1. Water Quality
Presented By: Group 2

3. River Water Quality
Dissolved Oxygen (mg O2 /L) – is required to maintain a balanced community of organisms in lakes, rivers, and the ocean.
Deoxygenation – the rate at which oxygen is consumed in oxidizing an oxygen-demanding waste.
Reaeration – the rate at which the oxygen is resupplied from the atmosphere.

4. Oxygen Saturation and Deficit
Saturation concentration (DOsat) – the amount of oxygen that can be dissolved in water at a given temperature.
Henry’s law constant (Kh) –
(1.36 x 10-3 moles/L-atm at 20°C)
Partial pressure of oxygen in the temperature
(PO2 ) – 21 percent or 0.21 atm

5. Formula for DOsat: DOsat = Kh x PO2 Formula for D: D = DOsat – DOact where: D = oxygen deficit DOact = ambient DO conc. from saturation

6. Example 8.2
Determine the saturation dissolved- oxygen concentration, Dosat at 20°C.
Solution:
Dosat = 1.36 x 10-3 mole/L-atm x 0.21 atm
= 2.85 x 10-4 mole / L
Convert to mg O2/L:
Dosat = 2.85 x 10-4 mole/L x 32 g O2/mole x 103 mg O2
mole O2 g O2
= 9.1 mg O2 /L

7. Example 8.3
Determine the dissolved-oxygen deficit, D, at 20°C for a river with an ambient dissolved-oxygen concentration of5 mg O2/L.
Solution:
D = 9.1 – 5 = 4.1 mg O2/L

8. Wetlands A site may be characterized as wetland if it is:
Is inundated and saturated with water for at least part of the year.
Has hydric soils
Supports predominantly hydrophytic plants

9. Wetlands Serve several important functions:
- water storage and flood mitigation
- filtration of water and removal of suspended solids, bacteria, nutrients
and toxic substances
- wildlife habitat
- biogeochemical cycling of materials
- removes substances that may impair
water quality