1. A Simpler Approach for Determining Biodegradation of SOCs in Wastewater Treatment Tim Ellis Associate Professor Dept. of Civil and Construction Engineering Iowa State University

2. Objective To evaluate technique to determine the biodegradation of specific organic compounds in wastewater treatment systems To evaluate technique to determine the biodegradation of specific organic compounds in wastewater treatment systems To use the measured biodegradation rate parameters to predict the performance of full-scale activated sludge plants To use the measured biodegradation rate parameters to predict the performance of full-scale activated sludge plants

3. Background Technique originally developed at Clemson University under direction of Les Grady Technique originally developed at Clemson University under direction of Les Grady Several assumptions in the technique Several assumptions in the technique  How the test is performed affects results  Using a low substrate to biomass ratio has least affect on measured rate constants  Measured dissolved oxygen concentration can be correlated to compound concentration

4. Basis of Technique Sample of mixed liquor obtained from operating wastewater treatment plant Sample of mixed liquor obtained from operating wastewater treatment plant Sample is placed in a respirometer vessel and aerated with O 2 Sample is placed in a respirometer vessel and aerated with O 2 Respirometer is sealed and DO concentration is continuously measured and recorded Respirometer is sealed and DO concentration is continuously measured and recorded

5. Typical Response

6. Biodegradation Model Based on substrate and biomass mass balances at steady-state Based on substrate and biomass mass balances at steady-state Monod kinetic relationship adequate Monod kinetic relationship adequate Requires knowledge of concentration of biomass degrading the target compound (competent fraction) Requires knowledge of concentration of biomass degrading the target compound (competent fraction)

7. Biodegradation Model (h -1 ) S (mg/L as COD)

8. Experimental Set-up CMAS D.O. Meter Data Acquisition InjectionPort WaterBathBiomassSample D.O. Probe Respirometric Vessel

9. Respirometric Response Raw Data Normalized Response 02004006008001000 4.00 6.00 8.00 10.00 12.00 14.00 0200 A B 04008001200 DO Conc. (mg/L) Time (s)

10. Participating Plants

11. Acetone

12. Ethylene Glycol

13. Furfural

14. Furfural Respirometric Response

15. Furfural and Furoic Acid

16. Furfural

17. Furoic Acid

18. Two-step model

19. Field Results - variability

20. Competent Biomass Assumption that COD fraction is a good estimate not always accurate Assumption that COD fraction is a good estimate not always accurate Required an alternative method to evaluate competent biomass when COD fraction not adequate Required an alternative method to evaluate competent biomass when COD fraction not adequate Proposed using a model calibration period Proposed using a model calibration period

21. Model Calibration Steady-state mass balance equation for effluent concentration Rearranged gives:

22. Acetone Competent Fraction

23. Furfural, furoic acid