Septic System Issues & Solutions: Technical Component

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Septic System Issues Solutions Technical
Component
Deborah Borden, University of Georgia

• Watershed Academy Athens, GA
• March 28-30, 2006

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Septic System Components
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Types of Decentralized Systems
Cluster Design
On-Site Wastewater Treatment (Septic Systems)
Large Community Systems
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A Few Facts From Georgia

• 25 of homes in the U.S. use on-site systems
• 40 in Georgia
• 75 of new homes
• 50,000 systems installed annually

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The Perception of Septic Systems

• A Temporary Solution

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Where did this perception come from?

• Historically for rural areas
• Suburban explosion after WWII
• Concentrated housing at the edge of town
• Homes temporarily used on-site systems until
  sewer came

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Todays Reality

• USEPA considers decentralized systems an integral
• part of the nations wastewater management
• infrastructure

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Advantages of Decentralized WW

• Low cost
• Capital Cost between 3-5k
• Maintenance costs 100/year
• Environmentally benign if properly sited,
  installed, and maintained
• Minor water contamination risk with failure
• Natural system

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Disadvantages of Decentralized WW

• Not all soils suitable
• Not the best system for industrial and commercial
  
• No periodic inspections required
• Sporadic maintenance if at all
• Greater potential for illicit discharge
• Limits density
• Advantage or disadvantage?

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Major Components

• Septic tank

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Septic Tank Function

• 1,000 to 1,500 gallon water tight tank
• Removal of large solids
• Limited organic decomposition (30)
• Protect absorption field from clogging

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Absorption Field Function

• Distributes wastewater from septic tank into soil
• Pipe and gravel
• Numerous other technologies

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Soil Function

• Transmits wastewater from absorption field to
  ground or surface water
• The treatment media
• Natural processes purify wastewater

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Household Wastewater

• Toilet, bath, kitchen, and laundry
• About 99.9 liquid and 0.1 solids
• Average production 70 gal/person/day
• Systems designed for 150 gal/bedroom/d
• 2 people in each bedroom

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Potential Contaminants in Wastewater

• Bacteria and viruses
• Nitrate
• Phosphorous
• Odors
• Anything else that goes into the system
• Cleaners, medicine, drain cleaners, paint,

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Wastewater Renovation in the Soil

• Natural soil processes
• Rapid organic matter decomposition
• Organic N in wastewater rapidly converted to
  nitrate
• Nitrate is mobile in soil
• Dilution only mechanism to keep groundwater
  nitrate levels low
• Minimum lot size?

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Wastewater Renovation in the Soil

• Phosphorous is fixed and immobile in soils
• Bacteria and viruses
• Greatest threat to human health
• Removal by "filtering" and die-off
• Movement in most soils lt2
• Reports of movement gt100 in sandy soils with
  high water table

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Types of Septic System Failures

• Partially treated ww rising to the soil surface
• Health hazard
• Odor
• Overland flow to surface water?

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Types of Septic System Failures

• Wastewater backs up into house
• Toilet wont flush
• Health hazard
• Odor

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Types of Septic System Failures

• Inadequate treatment before entering groundwater
• Commonly not considered - If toilet will flush,
  the system is working

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Common Causes of Early Failure

• Unsuitable soils
• Slow or fast perc rates
• Seasonal water tables
• Shallow rock
• Water restrictive soil horizons

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On-Site System Suitability Hall County
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Common Causes of Early Failure

• Installation faults
• System not at proper grade
• Damaged components
• System inspection should discover these

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Common Causes of Early Failure

• Site water management
• Gutter downspouts
• Run-on from paved areas and/or upslope areas

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Common Causes of Longer-term Failure

• Under-designed system
• Bedroom addition
• Abnormally high water use
• Lack of homeowner understanding
• Lack of periodic maintenance inspections
• Nothing lasts forever
• Properly sited, sized, and maintained system
  should last 30 years

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Extending Life of On-Site System
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Reduce Water Use(or at least be aware of amount
used)
Per Capita Water Use
Laundry, 22 gpd
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Water Conservation

• Fix leaks
• Low flow toilets, showerheads, dishwashers, etc.
• 1994 U.S. Energy Policy Act (EPACT)
• Reduces per capita water use by 10 to 20 gpd
• Reduce water pressure

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Graywater Separation

• 60-65 of total wastewater
• Bathtub or shower
• Laundry
• Toilet, kitchen and dishwasher not included
• Surface discharge requires EPD permit
• Graywater reuse in the future?

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Reduce Contaminant Loads in WW

• Use recommended amounts of household cleaners
• Do not
• Use every flush toilet bowl cleaners
• Flush unwanted medicines down toilet
• Drain chlorine-treated water into on-site systems
• Minimize use of garbage disposal

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Bacteria Additives

• Not shown conclusively to enhance performance
• Generally not recommended
• Amount of microorganisms added is minor
• Can result in abnormal amounts of suspended
  solids added to drainfield

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Maintenance

• Often homeowner responsibility
• Lack of understanding
• Pump septic tank
• Every 3-5 years (not required in GA)
• Minimizes addition of solids to drainfield and
  soil clogging
• Inspections
• Only post-construction inspections reqd
• Periodic inspections not required in GA

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Advanced Treatment Systems

• Aerobic treatment to lower BOD and suspended
  solids
• Overcomes soil and site limitations
• Should extend life of system
• Reduced solids to clog soil pores
• Additional maintenance required
• Additional expense

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Whats in the Future?
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Cluster or Community System

• Same total area as individual on-site systems
• Septic tank at every house
• Best soils for on-site system
• Advanced treatment
• Nitrogen and phosphorus removal

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Cluster or Community System

• Contract maintenance
• Public?
• Private?
• Drainfield can be green space
• Wastewater concentrated in small area
• Greater potential for groundwater contamination?

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Nitrogen and Phosphorus Removal

• Technology is currently available
• Not cheap
• Additional maintenance required
• May be required in sensitive environments
• P removal in shallow soils over fractured rock
  near water bodies
• N removal may be more widespread

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Contract System Operation/Ownership

• Contract operation
• Homeowner owns system
• Maintenance/guaranteed performance provided for
  monthly fee
• 3rd party ownership
• Company or government agency owns system
• Responsible for maintenance and operation

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Summary

• On-site systems are an economical and
  environmentally benign alternative to centralized
  wastewater treatment if
• soils are favorable,
• the system is suitable for the site and properly
  installed, and
• the system is properly and regularly maintained

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Summary

• Maintenance is the key
• Simple, but it must be done
• New technologies are becoming available to
  improve performance