Toxicity Testing: Nitrification Inhibition

1. Toxicity Testing: Nitrification Inhibition Jessica Shaw Environmental Supervisor City of Wenatchee

2. City of Wenatchee

3. What happened? Problems at the POTW NPDES Violations Lawsuit by Environmental Groups 1. High Strength 2. Inhibitory/Toxic Characteristics

4. Toxicity/Inhibition Methods • Dissolved Oxygen Uptake • Respirometer • Bacterial Growth Inhibition • Screening Method for Determination of Inhibition of Nitrification of Activated Sludge

5. Nitrification Ammonia Hydroxylamine  Nitrite  Nitrate NH4 NH2OH  ?  NO2  NO3 Nitrifying bacteria participate in the nitrification process and are generally more sensitive to toxic substances than other bacteria.

6. Method Development in Sweden • Low DO problems along the Swedish Coast in the 1980s  Nitrogen limits • By the 1990s treatment plants were upgraded and using nitrification to remove N • Nitrification problems compounded by toxic substances

7. Screening Method Advantages • Waste streams as well as specific chemicals can be tested. • Provides the % Inhibition of a test substance based on the nitrification rate of the activated sludge. • The test is specific to the POTW’s activated sludge. • Designed to be run at a POTW lab.

8. Required Equipment • Spectrophotometer • Ammonia meter/probe • Analytical Balance • Laboratory Shaker • Test tubes – 24 Large, 24 Small • Test tube racks • Funnels • Filter papers • pH strips • Automatic pipet • Thermometer • Beakers • Equipment for measuring Volatile Suspended Solids

9. The Method 1. Prepare the Activated Sludge Suspension. • Chemicals • Ammonium Sulfate • Sodium Bicarbonate • Potassium Phosphate, Monobasic Check pH and run VSS on Activated Sludge Suspension.

10. The Benchsheet

11. The Method 2. Set-up dilutions of the test substance.

12. The Bench Sheet

13. The Method 3. Add Activated Sludge Suspension and shake for 2 hours.

14. The Bench Sheet

15. The Method 4. Filter and Analyze for pH Temperature Nitrate Ammonia

16. Completed Bench Sheet

17. Modifications • Nitrate Method • Ammonia Method • pH

18. Quality Control • Reference Samples • Initial determination of Nitrification rate • Change in Ammonia concentration should be between 8 & 22 ppm

19. Quality Control continued… • VSS of Activated Sludge Suspension should be between 1500-6000 ppm • Adjustments can be made to the VSS, initial ammonia and incubation time to optimize the nitrification rate.

20. Calculations • Calculate the initial concentration of Nitrate in the test tubes (NTT,o) • Calculate the amount of volatile suspended solids in the test tubes (VSSTT)

21. Calculations continued… • Calculate the average nitrification rate of the reference samples (RNitr,c) • Calculate the nitrification rate of each dilution of the test substance (RNitr,s) RNitr = (NTT,f - NTT,o) = mg N (Time) (VSSTT) (g VSS) (h)

22. Final Calculation Calculate the percent inhibition. Average Ref. Rate – Sample Rate * 100% Average Ref. Rate

23. Typical Inhibition Curve

24. Using the Nitrification Inhibition Test • Start with WWTP influent and side streams • Industrial User Surveys and business specific surveys • Review WWTP data for clues

25. Using the Nitrification Inhibition Test • Research done in Sweden found that the following businesses had the highest % Inhibition: • Tanker Truck Washing • Chemical manufacturing • Food Processing • Printing

26. Results • WWTP Influent & Side Streams • Thiabendazole (TBZ) • The Printer

27. Influent Testing • Types of Samples • 24 hour composite • 1 hour composite • Grab

28. Results of Influent Testing • No inhibition was detected in the 24 hour or 1 hour composite samples <10% Inhibition • Grab samples from the influent were found to range from extremely inhibitory to slightly inhibitory. 90% to 15% Inhibition

29. Belt Filter Press • Analyzed the filtrate from the belt filter press • Ammonia concentration in filtrate = 780 ppm • Concentrations of Ammonia over 300 ppm can inhibit nitrification

30. Belt Filter Press Results

31. Thiabendazole (TBZ) • AKA Mertect, Decco Salt No. 19, Arbotect, Tecto, and Apl-Luster • WA State Fresh Fruit Packing Limits • Dust/Land 615 mg/L • POTW 50 mg/L • Percolation 5 mg/L

32. TBZ Results • When the nitrification rate of the activated sludge was slow, the TBZ showed increased inhibition

33. The Printer • Photo/X-ray Processing Survey & review of plant data • Hydroquinone • Used in X-ray, plate developing, black & white photography • Most X-ray developing solutions 1-5% • Some developing solutions are as high as 30%

34. Printing Waste Results • October 2003 • Sample collected of waste developer solution off equipment

35. Printing Waste Results • November 2003 • Sample collected from the point of discharge to sewer • 10 hour composite

36. No Nitrifying Bacteria!

37. Printing Waste Results • August 2004 • Collected another 10 hour composite at the point of discharge to sewer

38. Printing Waste Results • September 2004 • New Chemicals, no phenols just a few biocides

39. In Conclusion • Useful pretreatment resource • Pre-screening Method • Recent Testing: Car wash soaps & chemicals used at the plant

40. Primary Reference Inhibition of Nitrification in Municipal Wastewater – Sources, Effects, Evaluation and Remedies Dr. Karin Jönsson 2001, Department of Water & Environmental Engineering, Lund Institute of Technology Lund, Sweden

41. Contact Information Jessica Shaw City of Wenatchee Phone: (509) 664-3387 Email: jessicashaw@cityofwenatchee.com