Vacuum Sewers – A Viable Alternative for Coastal Areas

Soma Bhadra, PE www.consult-proteus.com

Denny Moss www.airvac.com

Conference on Coastal Engineering Practice 2011 San Diego, CA

Monday August 22, 2011

Why Vacuum Sewers?

Uses Differential Air Pressure

to Move Wastewater

When Gravity

Sewers have Constraints

Environmentally Sensitive Areas

Tight Working Areas

High Groundwater

Rock

Flat Rolling Terrain

Unstable Soil

Vacuum Sewers

• Small pipe sizes (4 to 10-inches)

• No manholes and cleanouts

• Shallow depths (3 – 5 feet)

• High Scouring velocities (8 – 18 fps)

• No exposure to sewer gas

• No I/I, Exfiltration prevented

Benefits

• Reduces costs

• Lines stay clean

• Reduce environmental impact

• Very low odor problems

• Leaks cannot go un-noticed

• Safe

4

Home Valve Pit Vacuum Sewer

Vacuum Station

Force main

How Vacuum Sewer Works

Home to Valve Pit

Air Intake

• Pit /Sump & Cone

• Vacuum Valve

• Sump Breather Unit

• Anti-flotation Collar

The Valve Pit

Vacuum System Layout

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 Buffer

3.1 - 15 30

Dual Buffer 15 - 30 60

Oak Island, North Carolina

81+miles of vacuum sewers

9 vacuum stations

4,500gpm pump station

10+ miles wastewater + reuse force main

400,000 gpd MBR WWTP

Service Areas and Vacuum Stations

9 Service areas, 1 Vacuum Station in each, 1 central Pump Station

Failing Septic System

Beach properties,

vacation rentals

Very flat High groundwater

Intracoastal Waterway

Hurricane prone

Wetlands + Environmenta

lly sensitive

12

Home Valve Pit Vacuum Sewer

Vacuum Station

Force main

How Vacuum Sewer Works

Collection System Design

SDR 21, Schedule 40 PVC fittings

O-Ring, Rieber gasket

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

Collection System

Vacuum Station

Incoming Vacuum Mains

Vacuum Pumps Collection Tank Sewage Pumps

Force Main

Standby Generator

Odor Control

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Vacuum Sewers – A Viable Alternative for Coastal Areas

Acknowledgement: Town of Oak Island, North Carolina Black & Veatch, Cary, NC

Soma Bhadra, PE (858) 353-2805 soma@consult-proteus.com www.consult-proteus.com Denny Moss (800) 247-8229, ext. 229 dennym@airvac.com www.airvac.com