1. Department of Civil Engineering
A Method for Developing Nutrient Criteria using Productivity Data: Brandywine River Case Study
John F. Davis, Ph.D., P.E.
Department of Civil Engineering
Widener University

2. Objectives of Presentation
Demonstrate a methodology using Productivity data to define critical nutrient concentrations that could be considered for criteria
(the critical nutrient levels shown in this presentation were developed to demonstrate the methodology, but are not accepted criteria values)

3. Approaches for Nutrient Criteria Development
Biomass ( max and mean standing crop)
Biomass growth rate (dB/dt)
Macroinvertebrate Indices
Diatom Indices
This study : Gross Primary Productivity calculated from Diurnal DO data

4. The Brandywine Study USGS and Chester Co. WRA
- Continuous Flow, DO, pH, temp. (1970’s)
Upstream Wastewater Discharges
- treatment levels: Secondary (1987)
Nitrification ( )
P removal (1993-)

5. The Brandywine Study Nutrient Data: Discharge Records
Ambient Monitoring
(USGS,State,County, research)

6. Logic Develop Nutrient – GPP relationship
Examine Frequency of DO and pH Violations as a function of GPP
Determine “Critical” Values of GPP
Apply GPP model to estimate nutrient concentration needed to reach Critical GPP as a function of growth duration

7. USGS Gages on Brandywine River
EB-BDT
WBM

11. Estimated SOP for EBDT

12. Light, Nutrients, Primary Productivity

13. Light, Nutrients, Primary Productivity
106CO2 + 16NO3 + HPO H2O+18H
C106H263 O110N16P + 138O2
Sunlight (Photosynthesis)
Dark (Respiration)
(Algal Cells)

14. C106H263 O110N16P Biomass: (CH2O)106 + (NH3)16+ (H3PO4)
Redfield ratio - C/N/P
= 106 / 16 / 1 Molar
= 41 / 7 / 1 Weight

15. Calculation of GPP and R
Odum:
At night:
Single Station method
Reaeration rate (ka)= f(v, d) Owens Eq.
R is computed from night data
GPP is computed for day data