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Septic
Tank Additives
Editor’s
Note: The following questions are based
on calls received over the National Small Flows Clearinghouse’s technical
assistance hotline. The information was compiled by the technical assistance
staff. If you have a question, call (800) 624-8301 or (304) 293-4191.
How does my septic system work?
Household wastewater flows into the septic tank, where it is collected
to separate the solids—both floatable and settleable—from the
liquid portion, called the “effluent.” During a retention time
of 24–48 hours, settleable (heavier) solids collect in the bottom
of the tank to form a sludge layer. Floatable solids, such as greases,
oils, and fats, collect at the surface to form a scum layer. The partially
clarified effluent empties into the soil absorption system.
The purpose of the soil absorption system is to further treat and provide
final disposal of the septic tank effluent. As the wastewater flows through
a soil absorption system, it is treated by natural processes (physical,
chemical, and biological) in the soil. This is how a septic system works
in treating wastewater through natural processes with minimal human intervention.
As with most processes found in nature, man has attempted to mitigate
the natural treatment process found in a septic system to enhance the
efficiency and capability of the system or correct a malfunction. This
has resulted in the manufacture and marketing of septic tank additives
to solve every possible problem a septic system may encounter.
What are the different types of septic tank
additives?
Recent interest in wastewater treatment and disposal has led to the use
of additives, stimulators, or enhancers for a septic system. It has been
suggested that additives can be used in a septic system to accelerate
digestion of biosolids, break up scum, improve settling through coagulation,
or rejuvenate a clogged soil absorption system. However, it should be
understood that, in most cases, the purpose of using an additive is to
digest or “liquefy/gasify” the solids in a septic tank, rejuvenate
stressed bacterial populations in the septic tank, or increase settleability
of solids in the septic tank.
There are two distinct categories of additives used in a septic system:
1) chemical, includes inorganic and organic compounds and 2) biological,
includes yeast, bacteria, and enzymes. There are approximately 1,200 additive
products on the market today, many of which contain enzymes that can be
purchased through septic tank pumpers, discount stores, and chemical companies.
Is there research on septic system additives?
Over the past 40 years, there have been several studies conducted on septic
tank additives; however, there is still some debate on their effectiveness.
Part of the problem stems from the number of additives that are marketed
and the lack of an established standard testing method for all additives.
Complicating this situation is the debate between additives manufacturers
and independent researchers regarding which effects are deemed beneficial
and which are deemed detrimental. Currently, there is contention as to
whether or not increasing the friability, or breakup, of the scum layer
or enhancing the anaerobic decomposition process is beneficial in septic
systems.
Notable studies conducted include university research by William Sack,
Ph.D., John T. Winneberger, Ph.D., and Rein Laak, Ph.D., as well as manufacturer
research by L&F and INTERBIO. Several other research studies on additives
were also conducted and are discussed in the following sections. Recently,
the National Association of Waste Transporters (NAWT) conducted an independent
field study on 12 septic tanks using additives. The data collected from
this study are currently being analyzed, and the results should be available
soon.
What are the beneficial or detrimental effects
of additives from various research studies conducted?
The beneficial effects of biological additives on the septic system are
still being debated, but two benefits may ultimately be identified. Based
on available literature, enzymatic products might have the ability to
reduce the amount of oil and grease in the septic tank. Second, under
septic tank bacterial “die-off” conditions, slight reductions
in the amount of effluent solids have been achieved by using additives.
A research study by Mark Gross, Ph.D. has shown that septic tank “die
off” conditions occur when the bacteria in a septic tank are destroyed
due to the presence of toxic substances. Die-off conditions were observed
when adding a concentration of 1.85 gallons of liquid bleach, 5.0 gallons
of liquid Lysol cleaner, or 11.3 grams of Drano drain cleaner to a standard
1,000-gallon septic tank. Other factors that can cause die-off include
the use of anti-bacterial agents, and, in certain cases, medications taken
by the homeowner.
However, research conducted by Winneberger, et al., suggests that some
biological additives may increase the biological activity to the point
where excess solids can be carried into the soil absorption system. This
occurs when anaerobic decomposition of solids causes the formation of
methane gas. As they rise, bubbles push solids up from the settled portion
of the septic tank. Ultimately, this may lead to solids “carryover”
to the soil absorption system where clogging can ensue.
Contrary to the ability of enzymatic products to reduce scum, the effects
of degradation in the scum layer are believed to be detrimental to a soil
absorption system. The scum layer “holds” fats, grease, and
floatables, preventing their escape to the soil absorption system. Enzymatic
products can “break up” this scum layer and increase its mobility,
allowing it to enter the soil absorption system.
Some chemical additives that have been used in septic systems include
hydrogen peroxide, sulfuric acid, formaldehyde, baking soda, and alum.
J. Harkin proposed that hydrogen peroxide could be used to restore the
infiltrative capacity of a failed or clogged soil absorption system. However,
it was also reported from another study that hydrogen peroxide could agitate
soils containing fines (clayey and loamy soil), destroying the soil structure,
thereby decreasing the soil’s permeability.
A number of products sold over-the-counter for soil absorption systems
and clogged drain pipes contain sulfuric acid, which is highly corrosive
in concentrated form. This could affect the microbial population in the
septic tank and soil absorption system, and contribute to structural weakness
when applied directly to a concrete tank. The use of sulfuric acid might
result in severe burns if it comes into contact with human skin.
It should be noted that the federal government does not control the use
and disposal of hazardous substances in small quantities purchased from
supermarkets. Additives used to control odor by controlling excessive
anaerobic growth may contain formaldehyde, paraformaldehyde, quarternary
ammonium, and zinc sulfate as active ingredients. Although these chemicals
are biodegradable with dilution, they are biocidal at full strength.
Organic chemicals used in additives include organic solvents or surfactants
that have been reformulated to make the product safe for the environment.
Even at these approved safe levels, napthalenes, alkanes, and benzenes
sometimes used as ingredients in portable toilet cleaners and deodorizers
are significant pollutants, and should not be added to a septic system.
Do I need to use an additive in my septic system
to keep it working?
A homeowner does not need to add a stimulator or an enhancer to a septic
tank that is designed, operated, and maintained properly—naturally
occurring bacteria are already present within human fecal matter. Contrary
to popular belief, yeast, dead chickens, possums, or raw hamburger do
not need to be added to the septic tank.
Chemical additives, such as caustic hydroxides and sulfuric acid, should
never be added to a septic system. Adding these products will destroy
the bacterial population in the septic tank, change the permeability characteristics
of the soil absorption system, and may cause groundwater contamination.
Often, manufacturers of biological additives market their use to restore
the bacterial balance in a septic tank on a monthly basis as part of a
routine maintenance program. This is not necessary because these bacteria
already reside in human feces.
There are special instances when the use of a biological additive may
be warranted, such as when homeowners take antibiotics or other prescription
medications. However, it should be noted that research is still needed
in this area.
Claims made on the effectiveness of additives to either eliminate pumping
of a septic tank or restore permeability of the soil absorption system
are unsubstantiated. No product will allow a homeowner to escape a regular
septic tank pumping and maintenance schedule.
The debate on the issue of using an additive can be resolved only through
a cooperative research effort from independent/unbiased researchers (such
as universities and research centers) and additive manufacturers to determine
their true effectiveness and reveal their limitations.
If you have additonal questions about septic tank additives, call NSFC
at (800) 624-8301 or (304) 293-4191.
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