Vacuum sewers are a viable alternative for wastewater collection in coastal areas. They use small diameter pipes and shallow depths, reducing costs. Vacuum sewers prevent leaks and infiltration, lowering environmental impacts. They work through a network of vacuum pipes connected to individual homes' valve pits. Wastewater is sucked through the vacuum pipes to a vacuum station and pumped through a force main. Vacuum sewers were successfully used for Oak Island, North Carolina's sewer system serving 4,500 homes across 81 miles of vacuum pipes serviced by 9 vacuum stations.

1. Vacuum Sewers – A Viable
Alternative for Coastal Areas
Conference on Coastal Engineering Practice 2011
San Diego, CA
Monday August 22, 2011
Soma Bhadra, PE
www.consult-proteus.com
Denny Moss
www.airvac.com

2. Why Vacuum Sewers?
Environmentally
Sensitive Areas
Tight Working
Areas
Uses High
When
Differential Groundwater
Gravity
Air Pressure
Sewers have
to Move Rock
Constraints
Wastewater
Flat Rolling
Terrain
Unstable Soil

3. Vacuum Sewers Benefits
• Small pipe sizes (4 to 10-inches) • Reduces costs
• No manholes and cleanouts • Lines stay clean
• Shallow depths (3 – 5 feet) • Reduce environmental impact
• High Scouring velocities (8 – 18 fps) • Very low odor problems
• No exposure to sewer gas • Leaks cannot go un-noticed
• No I/I, Exfiltration prevented • Safe

4. How Vacuum Sewer Works
Vacuum Vacuum
Home Valve Pit Force main
Sewer Station
4

5. Home to Valve Pit

6. Air Intake

7. The Valve Pit
• Pit /Sump & Cone
• Vacuum Valve
• Sump Breather Unit
• Anti-flotation Collar

8. Vacuum System Layout

9. Design Guide
D Design Max Design Max
(in) (gpm) (gpm) (# homes) (# homes)
4 40 55 60 85
6 105 150 165 235
8 210 305 330 470
10 375 545 585 850
Pit Type Peak (gpm) Maximum Peak (gpm)
Standard 0.5 - 1.5 3
Single
3.1 - 15 30
Buffer
Dual Buffer 15 - 30 60

10. Oak Island, North Carolina
81+miles of vacuum sewers 10+ miles wastewater + reuse
force main
9 vacuum stations
400,000 gpd MBR WWTP
4,500gpm pump station

11. Service Areas and Vacuum Stations
9 Service areas, 1 Vacuum Station in each, 1 central Pump Station
Failing Septic Beach Very flat High Intracoastal Hurricane Wetlands +
System properties, groundwater Waterway prone Environmenta
vacation lly sensitive
rentals

12. How Vacuum Sewer Works
Vacuum Vacuum
Home Valve Pit Force main
Sewer Station
12

13. SDR 21, Schedule 40
PVC fittings
O-Ring, Rieber gasket
Collection
System
Design 20 – 500 ft. at 0.2%
Slope with 1 to 1.5ft
lifts
18’ total available lift
at 16” Hg, 5’ used to
evacuate the sump’
13’ available for
sewage transport

14. Collection System

15. Vacuum Station
Incoming
Vacuum Mains
Force
Main
Vacuum Pumps Collection Tank Sewage Pumps
Standby
Generator
Odor Control

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33. Vacuum Sewers – A Viable
Alternative for Coastal Areas
Soma Bhadra, PE
(858) 353-2805
soma@consult-proteus.com Acknowledgement:
www.consult-proteus.com Town of Oak Island,
Denny Moss North Carolina
(800) 247-8229, ext. 229 Black & Veatch, Cary, NC
dennym@airvac.com
www.airvac.com