Christopher Hill December 6, 2006 CE 679 Application of Ballast Flocculation for Sanitary Sewer...

Christopher HillDecember 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?

• 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

Interceptor Sewer

WWTP

River

Actiflo

Disinfection

Sludge

Actiflo®

Screen

• Located in the collection system

• Does not meet EPA secondary treatment standards

• Cost effective

Application – WWTP Bypass

Headworks

River

Disinfection

Actiflo®

• Located at WWTP

• Mixing with the WWTP effluent to comply with permitting limits

• Cost effective

Secondary Treatment

Design – Flow MonitoringBasin 8

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

0:00 2:00 4:00 6:00 8:00 10:00 12:00 14:00 16:00 18:00 20:00 22:00 0:00

Time (hr)

Flo

w (

mg

d)

0.0

1.0

06/11/20010.92 inches/hr

Ra

in F

all

(in

)

Wet-Day Flow Dry-Day Flow Rain Fall

Inflow

Infiltration

• 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

• Coagulation– Chemical Coagulant – HRT 1 – 2 minutes– Rapid Mixing

(G = 500-1500 s-1)

V

PG

Jar Test/Pilot Study

Sizing TankV = (HRT) x Q = 1 min x 3472.5 gal/min = 3472.5 gal or 464.2 ft3

Mixing

Theoretical Power Requirement

P = G2 V = 12002(1.307x10-3 N*s/m2)13.2m3

= 24,844 W or 25 kW

Design – Flocculation

• Flocculation– Polymer– Sand (2 – 4 g/L)– HRT 1 – 2 minutes– Rapid Mixing

(G = 500-1500 s-1)

V

PG

Jar Test/Pilot Study

Sizing TankV = (HRT) x Q = 1 min x 3472.5 gal/min = 3472.5 gal or 464.2 ft3

Mixing

Theoretical Power Requirement

P = G2 V = 12002(1.307x10-3 N*s/m2)13.2m3

= 24,844 W or 25 kW

Design – Maturation

• Maturation– HRT 3 – 5 minutes – Slow Mixing

(G = 160 – 200 s-1)

Sizing TankV = (HRT) x Q = 3 min x 3472.5 gal/min

= 10,417 gal or 1,393 ft3

Mixing

Theoretical Power Requirement

P = G2 V

= 2002(1.307x10-3 N*s/m2)52.6m3

= 2,750 W or 2.8 kW

Design - Settler• Settler

– Overflow Rate 20 to 80 gal/ft2*min

– Typically 30 gal/ft2*min– Length: Width = 1:1 – Lamellar Tubes

Tank AreaA = Q / Vo

= 3472.5 gal/min / 30 gal/ft2*min = 115.75 ft2

Tank DimensionsL = W = A1/2

= 115.751/2

= 10.75 ft Use 11 ft

Design Criteria Between 45o and 60o InclineNominal Spacing 2 inIncline Length 3 to 6 ft

Design – Actiflo® System

• Assume Depth of 12 ft

Design - Microsand

4.8% of Q Sludge

Actiflo®

Influent Q

Hydrocyclone

1.2% of QRecycled

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?