How Septic Systems Work

A septic system, is a small scale sewage treatment system common in places such as on private islands where is not possible to have a connection to the main sewage pipes of a municipality. Traditionally a septic tank is a large, concrete or steel tank that is buried outside of the home.

Today the design of the tank usually incorporates two chambers which are separated by a dividing wall and has openings midway between the floor and ceiling of the tank. Wastewater enters the first chamber of the tank allowing solids to either float to the top in the form of scum or sink to the bottom in the form of sludge. The sludge is broken down via anaerobic bacteria (bacteria that exist without oxygen. The scum and other liquid components flow through the dividing wall into the second chamber where further settlement takes place.

The treated wastewater (effluent) then exits the septic tank into a leach field, which is also called a drain field. A leach field is made of perforated pipes buried in trenches filled with gravel. Dissolved wastes and bacteria in the water are trapped or adsorbed by soil particles or decomposed by microorganisms. This process removes disease-causing organisms, organic matter, and most nutrients (except nitrogen and some salts). The purified wastewater then either moves to the ground water or evaporates from the soil. The size of leach field depends on the amount of wastewater being produced and porosity of the soil. Soils that have a low porosity such as clay will require a larger leach field than highly porous soils such as sand.

Waste that is not decomposed by the anaerobic digestion and not pumped to the leach field remains in the tank and eventually has to be removed from. If the tank is not pumped the septic tank fills up and undecomposed wastewater discharges directly to the drainage field. This is both a costly and environmentally devastating disaster. Septic tanks only require emptying once a year but with careful management the schedule can be reduced to every 3 to five years. A properly designed, installed and maintained septic system requires only periodic inspection and should last around 50 years.

Potential Problems with Septic Tanks

There are numerous things to keep in mind when using a septic system on your island. Excessive dumping of grease, oil, hygiene products and other non biodegradable materials can block drains and cause odor problems thus they should not be allowed to enter the septic system. Avoid dumping chemicals such as herbicides, bleach, or any other harsh chemical into the system. These chemicals can damage the tank and kill important bacteria. Do not plant trees near the septic system as roots can cause the drain field to clog and or rupture the system. If the system is damaged or malfunctions, contact your local health or environmental authority before attempting any repairs. This is especially important on islands as they are particularly sensitive ecosystems. Improper repair can result in costly mistakes, environmental damage and health hazards.

Tips for Maintaining Your Septic System

The added isolation of being on an island means you want to minimize potential malfunctions and reduce the amount of times it needs to be emptied. Here are some tips for maintaining you septic system.

• Plant grass over the septic bed system but do not ant shrubs or trees as roots can damage the leach bed pipes.

• Promptly fix and water leaks or drips and make efforts to conserve water such as using low flow faucets.

• Be careful not to overload your system. This means do not run dishwashers, toilets and showers at the same time. Stagger your usage over the course of the day and week

• Do not use garbage disposals and minimize the solids that are added to the system. Increasing solids, decreases capacity thus increasing the frequency of pumpings. In addition do not pour fats or oils down the drain, these materials can clog septic tank pipes.

• Hire a licensed professional to pump the waste out of your tank and have the tank inspected for cracks and leaks. It is important to remember in many areas around the world, including the United States it is illegal to attempt to fix your own septic tank. Therefore don’t risk harm to yourself, others, or the environment. Hire a qualified professional to perform any maintenance or repairs.

In regions where there are numerous inhabited islands or regions that are highly developed there is most likely a companies that can come to your island to pump the tank and perform maintenance. Before installing a septic system on your island ensure that there is local septic service. In the event that septic service is not available consider investing in a composting toilet and filter bed system.

Sources:

http://www.agnr.umd.edu/users/wye/personel/Miller/septic.html

http://en.wikipedia.org/wiki/Septic_tank

Filed under: Sanitation & Development, Septic Systems