Household Wastewater Systems

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Household Wastewater Systems Mike Kizer OSU
Extension Biosystems Agricultural Engineering
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Typical Waste Water System
Well
Renovated Wastewater
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Wastewater System Regulation

• Regulatory agency in Oklahoma is Department of
  Environmental Quality (DEQ) 707 N. Robinson, OKC
  (Tel [phone])
• 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
  http//www.deq.state.ok.us/ECLSnew/septic.htm

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Minimum Lot Size for Wastewater Disposal Systems
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Wastewater System Separation Distances(distance
in feet)
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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

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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
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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

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Typical Septic Tank Installation Two-Chamber Tank
Baffles
House Foundation
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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)

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Effluent Disposal Area Options

• Absorption field
• Absorption trenches
• Infiltration chambers
• ET/Absorption trenches
• Lagoons
• Aerobic systems
• Authorized alternative systems

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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

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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.
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Cross-Section of Subsurface Absorption Trench
8-ft minimum distance to center of next trench
Perforated Pipe
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150 MAX.
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Lateral lines following the slope contour
150 max. length
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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

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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

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Cross-Section of ET/Absorption Trench
Cool-Warm Season Grass Mixture
Perforated Pipe
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Lagoons

• 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)

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Typical Lagoon Installation

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

4 ft

3 1
1 ft min.
7 ft
5 ft max.
Concrete Pad
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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.
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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

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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)
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EFFLUENT FROM SEPTIC TANK
WASTEWATER TO CHLORINATOR SPRINKLERS
DIFFUSER
Typical Aeration Chamber of Aerobic Treatment
System
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Stack-Feed Contact Tablet Chlorinator
Chlorine Tablet Feed Tubes
Effluent Outlet
Effluent Inlet
Ca(OCl)2 Tablets
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Pump Chamber and Surface Application System
Spray Heads
Access Hatch
Pump Pump Control Alarm Floats
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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

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Locating Waste Water System Components
Clean-outs on main sewer line
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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
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Locating Waste Water System Components
Largest roof vent on main sewer line
Clean-outs on main sewer line exiting house
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Regular green stripes in a dry lawn are the
lateral lines
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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

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Septic System Additives

• Biological
• Bacteria
• Yeast
• Enzymes
• Combination

• Chemical
• Acids
• Bases
• Organic Solvents
• Flocculants

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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

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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

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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

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Annual Cost of AdditivesAmherst, MA Retailers
Study - 1989(using manufacturers recommended
rates)

• Biological (11) 19.75/yr
• Solvents (3) 78.00/yr
• Acid/Base (8) 13.48/yr

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Annualized Pumping Cost(USPHS Pumping Frequency
Estimate) 150 Pumping Cost for 1000-gal tank
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Septic System AdditivesConclusions

• Biological additives are harmless but of little
  use
• 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.

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Waste Water System FailuresCommon 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

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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

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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

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Traffic Damage

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

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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)

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Garbage Disposals

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

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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

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