Section 2 TDEC - Fleming Training Center

Wastewater Collection Systems

Wastewater Collection  A wastewater collection system gathers the
used water from homes and businesses and
Systems conveys it to a wastewater treatment facility
 The used water comes from kitchens and
bathrooms or different processes of homes,
businesses and industries
 Additional water can also enter the collection
system from groundwater, surface water, and
stormwater

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Wastewater Collection Systems Wastewater Collection Systems

 The system must be kept in good operating  Proper operation and maintenance of the
conditions because if it fails… collection system is a way to protect the
 Blockages occur in the lines resulting in capital investment the community has made in
wastewater backups into homes and businesses the system so that it performs its intended
 Raw wastewater can bypass the treatment facility function and be used efficiently throughout the
resulting in contamination of surface waters and planned life of the system
public health issues  This is achieved by trained collection system
 Streets collapse – leaking sewer mains saturate operators who use manual and power
the ground surrounding the pipe and eventually
operated equipment to install, inspect, and
wash away the bedding materials leaving a void
that can cause a collapse in the street above
repair the system to keep it running
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Wastewater Collection Systems

“The better collection systems

operators are trained to do
their jobs, the more effectively
a wastewater treatment plant Intro to Wastewater
Treatment
can do its intended job.”*
Why do we treat waste?

* Operation and Maintenance of Wastewater Collection Systems – Vol. I, 7 th Edition

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Purpose of Wastewater Treatment What is Pure Water?

 To protect the environment and public health  Water is made up of two hydrogen
by: atoms and one oxygen atom
 Removing solids  “Pure” water is manufactured in
 Stabilizing organic matter labs, even rain and distilled water
 Removing pathogenic organisms H2O contain other substances called
impurities

 The majority of wastewater is just

water, a much smaller portion are
wastes
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Waste Solids Types of Waste

 Organic waste
 Total solids ◦ Contains carbon Sucrose

 Dissolved solids ◦ Will use up oxygen in water

 Suspended solids ◦ More food = More bugs = More oxygen used
 Settleable  Inorganic waste
 Nonsettleable Dissolved
Solids
500 mg/L ◦ Salts ◦ Gravel
 Floatable solids Total Solids
720 mg/L
◦ Metals ◦ Sand
 Organic and Colloidal
Solids
70 mg/L
Suspended
inorganic solids Solids
Settleable
220 mg/L
 Both may come from domestic or industrial waste
150 mg/L
Collection system job is to get all solids to WWTP
Solids

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Organic Waste Importance of Organic Matter

 Domestic wastewater contains a large amount of  Organic material consumes oxygen in water
organic waste  Bacteria will “feed” on organic matter and most
 Industries also contribute some amounts of organic need oxygen to be able to do this
wastes  We want these bacteria to “feed” on the organic
 Some of these organic industrial wastes come from matter and use it up in the treatment plant and not
vegetable and fruit packing, dairy processing, meat in our receiving water
packing, tanning and processing of poultry, oil, paper  High concentrations of organic material can
and fiber cause taste and odor problems in recreational
and drinking water
 Some material may be hazardous

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 Section 2 TDEC - Fleming Training Center

Oxygen Depletion Oxygen Depletion

 When organic wastes are discharged to a  Most living creatures, including fish, need
receiving stream bacteria begin to feed on it, oxygen to survive
these bacteria need oxygen for this process  In water this oxygen is present as dissolved
 As more organic waste is added to the receiving oxygen
stream, the bacteria reproduce  Most fish can survive with at least 5 mg/L DO
 As the bacteria reproduce, they use up more oxygen,
faster than it can be replenished by natural diffusion
from the atmosphere
 This can potentially cause a fish kill and odors
O2

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Dissolved Oxygen Oxygen Depletion

 There are two important factors that
can influence the amount of dissolved
oxygen present:
 Water Temperature
 Greater temperature  Less DO
 Lower temperature  More DO

 Organic matter
 One of the principal objectives of wastewater
 Organic material requires oxygen to
decompose treatment is to prevent as much of this “oxygen-
 More organic material requires more DO, demanding” organic material as possible from
and will tend to deplete water of DO entering the receiving water
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Water Pollution NPDES Permit

 Any condition caused by
human activity that
adversely affects the
quality of stream, lake,
ocean, or groundwater

 National Pollutant Discharge Elimination System

 Required by the Federal Water Pollution Act
Amendments of 1972 to help keep the nation’s water
suitable for swimming and for fish and other wildlife
 Regulates discharges
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Treatment Human Health

 Initial efforts for wastewater treatment came
from preventing disease outbreaks
 Most bacteria in wastewater are not harmful to humans
 The treatment plant actually removes the  Humans who have a disease caused by bacteria or
viruses can discharge some of these pathogens
organic matter the same way a stream would
 Many serious outbreaks of communicable diseases have
in nature, but it works more efficiently by been traced back to contamination of drinking water or
removing the wastes in secondary treatment food from domestic wastewater
 The treatment plant is designed and operated  Good personal hygiene is
to use natural organisms such as bacteria to your best defense against
stabilize and remove organic matter infections and disease
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Cryptosporidium Cholera Typical Wastewater

Diseases Characteristics
 Bacteria
 Cholera
 Dysentery Giardia  Fresh wastewater is usually a grey/dishwater
 Shigella color
 Salmonella Dysentary  Typically septic wastewater will have a black color
 Typhoid
 Viruses  Fresh domestic wastewater has a musty/earthy
 Polio odor
 Hepatitis (Jaundice) Hepatitis
 If the wastewater is allowed to go septic, this will
 Protozoa Polio change significantly to a rotten egg odor associated
 Giardia lamblia with the production of hydrogen sulfide gas
 Cryptosporidium parvum TDEC - Fleming Training Center TDEC - Fleming Training Center

Wastewater Treatment Processes Preliminary Treatment

Preliminary Primary Secondary  The main goal of preliminary treatment is to
Treatment Treatment Treatment remove as many solids as possible from the
 Screening wastewater stream
 Grit Removal
 Preaeration  This is accomplished by passing the
 Flow Metering and Sampling
wastewater through screens to filter out large
Tertiary
Disinfection
Solids solids and then slowing the water down to
Treat. (Advanced) Treatment settle out smaller solids
 Solids are removed and treated as solid waste
and not treated with the dissolved solids in the
wastewater
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Solids Preliminary Treatment

 Cause many problems in Solids Screening
collection and treatment  Variations: bar racks,
plant systems mechanical rotating, rotary
 Fill storage areas, clog drum screen
ditches and channels  Must be cleaned regularly to
 Interfere with mechanical prevent restriction of flow
systems
 Failure to keep a bar screen
 Associated with
taste/color/clarity clean can also result in a
problems in drinking water shockload
 Removes roots, rags, cans…
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Preliminary Treatment Preliminary Treatment

Aerated Grit Chamber
 1 ft/sec flow through
grit chamber
Muffin Monster  Used to remove grit –
Solids Shredding
 Comminuter – device used to reduce the size of the heavy, mainly inorganic
solid materials in the wastewater by shredding solids (sand, egg shells,
 Smaller solids can be settled out and cause less gravel, seeds, etc.)
problems with pumps downstream  Aeration also freshens wastewater and
 Can help with clogging problems from rags and wipes helps remove floatables
 Solids are not removed by a comminuter
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Wastewater Treatment Processes Primary Clarifier

Preliminary Primary Secondary Cross section of circular clarifier
Treatment Treatment Treatment

 Sedimentation and Flotation

Tertiary Solids
Disinfection
Treat. (Advanced) Treatment

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Scum removal
Primary Clarifier Wastewater Treatment Processes
Preliminary Primary Secondary
Treatment Treatment Treatment

 Biological Treatment
Mechanical  Sedimentation
Rectangular clarifier

 Goal of primary treatment is settle out more solids Tertiary Solids

Disinfection
 Velocity drops to < 1 fps Treat. (Advanced) Treatment
 Separates settleable and floatable solids
 Detention time ~ 1.5-2.0 hrs
 Raw water is gray
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Secondary Treatment Biological Constituents

 The main goal of secondary treatment is to  Many are human pathogens
remove organic waste from the wastewater  Most occupy a role in the treatment process
stream  They are:
 This is accomplished biologically by allowing  Bacteria
the waste to come into contact and be  Archaea
consumed by a population of microorganisms  Fungi/yeast
Amoeba ingesting alga

 The reduction of waste from the  Protozoa Paramecia conjugating

microorganisms occurs in some type of  Rotifers

biological reactor  Algae
 Viruses Human hepatitis A virus

34
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Biological Reactors Biological Reactors

 There are different ways the “bugs” can come  There are different ways the “bugs” can come
into contact with the waste into contact with the waste
 Fixed film reactors  Fixed film reactors

Rotating Biological
Trickling Filter Contactor
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Biological Reactors Biological Reactors

 There are different ways the “bugs” can come  Secondary treatment requires a balance of
into contact with the waste organic waste and oxygen to maintain a healthy
 Mixed reactors bug population for treatment

Oxidation Ditch Sequencing Batch Reactor Fine bubble diffusers Mechanical aeration
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Biological Reactors Wastewater Treatment Processes

 A secondary clarifier is used settle out solids Preliminary Primary Secondary
from the biological reactor to yield a treated Treatment Treatment Treatment
effluent

Tertiary Solids
Disinfection
Treat. (Advanced) Treatment
 Chemical Nitrogen and
Phosphorous Removal
 Biological Nutrient
Removal
Secondary Clarifier  Multimedia Filtration

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Wastewater Treatment Processes Disinfection

Preliminary Primary Secondary  Purpose is to kill
Treatment Treatment Treatment
pathogenic organisms still
in wastewater

 Typically wastewater must

Tertiary
Disinfection
Solids contain 200 cfu/100mL for
Treat. (Advanced) Treatment Fecal coliforms or 126
 Ultraviolet Irradiation cfu/100mL for E. coli to be
 Chlorine Gas
 Sodium Hypochlorite considered “disinfected”
 Calcium Hypochlorite

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Bleach Chlorine Contact Chamber

Solids Treatment

Primary Secondary
Treatment Treatment

Ton Chlorine Cylinders

Solids
Treatment
Tablet  Digestion
Hypochlorination  Dewatering
 Disposal
System
UV system
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Effluent Discharge
 Most wastewater is discharged to a receiving
Anaerobic Digester
stream, river, lake or ocean.
Gravity Thickener Belt Press  Some is reclaimed or reused on golf courses,
cemeteries, parks, etc.
Trucking Solids Gravity Filter Bed

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Gravity
Small Diameter Gravity Systems (SDGS)
Wastewater
Pressure (STEP and Grinder Pump)  Defined: water supply
Vacuum of a community or
industry after it has
been used
 Treatment: “onsite” or
Wastewater Collection offsite (“centralized”)
Systems  Offsite treatment
requires a “collection
and conveyance”
system
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Wastewater Collection and Conveyance Wastewater Collection and

System Conveyance System
Collection System Components  Manholes are installed in lateral, main, trunk, and
intercepting sewers for the purpose of placing persons,
Pumping equipment, and materials into these sewers for
Station
Manhole inspection, maintenance, and the removal of solids from
Gravity
cleaning operations
Force Sewer  Manholes must be installed:
Main  At the ends of any line 8” in diameter or
Gravity
Sewer larger line
 Changes in grade, size of pipe or alignment
 At intersections
Manholes should be placed Constant minimum slope is
Minimum  And not greater than 400 ft on a 15”
every 300-500 feet apart to required to provide a velocity
provide access for
size is 4”
of at least 2 fps to avoid
diameter and smaller sewers or 500 ft on
inspections and cleaning solids depositing
18-30” sewers
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Wastewater Collection and Wastewater Collection and

Conveyance System Conveyance System
 Hydrogen sulfide is made in the collection system and
 Horizontal Separation – sewers should be laid
can:
with at least 10 feet of horizontal clearance from
 Make waste more difficult to treat
any existing or proposed water line
 Damage concrete structures
 Vertical Separation – when sewers must cross a  Cause odor problems
water line, they should be laid 18” below the  Biological activity in long, flat sewer lines will likely
bottom of the water line cause:
 Hydrogen sulfide production
 Oxygen deficiency in sewers, manholes or wet wells
 Metal and concrete corrosion
 Chlorine can be used in the collection system or at
the plant headworks to oxidize hydrogen sulfide
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Oil and Grease What are the Wastewater Flows?

 Generally listed under one heading called FOG (fats, oils  Sanitary Sewer:
and greases) as it is often not important to know the  Domestic and
exact make-up of this group of components. industrial waste
 Storm water:
 Snow melt, street
wash, etc.
 Combined sewer:
 Sanitary plus storm
 Example: Nashville
 Infiltration/Inflow
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I/I I/I
 Inflow – Water discharged into a sewer system and
service connections from such sources as, but not
limited to, roof leaders, cellars, yard and area drains,
foundation drains, cooling water discharges, drains
from springs and swampy areas, around manhole
covers or through holes in the covers, cross
connections from storm and combined sewer
systems, catch basins, storm waters, surface runoff,
street wash waters or drainage.
 Inflow differs from infiltration in that it is a direct discharge
into a sewer rather than a leak in the sewer itself.
55 56
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I/I Infiltration Locations

 Infiltration – the seepage of groundwater
into a sewer system, including service
connections.
 Seepage frequently occurs through defective or cracked
pipes, pipe joints, connections or manhole walls.
 Due to age and condition of system and portion of
system submerged in groundwater
 Exfiltration – liquid wastes and liquid-carried
wastes that unintentionally leak out of a
sewer pipe system and into the environment
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Wastewater flow rates Wastewater flows: Why do we care?

 Rule of thumb:  Collection and conveyance system design
 US domestic is about 70-100 gpd/person  Are they getting shorter or longer as the years go on?
 Developing countries: 5 to 50 gpd/capita  Getting longer and further away from the treatment
 Other: depends on facility (industry, commercial, etc.) plant means the water spends more time in the
 I/I can be significant system, which also means water easily becomes septic
 Units:  Treatment system design
 3.7854 liters per gallon  Hydraulic criteria: must be able to pass peak flows
 In U.S., gallons most frequent  Treatment criteria: meeting treatment standards often
unit of volume depends on “hydraulic residence time”
 MGD = million gallons per day  e.g. MG / MGD = days = residence time
 Concentration: mg/L or lbs/MG  Growth projections (population, development)
59 60
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“Diurnal variations” in domestic

Factors Effecting Flow Rates wastewater flows
 Geographical location & socioeconomic
conditions
 Type of development
 Season (I/I)
 Climate (I/I)
 Time of Day

61 62
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O&M of Collection Systems Building Service Lateral

 The facilities should be kept in good operating
 Connects internal
condition 2-Way Cleanout Property Line House
plumbing to street
 What happens when collection systems fail sewer
due to lack of or improper operation and Curb Sidewalk  Usually homeowner
is responsible
maintenance? Main Sewer Line  Cleanout minimum
 SSO – Sanitary Sewer Overflow Sewer Lateral Standard Cleanouts
3 ft from
 Blockages occurring in the sewer line that result in City Property Owner foundation
backups into homes, businesses and other customer Lower Lateral Upper Lateral  Typically 4 inch
facilities diameter
Typical dwelling served by a main sewer in the street
 Bypassing raw wastewater  Slope ¼ inch per
 Street collapse foot minimum, 2%
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Conventional Gravity Sewer Conventional Gravity Sewer

 Uses natural slope of land to flow by gravity  Scouring velocity- 2 ft/sec
 Manholes every 400-500 ft  Flow < 2 ft/sec may lead to settling out of solids,
 State requirement: manhole at distance  400 ft for sewers stoppages, production of odors including toxic
15 inches or less and 500 ft for sewers 18 to 30 inches hydrogen sulfide, corrosive conditions
 Pump or lift station  Sewer not less than 2 ½ ft deep

Water Surface Force Main Water Surface Force Main

(Under Pressure) (Under Pressure)
Manholes Manholes

Sewer Line Sewer Line

Flow (Gravity Flow) Flow (Gravity Flow)
Pumping Pumping
Sewer Line Station Sewer Line Station
(Gravity Flow) TDEC - Fleming Training Center
(Gravity Flow) TDEC - Fleming Training Center
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Gravity Collection Sewer Gravity Collection Sewer

 Building sewer – a gravity-flow pipeline connecting a
building wastewater collection system to a lateral or
branch sewer
 The building sewer may begin at the outside of the building’s
foundation wall or some distance (2-10 ft) from the wall,
depending on local sewer ordinances
 Also called house connection or service connection
 Lateral sewer – a sewer that discharges into a branch
Treatment
Lateral Sewer or other sewer and has no other common sewer
Plant
Branch Sewer tributary to it
Main Sewer  Sometimes called a “street sewer” because it collects
Trunk Sewer wastewater from individual homes
Intercepting Sewer
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Gravity Collection Sewer Sewer Manhole

 Branch sewer – a sewer that receives wastewater from a  Place people, equipment Manhole frame
relatively small area and discharges into a main sewer and materials into sewer and cover
serving more than one branch sewer area for inspection, Brick course for
 Main sewer – a sewer line that receives wastewater from maintenance and cleaning adjusting frame and
cover to final grade
many tributary branches and sewer lines and serves as an
outlet for a large tributary or is used to feed an  May not have steps since
Steps
intercepting sewer hazardous if corroded
 Trunk sewer – a sewer that receives wastewater from  Minimum barrel diameter Sewer
many tributary branches or sewers and serves a large 48 inches
territory and contributing population  Inspected annually
 Intercepting sewer – a sewer that receives a flow from a  Reinforced concrete, brick,
number of other large sewers or outlets and conducts fiberglass
the waters to a point for treatment or disposal
Side section Front section
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(partial)

Inverted Siphon Air Jumper

 Sewer lines installed lower than the normal gradient  Air jumpers are sometimes constructed as part of an inverted siphon
of the sewer line to pass under obstructions such as  Since the siphon is completely filled with wastewater, a blockage in the
flow of air in the sewer line occurs without an air jumper
watercourses and depressed roadways
 This blockage may cause a continuous release of toxic, odorous and
 Wastewater is pushed through the siphon by the corrosive hydrogen sulfide at the upstream siphon manhole
pressure resulting from the upstream sewer being  Installation of jumpers prevents this from happening by providing the
higher than the downstream sewer downstream flow of air that usually occurs above the wastewater in a
partially filled sewer line
Existing Ground
Drainage channel, Drainage channel,
Inlet highway or other highway or other
obstruction Inlet
Manhole Outlet obstruction Outlet
Manhole
Manhole Manhole
Flow Flow
Flow Flow
Air jumper Air jumper
Ductile iron pipe(s) Ductile iron pipe(s)
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Small Diameter Gravity Sewer (SDGS) Small Diameter Gravity Sewer (SDGS)
 Alternative wastewater collection system installed in
areas where deep excavation is a concern, and in
areas that are hilly or flat
 SDGS uses a smaller diameter pipe than
conventional gravity sewers due to less solids
 Follows the surface contour of the land, reducing the
amount of excavation and construction costs
 Septic tanks onsite discharge to small diameter
gravity main
 Discharges effluent by gravity, pump or siphon
 Minimum velocity 0.5 ft/sec Minimum velocity 0.5 ft/sec
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STEP – Septic Tank Effluent Pump

Interceptor Tank Lift Station
 Simple reinforced
 Septic tank concrete or fiberglass
wet well after septic
 Removes floating and
tank
settleable solids
 Submersible pump
 Levels out flows Precast concrete, fiberglass, operated by mercury
 Sludge solids decompose HDPE or coated steel common.
float switches
anaerobically
 Also on gravity mains
 Regular inspection to measure liquid level, depth to allow gravity flow at
of sludge & thickness of scum shallow depth
 NO tank additive works
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STEP System STEP System

S – Septic
T – Tank
E – Effluent
P – Pump

 Septic tank effluent pump with filter

 Float activated mercury switch controls pump
 Keep OUT: eggshells, plastic, bones, grease
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Vent & Air Release Valve Pressure Sewers

 Vent maintains flow in
SDGS main
 Air release valve-vents
air at high points in
main that would
restrict flow
 Gases vented from
 Reasons:
main often quite
odorous- use activated  Topography: Flat terrain or high slope
carbon filter, soil bed  Rocky soil
masking agent  High groundwater table
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Pressure Sewers - Components Grinder Pump System

 4” gravity building  Submersible centrifugal pump with comminuting blade
sewer at 2% slope cuts and shreds solids in wastewater
 Holding tank  Pump unit acts to pressurize WW to move it through
 Grinder pump & sewer
controls  WW flows from pump
 Valves to isolate vault to pressurized
system main via a pressurized
 Pressure main service line
 Grinder pump serving
a home is usually
1-2 hp
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Progressive Cavity Grinder Pump Progressive Cavity Grinder Pump

 Creates pressure that  Check & gate valve on
moves WW through discharge prevent backflow
sewer  Excavation not deep: 5-8 ft
 Reduces size of solids  Uses small diameter
 Pump, motor, grinder, pressure lines
pipes, valves, controls  Odors associated with
improper venting
 Pressure sensor
measures liquid level  Maintenance: solids lodged
in cutting blade
 Disadvantage: FOG is
transported
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Pressure Sewer vs. Gravity Sewer Automatic Air Release Assembly

 Higher energy costs for pumping  Located in high point of pressure sewer
 Greater costs for pumping facilities  Release air pockets that would reduce flow capacity
 Deep trenches not necessary
 Inverted siphons not needed to cross roads
and rivers
 Smaller pipes often needed
 Fewer stoppages (system pressurized)
 No I&I – no extra capacity needed
 No root intrusion, air tight system

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Pressure Sewer Cleaning Pigging Port

 Must have access for  Installed to insert pig to clean inside sewer
maintenance  The poly pig is forced through the pipe under pressure
 Manholes or access boxes  Replaces manhole needed in gravity sewer
must have valves and pipe  Radio beacon device allows operator to track pig location
spools that can be removed
for cleaning the pipe
 Polyurethane pigs and swabs
are slightly larger or the same
size as the main to be cleaned
 Pigging typically done during
low flow periods Pipe with sludge before cleaning

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Vacuum Sewer
Vacuum Sewer Layout Components
 Applications: flat or rolling terrain, unstable soil, high
water table, rocky terrain, urban development in rural
areas
 3 Components:
 On-site valve pit
 Vacuum collection
piping  Gravity building sewer to vacuum interface unit
 Central vacuum
 Vacuum interface unit seals vacuum service
station
 Once 3 gal WW accumulate, valve opens to allow atmospheric
air to force WW into vacuum branch
 Vacuum main sends WW to treatment facility
 Minimum slope vacuum main is 0.2 ft/sec
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Typical Fiberglass Valve Pit

With External Breather Vacuum Sewer – How Does It Work?
 WW flows by gravity (1) into 30 gal
holding tank
 As WW level rises, air is compressed
in sensor tube connected to valve 2 4
controller (2)
 Sensor signals valve to open until tank
contents are evacuated (3)
 The spring-loaded interface valve (4) is
controlled pneumatically and needs no
electricity
1
 External breather is a 1 ¼ inch
polyurethane pipe anchored in ground 3
by concrete
 Breather pipe must be watertight and
has domed cover to keep insects out
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Isolation Valve Typical Vacuum Station

 Plug or gate valves  Steel or fiberglass
Stem Seal collection tank (1) acts like
isolate portions of Bonnet wet well.Vacuum switches
vacuum sewer for on reservoir tank (2)
repairs and maintenance Body
regulate vacuum pumps (3).
Level control probes in
 Typical interval is 1500 collection tank regulate 3 2
to 2000 ft the WW pumps (4).
 Also located at both  Daily operating tasks:
sides of a bridge  Visual check of gages and
charts
crossing and at both Plug  Record pump run times
1
sides of an area of  Check oil & block 4
unstable soil temperature
TDEC - Fleming Training Center TDEC - Fleming Training Center

Typical Vacuum Station Vacuum Sewer Advantages

 Small pipe sizes, typically 3, 4, 6, 8 and 10 in
 1 station serves  Easy to avoid underground obstacles
200-300 customers  Shallow installation (2 to 4 ft) eliminates need for wide
deep trenches reducing excavation costs and
environmental impact
 Vacuum pumps  High scouring velocity reduces blockages and keeps
operate 3-5 hrs/day wastewater aerated and mixed
 No infiltration - leaks easily noted
 Reduced infiltration leads to reduced size and cost of
 Pumps are typically treatment plant
20 hp  No manholes
 Only power source at vacuum station
TDEC - Fleming Training Center
TDEC - Fleming Training Center
TDEC - Fleming Training Center

Wastewater & Collection Systems Overview 33

 Section 2 TDEC - Fleming Training Center

Vacuum Sewer O & M

 No odor problems
 System is sealed; large air input with flow
 No corrosion problems
 Corrosion resistant PVC, ABS, rubber, stainless steel
 Malfunctions:
 Break in vacuum line
 Valve malfunction
 Closed isolation valve
 O&M of vacuum systems are more difficult than a low
pressure system because it is harder to maintain a
vacuum due to the number of inlets and valves to the
system
TDEC - Fleming Training Center

34 Wastewater & Collection Systems Overview