undesirable substance in a mixture Sources of Chemical Contaminants fertilizer: a substance used to provide nutrients to plants, usually for the purpose of increasing crop production herbicide: a chemical substance used to kill or slow the growth of certain plants; often used to kill weeds that compete with crop plants pesticide: a chemical substance used to kill animal pests; often used to kill insects that damage crop plants -We use road salt, gravel, and sand in the winter to prevent ice from forming on roads -Surface water and groundwater both travel through various kinds of rock. Minerals from rock dissolve in the water. -Industries and vehicles that burn fossil fuels release many chemicals into the air. Some of these chemicals react with water vapour in the atmosphere to form acid rain -Transportation industry is a major polluter of freshwater sources -Sources of water are sometimes vulnerable to biological contamination and must be monitored closely

5. 11.3 Testing Water Quality turbid: not clear; containing tiny specks of sediment or other solid matter thermal pollution: artificially raising the temperature (for example, of water) Measure depth when Secchi Disk disappears Temp can indicate levels of O2 An indicator that turns different colours in acidic and basic solutions Conductivity apparatus is used to determine whether a solution can carry a current Chemically treated paper test strips

6. 11.4 Watersheds watershed: an area surrounded by high land and drained by a river and its tributaries; all runoff from within the watershed; leaves the watershed at the same exit Ex. The Great Lakes Basin -The Ontario legislature created 36 Conservation Authorities (CAs) in 1946 that protect and manage local watersheds -In 1987, Canada and the United States signed The Great Lakes Water Quality Agreement -Organisms that “feed” on specific pollutants can be used to break pollutants down and remove them from the environment. bioremediation: the use of living things (micro-organisms, fungi, and green plants) to remove contaminants from a polluted environment 11.7 Wastewater Treatment What happens to dirty water that flows down the drain when you flush the toilet or wash your clothes? sewer system: a network of pipes that transports dirty or used water to a waste water treatment facility

8. 1. Preliminary Treatment Wastewater passes through a bar screen, which removes objects such as sticks, rocks, and garbage. The wastewater is slowed down as it enters the grit tank to allow sand, gravel, and other heavy materials to settle to the bottom. Debris from the bar screen and grit tank is trucked to a landfill. 2. Primary Treatment The wastewater flows into a primary settling tank where it is held for several hours. Solid particles settle to the bottom of the tank. 3. Secondary Treatment Next, a biological treatment process removes organic matter from the wastewater. Adding oxygen encourages micro-organisms to grow and eat the organic matter. This is the same as the natural decomposition process—only sped up. Any remaining solids settle to the bottom of the clarifier. 4. Final Treatment The wastewater is disinfected with chlorine to kill harmful organisms. The clean water is then released into Lake Ontario. 5. Solids Processing The primary solids from the primary settling tank and the secondary solids from the clarifier are sent to the digester. Micro-organisms use organic material in the solids as food and convert it to methane gas. This gas can be used to produce electricity or to heat the plant. After 15 days in the digester, bio-solids (wet, soil-like material) are sent to the landfill or are incinerated. Bio-solids are high in nutrients, such as nitrogen and phosphorus, and can be used as fertilizer