Science 8: Unit E: Salt and Freshwater Systems Topic 6 – Water Quality and Water Management

How Can You Determine Water Quality? Just because water is clear, does NOT mean it’s potable. Just because water is clear, does NOT mean it’s potable. Amount and types of dissolved minerals in the water; pH of the water; amount of dissolved oxygen, salinity, presence of heavy metals and types of micro-organisms living in the water. Amount and types of dissolved minerals in the water; pH of the water; amount of dissolved oxygen, salinity, presence of heavy metals and types of micro-organisms living in the water. Water quality is periodically checked using water samples taken from different areas of the water source. Water quality is periodically checked using water samples taken from different areas of the water source. If a water sample is found to be toxic, the water cannot be used for human or animal consumption. If a water sample is found to be toxic, the water cannot be used for human or animal consumption.

Direct and Indirect Uses of Water Direct Uses – Water used for domestic/personal uses. Direct Uses – Water used for domestic/personal uses. Indirect Uses – Water used for agricultural/ industrial purposes. Indirect Uses – Water used for agricultural/ industrial purposes. 73% of water is used for agriculture, 22% for industry and only 5% for direct domestic uses. 73% of water is used for agriculture, 22% for industry and only 5% for direct domestic uses. There are benefits and drawbacks to each of the above uses of water (eg. benefits = jobs, drawback = harmed ecosystems) There are benefits and drawbacks to each of the above uses of water (eg. benefits = jobs, drawback = harmed ecosystems)

Acids and Bases Acids and bases are water-based solutions containing hydrogen (H + ) and hydroxide ions (OH - ). Acids and bases are water-based solutions containing hydrogen (H + ) and hydroxide ions (OH - ). Measured on a pH scale. The lower the pH, the more acidic the solution, the higher the pH, the more basic or alkaline the solution. Measured on a pH scale. The lower the pH, the more acidic the solution, the higher the pH, the more basic or alkaline the solution. If a solution measures 7 on the pH scale, it’s neutral. Water is neutral. If a solution measures 7 on the pH scale, it’s neutral. Water is neutral.

Bioindicator Species Bioindicator Species – species that are very sensitive to changes in the ecosystems and/or presence of pollutants. They are helpful because they can tell scientists about how different chemicals interact with an ecosystem. Bioindicator Species – species that are very sensitive to changes in the ecosystems and/or presence of pollutants. They are helpful because they can tell scientists about how different chemicals interact with an ecosystem. Amphibians and certain invertebrates (insects) are considered good bioindicators because they are the most sensitive to pollutants. Amphibians and certain invertebrates (insects) are considered good bioindicators because they are the most sensitive to pollutants.

Purifying Water To be made potable, water must be treated: it must be screen, mixed, filtered, and healthy chemicals (eg. fluoride) need to be added. To be made potable, water must be treated: it must be screen, mixed, filtered, and healthy chemicals (eg. fluoride) need to be added. After water has been used by humans, the solid and liquid waste (sewage) has to be treated again before it can go back to the water supply as effluent. After water has been used by humans, the solid and liquid waste (sewage) has to be treated again before it can go back to the water supply as effluent. In rural areas a septic tank is used to help treat sewage. In rural areas a septic tank is used to help treat sewage. In drier areas, desalination, distillation and reverse osmosis (forcing water to go from more to less concentrated solutions) are used to purify water. In drier areas, desalination, distillation and reverse osmosis (forcing water to go from more to less concentrated solutions) are used to purify water.