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Water Quality Parameters

Water Quality Parameters. Dissolved Oxygen. Introduction. Ponds and aquatic systems containing free oxygen molecules are aerobic ; those without are anaerobic .

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Water Quality Parameters

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  1. Water Quality Parameters Dissolved Oxygen

  2. Introduction • Ponds and aquatic systems containing free oxygen molecules are aerobic; those without are anaerobic. • Anaerobic aquatic systems will not support higher life forms such as fish and bacteria. They are characterized by the presence of noxious chemicals such as hydrogen sulfide, which can cause odors. • Anaerobic conditions are normally found in bottom sediments and dirty filters

  3. When does Dissolved Oxygen become a problem? • At 20 C (room temperature) the maximum amount of oxygen that can be dissolved is 9 ppm. • If the water temperature is less than 20 C, it may have more oxygen dissolved in it. • A dissolved oxygen level of 9-10 ppm is considered very good. • At levels of 4 ppm or less, some fish groups (example- bass and trout) will begin to decline. • Sludge worms and leeches are able to survive in water with low dissolved oxygen levels.

  4. Sources of the Dissolved Oxygen • Air consists of 21 percent oxygen and approximately 75 percent nitrogen by volume. Oxygen dissolves poorly in water and can only exist there at a low concentration. • The level of oxygen in the water moves naturally during the day and night and also from season to season. This is because plants use photosynthesis, or make oxygen from sunlight, during the day and respire or use oxygen during the night. • Low dissolved oxygen levels may occur during warm, stagnant conditions that prevent mixing.

  5. The Impact Dissolved Oxygen has on the organism in the water • Total dissolved gas amounts in water should not be above 110 percent. Amounts above this level can be harmful to aquatic life. • Fish in waters containing excessive dissolved gases may suffer from "gas bubble disease"; however, this is a very rare occurrence. The bubbles or emboli block the flow of blood through blood vessels causing death. • External bubbles (emphysema) can also occur and be seen on fins, on skin and on other tissue. Aquatic invertebrates are also affected by gas bubble disease but at levels higher than those lethal to fish.

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