Your carbon footprint is not the only measure of the sustainability of your lifestyle. An ecologically sustainable life is in natural balance and respectful of humanity's dependence on the Earth's natural ecological cycles. Preserving precious water resources, clean air and open land are necessary to maintaining the earth’s ecological cycles. One of the steps that a large portion of us can take is to understand and maintain our septic systems. It is estimated by various sources that 25-35% of all US homes use septic systems.
There are many different types of septic system designs. The most common type used for single family homes consists of a septic tank and leach field. A septic tank can be an anaerobic (without air) tank or an aerobic tank (with air). The anaerobic system is a single chamber tank that receives the toilet and drain waste from the house and allows the solids to settle down to the bottom of the tank where the anaerobic bacteria that live in the tank digest the organic materials while the effluent (water around all that stuff) flows out to the leach field to be purified by passing through soil until it reaches the groundwater. Scum consisting of oil and grease floats on top of the water layer and can be pulled into the leach field limiting its effectiveness.
The septic tank effluent water is either pumped or allowed to flow to a leach field or other soil absorption system, where it percolates into the soil, which provides final treatment by removing harmful bacteria, viruses, and nutrients. Suitable soil is necessary for successful waste water treatment. The “percolation rate” is the rate at which water moves through soil. The acceptable rates are between one minute and one hour per inch of soil. Take either more or less time for the water to pass through your soil and the natural soil is unsuitable for treatment of the waste water. If the water moves too slowly through the soil the leach field will flood with contaminated, foul smelling water or the water will back up into the house. If the water moves too quickly thought the soil the water will be untreated and contaminate nearby ground or surface water.
An aerobic system consists of a multi chamber tank or several tanks. After separation of solids in the first tank waste is forced through a filter into a second chamber or tank where air is pumped in to enhance aerobic bacteria which decomposes the organic material. The waste then flows into a third chamber or settling chamber which collects the bacteria and passes the liquid on to the leach field or drip field. Aerobic systems can remove more than 90% of the organic material and suspended solids within the tanks themselves, but require much more maintenance. (These systems are like the British sports cars of the septic world.) The biological load delivered to the leach field or other absorption system is much reduced and would allow (if permitted under regulation) the successful treatment of septic waste where soils are rocky, impermeable or groundwater is particularly shallow.
Indoor water use in the typical single-family home is between 50-70 gallons per person per day. Septic systems are sized by bedrooms, which is an estimate of the number of people living in a home. However, even if the number of people living within your home is appropriate for the size of the septic system, you can still overload the system. Use too much water in a short period of time and the system will be overwhelmed. Each time the system is overwhelmed untreated sewage will leave the tank and begin to clog the leach field. A leaky toilet alone can add as much as 200 gallons of waste water to the system each day. The less water used the less water enters the septic system, and reduces the risk of failure. If the amount of waste water entering the system is more than the system can handle, the waste water containing raw sewage eventually backs up into the house or yard and creates a health hazard. By the time you can smell or see a problem, however, the damage to the leach field might already be done. Replacement of a leach field can run to the tens of thousands of dollars. So caring for your septic system not only cares for the earth but also cares for your wallet. By limiting your water use and spreading out peak demands on the system you can reduce the amount of waste water your system must treat. When you have your system inspected and pumped as needed, you reduce the chance of system failure.
The US EPA’s Homeowner’s Guide to Septic Systems is a terrific basic guide to caring for and maintaining your septic system. Follow the Dos and Don’ts and your septic system may last forever. Remember though, what goes into your septic system goes into the earth. Rethink the products you use to clean your house. Paint, solvents, gasoline, insecticides and poisons should never go down your drain. Every chemical you pour down your drain is buried in your yard. In a multitude of ways your yard is part of the earth’s yard.