Water Resources Center
OSTP

The Water Resources Center is affiliated with the College of Food, Agricultural and Natural Resource Sciences and University of Minnesota Extension.

Antibacterial Products in Septic Systems

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An onsite sewage treatment system or “septic system” is a very effective way to safely recycle household wastewater back into the natural environment. A soil treatment based onsite system will remove all pathogens and most of the nutrients contained in wastewater if it is properly designed, installed, operated and maintained. “Operation” refers to everything we do or put into the system.

To achieve proper treatment, a septic system is very dependent on millions of naturally occurring bacteria throughout the system. We add many of these good bacteria through the wastes and materials typically found in wastewater. Anaerobic bacteria in the septic tank decompose organic materials in the wastewater and aerobic bacteria in the soil destroy disease-causing pathogens.

The use of antibacterial or ‘disinfectant’ products in the home can and do destroy good and bad bacteria in the treatment system. Normal use amounts of these products will destroy some beneficial bacteria but the population will remain sufficient and recover quickly enough to not cause significant treatment problems. Excessive use of these products in the home can cause significant and even total destruction of the population. Often the use of a single product or single application will not cause major problems but the accumulative affect of many products and many uses throughout the home may add up to an excessive total and cause problems.

More research is needed to determine ‘what is excessive?’ and which products are more or less harmful to systems. Recently many products are being marketed as “antibacterial”. Consumers and on-site professionals working to diagnose treatment system problems have many questions about individual products. Questions like ‘how antibacterial is antibacterial?’ and ‘which products are better or worse than others?’ are a couple of them.

Several professionals have reported problems with low or no bacterial activity in systems and upon the removal of antibacterial products from the home, beneficial bacterial activity returns and desired treatment functions resume. These products affect all treatment systems but because of special attention being paid to new ‘alternative’ treatment technologies now being introduced into the on-site industry, it is possible that some systems may be more affected by fluctuating bacterial numbers due to antibacterial products than other systems. More research needs to be done on this as well.

What are these antibacterial products we are talking about? They include: ‘antibacterial’ hand soaps, tub, tile and shower cleaners, drain cleaners, toilet bowl cleaners, laundry bleach products, and others. Also included are ‘antibiotics’ that may be prescribed for medical treatment. These are products that are found in nearly all homes. They often carry a “safe for septic systems” statement printed on the label. The question may be “How Safe?”

The University of Minnesota Extension Service Septic System Owner’s Guide suggests:

To improve septic system performance:

  • Do not use ‘every flush’ toilet bowl cleaners
  • Reduce use of drain cleaners by minimizing the amount of hair, grease, and food particles that goes down the drain
  • Reduce use of cleaners by doing more scrubbing with less cleanser
  • Use the minimum amount of soap, detergent and bleach necessary to do the job. Frequent use of detergents with bleach additives is excessive amounts of bleach.
  • Use minimal amounts of mild cleaners, as needed only
  • Route chlorine-treated water from swimming pools and hot-tubs outside of the septic system
  • Dispose of all solvents, paints, antifreeze, and chemicals through local recycling and hazardous waste channels
  • Do not flush unwanted prescription or over the counter medications down the toilet

All of the practices above work toward preventing the loss of beneficial bacteria throughout the system. Bacterial additives (enzymes, starters) are not necessary and will not compensate for excessive use of antibacterial products.

It might be that in an effort to be “super clean” and protective of the families health through the use of antibacterial products in our homes, we might compromise our health in another way – by damaging our on-site sewage treatment system!