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Christopher Hill December 6, 2006 CE 679

Christopher Hill December 6, 2006 CE 679. Application of Ballast Flocculation for Sanitary Sewer Overflow Management. North Dakota State University. Outline. Problem Overview Introduction Application Design Conclusion. Problem Overview. What are SSOs ? What is the cause of SSOs ?

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Christopher Hill December 6, 2006 CE 679

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  1. Christopher HillDecember 6, 2006CE 679 Application of Ballast Flocculation for Sanitary Sewer Overflow Management North Dakota State University

  2. Outline • Problem Overview • Introduction • Application • Design • Conclusion

  3. Problem Overview • What are SSOs? • What is the cause of SSOs? • Why are SSOs a problem? • What is the frequency of SSOs? • How are SSOs managed?

  4. Ballasted Flocculation • What is ballasted flocculation? • Why ballasted flocculation? • Actiflo®, DensaDeg®, Sirofloc®

  5. Actiflo® System

  6. Application – Satellite Basin • Located in the collection system • Does not meet EPA secondary treatment standards • Cost effective Interceptor Sewer Screen Sludge Actiflo® Actiflo WWTP Disinfection River

  7. Application – WWTP Bypass Headworks • Located at WWTP • Mixing with the WWTP effluent to comply with permitting limits • Cost effective Secondary Treatment Actiflo® Disinfection River

  8. Design – Flow Monitoring • Base on flow monitoring, develop model for sewer system. • Typically designed for 5 year return period storm • Design peak wet weather flow = 15 MGD

  9. Design - Pretreatment • Design Flow • Ramp-up 150% Q • Ramp-down 50% Q • Hydraulically 200% Q • Pretreatment • Screening (3 – 6 mm) • 2 x 10 MGD Q = 10 MGD 2 x 5 MGD

  10. Design – Coagulation Jar Test/Pilot Study • Coagulation • Chemical Coagulant • HRT 1 – 2 minutes • Rapid Mixing (G = 500-1500 s-1) Sizing Tank V = (HRT) x Q = 1 min x 3472.5 gal/min = 3472.5 gal or 464.2 ft3 Mixing Theoretical Power Requirement P = G2 m V = 12002(1.307x10-3 N*s/m2)13.2m3 = 24,844 W or 25 kW

  11. Design – Flocculation Jar Test/Pilot Study • Flocculation • Polymer • Sand (2 – 4 g/L) • HRT 1 – 2 minutes • Rapid Mixing (G = 500-1500 s-1) Sizing Tank V = (HRT) x Q = 1 min x 3472.5 gal/min = 3472.5 gal or 464.2 ft3 Mixing Theoretical Power Requirement P = G2 m V = 12002(1.307x10-3 N*s/m2)13.2m3 = 24,844 W or 25 kW

  12. Design – Maturation • Maturation • HRT 3 – 5 minutes • Slow Mixing (G = 160 – 200 s-1) Sizing Tank V = (HRT) x Q = 3 min x 3472.5 gal/min = 10,417 gal or 1,393 ft3 Mixing Theoretical Power Requirement P = G2 m V = 2002(1.307x10-3 N*s/m2)52.6m3 = 2,750 W or 2.8 kW

  13. Design - Settler • Settler • Overflow Rate 20 to 80 gal/ft2*min • Typically 30 gal/ft2*min • Length: Width = 1:1 • Lamellar Tubes Tank Area A = Q / Vo = 3472.5 gal/min / 30 gal/ft2*min = 115.75 ft2 Tank Dimensions L = W = A1/2 = 115.751/2 = 10.75 ft Use 11 ft Design Criteria Between 45o and 60o Incline Nominal Spacing 2 in Incline Length 3 to 6 ft

  14. Design – Actiflo® System • Assume Depth of 12 ft

  15. Influent Q 1.2% of Q Recycled Sand Actiflo® Hydrocyclone 4.8% of Q Sludge Clarified Water 6% of Q Sludge Handling River WWTP Design - Microsand • 2 – 4 g/L of Microsand • Total Volume – Coagulation = 3,375 ft3 or 95,600 L • The system requires 191.2 - 382.4 kg (421.5 - 843 lb) • Sludge = 10 MGD x 0.048 = 480,000 gal/day

  16. Actiflo® Design

  17. Actiflo® Design

  18. Conclusions • Evaluation of Alternatives • Design • Pilot Study • Disadvantages

  19. Questions?

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