Vacuum Wastewater Conveyance Systems
PHILIP CRINCOLI and RICH NARET Airvac Vacuum Technologies Philip Crincoli Northeast Regional Manager
Aqseptence Group, Inc. 4217 N Old US Highway 31 Rochester, IN 46975 USA
1-800 AIRVAC 9 x3083 Direct +1 908-600-1055
https://www.aqseptence.com/app/en/keybrands/airvac/
Page 2 Rich Naret, P.E. Senior Engineering Manager
Aqseptence Group, Inc. 4217 N Old US Highway 31 Rochester, IN 46975 USA
1-800-AIRVAC-9 Direct +1 727-215-8964
https://www.aqseptence.com/app/en/keybrands/airvac/
Page 3 Our Global Organization Global Product Lines
Water Water Intake Vacuum Water Well Industrial & Oil & Gas Filtration & Mining Treatment Systems Technology Screens Architectural Screens Thickening Screens Systems Systems Screens Systems
Location Aarbergen Karlsruhe Hanau New Brighton New Brighton New Brighton Lugo Brisbane (Germany) (Germany) (Germany) (USA) (USA) (USA) (Italy) (Australia)
Key Brand
Market = Water and = Power = Municipal = Water = Food & = Petro- = Mining = Mining waste water = Potable = Train resources beverage chemicals = Other utilities water = Industrial = Agriculture = Pulp & paper industries = Building = Architectural = Marine = OEM
Page 4 LEARNING OBJECTIVES
1. Overview of Vacuum Wastewater Technologies
2. Types of Systems-Industrial and Municipal
3. Components of a Vacuum Wastewater System
4. How It Works, Why, Costs, Design and Advantages
5. Case Studies and Regional Applications
Page 5 History of Vacuum Technology
▪ First used in Europe in 1870. Patented in US in 1888
▪ Technology introduced to the U.S. by the Electrolux Company
▪ First US indoor/industrial system was installed in early 1970s at Scott Paper in AL. First US Municipal system was installed in the early 1970’s in Martingham Cty, MD.
▪ Several vacuum manufacturers have been involved in the indoor and outdoor markets Drawing showing early vacuum since the late 1960s but Airvac is only system principles company working within all market segments And layouts of actual system In Prague and Amsterdam – circa 1870 ▪ Several other vacuum manufacturers are active globally, primarily in Asia and Europe
Page 6 Systems world-wide
Nearly 500 vacuum systems in North America Including Puerto Rico & Bahamas
~ 1500 vacuum systems in 40 countries around the world
Page 7 States with Vacuum Systems As of Dec 31, 2020
448 vacuum systems in 31 states, Puerto Rico & Bahamas
448 vacuum systems in 31 states, Puerto Rico & Bahamas
TYPE #
Municipal 339
Commercial 26
Industrial 4
Marine 31
Monitoring 6
By others 42
Total 448
Page 8 How it Works
Vacuum technology uses a pressure differential between atmospheric pressure and negative pressure (vacuum) as the propelling force to move liquid in a sealed piping system
The vacuum is created by vacuum pumps at a central vacuum station. Vacuum technology is used a many markets. The 2 primary ones are ▪ Indoor vacuum systems used in a variety of applications ▪ Outdoor/buried systems used in the municipal market
Page 9 How it Works
Theory of Operation
3 main Components How It Works
As valves open and admit atmospheric air, vacuum levels will drop to 16” Hg. This is sensed at the vacuum station & the vacuum pumps come on to restore vacuum to 20” Hg.
3) A normally closed interface valve in the valve pit keeps vacuum 1) Vacuum pumps on the main create a vacuum on the collection tank & 4) Interface valve then shut off opens, contents sucked out, followed by atmospheric air and differential pressure propels sewage toward vacuum station 2) Vacuum mains connected to the tank extend the vacuum to each valve pit
Page 11 Airvac Vacuum Sewer Systems How it Works
Page 12 Major Components
Page 13 Vacuum Plan View
A centrally located vacuum station allows for the service area to be divided into zones:
• Keeps line sizes small
• Is better from a hydraulic (vacuum & friction loss) standpoint
• Provides more operational flexibility
Page 14 COMPONENT 1 – VALVE PIT
Gravity flow from house to the valve pit
No electricity is required at the valve pit
Page 15 Typical Valve Pit Components
All valve pits have the same basic components:
•A sewage sump
•A chamber to house the valve
•An interface valve
•Piping to transmit the sewage from the sump, through the valve and out to the vacuum main
Page 16 Cold Weather Valve Pit
Recommended in climates where there are extended periods of freezing temperatures
Same basic valve pit as shown in previous slide but with these modifications:
• Insulation is added in the upper cone wall
• An insulated lid insert is used below the cast iron frame & cover Shown is a special cold weather valve pit.
Page 17 Valve Pit Operation
Positive 4) Differential pressure propels Negative pressure: sewage toward vacuum station pressure: Atmospheric air Vacuum in main from Air Terminal
2) Vacuum from in 3) Valve opens and the front of valve is contents are sucked applied to the back out of the sump via of the valve via tubing the suction pipe followed by several 1) As sump fills, air seconds of trapped in sensor atmospheric air pipe is transmitted via tubing to the valve controller
Page 18 Typical 3” Interface Valve
▪ Vacuum valves are designed for Pneumatic operation- no electrical power is required
▪ Vacuum valves used in the municipal market must be capable of passing a 3” solid
Shown is a cutaway Airvac 3” interface valve made in the US.
Page 19 Airvac Vacuum Sewer Systems Airvac in Action
Page 20 Cast Iron Valve Pit Covers
▪ Pits must be H-20 traffic rated (not just the cover but the entire valve pit)
▪ Usually installed in right- of-way
▪ Concrete collar used for traffic situations
Page 21 Building sewer from house
Air terminal has 2 functions:
• Source of atmospheric air needed for valve Building sewer operation is typically 4” or 6” • Prevents vacuum from pulling traps dry Gravity flow from house to Vacuum Main Valve pit
Page 22 6” Air Terminal (AT) 1 per Valve Pit
Valve Pit Air Terminal
Page 23 Air Terminal
Available in simulated stone or utility green
Can add options such as cycle counter or alarm monitoring system
Operator accessible in R-O-W
Page 24 Typical valve pit sharing
Page 25 Valve Pit Gravity Stub-outs
Purpose
To extend service to the property line
We don’t want homeowner’s contactor to get near the pit when connecting
Homeowner’s contractor just needs to connect pipe to pipe
Stop-coupling to keep pipe Typically 6 ft long & from being pushed in too far then capped
Page 26 Valve pit Coring Holes for Gravity stub-out
4 possible gravity inlets @ 90⁰
(2 shown; 2 on other side as well)
Holes field cut ~ 18” above base of sump
Page 27 Concrete Buffer Tanks For large water users
Vacuum valve(s) installed in a concrete manhole with formed sumps
Service Line
Vacuum Main
Sump
Page 28 COMPONENT 2 – VACUUM MAINS
Vacuum Gravity
Page 29 Pipe Material
▪ 4”, 6”, 8”, 10” & 12”
▪ SDR 21 PVC or Sch 40 PVC
▪ “Rieber” Type Gasket
Page 30 Rieber Gasket
▪ Factory installed, double-lipped locked- in gasket
▪ Reduces installation problems
▪ Leak proof joints
Page 31 Vacuum Main Fittings
• Can be solvent weld or gasketed (Rieber type gasket) • Can be fabricated, assembled or molded • Pressure rated fittings used (not DWV) • Tee fittings are not allowed
Page 32 Sawtooth Profile “lifts”
Ensures an open passage of air between the vacuum station and interface valve at the extreme end
Flow
Page 33 Vacuum mains Level, uphill and downhill transport
500 ft @ 0.20% Slope Flow 20 ft Flow 0.25’ fall
Level – use “lifts” to maintain same elevation Uphill – space lifts closer together (drop (drop 1 ft then gain it back with 1 ft lift) 0.25 ft then gain 1 ft or more with a lift)
Fall between lifts: 0.20% or 0.25 ft whichever is greater
Flow Downhill – follow ground slope Flow
Page 34 Static Loss Limit – 13 ft How was this determined?
Vacuum Pump 30” Hg = 34’ Water – Pure vacuum
20” Hg = 23’ Water Normal Operating Range 16” Hg = 18’ Water
Using the low end 18’ total available lift 35 - 5’ used to evacuate the sump 13’ available for transport
Page 35 Static Loss Pressure vs vacuum
Pump/pressure sewer
Static loss is the actual elevation difference between the pump and the highest point in the pipeline
Vacuum
Static loss is a calculated value based on an empirically derived equation.
In addition, no energy is “regained” when going downhill. Every “lift” in a given flowpath has an associated calculated static loss with the static loss on that flowpath cumulative.
Page 36 Flow Path Example
1
VACUUM COLLECTION MAIN #3 MAIN #1 STATION
8+13 MAIN #2 0+00 AIRVAC Valves 2+00
0+00 6+00 21+40 B Flow path goes BRANCH B 2 6 from the very end
26+50 BUFFER of each main or TANK 0+00 BRANCH C (10GPM) branch to the 30+15 12+95 C vacuum station
34+15 16+50
36+00 18+10 38+95 In this example, 0+00 D 44+40 22+50 there are 7 flow TYPICAL HOMES 2+80
48+00 paths BRANCH D BRANCH
F 30+30 G E 53+95 8+30 4 5 3 7
Page 37 Vacuum piping Diameters & Lengths
Pipe Diameter Maximum Where Used Recommended (inches) Length (ft)
3 Service Lateral 300
Branch Line / End of 4 2,000 Main Line
Limited by static & 6, 8, 10, 12 Main Line friction losses
Page 38 Vacuum Piping Design capacity
Recommended design Max # Vacuum main flow EDUs
4” 38 gpm 60
6” 105 gpm 165
8” 210 gpm 330
10” 375 gpm 585
3.5 per/hse - 75 gpd - 3.5 peak Assumes 1 EDU = 0.64 gpm [75 gpcd x 3.5 per/hse x 3.5 peak factor] / 1440 min/day
Page 39 Line Sizing Example
Vacuum Max # main EDUs 4” 60 41 15 35 100 6” 165 8” 330 50 55 10” 585 Vac 141 45 Sta 231 42 Vacuum Color main code 12 10 4” 20 179 152 62 42 6” 52 15 25 20 8” 10”
Page 40 Main Line or Branch Line Connections
▪ Connections to the main are made “over-the-top” by using a wye fitting in the vertical position or by rolling the wye to a 45 degree angle.
▪ A tee is never used
Page 41 Pit to main connection Flex Connector
This is a fixed point
Flex connector provides a degree of flexibility to allow connection while avoiding overuse of fittings
This is also a fixed point most likely at a different elevation than the pit opening
Page 42 Isolation Valve
▪ Resilient-wedge gate valves
▪ At the beginning of each branch
▪ On the main line near the branch connection
▪ Intervals no greater than 1500 ft on main line
Page 43 Vacuum Main Testing
DAILY TESTING TMVP (Trailer Mounted Vacuum Pump) 2 hr @ 22 in. Hg used for testing allowable loss of 0.5 in. Hg
FINAL TESTING 4 hr @ 22 in Hg allowable loss of 1.0 in. Hg
Page 44 COMPONENT 3- VACUUM STATION
Page 45 MAJOR COMPONENTS - VACUUM STATION
Equipment typically housed in a 2-level building
Vacuum Pumps & Control Panel on top floor
Sewage Pumps & Collection tank in basement
Page 46 PacVac For small to medium sized projects (75-550 conn)
By AIRVAC • Prefabricated building (top part) • Vacuum pumps • Sewage Pumps • Control Panel • Collection tank • Generator (Generator could be supplied by others as well)
By Contractor • Basement vault • Place skid & building on vault • related site work
Page 47 EFI Prefab Building For PacVac
▪ Single enclosure dimensions up to 16’ x 62’
▪ Placement on piers, slab or foundation wall
▪ Available with or without floors
▪ Code constructed
▪ Electrical and mechanical systems outfitted Example of an EFI prefabricated building ▪ Various exterior finishes
▪ Various roof shapes and materials
Page 48 Prefabricated Vacuum Station
Page 49 PacVac – Longwood, FL
Page 50 PacVac -Broadcreek PSD, SC
Featured in March 2020 Water & Waste Digest magazine Cover Story
Page 51 Custom Over/under configuration for larger projects (> 550 conn)
By AIRVAC • Vacuum pumps • Sewage Pumps • Control Panel • Collection tank (equipment supplied on skids)
By Contractor • Construct building • Place skid(s) in building • Generator • Related site work
Page 52 Typical Vacuum Station skid
CONTROL PANEL (on back side)
COLLECTION TANK
SEWAGE PUMPS VACUUM PUMPS
Page 53 Emergency Generator
A standby generator provides uninterrupted service during power outages.
May be either a fixed, permanent generator or a portable generator
Page 54 Odor control Bio-filter
Exhaust from vacuum pumps is distributed evenly throughout bio-filter
Page 55 Vacuum Stations
Englewood, FL Charlotte Co, FL Crystal River, FL
Sarasota Co, FL Martin Co, FL Ponte Vedra, FL
Page 56 Vacuum Stations
Bend, OR Hooper, UT Provincetown, MA
Ocean Shores, WA Alloway, NJ Albuquerque, NM
Page 57 Vacuum Stations
Plum Island, MA Barnstable, MA Lake Chautauqua, NY
Steamburg, NY Central Boaz, WV Orangefield, TX
Page 58 Next generation Technology & Case studies
Next generation technology
Various case studies Solar Monitoring Light
• Solar Monitoring Light as the first level of monitoring available • Identifies a hung open valve by a flashing light • Low cost • Easy to install • Old systems can be updated • Mounted on 4” air intake or on Airvac Dedicated Air Terminal
Page 60 Airvac Monitoring System
• Monitor each valve pit with: • Valve cycle • Valve Open Time • Hung Open Valve • Sump Level • Monitor end of line vacuum level • Monitor vacuum pumps runtime • Monitor sewage pumps run time • Customized alarms • Ability to track trends • Ability to pin point problems
Page 61 Vacuum Technology Systems Internet of Things & Artificial Intelligence
Page 62 Airvac Company Profile Vacuum Technology Systems Internet of Things & Artificial Intelligence
Target: (PDS) Further develop our IoT & AI portfolio ❖ SMART (Strategic Monitoring for Advanced Remote Transfer) ❖ Use AI to recognize imbalances before they occur & react accordingly without operator interface
❖ Proactively purges the system prior to high flow periods
❖ AI to decrease vacuum pump noise, heat & power cost, while improving system performance
❖ (2.0) Automatically corrects low vacuum alarms after hours/weekend
Page 63 Airvac Company Profile Alloway Twp NJ Vacuum Station Alloway, NJ Vacuum Station
Page 64 Alloway Township NJ Vacuum Sewer System
▪ 1 Vacuum Station replaced 3 pump stations ▪ 2500 population ▪ Completed in 2009 ▪ SW NJ near junction of Delaware River and Delaware Bay ▪ Very high-water table and tidal ▪ Leaking septic tanks ▪ Survived and continued to run during major hurricane ▪ Sister town of Quinton experienced gravity system failure and sewage discharges during same hurricane event
Page 65 Alloway Twp NJ Vacuum Station Alloway, NJ Vacuum Station
https://youtu.be/-jkN-gzzrIs
▪ Project saved over 25% over standard gravity ▪ Excavation was 4-6 feet vs 22-24 feet in depth ▪ Excavation was 4-6 feet wide vs entire street ▪ System was first in kind in State of NJ in 2009 ▪ Design Firm working on new 2020 project now ▪ No sewage discharge during hurricane after area floods ▪ System remained fully operational during hurricane ▪ System is designed to work under water & power outage ▪ Limited I & I as system is closed under pressure ▪ Saved $180 annually in sewer bills for residents
Page 66 Plum Island, MA
Page 67 Provincetown, MA
Page 68 VA Beach, VA
Page 69 Ocean Shores, Washington (Station 2)
Page 70 Oak Island, NC
Page 71 Community of Rockridge Indian River County, FL
Page 72 How It Works Industrial Indoor Systems
https://www.youtube.com/watch?v=MSEaseApvzE Vacuum Liquid Conveyance Systems
Technology Applications
▪ FDA Regulated and Food Processing Facilities ▪ Manufacturing Sites (Steel, power & Chemical Plants) ▪ Leachate Control Systems at Landfills ▪ Brownfield Site Construction ▪ Green and LEED Projects (Solvis & Calamigos) ▪ Stadiums, exhibition halls & Arenas ▪ Transportation: Trains, Planes, Cruise Ships ▪ Municipal Sewer Systems Vacuum Liquid Conveyance Systems Outdoor Systems Can Be Municipal or Industrial/Commercial Problem Solving Industrial Systems Case Study for Outdoor Industrial
Eli Lilly-Eco Services (Solvay) - Kimberly Clark (underground)
Background • Major firms in pharmaceuticals, chemicals & manufacturing • Locations in Indiana, Louisiana and Alabama • Systems boast longevity and reliability. KC installed in 1972.
Situation • Excavation of these older sites was not safe or practical • Site challenges included high water table, underground hazards: unknown utilities, buried chemicals and areas of high truck traffic subject to frequent ground shifting • Brownfields site alternative for wastewater conveyance system
Solution • Vacuum sewage systems tie in multiple buildings • The system conveys all wastewaters (Black & Gray) • Eco since 1979, KC since 1972 & Lilly since 1981 Case Study for Pharma Cleanroom
Merck (Cleanroom) – FDA Validated Environment
Background • One of the largest vaccine manufacturing sites in world (BSL-1) • Location undergoes frequent renovation • Syringe Washing operation in Cleanroom (Gardasil, Hep C) • Needed wastewater conveyance system to separate streams
Situation • Cleanroom in tight space would not allow gravity system • Access to area limited & many obstacles in place • Zero tolerance system leaks & no room for dual containment
Solution • Piping & system controllers placed in walls/ceilings/attics • Separation of chemical & biological streams in 3 vats • Single vacuum source maintains negative pressure - no leaks • No Dual Containment piping necessary • Merck collaborated on a customized touch screen system for all controls of the vacuum wastewater system in the Clean Room which includes remote monitoring • System has been in operation since 1992 Case Study Entire Building
Roche-Basel, Switzerland (Labs & R&D)
Background • New 10 floor facility w/ modular design for frequent changes • 6 floors above and 4 floors below ground • Over 70 small labs & 4 large full floor labs, office, R&D • High visibility state-of-art campus in downtown Basel
Situation • Areas can be changed from office to lab to R&D • All furniture, basins are movable • Moves allow for easy hook ups and change outs • S3 Level (BSL 4) in certain areas includes air burned
Solution • 270 vacuum floor drains installed allow optional usage • 12 autoclaves in basement also on vacuum • 2 vacuum stations supply negative pressure for building • System can handle higher temperature and ph liquids also Case Study-Indoor Sanitation
Leidos Corporation-Boyers, PA (R&D Lab)
Background • Facility is located 220 feet underground • Leidos needed a highly secure R&D facility for experiments • Former division of SAIC Corporation • Location is part of Iron Mountain high security facility
Situation • Due to facility depth, no gravity option on wastewater • Minimization of wastewater discharge due to cost • Sustainable solution that recycles almost all water on site
Solution • The vacuum system hooked to bioreactor treatment • All lab & gray water, & most of black water recycled on site • Vacuum toilets capture toilet plume as air/water drawn downward • Small filter sludge disposed offsite Toilet Plume on typical gravity toilet. When you flush the waste down the drain and it creates an aerosol of germs and waste materials into the atmosphere. Negative Pressure Vacuum toilets pull all waste, water and germs downward into the system via vacuum while using only one quart of water per flush. NJ & PA State projects Municipal & Industrial
> Alloway Township, Alloway, NJ: Sold and Operating since 2009
> Lower Township, NJ: Cape May County Construction begins Spring 2021
> Central NJ: Design Phase, Expected Construction 2022
> Clark, NJ: Design and Construction by SNC Lavalin/Gilbane Construction in 2020-1
> Leidos Mine, Boyers, PA: Indoor wastewater collection system that recycles all water 2017
> Merck, West Point, PA: Vacuum wastewater system for indoor Cleanroom operation 1992
> 2 Other smaller municipal operations in western PA including Beallsville
Page 83 MD State projects All Municipal outdoor in nature
> Martingham Utilities: Talbot County, 140 Pits, 175 Connections, circa 1972
> Somerset County Sanitary District: Crisfeld, 157 Pits, 300 Connections, Circa 1997
> Somerset/Fairmount: 159 Pits, 238 Connections, Circa 1981
> Queen Anne County: Cloverfields and Bay City, 2175 Pits, 5200 Connections, Circa 181, 94, 95
> Cedar Cove: Spyglass, 19 Pits, 156 Connections, Circa 1985
> Swan Point: Charles County-LaPlata, 109 Pits, 175 Connections, Circa 1988
> Ocean Pines Retrofit: 2351 Pits, 5000 connections with 15 stations, Circa 1976
> Signature Club: 266 Pits, 427 Connections, Circa 2015
Page 84 Advantages & Applicability
Cost savings
Many environmental advantages Cost Savings
Vacuum Gravity Shallow, narrow trenches = less excavation
Dewatering minimized
Smaller equipment
Smaller diameter pipes
1 vacuum station can replace 6 or 7 lift stations
Page 86 Reduced Impacts From Construction
▪ Less surface disruption ▪ Less restoration ▪ Vertical & horizontal routing flexibility
Page 87 Energy Conservation
No I&I = reduced wastewater load to treatment plant
1 Vacuum 7 Lift 1 vacuum station typically Station Stations replaces 6 or 7 gravity lift stations eliminating the 2 vacuum pumps need to pump & re-pump 2 sewage pumps 14 sewage pumps 4 pumps total 14 pumps total
Page 88 Protects Ecosystem
Completely sealed system (no spillage = no permit violations)
Self scouring (unlike gravity where period cleaning is req’d)
Infiltration & Inflow eliminated
A leak in a gravity sewer can go undetected/uncorrected and allowed to continue to pollute for a long period of time
A leak in a vacuum system is automatically detected and MUST be corrected for the system to continue to function economically
Page 89 Operator Friendly
Completely sealed system
No operator contact with raw sewage
Page 90 Aesthetics
Vacuum stations are typically designed to take on the character of the neighborhood
The vacuum station on the left is in the same neighborhood as the house on the right
Page 91 Advantages in hurricane prone areas
WWTP not inundated with Sealed system prevents I&I so plant is not overwhelmed I&I
Less In coastal areas 1 vacuum station typically replaces 7 lift preparation stations; less storm prep required of staff required
Uninterrupted All vacuum stations have emergency generators which service provide uninterrupted service to the customer
Safer working Fixed generators automatically start…no need to expose conditions maintenance staff to severe weather
If water levels rise to the point where the Air Terminals As last resort are flooded, the system can be powered off to prevent the system can damage to system components. After the threat is over, be shut down service to customers can quickly be restored
Page 92 Where does it apply?
• New developments • Existing communities • Flat / rolling terrain • Rock / high groundwater • Sandy / unstable soil • Sensitive eco-system
Page 93 Subsurface conditions
If any (or better yet, a combination) of the following conditions are present, the narrow and shallow trenches associated with vacuum give it a cost advantage over gravity
• High groundwater table • Sandy and unstable soils • Rock • Buried obstacles
Page 94 Sensitive Eco-System
Sensitive Eco-systems that suffer from nitrogen overloading from leaky septic tanks benefit from a system that is environmentally friendly.
• Completely sealed system
• Eliminates infiltration and inflow
• No exfiltration
Page 95 Ideal candidate
• An existing community on septic tanks
• 100 to 2000 connections
• Primarily residential
• Flat topography or not much elevation to overcome
• One or more subsurface difficulties to overcome
Bonus: If the area also is environmentally sensitive.
The more difficult the project, the more likely vacuum is cost-effective.
Page 96 Not particularly good candidates
• Projects with not many connections (<30)
• Projects with too much elevation to overcome
• A project with all commercial/industrial users, especially if in a highly dense area
• Lake communities where the houses are at an elevation well below (10 ft. or more) the road.
• Areas with repetitive up and down topography
• New developments that could easily be served by gravity with only 1 or maybe even no lift stations
Page 97 Cost Comparison to Gravity & Low Pressure
Capital Costs
Operation & Maintenance Vacuum vs Gravity
Page 99 Vacuum vs Gravity General comparison
ITEM VACUUM GRAVITY Smaller pipe, narrower & Larger pipe, wider & deeper Excavation shallower trenches = less trenches = significantly more excavation excavation
Typical trench depth < 5 ft Could be as great as 30 ft
Narrow, shallow trenches Wide, deep trenches result in Surface restoration keep this to a minimum major surface restoration
Common due to constant slope Unforeseen utility Can be avoided w/out and straight line between conflicts change orders required manholes
Yes. Operator exposed to raw Operator exposed to No. Operator never sewage at manholes, lift station sewage exposed to raw sewage wetwell
Infiltration & Inflow Completely closed system I&I is common
Sewage cannot escape; air Sewage can go into ground and Leaks comes in & is detected at the go undetected for a long time VS
Up to 60% cost savings; more operator friendly; environmentally safer
Page 100 Vacuum vs Gravity Capital costs
Component Installed Costs Comment
Vacuum mains are two pipe size smaller than gravity mains (4”,6” & 8” vs 8”, 10” & 12”) Installed costs for vacuum mains Vacuum requires significantly less Sewer mains are ~25-75% lower than gravity excavation & surface restoration mains (installed in much shallower and narrower trenches) Large Advantage: Vacuum
Valve pits About the same quantity of vs. manholes as valve pits and the Advantage: neither manholes installed cost for each is similar
When no lift station is req’d Vacuum station can cost 20-30% Vacuum Large Advantage: Gravity more than a lift station (LS have station vs. less equipment plus no building When multiple lift stations are lift station req’d) req’d Advantage: Vacuum
The more pipe footage required, the more advantage the vacuum has. Also, the more lift stations that gravity requires, the more advantage that vacuum has.
Page 101 Vacuum vs Gravity O&M - Labor & Power
Component Comment
Line break in vacuum must be fixed while one in gravity could go unnoticed/unfixed. Periodic Labor jetting of gravity mains could be required while (piping network) vacuum is self scouring Advantage: neither or slight advantage Vacuum
Preventive maintenance required for vacuum Labor valves & some service calls required while not (vacuum valves vs. much to do with manholes manholes) Large Advantage: Gravity
If no Lift stations req’d Large Advantage: Gravity If 1 Lift station req’d Power Advantage: Gravity If multiple lift stations req’d Advantage: Vacuum
Page 102 Vacuum vs Gravity O&M - Equipment Rebuild/Replacement
Component Rebuild/Replacement Costs Comment
Equipment Both have sewage pumps, electrical Replacement This is a function of the actual controls and a tank. But a vacuum equipment req’d in the vacuum station also has vacuum pumps (vacuum station station/lift station vs. lift station) Advantage: Gravity
Example 300 valves, $50, 15 yrs = $1,000/yr Vacuum 300 controllers, $50, 10 yrs = $1,500/yr $50/valve (every 15 yrs) vs $50/controller (every 10 yrs) Equipment $$?? Rebuild (valves Manholes vs. manholes) Typically no rebuild costs Advantage: Gravity although sealing to prevent I&I (even though R&R of vacuum is fairly could be req’d insignificant)
Page 103 Vacuum vs Gravity Capital Cost –general comparison
< 50 50-200 > 200 connections connections connections
Gravity
Tossup
Vacuum
Systems serving 50 - 200 connections generally favor gravity but tendency tilts toward vacuum the more difficult the conditions
Page 104 Vacuum vs Gravity O&M Cost – General comparison
< 50 50-200 > 200 connections connections connections
Gravity
Tossup
Vacuum
O&M for systems serving 50 - 200 connections generally favor gravity but tendency tilts toward vacuum if multiple Lift Stations are required, gravity main jetting is required, and I&I issues come up
Page 105 Vacuum vs Gravity Life Cycle comparison
A Life Cycle analysis considers both capital costs & annual O&M costs over time brought back to today’s cost (Present Worth)
Due to the many variables involved, every project must be evaluated to determine which system is cost effective. The historical general trend is shown below:
Cost < 50 conn 50-200 conn > 200 conn
Capital Cost Gravity Can go either way Vacuum
Gravity although when Gravity although when Annual O&M Gravity multiple LS are req’d O&M multiple LS are req’d O&M for vacuum could be less for vacuum could be less Typically Generally a toss-up Life Cycle Cost Gravity (Engineer/owner Typically Vacuum preference)
Page 106 Vacuum vs Low Pressure
Page 107 Vacuum vs Low Pressure General Comparison
ITEM VACUUM LOW PRESSURE (GP) # houses served Typically 2; up to 4 1 by 1 unit
Power supply 1 source @ vacuum station Power required at each house
Standby At vacuum station None. Not practical at each GP generator
Valve & controller rebuild < Rebuild cost GP rebuild > $1,200 $100
Rebuild Valve: 15 yrs GP: 5 to 7 years frequency Controller: 10 yrs
Typically requires 2 persons due Emergency Typically only requires 1 person to weight of unit & dealing maintenance w/electricity
Sewage cannot escape; air Under pressure goes into ground, Leaks comes in & is detected at the can go undetected VS
Lower O&M, more operator friendly, environmentally safer
Page 108 Vacuum vs Low Pressure Capital Cost comparison
Component Installed Costs Comment
Vacuum mains are typically Installed costs for vacuum one pipe size larger than Sewer mains mains are ~10-15% higher pressure mains (4”,6” & 8” vs than pressure mains 3”, 4” & 6”) Advantage: Low Pressure
Installed costs of units are similar. But a GP is required for Valve pits Fewer units = less $$ vs. grinder every house while 2 or more pumps houses can share a VP. Large advantage: Vacuum (EX: 100 GPs vs 40-50 VPs)
When no lift station is req’d Vacuum station can cost 20- Large Advantage: Low Vacuum 30% more than master lift Pressure station vs. station (Lift stations have less lift station equipment plus no building is If a master Lift station is req’d) req’d Advantage: Low Pressure
From a capital cost standpoint, the larger the project, the more the “valve pit vs. grinder pump” cost savings begin to favor vacuum.
Page 109 Vacuum vs Low Pressure O&M - Labor & Power
Component Comment
Similar effort is required to maintain the piping Labor network of both systems (piping network) No advantage either way
Similar effort is required to maintain GP vs a vacuum valve. But 1 GP is required for every house Labor while 2 or more houses can share a VP resulting in (vacuum valves vs. fewer units to maintain) grinder pumps) (EX: 100 GPs vs 40-50 VPs) Advantage: Vacuum
The power for all GP’s collectively in a system typically is less than the power for a vacuum station. But when a master lift station is also required for low pressure, the power costs can go Power the other way Advantage: Low Pressure (typically) but could swing to vacuum when a master LS is req’d
Page 110 Vacuum vs Low Pressure O&M - Equipment Rebuild/Replacement
Component Rebuild/Replacement Costs Comment
Equipment Both have sewage pumps, electrical Replacement This is a function of the actual controls and a tank. But a vacuum equipment req’d in the vacuum station also has vacuum pumps (vacuum station station/lift station vs. lift station) Advantage: Low Pressure
Example 300 valves, $50, 15 yrs = $1,000/yr Vacuum 300 controllers, $50, 10 yrs = $1,500/yr $50/valve (every 15 yrs) Equipment vs $50/controller (every 10 yrs) Rebuild (valves 600 GPs, $1000, 7 yrs = $85,700/yr vs. grinder Grinder Pump pumps) The significantly lower rebuild cost $1000 - $1200/GP combined with half as many units = (every 5-7 yrs) Huge Advantage: Vacuum
This is the single largest factor that affects the life cycle cost which tilts the advantage toward vacuum. The larger the project (i.e. the more GPs that are req’d), the more likely that vacuum will prevail
Page 111 Vacuum vs Low Pressure Capital cost – general comparison
< 50 50-200 > 200 connections connections connections
Low Pressure
Tossup
Vacuum
Systems serving 50 - 200 connections generally favor Low pressure.
Unlike gravity where difficult conditions tilt toward vacuum, this is not the case with low pressure as they have the same advantages as vacuum in difficult conditions.
Page 112 Vacuum vs Low Pressure O&M Cost – general comparison
< 50 50-200 > 200 connections connections connections
Low Pressure
Tossup
Vacuum
Page 113 Vacuum vs Low Pressure Life Cycle Cost comparison
A Life Cycle analysis considers both capital costs & annual O&M costs over time brought back to today’s cost (Present Worth)
Due to the many variables involved, every project must be evaluated to determine which system is cost effective. The historical general trend is shown below:
Cost < 50 conn 50-200 conn > 200 conn
Capital Low Pressure Cost Can go either way Vacuum
Annual Low Pressure O&M Can go either way Vacuum
Typically Low Life Cycle Generally a toss-up Typically Pressure Cost (Engineer/owner Vacuum preference)
Page 114 Wrap-up
Reference Material
Review Reference material Vacuum sewers
There are 3 main reference documents on vacuum sewers
Page 116 EPA Manual EPA/625/1-91/024
• Includes chapters on Low- pressure sewers, vacuum sewers and small-diameter gravity sewers
• This was published in 1991
• At the time and until the WEF Manual was published in 2008, was considered to be the industry standard for alternative sewer systems in the US.
• Rich Naret, P.E, (Airvac) authored the vacuum chapter
Page 117 WEF Manual WEF MOP FD-12, 2nd ed
• This was an update of the 1991 EPA Manual
• Includes chapters on Low- pressure sewers, vacuum sewers and small-diameter gravity sewers
• This was published in 2008
• The content is still mainly relevant although some things have changed in each of the technologies
Page 118 WEF Manual WEF MOP FD-12, 2nd ed
• The vacuum sewer chapter contains the most current information on vacuum sewers
• Vacuum chapter authored by Rich Naret, P.E. (Airvac)
• Includes sample regulations on vacuum sewers that states can use as a guideline
Page 119 Airvac Design Manual
Airvac’s 2018 Design Manual contains all the design criteria needed to complete the design. Chapters include:
•Introduction •Design Flows •Vacuum Station Design •Vacuum Main Design •Valve Pits •Buffer tanks •System Alarm & Monitoring •Airvac Services
Page 120 Airvac Design Manual
There are tables at the end of each chapter summarizing the “do’s and don’ts” associated with that particular chapter topic
Page 121 Airvac Design Manual Do’s and Don’ts
There are tables at the end of each chapter summarizing the “do’s and don’ts” associated with that particular chapter topic
Some major topics
Vacuum main design: pipe & fittings to use, line layout guidelines, line sizing, situations to avoid, etc.
Valve pit design: oversharing of pits, selecting the proper pit, max peak flow to a valve pit, etc.
Vacuum station design: vacuum pump sizing rules, sewage pump sizing rules, collection tank sizing rules
NOTE: The do’s and don’ts in Airvac’s Design manual are specific to Airvac’s design philosophy which is proprietary and may not apply to other vacuum manufacturers.
Page 122 Review Why vacuum sewers?
What are some reasons why you should consider vacuum sewer systems?
1. Lower Construction cost 1. Reduce trench depth and width 2. Eliminate manholes in streets 3. Eliminate lift stations
2. Less maintenance than other alternative sewers
3. Operates during power outage
4. No odors as it’s a closed system
5. No exfiltration / leaks to the environment
6. Less disruptive and safer construction
Page 123 Review Why vacuum sewers?
What are the three main components of a vacuum sewer system?
nValve pits, vacuum mains and vacuum station
How can vacuum sewer systems save money?
nVacuum sewers save money where excavation costs of gravity sewers is high (50+ homes, flat terrain or rolling hills, high water table, rock or unstable ground, etc.)
What are some environmental benefits of using vacuum sewer systems?
Elimination of I/I is possible No leaks to the environment even if a sewer pipe breaks Routing flexibility saves trees & shrubs Minimal operator contact with sewage Potential lower energy consumption
Page 124 Review Benefits and Advantages of Vacuum Sewers
What are some other benefits of installing vacuum sewer systems?
–Minimal impact on local traffic and businesses especially during construction –No confined space or trapped gasses issues during repairs. –Minimal exposure of employees to sewage –Best system in areas prone to flooding, heavy onshore flows and high groundwater –Standby generator at Vac Station allows operation thru catastrophic weather –Excellent solution for seasonal flow variation such as resort areas –Immediate leak detection and quick location avoids environmental problems –No line blockages as materials moves thru lines at 15-18 fps –All mains are PVC or PE which can flex in shifting ground –Only 1 source of power (no electrical homeowner service upgrade) –Up to 4 homes can be hooked to valve pit
Page 125 Review Benefits
What are some other benefits of installing vacuum sewer systems? The system is designed to run during flooding, freezing, blizzards, power outages, heavy onshore flows, hurricanes and other catastrophic weather
–Safety during construction –Odor and corrosion minimized –O&M costs favor larger projects w/ est. valve repair costs at $50-100 every 10-15 years –Since system utilizes air intake, there is aerobic action on sewage prior to treatment –Minimization of sewage discharge as system will pull liquid in rather than leak sewage out –Sewage build up in lines is eliminated due to scouring action in lines –Only electrical connection is at the Vac Station where there is standby back up generator –Grease and Sand do not affect operation of the Valves or Mains. –Grease and Sand do not affect any mechanical parts of the system
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