brian benham biological systems engineering center for watershed studies septic systems function and...
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Brian BenhamBiological Systems Engineering Center for Watershed Studies
Septic Systems Function and Maintenance
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OutlineReview components, function
and maintenance of conventional gravity-flow septic system
Discuss septic system site considerationsIntroduce alternative
septic systemsBriefly review on-
site regulationsWater quality implications
associated with using on site systemsGeneral Septic System Dos and Don’ts
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Typical System ComponentsHousehold Collection SystemSeptic TankEffluent Distribution
Distribution BoxPump/Dosing System
Drainfield / Absorption System
Replacement Area
3http://geoscape.nrcan.gc.ca/h2o/bowen/quality_e.php
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Septic TankCompartmented tank or
series of tanksConcrete, fiberglass, polyethylene
Primary treatment – solids separation
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Two Compartment Septic Tank
5Lesikar, 1999; On-site wastewater treatment systems, L-5234
Sludge
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Distribution Box
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Drain/Absorption Field
7http://www.thenaturalhome.com/infiltratorandpipe.jpg
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Trench w/ gravel
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Infiltration Chamber
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How does septic system work?
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What causes septic systems to fail?Problems:
Clogging of distribution system and/or drainfield by solids AND bacterial mats
Disruption of septic tank flora
Causes: Reduced hydraulic retention time
due to excessive solids/sludge build up in septic tank
Excessive flow into septic tank and drainfield (too much water, too often)
Use of harsh chemicals
Addition of oils/greases/fine particles that flow into and clog drainfield
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Signs of septic system failureBad odors around the
drainfield especially after heavy water use or rainfall
Soggy soil, wet spots with lush green grass growth over drainfield or septic tank
Standing water in drainfieldSlow draining fixtures Plumbing back-ups High levels of coliform
bacteria or nitrate in nearby wells
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Tips to keep septic system working…Reduce volume entering system
Use less water – consider low flow toilets, shower heads, etc.
Do laundry a little at a time – 1 to 3 loads a day.Reduce water softener recharge cycle
Perform system inspection regularly and pump septic tank when needed or on regular interval
Don’t use garbage disposalAvoid harsh cleaners; use all cleaners sparinglyMaintain good grass cover over drainfieldProtect drainfield from excess runoff
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Practice Water Conservation
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Objective Reduce volume of
water flowing into septic tank
Conserve water
OutcomeLonger retention time
(more opportunity for solids settling)
Longer usable life for drainfield
Reduced energy use
Action Typical Use Conservative Use
Toilet flushing 6 (old standard) 1.5-3 (low flow)
Tub bath 30 (half filled) 15 (quarter filled)
Shower (10 min.) 50 (5 gal/min flow) 25 (2.5 gal/min flow)
Shower (3 min.) 15 (5 gal/min flow) 7.5 (2.5 gal/min flow)
Laundry (top load) 50-60 (older models) 40 (newer models)
Laundry (front load) 33 (older models) 17-28 (newer models)
Source: University of Minnesota Cooperative Extension Service
Action Typical Use Conservative Use
Dishwashing (machine)
12-15 (old model regular cycle)
6-9 (new model regular cycle)
Dishwashing (hand) 16 (faucet rinse) 6 (basin rinse)
Teeth brushing 2 (faucet running)1/8 (wet brush,
brief rinse)
Hand washing 2 (faucet running) 1 (basin, brief rinse)
Shaving 3-5 (faucet running) 1 (basin, brief rinse)
Source: University of Minnesota Cooperative Extension Service
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Septic Tank Pump OutFrequency
Depends on water use (volume of water entering tank) and material put into tank
Two rules of thumb Every 3 to 5 years When solids (sludge)
accumulation is 30 to 50% of tank volume.
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Pump Out 101: Pumper should:
Note liquid level which can indicate leaks (too low) or problems with drainfield (too high)
Look for back flow from drainfield
Pump tank completelyCheck tank for signs of
damage
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VA Dept. of Health FLASH module
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http://www.vdh.state.va.us/EnvironmentalHealth/Onsite/howsystemsworks/septictank.htm
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Septic Tank Pumping Frequency Based on Tank and Household Size
Household Size
(number of people)
1 2 3 4 5 6
Num
ber of Years
Tank S
ize (gallons)
750 9.1 4.2 2.6 1.8 1.3 1.0
1000 12.4 5.9 3.7 2.6 2.0 1.5
1250 15.6 7.5 4.8 3.4 2.6 2.0
1500 18.9 9.1 5.9 4.2 3.3 2.6
1750 22.1 10.7 6.9 5.1 3.9 3.1
2000 25.4 12.4 8.1 5.9 4.5 3.7
2250 28.6 14.0 9.1 6.7 5.2 4.2
2500 31.9 15.6 10.2 7.5 5.9 4.8
GET PUMPED! 18
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RegulationsState-wide regulations address
acceptable materials and construction standards for septic system componentsSystem capacity
Tank/treatment unit Drainfield and replacement area
Location: minimum distances from buildings, wells, springs, etc.
Site suitability and assessment protocols
Chesapeake Bay Preservation ActRequires pump out every 5 years
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Sizing Septic Tank
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Tank size is function of amount of sewage generated and water use (rules of thumb)
Lesikar, 1999; On-site wastewater treatment systems, L-5227
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Site and Soil AssessmentDepth to
GroundwaterBedrockImpermeable layers
Soil mottling (indicates high water table)
Permeability (too low and too high)
Adjacent featuresProperty lines, structures, wells,
springs, surface water, etc.
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22Zipper, 2009; On-Site Sewage Treatment Alternatives, VCE448-407
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Locating & Sizing DrainfieldPercolation (perc) tests
determine Permeability.
Must have sufficient, but not excessivly permeable soils.
Drainfield size is function of how much wastewater is generated and soil permeability.
Tighter (finer textured) soils require larger drainfields.
Slope must be considered.
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Setback Distances
2412 VAC 5-610-10 et seq., Sewage Handling and Disposal Regulations
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Alternatives: Mound SystemRaised drainfield; sand fill above the soil surface. Overcome site restrictions such as slowly permeable
soil, shallow permeable soil over creviced or porous bedrock, and permeable soil with high water tables.
Effluent is applied to system in timed doses using pump
25Zipper, 2009; On-Site Sewage Treatment Alternatives, VCE448-407
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Alternatives: Mound System
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Alternatives: Shallow-Placed SystemsSystems with drainfields within 18 inches of the surface
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Low-pressure Distribution
Trickle IrrigationZipper, 2009; On-Site Sewage Treatment Alternatives, VCE448-407
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Alternatives: Aerobic Treatment UnitATU is a mechanical system that treats
effluent using processes that require oxygenIncludes aeration chamber, a mechanical
agitator, and a sludge settling compartment.
28Zipper, 2009; On-Site Sewage Treatment Alternatives, VCE448-407
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Alternatives: Constructed Wetland
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VDH FLASH for pumped systemshttp://www.vdh.state.va.us/EnvironmentalHealth/Onsite/howsystemsworks/pumpsystem.htm
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New Regulations for AOSSNew operation and maintenance requirements for owners
of alternative onsite sewage systems (AOSS)Annual inspections by a licensed AOSS operator.
Additional inspections depending on system complexityFirst inspection is due by April 7, 2011. Reports filed
electronically with VDH by the operator (inspector). Must maintain an Operations and Maintenance Manual and
operators log. Documents should transfer on sale. AOSS’s permitted after April 7, 2010 will have sampling
requirement to verify the performance.Local Health Department can provide additional dertails.
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For help finding a Onsite Sewage Systems Operator, Call your Local Health Department
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Septic Systems Costs Vary GreatlyCost vary primarily because of the type of system and
site specific factors (soil, slope, etc.)VA Department of Conservation and Recreation bases
cost share amounts in TMDL implementation watersheds on the following estimates
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Pumpout $150 – 300
Repairs $300 – 4,000
Septic system replacement/installation $3,000 – 8,000
Septic system with pump $4,500 – 9,000
Alternative waste treatment systems $15,000 – 20,000
Connection to public sewer $2,000 – 6,000
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Risks to Water QualitySurface and groundwater
contamination possible
Nitrogen Nitrogen in effluent
40 mg/L (approx.) 75%, ammonia; 25% organic
Ammonium (NH4+ )
converted to Nitrate (NO3-)
NO3- mobile in both saturated and unsaturated soil conditions.
Limited risk contaminants Chlorides
Phosphorus
Emerging contaminants
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Metals
Microorganisms
http://wrri.nmsu.edu/publish/watcon/proc51/mcquillan.pdf
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Emerging ContaminantsPharmaceuticals and
Personal Care Products (PPCPs)USGS study – 139 streams in 30 states:
82 of 95 antibiotics, prescription & non-prescription drugs, steroids, & hormones were found in at least 1 sample
Surface and groundwater at risk
Current treatment technologies and monitoring do not target PPCPs
Fate and transport in soil and water unclear
Environmental/ health impacts unclear
Proper disposal is CRITICAL
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Kolpin, D.W. et al. 2002. “Pharmaceuticals, hormones, & other organic wastewater contaminants in U.S. streams, 1999-2000: A national reconnaissance.” Environmental Science & Technology. 36(6):1202-1211
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Septic Systems DosKnow where your septic system is.
Have your septic system inspected and pumped as needed.
Keep records of repairs, pumpings, inspections, permits
Use commercial cleaners and detergents in moderation. Mild detergent or baking soda is preferable.
Plant only grass over and near your septic system.
Keep water usage to a minimum.
Divert surface water (runoff, irrigation, etc.) away from the drainfield.
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Septic Systems Don’tsDon’t treat your septic system as a trash can. Avoid
introducing fine/floating solids and material that are difficult to digest (avoid using garbage disposal).
Don’t drive or park vehicles on any part of your septic system. Doing so can compact the drainfield or damage the pipes, tank, or other septic system components.
Don’t build or pave over drainfield or your replacement area.
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Add VT pub
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www.epa.gov/owm/septic/pubs/homeowner_guide_long.pdf http://pubs.ext.vt.edu/448/448-407/448-407.pdf
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Brian BenhamExtension Specialist
Website: www.wellwater.bse.vt.edu
Email: [email protected]
Ph: 540-231-5705