Slime, Slime, Slime!

1. Slime, Slime, Slime! Toni Glymph Environmental Toxicologist Wisconsin DNR

2. Slime Bulking • There is a condition in wastewater treatment often called slime bulking. • Occurs when bacteria “over-produce” the lipopolysaccharide normally found outside the bacteria cell wall. • Found most often in industrial wastewater treatment systems, but may also occur in municipal systems.

3. Slime Bulking • What makes the bacteria “over-produce” lipopolysaccharide? • Lack of sufficient nutrients (mostly nitrogen) • Excess organic acids

4. Slime Bulking Gram (+) Gram (-) Polysaccharide “Slime Layer” Lipopolysaccharide “Slime Layer” Cell Wall Phospholipid Lipoprotein Cell Wall Cell Membrane Cell Membrane

5. Slime Bulking • 3 main elements are required in the development of the cell wall components. • They make up 18% of the dry weight of the cell components. • Nitrogen (15%) • Phosphorus (2%) • Sulfur (1%)

6. Slime Bulking • Nitrogen is required to makeup the lipoprotein layer • Phosphorus is required to make up the phospholipid layer. Gram (-) Lipopolysaccharide “Slime Layer” Phospholipid Lipoprotein Cell Wall Cell Membrane

7. Slime Bulking • When Phosphorus is deficient, a small amount of extra lipids (fat) is added to the slime layer. Gram (-) Lipopolysaccharide “Slime Layer” Lipid Lipoprotein Cell Wall Cell Membrane

8. Slime Bulking • When Nitrogen is deficient a larger amount of “fat” is added to the slime layer.. Gram (-) Lipopolysaccharide “Slime Layer” Lipid Lipid Cell Wall Cell Membrane

9. Slime Bulking • When slime bulking occurs, nitrogen and phosphorus are the nutrients that are usually deficient. • Slime bulking is more severe when nitrogen is deficient. • Nutrient ratio 100:10:1 (BOD:N:P)

10. Slime Bulking • Excess Organic Acids • A ready food source that does not contain nitrogen • Usually added through sludge processing recycle streams (anaerobic digester supernatant) • Any other anaerobic process side stream

11. Slime Bulking • India Ink stain • When India ink is added to a drop of mixed liquor the carbon black particles penetrate the floc from outside to inside • The lipopolysaccharide prevents the India ink from penetrating the floc particle.

12. Slime Bulking India Ink Stain

13. Slime BulkingIndia Ink Stain

14. Slime Bulking Case Study • Industry • 2 SBRs • excessive filamentous bacteria • severe nutrient deficiency (nitrogen) • severe bulking problems • discharging 60% of the flow to WWTP

15. Slime Bulking Case Study • WWTP • very few filamentous bacteria • severe bulking problems • having difficulty dewatering sludge

16. Slime Bulking (Industry Tank #1)

17. Slime Bulking (Industry Tank #2)

18. Slime Bulking (WWTP Mixed Liquor)

19. Slime Bulking (WWTP Digester Supernatant)

20. Slime Bulking Case Study - Conclusions • Due to poor operations and severe nitrogen deficiency, excess lipopolysaccharides were being produced in the SBR tanks. • This slime was being discharged into the WWTP and accumulated over time. • Present in the aeration basin, clarifiers and digesters.

21. Slime Bulking • Operational Considerations • The solution involves adding the deficient nutrient • Ammonia to provide nitrogen • Phosphoric acid to provide phosphorus

22. Slime Bulking • Operational Considerations • There is no nutrient deficiency if, in a filtered (.045 um) effluent sample: • ammonia + nitrate is > 1 mg/L and, • soluble orthophosphate is > 0.5 mg/L

23. Slime Bulking • The excess lipopolysaccharide can only be wasted out of the system. • You have to stop the bacteria from producing the excess amounts. • Making sure sufficient nutrients are available • Adding anaerobic recycle streams slowly and/or add more organisms (increase return) when excessive amount of organic acids are present.