Application of Ballast Flocculation for Sanitary Sewer Overflow
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®, Densa. Deg®, Sirofloc®
Actiflo® System
Application – Satellite Basin Screen • Located in the collection system Interceptor Sewer Sludge Actiflo® Disinfection WWTP River • Does not meet EPA secondary treatment standards • Cost effective
Application – WWTP Bypass Headworks Secondary Treatment • Located at WWTP Actiflo® Disinfection River • Mixing with the WWTP effluent to comply with permitting limits • Cost effective
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 – 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 • Coagulation – Chemical Coagulant – HRT 1 – 2 minutes Sizing Tank – Rapid Mixing V = (HRT) x Q (G = 500 -1500 s-1) = 1 min x 3472. 5 gal/min = 3472. 5 gal or 464. 2 ft 3 Mixing Theoretical Power Requirement P = G 2 m V = 12002(1. 307 x 10 -3 N*s/m 2)13. 2 m 3 = 24, 844 W or 25 k. W
Design – Flocculation • Flocculation – Polymer – Sand (2 – 4 g/L) – 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 ft 3 Mixing Theoretical Power Requirement P = G 2 m V = 12002(1. 307 x 10 -3 N*s/m 2)13. 2 m 3 = 24, 844 W or 25 k. W
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 ft 3 Mixing Theoretical Power Requirement P = G 2 m V = 2002(1. 307 x 10 -3 N*s/m 2)52. 6 m 3 = 2, 750 W or 2. 8 k. W
Design - Settler • Settler – Overflow Rate 20 to 80 gal/ft 2*min – Typically 30 gal/ft 2*min – Length: Width = 1: 1 – Lamellar Tubes Design Criteria Between 45 o and 60 o Incline Nominal Spacing 2 in Incline Length 3 to 6 ft Tank Area A = Q / Vo = 3472. 5 gal/min / 30 gal/ft 2*min = 115. 75 ft 2 Tank Dimensions L = W = A 1/2 = 115. 751/2 = 10. 75 ft Use 11 ft
Design – Actiflo® System • Assume Depth of 12 ft
Design - Microsand Influent Q 1. 2% of Q Recycled Sand Actiflo® Clarified Water 6% of Q Sludge Handling River • • Hydrocyclone 4. 8% of Q Sludge WWTP 2 – 4 g/L of Microsand Total Volume – Coagulation = 3, 375 ft 3 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?
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