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Household Wastewater Systems


Typical Waste Water System Well Renovated Wastewater 2 acres 2 acres Lagoon 1 acre 1 acre Subsurface (slow perc.) acre acre Subsurface ... – PowerPoint PPT presentation

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Title: Household Wastewater Systems

Household Wastewater Systems Mike Kizer OSU
Extension Biosystems Agricultural Engineering
Typical Waste Water System
Renovated Wastewater
Wastewater System Regulation
  • Regulatory agency in Oklahoma is Department of
    Environmental Quality (DEQ) 707 N. Robinson, OKC
    (Tel 405-702-6100)
  • DEQ field offices in many counties Check
    local listing under Oklahoma State of
  • Regulations are outlined in Title 252 of
    Oklahoma Administrative Code, Ch. 641
  • DEQ wastewater system website

Minimum Lot Size for Wastewater Disposal Systems
Disposal System Type Water Supply Source Water Supply Source
Disposal System Type Private Well Public Supply
Aerobic w/ sprinklers ¾ acre ½ acre
ET/Absorption Trench 1 acre 1 acre
Subsurface (fast perc.) ¾ acre ½ acre
Subsurface (slow perc.) 1 acre 1 acre
Lagoon 2 ½ acres 2 ½ acres
Wastewater System Separation Distances (distance
in feet)
Tanks (septic, pump, aeration) Perforated Pipe or Chamber Solid Pipe Lagoon Sprinkler Head Spray Head
Private Well 50 / 100 50 / 100 50 / 100 50 / 100 50 / 100 15
Public Well 300 300 50 300 300 15
Buildings 5 5 NA 50 NA NA
Other Structure NA 10 NA NA NA NA
Water Line 5 15 10 15 15 NA
Property Line 5 5 5 10 5 5
Stream/Lake 15 15 NA 15 15 15
Drains 15 15 NA 15 NA 15
Wastewater System Components
  • Water-tight sewer lines
  • Septic tank
  • Disposal system
  • Subsurface drain field
  • Absorption trenches
  • Infiltration chambers
  • ET/Absorption trenches
  • Aerobic system with sprinkler
  • Total retention lagoons
  • Pre-approved alternative disposal systems

Screen vent pipe opening to prevent blockage by
birds, squirrels, etc.
  • Household Plumbing Sewer and Vent System
  • Sewer lines in the house collect waste water for
    conveyance to the septic tank
  • Roof vents and the traps under sinks, tubs,
    showers, toilets and wall/floor drains prevent
    sewer gas from entering the house.

Main Sewer Pipe
Septic Tank
  • All household wastewater systems will have a
    septic tank
  • Microbial action digests solid wastes
  • Liquids flow through tank to disposal area
  • Tank size
  • 1000 gallon liquid capacity (4-BR house or less)
  • Add 250 gallons per additional bedroom

Typical Septic Tank Installation Two-Chamber Tank
House Foundation
Wastewater Piping Materials
  • Water-tight Sewer Conveyance Lines
  • Cast iron
  • PVC (Sch. 40 is preferred weight)
  • Transite (asbestos-cement)
  • Orangeburg (paper-tar product old houses)
  • Drain Field Lines
  • Perforated PVC
  • Polyethylene infiltration chambers
  • Clay tile (old houses)

Effluent Disposal Area Options
  • Absorption field
  • Absorption trenches
  • Infiltration chambers
  • ET/Absorption trenches
  • Lagoons
  • Aerobic systems
  • Authorized alternative systems

Subsurface Absorption Field Approval
  • Percolation Test
  • 3 test holes in drainage area perc at a rate of
    60 min/inch of water or faster
  • Soil Profile Description
  • 3 test holes without any of the following
  • (1) impervious material (bedrock, clay pan)
  • (2) water saturated soil (discoloration)
  • (3) loamy coarse sand or coarser soil, or
  • (4) sandy clay or finer soil

The size and type of waste water disposal system
is very dependent on the soil at the building
site. Even before a percolation test or soil
profile evaluation you can get an idea of site
suitability from the county soil survey.
Cross-Section of Subsurface Absorption Trench
8-ft minimum distance to center of next trench
Perforated Pipe
150 MAX.
Lateral lines following the slope contour
150 max. length
Infiltration Chambers
  • Polyethylene infiltration chamber has 100 open
    volume vs. 50 for gravel-filled absorption trench
  • Corrugated design gives strength to support
    ground traffic over its 2-ft width
  • Chamber cost per unit length is approximately
    equal to unit cost of perforated PVC pipe, plus
    gravel and installation

ET/Absorption Trench System
  • Used when soil percolation rate is too slow for
    ordinary subsurface absorption trenches
  • Uses evapotranspiration (ET) of grasses plus soil
    absorption to dispose wastewater
  • Plant a mix of cool and warm season grasses for
    year-round ET

Cross-Section of ET/Absorption Trench
Cool-Warm Season Grass Mixture
Perforated Pipe
  • Used when soil percolation rate is too slow for
    soil absorption systems
  • Require 2 ½ acre minimum lot size
  • Fencing required around the lagoon
  • Size based on house size, and rainfall and
    evaporation of geographic zone
  • Must retain all wastewater (no overflow)

Typical Lagoon Installation
  • 2.5 acre minimum lot size required
  • 4-ft high fence required
  • lagoon size based on house size and local

4 ft

3 1
1 ft min.
7 ft
5 ft max.
Concrete Pad
Location Lagoon Size The required size of
total retention waste water lagoons (because of
their annual hydraulic balance) makes them less
desirable the farther east you build in Oklahoma.
Aerobic Systems
  • Used to treat septic tank effluent where
    subsurface disposal is not possible
  • Bubbling air through effluent supports aerobic
    bacteria for further digestion
  • Exposure to oxygen kills most pathogens
  • Chlorination allows surface land application of
    wastewater through sprinklers

Onsite Aerobic Treatment System
Onsite aerobic treatment systems treat septic
tank effluent further by aerobic digestion,
chlorination to kill pathogens, and surface
application through a spray head sprinkler system.
(Septic Tank)
Typical Aeration Chamber of Aerobic Treatment
Stack-Feed Contact Tablet Chlorinator
Chlorine Tablet Feed Tubes
Effluent Outlet
Effluent Inlet
Ca(OCl)2 Tablets
Pump Chamber and Surface Application System
Spray Heads
Access Hatch
Pump Pump Control Alarm Floats
Finding Waste Water System Components
  • Waste water components are normally downhill from
    the house (gravity flow)
  • Septic tank can be no less than 5 feet, and is
    normally no more than 50 feet from house
  • Two-way sanitary sewer clean-outs located
  • Within 5 feet of the house
  • Within 5 feet of every bend greater than 45º
  • Every 100 feet of straight sewer line
  • Grass over septic tank may be brown in summer
  • Grass over drain field will be greener in summer

Locating Waste Water System Components
Clean-outs on main sewer line
Locating Waste Water System Components
2 1/2-inch roof vent on branch line
4-inch roof vent on main sewer line
Sewer system roof vents
Locating Waste Water System Components
Largest roof vent on main sewer line
Clean-outs on main sewer line exiting house
Regular green stripes in a dry lawn are the
lateral lines
Household Water Use
  • Typical Usage 50-100 gallons/person-day
  • Clothes washer 30-50 gallons/load
  • Dishwasher 7-15 gallons/load
  • Garbage Disposal 4 - 6 gallons/day
  • Shower/Bathtub 25-60 gallons/use
  • Ordinary toilet 1.6 - 5 gallons/flush
  • Water softener 50-100 gallons/regeneration

Septic System Additives
  • Biological
  • Bacteria
  • Yeast
  • Enzymes
  • Combination
  • Chemical
  • Acids
  • Bases
  • Organic Solvents
  • Flocculants

Biological Additives
  • Will not eliminate need for tank pumping
  • 20 of sludge is inorganic (indigestible)
  • Billions of bacteria live in septic tanks-- a
    few million more have little effect
  • If natural bacteria have been killed, added
    bacteria will die also
  • Normal population is restored in 30-60 hours even
    if 99.99 has been killed

Maximum Safe Levels of Cleaners (Single dose in
1000-gallon septic tank)
  • Bleach (5.25 Cl) 1.3 gallons
  • Cleansers/Disinfectants 2.5 gallons
  • Drain Cleaners 0.65 ounces

Chemical Additives
  • Strong Acids and Bases
  • Disrupt normal tank biological activity
  • Harm soil structure in drain field
  • Organic Solvents
  • Clean thin layers of sewer line build-up
  • Contaminate ground water

Annual Cost of Additives Amherst, MA Retailers
Study - 1989 (using manufacturers recommended
  • Biological (11) 19.75/yr
  • Solvents (3) 78.00/yr
  • Acid/Base (8) 13.48/yr

Annualized Pumping Cost (USPHS Pumping Frequency
Estimate) 150 Pumping Cost for 1000-gal tank
Family Size Pumping Freq. Annual Cost
2 20 yrs 7.50/yr
3 12 yrs 12.50/yr
4 8 yrs 18.75/yr
5 6 yrs 25.00/yr
6 4 yrs 37.50/yr
Septic System Additives Conclusions
  • Biological additives are harmless but of little
  • Chemical additives can damage septic system and
    contaminate ground water
  • Dont use if active ingredients are unspecified
  • Annualized cost of additives is about the same as
    for tank pumping on recommended schedule
  • These products make a lot of money for the
    people that sell them.

Waste Water System Failures Common Causes
  • Hydraulic overloading (too much water)
  • Solids migration to drain field
  • Failure to pump tank on schedule
  • Baffle failure
  • Root intrusion into sewer lines
  • Traffic damage to drain field
  • Garbage disposal overuse

Reducing Hydraulic Loading
  • Equipment Adjustments
  • Low flow toilets (1.6 gpf and 0.6 gpf)
  • Water-saving showerheads
  • Front-loading washing machines
  • Lifestyle Adjustments
  • Shower vs. bath
  • Distribute laundry loads throughout week
  • Distribute bathing morning evening
  • Full loads only for washer dishwasher

Root Damage
  • Plant no trees or shrubs near sewer lines
  • Copper sulfate to kill tree/shrub roots
  • Treatment is not toxic to plants
  • Once intruding roots are killed, absorption ends
  • Add ½ cup of crystals to distribution box or to
    cleanout downstream from septic tank
  • If added through toilet, 2 pounds of crystals are
    needed (not harmful to tank bacteria)
  • See OSU CR-6428 for more information

Traffic Damage
  • No vehicle parking over drain field
  • No vehicle traffic except lawn mowers
  • No traffic at all if ground is saturated

Solids Drain Fields
  • Solids must be retained in septic tank
  • Baffles should be inspected when tank is
    inspected or pumped
  • Use of additives that liquefy sludge and scum
    can lead drain field failure
  • Septic tanks like fuses in electrical wiring
    (failure in controlled location cheap to fix)

Garbage Disposals
  • Add to hydraulic load (running water)
  • Add to solids (more frequent pumping)
  • Poorer digestion environment
  • (CarbonNitrogen ratio is more unfavorable)

Water Softeners Septic Systems
  • Salt does not affect septic tank functioning
  • Added hydraulic load (regeneration water)
  • Use water meter or sensor controlled regeneration
    rather than time clock alone
  • Added sodium can affect marginal drain fields
    (dispersal of clays slows perc rate)
  • Use potassium chloride (KCl) salt if a problem

MWPS-24 HomeASyst OK DEQ
Ch. 641 Onsite Domestic Sewage Worksheet 3 Disposal Handbook
On-Site Wastewater System Resources
If you dont maintain your on-site wastewater
system, it will demand your attention when it is
most inconvenient.