1. 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

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
Screen
Interceptor Sewer
Sludge
Actiflo®
Actiflo
Disinfection
WWTP
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 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

10. Design – Coagulation Jar Test/Pilot Study Sizing Tank Mixing
Chemical Coagulant
HRT 1 – 2 minutes
Rapid Mixing
(G = s-1)
Jar Test/Pilot Study
Sizing Tank
V = (HRT) x Q
= 1 min x gal/min
= gal or 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 Sizing Tank Mixing
Polymer
Sand (2 – 4 g/L)
HRT 1 – 2 minutes
Rapid Mixing
(G = s-1)
Sizing Tank
V = (HRT) x Q
= 1 min x gal/min
= gal or 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 Sizing Tank Mixing Maturation HRT 3 – 5 minutes
Slow Mixing
(G = 160 – 200 s-1)
Sizing Tank
V = (HRT) x Q
= 3 min x 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 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
= gal/min / 30 gal/ft2*min
= ft2
Tank Dimensions
L = W = A1/2
= /2
= 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. 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 kg ( lb)
Sludge = 10 MGD x = 480,000 gal/day

16. Actiflo® Design

17. Actiflo® Design

18. Conclusions Evaluation of Alternatives Design Pilot Study
Disadvantages

19. Questions?