“Technology has made large populations possible;
large populations now make technology indispensable.”
Joseph Wood Krutch, 1932
IntroductionThe French are considered the
first to use an underground septic tank system in the 1870s. By the
mid 1880s, two-chamber, automatic siphoning septic tank systems,
similar to those used today, were being installed in the United
States. Even now, more than a century later, septic tank systems
represent a major household wastewater treatment option. Fully
one-fourth to one-third of the homes in the United States use such a
system [1].
On-site sewage disposal systems are used in rural areas where houses
are spaced so far apart that a sewer system would be too expensive to
install, or in areas around cities where the city government has not
yet provided sewers to which the homes can connect. In these areas,
people install their own private sewage treatment plants. As
populations continue to expand beyond the reach of municipal sewer
systems, more families are relying on individual on-site wastewater
treatment systems and private water supplies. The close proximity of
on-site water and wastewater systems in subdivisions and other
developed areas, reliance on marginal or poor soils for on-site
wastewater disposal, and a general lack of understanding by homeowners
about proper septic tank system maintenance pose a significant threat
to public health. The expertise on inspecting, maintaining, and
installing these systems generally rests with the environmental health
staff of the local county or city health departments.
These private disposal systems are typically called septic tank
systems. A septic tank is a sewage holding device made of concrete,
steel, fiberglass, polyethylene, or other approved material cistern,
buried in a yard, which may hold 1,000 gallons or more
of wastewater. Wastewater flows from the home into the tank at one end
and leaves the tank at the other
(Figure 10.1 [2]).
Proper maintenance of septic tanks is a public health necessity.
Enteric diseases such as cryptosporidiosis, giardiasis, salmonellosis,
hepatitis A, and shigellosis may be transmitted through human
excrement. Historically, major epidemics of cholera and typhoid fever
were primarily caused by improper disposal of wastewater. The earliest
epidemiology lesson learned was through the
effort of Dr. John Snow of England (1813–1858) during a devastating
cholera epidemic in London [3]. Dr. Snow, known as the father of field epidemiology,
discovered that the city’s water supply was being contaminated by
improper disposal of human waste. He published a brief pamphlet, On
the Mode of Communication of Cholera, suggesting that cholera is a
contagious disease caused by a poison that reproduces in the human
body and is found in the vomitus and stools of cholera patients. He
believed that the main, although not only, means of transmission was
water contaminated with this poison. This differed from the commonly
accepted belief at the time that diseases were transmitted by inhaling
vapors.
Treatment of Human Waste
Safe, sanitary, nuisance-free disposal of wastewater is a public
health priority in all population groups, small and large, rural or
urban. Wastewater should be disposed of in a manner that ensures that
- community or private
drinking water supplies are not threatened;
- direct human exposure is not possible;
- waste is inaccessible to vectors, insects, rodents, or other
possible carriers;
- all environmental laws and regulations are complied with; and
- odor or aesthetic nuisances are not created.
In
Figure 10.2, a straight pipe
from a nearby home discharges untreated sewage that flows from a
shallow drainage ditch to a roadside mountain creek in which many
children and some adults wade and fish. The clear water
(Figure 10.3)
is quite deceptive in terms of the health hazard presented. A 4-mile walk along the creek revealed 12 additional pipes that
were also releasing untreated sewage. Some people in the area
reportedly regard this creek as a source of drinking water.
Raw or untreated domestic wastewater (sewage) is primarily water,
containing only 0.1% of impurities that must be treated and removed.
Domestic wastewater contains biodegradable organic materials and, very
likely, pathogens. The primary purpose of wastewater treatment is to
remove impurities and release the treated effluent into the ground or
a stream. There are various processes for accomplishing this:
- Centralized
treatment—Publicly owned treatment works (POTWs) that use primary
(physical) treatment and secondary (biologic) treatment on a large
scale to treat flows of up to millions of gallons or liters per day,
- Treatment on-site—Septic tanks and absorption fields or variations
thereof, and
- Stabilization ponds (lagoons)—Centralized treatment for populations
of 10,000 or less when soil conditions are marginal and land space is
ample.
Not included are pit privies and compost toilets. Historically,
wastewater disposal systems are categorized as water-carrying and
nonwater-carrying. Nonwater-carried human fecal waste can be contained
and decomposed on-site, the primary examples being a pit privy or
compost toilet. These systems are not practical for individual
residences because they are inconvenient and they expose users to
inclement weather, biting insects, and odors. Because of the depth of
the disposal pit for privies, they may introduce waste directly into
groundwater. It should be noted that these types of systems are often
used and may be acceptable in low-water-use conditions such as small
campsites or along nature trails [4–6].
On-site Wastewater Treatment Systems
As urban sprawl continues and the population increases in rural areas,
the cost of building additional sewage disposal systems increases. One
of the prime reasons for annexation is to increase the tax base
without increasing the cost of municipal government. The governments
involved often buy into short-term tax gains at massive long-term
costs for eventual infrastructure improvements to annexed communities.
Installing septic tank systems is common to provide on-site disposal
systems, but it is a temporary solution at best. Because property size
must be sufficient to allow space for septic system replacement, the
cost to the municipality installing a centralized sewer system will be
dramatically increased because of the large lot size.
Two microbiologic processes occur in all methods that attempt to
decompose domestic wastewater: anaerobic (by bacteria that do not
require oxygen) and aerobic (by bacteria that require oxygen)
decomposition. Aerobic decomposition is generally preferred because
aerobic bacteria decompose organic matter (sewage) at a rate much
faster than do anaerobic bacteria and odors are less likely.
Centralized wastewater treatment facilities use aerobic processes, as
do most types of lagoons. Septic tank systems use both processes.
Septic Tank Systems
Approximately 21% of American homes are served by on-site sewage
disposal systems. Of these, 95% are septic tank field systems. Septic
tank systems are used as a means of on-site wastewater treatment in
many homes, both in rural and urban areas, in the United States. If
maintained and operated within acceptable parameters, they are capable
of properly treating wastewater for a limited number of years and will
need both routine maintenance and eventually major repairs. Proper
placement and installation is a key to the successful operation of any
on-site wastewater treatment system, but septic tank systems have a
finite life expectancy and all such systems will eventually fail and
need to be replaced.
Figure 10.4 shows a typical rural home with a well
and a septic system.
Septic tank systems generally are composed of the septic tank,
distribution box, absorption field (also known as the soil drainfield),
and leach field. The septic tank serves three purposes: sedimentation
of solids in the wastewater, storage of solids, and anaerobic
breakdown of organic materials.
To place the septic tank and absorption field in a way that will not
contaminate water wells, groundwater, or streams, the system should be
10 feet from the house and other structures,
at least 5 feet from property lines, 50 feet from water wells, and 25 feet from streams. The entire
system area should be easily identifiable. There have been occasions
when owners have paved or built over the area. The local health code
authorities must be consulted on required distances in their area
because of soil and groundwater issues.
Aerobic, or aerated, septic systems use a suspended growth wastewater
treatment process, and can remove suspended solids that are not
removed by simple sedimentation. Under appropriate conditions, aerobic
units may also provide for nitrification of ammonia, as well as
significant pathogen reduction. Some type of primary treatment usually
precedes the aerated tank. The tanks contain an aeration chamber, with
either mechanical aerators or blowers, or air diffusers, and an area
for final clarification/settling. Aerobic units may be designed as
either continuous flow or batch flow systems. The continuous flow type
are the most commercially available units. Effluent from the aerated
tank is conveyed either by gravity flow or pumping to either further
treatment/pretreatment processes or to final treatment and disposal in
a subsurface soil disposal system. Various types of pretreatment may
be used ahead of the aerobic units, including septic tanks and trash
traps.
The batch flow system collects and treats wastewater over a period of
time, then discharges the settled effluent at the end of the cycle [8].
Aerobic units may be used by individual or clustered residences and
establishments for treating wastewater before either further
treatment/pretreatment or final on-site subsurface treatment and
disposal. These units are particularly applicable where enhanced
pretreatment is important, and where there is limited availability of
land suitable for final on-site disposal of wastewater effluent.
Because of their need for routine maintenance to ensure proper
operation and performance, aerobic units may be well-suited for
multiple-home or commercial applications, where economies of scale
tend to reduce maintenance and/or repair costs per user. The lower
organic and suspended solids content of the effluent may allow a
reduction of land area requirements for subsurface disposal systems.
A properly functioning septic tank will remove approximately 75% of
the suspended solids, oil, and grease from effluent. Because the
detention time in the tank is 24 hours or less, there is not a major
kill of pathogenic bacteria. The bacteria will be removed in the
absorption field (drainfield). However, there are soils and soil
conditions that prohibit the ability of a drainfield to absorb
effluent from the septic tank.
Septic tanks are sized to retain the total volume of sewage produced
by a household in a 24-hour period. Normally a 1,000-gallon tank is the minimum size to use. State or local codes generally
require larger tanks as the potential occupancy of the home increases
(e.g., 1,250 gallons for four bedrooms) and may require
two tanks in succession when inadequate soils require alternative
system installation.
Figure 10.5 shows a typical septic tank.
Distribution boxes are not required by most on-site plumbing codes or
by the U.S. Environmental Protection Agency. When used, distribution
boxes provide a convenient inspection port. In addition, if a split
system absorption field is installed (two separate absorption trench
systems), the distribution box is a convenient place to install a
diversion valve for annually alternating absorption fields.
Absorption Field Site Evaluation
The absorption field has a variety of names, including leach field,
tile field, drainfield, disposal field, and nitrification field. The
effluent from the septic tank is directed to the absorption field for
final treatment. The suitability of the soil, along with other factors
noted below, determines the best way to properly treat and dispose of
the wastewater.
Most, but unfortunately not all, states require areas not served by
publicly owned sewers to be preapproved for on-site wastewater
disposal before home construction through a permitting process. This
process typically requires a site evaluation by a local environmental
health specialist, soil scientist, or, in some cases, a private
contractor. To assist in the site evaluation process, soil survey maps
from the local soil conservation service office may be used to provide
general information about soils in the area.
The form shown in
Figure 10.6 is typical of those used in conducting a
soil evaluation.
Sites for on-site wastewater disposal are first evaluated for use with
a conventional septic tank system. Evaluation factors include site
topography, landscape position, soil texture, soil structure, internal
drainage, depth to rock or other restrictive horizons, and useable
area. If the criteria are met, a permit is issued to allow the
installation of a conventional septic tank system. Areas that do not
meet the criteria for a conventional system may meet less-restrictive
criteria for an alternative type of system.
Many sites are unsuitable for any type of on-site wastewater disposal
system because of severe topographic limitations, poor soils, or other
evaluation criteria. Such sites should not be used for on-site
wastewater disposal because of the high likelihood of system failure.
Some states and localities may require a percolation test as part of
the site evaluation process. As a primary evaluation method,
percolation tests are a poor indicator of the ability of a soil to
treat and move wastewater throughout the year. However, information
obtained by percolation tests may be useful when used in conjunction
with a comprehensive soil analysis.
Absorption Field Trench
A conventional absorption field trench
(Figure 10.7), also known as a
rock lateral system,
is the most common system used on level land or land with moderate
slopes with adequate soil depth above the water table or other
restrictive horizons. The effluent from the septic tank flows through
solid piping to a distribution box or, in many cases, straight to an
absorption field. With the conventional system and most alternative
systems, the effluent flows through perforated pipes into
gravel-filled trenches and subsequently seeps through the gravel into
the soil.
The local regulatory agency should be consulted about the acceptable
depth of the absorption field trench. Some states require as much as 4
feet of separation beneath the bottom of the trench and
the groundwater. The depth of absorption field trenches should be at
least 18 inches, and ideally no deeper than 24 inches. The absorption field pipe should be laid flat with no
slope. There should be a minimum of 12 to 18 inches of acceptable soil below the bottom of the trench to any bedrock,
water table, or restrictive horizon. The length of the trench should
not exceed 100 feet for systems using a distribution box.
Serpentine systems may be several hundred feet long and should be
filled with crushed or fragmented clean rock or gravel in the bottom 6
inches of the trench. Perforated 4-inch diameter pipe is laid on top of the gravel then covered
with an additional 2 inches of rock and leveled for a total
of 12 inches. A geotextile material or a biodegradable
material such as straw should be placed over the gravel before
backfilling the trench to prevent soil from clogging the spaces
between the rocks.
One or more monitoring ports should be installed in the absorption
area extending to the bottom of the gravel to allow measurement of the
actual liquid depth in the gravel. This is essential for subsequent
testing of the adequacy of the system.
As a general rule, using longer and narrower trenches to meet square
footage requirements produces a better working and longer lasting
ground absorption sewage disposal system. Studies have shown that as
septic systems age, the majority of effluent absorption by the soil is
provided by lateral movement through the trench sidewalls. Longer and
narrower trenches (such as 400 feet long by 2 feet wide instead of 200 feet by 4 feet to
obtain 800 square feet) greatly increase the sidewall area of the
system for lateral movement of wastewater.
Alternative Septic Tank Systems
As the cost of land for home building increases and the availability
of land decreases, land that was once considered unsuitable is being
developed. This land often has poor soil and drainage properties. Such
sites require a considerable amount of engineering skill to design an
acceptable wastewater disposal system. In many cases, sites are not
acceptable for seepage systems within a reasonable cost. These systems
are primarily regulated by state and local government and, before use,
approval must be obtained from the appropriate regulatory agencies.
Even if a site is approved in one state or county jurisdiction, a
similar site may not be approved in another.
The primary difficulty with septic tank systems is treating effluent
in slowly permeable or marginal soils. Low-water-use devices, when
installed, may make it possible to use a small percentage of septic
tank systems in marginal soil. However, low-water-use devices are
usually required as part of a larger effort to develop a usable
alternative sewage disposal system. Alternative sewage disposal
methods that can be used if regular subsurface disposal is not
appropriate are numerous [11]. Some of the more common alternative
systems are described below.
Mound Systems
A mound system (Table 10.1) is elevated above the natural soil surface
to achieve the desired vertical separation from a water table or
impervious material. The elevation is accomplished by placing sand
fill material on top of the best native soil stratum. At least 1 foot
(304.8 mm) of naturally occurring soil is necessary for a mound system
to function properly. Minimizing water usage in the home also is
critical to prevent effluent from weeping through the sides of the
mound (Figure 10.8).
When a mound system is constructed, the septic tank usually receives
wastewater from the house by gravity flow. A lift station is located
in the second compartment or in a separate tank to pump the effluent
up to the distribution piping in the mound. Floats in the lift station
control the size of the pumped effluent dose. An alarm should be
installed to alert the homeowner of pump failure so that repairs can
be made before the pump tank overfills.
Low-Pressure Pipe Systems
Low-pressure pipe (LPP) systems may also be used where the soil
profile is shallow. These systems are similar to mounds except that
they use naturally occurring soil as it exists on-site instead of
elevating the disposal field with soil fill material. LPP systems are
installed with a trenching machine at depths of 12 to 18 inches (304.8
to 457.2 mm). The LPP system consists of a septic tank, high-water
alarm, pumping tank, supply line, manifold, lateral line, and
submersible effluent pump
(Figure 10.9).
When septic tank effluent rises to the level of the pump control in
the pumping tank, the pump turns on, and effluent moves through the
supply line and distribution laterals. The laterals contain small
holes and are typically placed 3 to 8 feet apart.
From the trenches, the effluent moves into the soil where it is
treated. The pump turns off when the effluent falls to the lower
control. Dosing takes place one to two times daily, depending on the
amount of effluent generated. Pump malfunctions set off an alarm to
alert the homeowner. The time between doses allows the effluent to be
absorbed into the soil and also allows oxygen to reenter the soil to
break down solids that may be left behind. If the pump malfunctions,
an alarm notifies the homeowner to contact a qualified septic system
contractor. The pump must be repaired or replaced quickly to prevent
the pump tank from overflowing. Table
10.2 shows the advantages and
disadvantages of LPP systems.
Plant-rock Filter Systems (Constructed Wetlands)
Considered experimental in some states, plant-rock filter systems are
being used with great success in Kentucky, Louisiana, and Michigan.
Plant-rock filters generally consist of a septic tank
(two-compartment), a rock filter, and a small overflow lateral
(absorption) field. Overflow from the septic tank is directed into the
rock filter. The rock filter is a long narrow trench (3 to 5 feet
wide and 60 to 100 feet
long) lined with leak-proof polyvinyl chloride or butylplastic to
which rock is added. A 2- to 4-inch diameter rock
is used below the effluent flow line and larger rock above
(Figure 10.10).
Plant-rock filter systems are typically sized to allow 1.3 cubic feet
of rock area per gallon of total daily waste flow. A typical
size for a three-bedroom house would be 468 square feet of interior
area. Various width-to-length ratios within the parameters listed
above could be used to obtain the necessary square footage. The
trenches can even be designed in an “L” shape to accommodate small
building lots.
Treatment begins in the septic tank. The partially treated wastewater
enters the lined plant-rock filter cell through solid piping, where it
is distributed across the cell. The plants within the system introduce
oxygen into the wastewater through their roots. As the wastewater
becomes oxygenated, beneficial microorganisms and fungi thrive on and
around the roots, which leads to digestion of organic matter. In
addition, large amounts of water are lost through evapotranspiration.
The kinds of plants most widely used in these systems include
cattails, bulrush, water lilies, many varieties of iris, and nutgrass.
Winter temperatures have little effect because the roots are doing the
work in these systems, and they stay alive during the winter months.
Discharge from wetlands systems may require disinfection. The
advantages and disadvantages of the plant-rock filter system are shown
in Table 10.3.
Maintaining On-site Wastewater Treatment SystemsDos and don’ts inside the
house:
- Do conserve water. Putting
too much water into the septic system can eventually lead to system
failure. (Typical water use is about 60 gallons per day
for each person in the family.) The standard drainfield is designed
for a capacity of 120 gallons per bedroom. If near
capacity, systems may not work. Water conservation will extend the
life of the system and reduce the chances of system failure.
- Do fix dripping faucets and leaking toilets.
- Do avoid long showers.
- Do use washing machines and dishwashers only for full loads.
- Do not allow the water to run continually when brushing teeth or
while shaving.
- Do avoid disposing of the following items down the sink drains or
toilets: chemicals, sanitary napkins, tissues, cigarette butts,
grease, cooking oil, pesticides, kitty litter, coffee grounds,
disposable diapers, stockings, or nylons.
- Do not install garbage disposals.
- Do not use septic tank additives or cleaners. They are unnecessary
and some of the chemicals can contaminate the groundwater.
Dos and don’ts for outside
maintenance:
- Do maintain adequate vegetative cover over the absorption field.
- Do not allow surface waters to flow over the tank and drainfield
areas. (Diversion ditches or subsurface tiles may be used to direct
water away from system.)
- Do not allow heavy equipment, trucks, or automobiles to drive across
any part of the system.
- Do not dig into the absorption field or build additions near the
septic system or the repair area.
- Do make sure a concrete riser (or manhole) is installed over the
tank if not within 6 inches of the surface, providing easy
access for measuring and pumping solids. (Note: All tanks should have
two manholes, one positioned over the inlet device and one over the
outlet device.)
There is no need to add any
commercial substance to “start” or clean a tank to keep it operating
properly. They may actually hinder the natural bacterial action that
takes place inside a septic tank. The fecal material, cereal grain,
salt, baking soda, vegetable oil, detergents, and vitamin supplements
that routinely make their way from the house to the tank are far
superior to any additive.
Symptoms of Septic System Problems
These symptoms can mean you have a serious septic system problem:
- Sewage backup in drains or
toilets (often a black liquid with a disagreeable odor).
- Slow flushing of toilets. Many of the drains will drain much slower
than usual, despite the use of plungers or drain-cleaning products.
This also can be the result of a clogged plumbing vent or a nonvented
fixture.
- Surface flow of wastewater. Sometimes liquid seeps along the surface
of the ground near your septic system. It may or may not have much of
an odor and will range from very clear to black in color.
- Lush green grass over the absorption field, even during dry weather.
Often, this indicates that an excessive amount of liquid from the
system is moving up through the soil, instead of down, as it should.
Although some upward movement of liquid from the absorption field is
good, too much could indicate major problems.
- The presence of nitrates or bacteria in the drinking water well
indicates that liquid from the system may be flowing into the well
through the ground or over the surface. Water tests available from the
local health department will indicate whether this is a problem.
- Buildup of aquatic weeds or algae in lakes or ponds adjacent to your
home. This may indicate that nutrient-rich septic system waste is
leaching into the surface water, which may lead to both inconvenience
and possible health problems.
- Unpleasant odors around the house. Often, an improperly vented
plumbing system or a failing septic system causes a buildup of
disagreeable odors.
Table 10.4 is a guide to
troubleshooting septic tank problems.
Septic Tank Inspection
The first priority in the inspection process is the safety of the
homeowner, neighbors, workers, and anyone else for which the process
could create a hazard.
- Do not enter septic tanks or
cesspools.
- Do not work alone on these tanks.
- Do not bend or lean over septic tanks or cesspools.
- Note and take appropriate action regarding unsafe tank covers.
- Note unsanitary conditions or maintenance needs (sewage backups,
odor, seepage).
- Do not bring sewage-contaminated clothing into the home.
- Have current tetanus inoculations if working in septic tank
inspection.
Methane and hydrogen sulfide
gases are produced in a septic tank. They are both toxic and
explosive. Hydrogen sulfide gas is quite deceptive. It can have a very
strong odor one moment, but after exposure, the odor may not be
noticed.
Inspection Process
As sewage enters a septic tank, the rate of flow is reduced and heavy
solids settle, forming sludge. Grease and other light solids rise to
the surface, forming a scum. The sludge and scum
(Figure 10.11) are
retained and break down while the clarified effluent (liquid) is
discharged to the absorption field.
Sludge eventually accumulates in the bottom of all septic tanks. The
buildup is slower in warm climates than in colder climates. The only
way to determine the sludge depth is to measure the sludge with a
probe inserted through an inspection port in the tank’s lid. Do not
put this job off until the tank fills and the toilet overflows. If
this happens, damage to the absorption field could occur and be
expensive to repair.
Scum Measurement
The floating scum thickness can be measured with a probe. The scum
thickness and the vertical distance from the bottom of the scum to the
bottom of the inlet can also be measured. If the bottom of the scum
gets within 3 inches of the outlet, scum and grease can
enter the absorption field. If grease gets into the absorption field,
percolation is impaired and the field can fail. If the scum is near
the bottom of the tee, the septic tank needs to be cleaned out. The
scum thickness can best be measured through the large inspection port.
Scum should never be closer than 3 inches to the bottom of
the baffle. The scum thickness is observed by breaking through it with
a probe, usually a pole.
Sludge Measurement
To measure sludge, make a sludge-measuring stick using a long pole
with at least 3 feet of white cloth (e.g., an old towel) on
the end. Lower the measuring stick into the tank, behind the outlet
baffle to avoid scum particles, until it touches the tank bottom. It
is best to pump each tank every 2 to 3 years. Annual checking of
sludge level is recommended. The sludge level must never be allowed to
rise within 6 inches of the bottom of the outlet baffle. In
two-compartment tanks, be sure to check both compartments. When a
septic tank is pumped, there is no need to deliberately leave any
residual solids. Enough will remain after pumping to restart the
biologic processes.
References
- University of California
Cooperative Extension, Calaveras County. Septic tanks: the real poop.
San Andreas, CA: University of California Cooperative Extension,
Calaveras County; no date. Available from URL:
http://cecalaveras.ucdavis.edu/realp.htm.
- University of Nebraska-Lincoln. Residential on-site wastewater
treatment: septic system and drainfield maintenance. Lincoln, NE:
University of Nebraska-Lincoln; 2000. Available from URL:
http://ianrpubs.unl.edu/wastemgt/g1424.htm.
- Rosenberg CE. The cholera years. Chicago: The University of Chicago
Press; 1962.
- Salvato J, Nemerow NL, Agardy FJ, editors. Environmental
engineering. 5th ed. New York: John Wiley and Sons; 2003.
- Advanced Composting Systems. Phoenix composting toilet system.
Whitefish, MT: Advanced Composting Systems; no date. Available from
URL:
http://www.compostingtoilet.com.
- BioLet USA, Inc. Composting toilets. Newcomerstown, OH: BioLet USA,
Inc.; no date. Available from URL:
http://www.biolet.com.
- Mankl K, Slater B. Septic system maintenance. Columbus, OH: The
Ohio State University Extension; no date. Available from URL:
http://ohioline.osu.edu/aex-fact/0740.html.
- Hutzler NJ, Waldorf LE, Fancy J. Aerated tanks (aerobic units).
In: Performance of aerobic treatment units. Madison, WI: University of
Wisconsin – Madison; no date. Available from URL:
http://www.ci.austin.tx.us/wri/treat5.htm.
- Center for Disease Control. Basic housing
inspection. Atlanta: US Department of Health and Human Services; 1976.
- Purdue Research Foundation. Environmental education software
series. West Lafayette, IN: Purdue Research Foundation; 1989.
Available from URL:
http://www.inspect-ny.com/septic/trench.gif.
- North Carolina Cooperative Extension Service. On-site wastewater
treatment websites. Jacksonville, NC: North Carolina Cooperative
Extension Service; 2002. Available from URL:
http://www.ces.ncsu.edu/onslow/staff/drashash/enved/
sepsites.html.
- Clay Township Regional Waste District. Septic systems.
Indianapolis: Clay Township Regional Waste District; 2004. Available
from URL:
http://www.ctrwd.org/septics.htm.
- Jackson Purchase Resource Conservation and Development Foundation,
Inc. Septic systems: an overview. Cynthiana, KY: Jackson Purchase
Resource Conservation and Development Foundation, Inc.; no date.
Available from URL:
http://www.jpf.org/LRV/septic.htm.
Additional Sources of
Information
Agency for Toxic Substances and Disease Registry. Science page, Office
of the Associate Administrator for Science. Atlanta: US Department of
Health and Human Services; no date. Available from URL:
http://www.atsdr.cdc.gov/science/.
American Society of Civil Engineers. Available from URL:
http://www.asce.org.
Burks BD, Minnis MM. Onsite wastewater treatment systems. Madison, WI:
Hogarth House, Ltd.; 1994. Textbook and reference manual on all
aspects of on-site treatment.
International Code Council. International private sewage disposal
code, 2000. Falls Church, VA: International Code Council; 2000.
National Onsite Wastewater Recycling Association (NOWRA). Available
from URL: http://www.nowra.org or 1-800-966-2942.
National Small Flows Clearinghouse. Available from URL:
http://www.nesc.wvu.edu/nsfc/nsfc_index.htm or 1-800-624-8301.
US Army Corps of Engineers. Available from URL:
http://www.usace.army.mil.
Table 10.1. Mound System Advantages and
Disadvantages
Advantages |
Disadvantages |
May be used
in areas with high groundwater, bedrock, or restrictive clay
soil near the surface |
Must be
installed on relatively level lots |
Space
efficient compared to conventional rock lateral systems |
Periodic
flushing of the distribution network is required |
Allows home
building in areas unsuitable for below grade systems |
System may
be expensive |
Water
softener wastes, common household chemicals, and detergents
are not harmful to this system |
System may
be difficult to design |
Regular
inspection of the pumps and controls necessary to maintain
the system in proper working condition |
|
Table 10.2. Low-pressure Pipe Systems
Advantages and Disadvantages
Advantages |
Disadvantages |
Space requirements are nearly half
those of a conventional septic tank system |
Some low-pressure pipe systems may
gradually accumulate solids at the dead-ends of the lateral
lines, therefore maintenance is required |
Can be installed on irregular lot
shapes and sizes |
Electric components are necessary |
Can be installed at shallower depths
and requires less topsoil cover |
Design and installation may be
difficult; installers with experience with such systems
should be sought |
Provides alternating dosing and
resting cycles |
|
Installation sites are left in their
natural condition |
|
Table 10.3. Plant-rock Filter System
Advantages and Disadvantages
Advantages |
Disadvantages |
Approximately one-third the size of
conventional septic tank absorption field systems
|
May be slightly more costly to
install |
Disinfection required for effluent
discharge |
|
Can be placed on irregular or
segmented lots |
May not find installers
knowledgeable about the system |
May be placed in areas with shallow
water tables, high bedrock, or restrictive horizons |
Life span of the system is unknown
because of its relative newness |
Relatively low maintenance |
Perception of being unsightly to
some |
Table 10.4. Septic Tank System
Troubleshooting
Problem |
Possible Cause(s) |
Remedies |
Wastewater backs up into the building or plumbing fixtures
sluggish or do not drain well. |
Excess water entering the septic tank system, plumbing
installed improperly, roots clogging the system, plumbing
lines blocked, pump failure, absorption field damaged or
crushed by vehicular traffic. |
Fix
leaks, stop using garbage disposal, clean septic tank and
inspect pumps, replace broken pipes, seal pipe connections,
avoid planting willow trees close to system lines. Do not
allow vehicles to drive over or park over lines. Contact
local health department for guidance. |
Wastewater surfaces in the yard. |
Excess water entering the septic tank system, system
blockage, improper system elevations, undersized soil
treatment system, pump failure, absorption field damaged or
crushed by vehicular traffic. |
Fix
leaks, clean septic tank and check pumps, make sure
distribution box is free of debris and functioning
properly, fence off area until problem is fixed, call in
experts. Contact local health department for guidance. |
Sewage odors indoors. |
Sewage surfacing in yard, improper plumbing, sewage backing
up in the building, trap under sink dried out, roof vent
pipe frozen shut. |
Repair plumbing, clean septic tank and check pumps, replace
water in drain pipes, thaw vent pipe. Contact local health
department for guidance. |
Sewage odors outdoors. |
Source other than owner’s system, sewage surfacing in yard,
manhole or inspection pipes damaged or partially removed,
downdraft from vent pipes on roof. |
Clean
tank and check pumps, replace damaged inspection port
covers, replace or repair absorption field. Contact local
health department for guidance. |
Contaminated drinking water or surface water. |
System too close to a well, water table or fractured
bedrock; cesspool or dry well being used; improper well
construction; broken water supply or wastewater lines.
Improperly located wells must be sealed in strict accordance
with state and local codes. |
Abandon well and locate a new one far and upslope from the
septic system, fix all broken lines, stop using cesspool or
drywell. Contact local health department for guidance. |
Distribution pipes and soil treatment system freeze in
winter. |
Improper construction, check valve in lift station not
working, heavy equipment traffic compacting soil in area,
low flow rate, lack of use. |
Examine check valve, keep heavy equipment such as cars off
area, increase water usage, have friend run water while away
on vacation, operate septic tank as a holding tank, do not
use antifreeze. Contact local health department for
guidance. |