Christopher Hill December 6, 2006 CE 679 Application of Ballast Flocculation for Sanitary Sewer Overflow Management North Dakota State University Christopher Hill December 6, 2006 CE 679

Outline Problem Overview Introduction Application Design Conclusion

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?

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

Actiflo® System

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

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

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

Design - Pretreatment Design Flow Pretreatment 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

Design – Coagulation Jar Test/Pilot Study Sizing Tank Mixing Chemical Coagulant HRT 1 – 2 minutes Rapid Mixing (G = 500-1500 s-1) Jar Test/Pilot Study 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

Design – Flocculation Jar Test/Pilot Study Sizing Tank Mixing 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

Design – Maturation Sizing Tank Mixing 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

Design - Settler Tank Area Tank Dimensions Design Criteria 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

Design – Actiflo® System Assume Depth of 12 ft

Design - Microsand 2 – 4 g/L of Microsand 4.8% of Q Sludge Actiflo® Influent Q Hydrocyclone 1.2% of Q Recycled Sand River Clarified Water 6% of Q Sludge Handling WWTP 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

Actiflo® Design

Actiflo® Design

Conclusions Evaluation of Alternatives Design Pilot Study Disadvantages

Questions?