1. Water Quality Indicators
Physical Indication of Water Pollution

2. To a great extent, the success or failure of an aquatic ecosystem is determined by water quality

3. Water Quality Variables
Temperature
Dissolved oxygen
Total ammonia-nitrogen, NH3, NO-2
Alkalinity & Hardness pH
Turbidity
Salinity

4. How water quality values are expressed as:
Parameter
Value
Dissolved oxygen
mg/L or ppm
Water temperature
Degrees C or F pH
Total ammonia nitrogen
Nitrite
Hardness
mg/L or ppm CaC03
Salinity
g/L or ppt salt

5. Temperature
Normal temperature: 22 degrees C Sources: sunlight, thermal pollution Effects: amount of oxygen that can dissolve, photosynthetic rate, metabolic rates change, sensitivity to toxic wastes
Water temperature fluctuates seasonally, resulting in thermal stratification in deeper water.

6. Dissolved oxygen and water temperature
dissolved oxygen and water temperature usually vary over a 24 hour cycle.
Surface dissolved oxygen, mg/L
Surface water temperature, °C 15 31 29 10
summer 27 5 25
6 a.m.
noon
6 p.m.
midnight
6 a.m.

7. Dissolved oxygen and water temperature
Stratification can cause dissolved oxygen and temperature to vary at different depths in the same pond.
Epilimnion
Thermocline
Hypolimnion
High temperature
High dissolved oxygen
Low dissolved oxygen
Low temperature
In general the minimum DO should be ≥ 60% of saturation or ≥ 5 ppm (mg/L)

8. Turbidity Measures the amount of suspended particles in water
Too turbid, then what are the effects?
Temperature rises
Fish may have difficult finding a mate
Clogs fish gills

9. pH
pH is a measure of acidity (hydrogen ion concentration) in water or soil.

10. pH Values of Water The pH range of freshwater is 6 to 8.
The acidity of water is gauged by its pH , which is a measure of the concentration of the hydrogen ion (H + ) in the solution according to the relationship pH = −log(H + ). The higher the concentration of H + in the water, the lower its pH, and the greater its acidity. Acid waters have a pH less than 7 (neutral pH is 7), with the most acid waters at pH 1 or less. Basic (alkaline) waters have a pH greater than 7, with the most basic waters at pH 14.
The pH range of freshwater is 6 to 8.
The average pH of sea (ocean water) is 8.1.

11. Effects of low pH
Acid deposition has many harmful ecological effects when the pH of most aquatic systems falls below 6 and especially below 5.
Here are some effects of increased acidity on aquatic systems:
As the pH approaches 5, non-desirable species of plankton and mosses may begin to invade, and populations of fish such as smallmouth bass disappear.
Below a pH of 5, fish populations begin to disappear, the bottom is covered with un-decayed material, and mosses may dominate near shore areas.
Below a pH of 4.5, the water is essentially devoid of fish.

12. Effects of High pH (basic)
When the pH of freshwater becomes highly alkaline (e.g. 9.6), the effects on fish may include:
death, damage to outer surfaces like gills, eyes, and skin and an inability to dispose of metabolic wastes.
High pH may also increase the toxicity of other substances. For example, the toxicity of ammonia is ten times more severe at a pH of 8 than it is at pH 7. It is directly toxic to aquatic life when it appears in alkaline conditions. Low concentrations of ammonia are generally permitted for discharge.

13. Total Ammonia Nitrogen
Ammonia exists in two forms in the water:
NH3 ( this is called unionized ammonia )
NH4+ ( this is called ionized ammonia )
Together, these two forms of ammonia are called TAN which means total ammonia nitrogen
The ratio of ammonia and ammonium varies in an equilibrium determined by pH and water temperature.
Ammonia as a % of total ammonia nitrogen

14. Effects of TAN
NH3 is the principal form of toxic ammonia. It has been reported toxic to freshwater organisms at concentrations ranging from 0.53 to 22.8 mg/L.
Toxic levels are both pH and temperature dependent. Toxicity increases as pH decreases and as temperature decreases.
Plants are more tolerant of ammonia than animals, and invertebrates are more tolerant than fish. Hatching and growth rates of fishes may be affected. In the structural development, changes in tissues of gills, liver, and kidneys may also occur. Toxic concentrations of ammonia in humans may cause loss of equilibrium, convulsions, coma, and death.

15. Soft and Hard Water
Water hardness and softness has nothing to do with its touch and feel. It is more about chemical compounds dissolved in it. They are both safe for human consumption.
Pure water (like clean rainwater) is soft water.
It only becomes hard when it comes into contact with rock layers made up of compounds such as calcium or magnesium, and dissolves in it.

16. Hard Water vs Soft Water
When it boils down, the major difference between hard and soft water can best be seen while doing household chores. Hard water is to blame for dingy looking clothes, dishes with spots and residue, and bathtubs with lots of film and soap scum. Even hair washed in hard water may feel sticky and look dull. Hard water can take a toll on household appliances as well and use up more energy. The elements of hard water are to blame for all of these negative factors, as soap is less effective due to its reaction to the magnesium and calcium. The lather is not as rich and bubbly.

17. Salinity NaCl Fresh water is less than 2 g/L
Brackish water is 2 g/L to 34 g/L
NaCl
Sea water is more than 34 g/L