1. Integrated Watershed Management
Session Water Quality Modeling -- Dissolved Oxygen Sinks & Nutrients
BOD (Biochemical Oxygen Demand)
Respiration
Sediment oxygen Demand (SOD)
Nitrification
University of Houston -- Integrated Watershed Mangement -- Session CIVE Spring 2006

2. BOD (Biochemical Oxygen Demand)
OM is hard to measure, so we measure it effect
Place sample of OM in bottle, shake & Stopper
Measure DO over a short time -- 5 days
OM + O2 ---> CO2 + NO3 + PO4
The O2 consumed is the BOD
University of Houston -- Integrated Watershed Mangement -- Session CIVE Spring 2006

3. University of Houston -- Integrated Watershed Mangement -- Session 10 CIVE7397 -- Spring 2006

4. Typical BOD Calculation
Add 10 ml sample to water up to 300 ml
Initial DO = 9 mg/l
5 day DO = 6 mg/l
BOD5 = 9-6 / (10 / 300) = 90 mg/l
Dilution is 1:30 and DO loss is 3 mg/l
therefore, 3 * 30 = 90 mg/l
University of Houston -- Integrated Watershed Mangement -- Session CIVE Spring 2006

5. Typical BOD Values Source CBOD5 (mg/l) CBODU (mg/l) NBODU (mg/l)
Org-N (mg/l)
NH3 -- N (mg/l)
Raw Sewage
180
220 20 28
Primary Effluent
120
150 12
Secondary Effluent 2 10
CSO’s
170 6 3
Storm Water 19 25
0.6
University of Houston -- Integrated Watershed Mangement -- Session CIVE Spring 2006

6. A Few Observation on BOD
BOD is not a substance, it is a measurement
Receiving waters will feel the effect of BODU not just BOD5
BOD curves vary greatly depending on the waste
Paper mill effluent has no NBOD
WWTP secondary effluent NBOD does not have lag time
Ethylene glycol BOD ,000 mg/l
University of Houston -- Integrated Watershed Mangement -- Session CIVE Spring 2006

7. Equation for Typical BOD Curve
L = Lo (1 - e (-kt))
L = BOD (mg/l)
Lo = BODU (mg/l)
K = BOD Decay Rate (1/day)
Typical Values for k
0.35 Raw Sewage Bugs love this stuff
Primary Effluent -- OK but not as good as raw
Secondary effluent -- Tough stuff to swallow
University of Houston -- Integrated Watershed Mangement -- Session CIVE Spring 2006

8. 1st Order Kinetics Dc/dt -kc C = c0 * e –kt Board Diagram
University of Houston -- Integrated Watershed Mangement -- Session CIVE Spring 2006

9. Photosynthesis & Respiration
Aquatic Plants Affect DO
Respiration: The process of breaking down food to create energy
Occurs continually
Diurnal DO Cycle
University of Houston -- Integrated Watershed Mangement -- Session CIVE Spring 2006

10. SOD (Sediment Oxygen Demand)
OM, algae & solids etc. eventually end up settling to the bottom
The oxidation process continue in the sediment causing an oxygen demand
Two important reasons:
Can be the major sink for DO
Stores the pollutant history of the stream
University of Houston -- Integrated Watershed Mangement -- Session CIVE Spring 2006

11. Nitrification 2NH3 + 4O2  2HNO3 + 2H20 Nitrification DO Demand
University of Houston -- Integrated Watershed Mangement -- Session CIVE Spring 2006

12. Putting everything together
Sources
Reaeration
Photosynthesis
Sinks
BOD from OM
Respiration
SOD
Nitrification
University of Houston -- Integrated Watershed Mangement -- Session CIVE Spring 2006

13. Texts & Assignments
“Watershed Based National Pollutant Discharge Elimination System (NPDES) Permitting Implementation Guidance’” US Environmental Protection Agency, Dec
Section 2
University of Houston -- Integrated Watershed Mangement -- Session CIVE Spring 2006

14. Next Session Steps 1 & 2 Defining the watershed
Identifying the stake holders
Project problem identification
University of Houston -- Integrated Watershed Mangement -- Session CIVE Spring 2006