Septic Tank Additives  -  (Taken from Small Flows Quarterly Magazine)

Editor’s Note: The following questions are based on calls received over the National Small Flows Clearing- house’s technical assistance hot line. 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 theseptic 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 surfaceto 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, manhas attempted to mitigate the natural treatmentprocess found in a septic system to enhance theefficiency and capability of the system or correcta malfunction. This has resulted in the manufacture and marketing of septic tank additives tosolve every possible problem a septic systemmay 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 onavailable literature, enzymatic products mighthave the ability to reduce the amount of oil andgrease in the septic tank.  Second, under septictank bacterial "die-off" conditions, slight reductions in the amount of effluent solids have beenachieved by using additives.

A research study by Mark Gross, Ph.D. has shownthat septic tank "die off" conditions occur whenthe bacteria in a septic tank are destroyed dueto the presence of toxic substances. Die-off conditionswere observed when adding a concentration of 1.85 gallons of liquid bleach, 5.0gallons of liquid Lysol cleaner, or 11.3 grams of Drano drain cleaner to a standard 1,000-gallonseptic tank. Other factors that can cause die-off include the use of anti-bacterial agents, and, in certain cases, medications taken by the home-owner.  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 productsto reduce scum, the effects of degradation in thescum layer are believed to be detrimental to asoil absorption system. The scum layer "holds"fats, grease, and floatables, preventing their escape to the soil absorption system. Enzymaticproducts can "break up" this scum layer and increase its mobility, allowing it to enter the soilabsorption system.

Some chemical additives that have been usedin septic systems include hydrogen peroxide, sulfuric acid, formaldehyde, baking soda, and alum.J. Harkin proposed that hydrogen peroxide couldbe 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, therebydecreasing 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 themicrobial 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 includeorganic 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 sometimesused as ingredients in portable toilet cleanersand deodorizers are significant pollutants, andshould 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 septictank.

Chemical additives, such as caustic hydroxides and sulfuric acid, should never be added toa septic system. Adding these products will destroy the bacterial population in the septic tank,change the permeability characteristics of thesoil absorption system, and may cause groundwater contamination.   Often, manufacturers of biological additives market their use to restore thebacterial balance in a septic tank on a monthlybasis as part of a routine maintenance program.This is not necessary because these bacteria already reside in human feces.