When non-biodegradable waste items (like cigarette butts, cotton swabs, and menstrual hygiene products) are flushed down toilets, they end up in your septic tank. These solids float on the surface of the wastewater and form a layer called scum.
The heavier materials settle to the bottom of the tank as sludge. The remaining liquid is discharged through a pipe into an absorption area in the soil outside your home called a drain field or leach field. Click Here to learn more.
Wastewater is black water from toilets and grey water from sinks, bathtubs, showers, and washing machines. It flows through a sewer line that slopes toward your septic tank. The wastewater enters the tank through an inlet pipe. The tank is a buried, watertight container made of concrete, fiberglass, or polyethylene. It holds the wastewater long enough for solids to separate by settling and flotation. The septic tank is usually situated 50 feet or more away from the house.
Oils and other substances lighter than water float to the top of the wastewater in the tank, forming a layer known as scum. Bacteria in the septic tank do their best to break down these substances. Solids that are heavier than water settle to the bottom of the tank, forming a sludge layer. The septic tank has a liquid waste outlet, called an effluent pipe, that moves the pre-processed liquid out of the septic tank.
The septic tank must be emptied periodically to avoid overflow or clogs. The amount of wastewater that needs to be pumped out depends on the tank’s volume, the amount of organic solids, and other factors.
Once the septic tank is empty, the liquid waste moves through a distribution system of pipes and into an absorption field or soakaway. These are usually composed of trenches containing perforated pipes and gravel covered by a layer of soil. Filtration, evaporation and natural soil processes further break down the wastewater.
Some septic systems have additional treatments to eliminate phosphorous and nitrogen from the wastewater before it enters the groundwater supply. It is important to keep non-organic materials out of the septic tank and system, because they can block solids from entering the drain field and cause other problems. It is also a good idea to map out your septic system components and mark them with stakes, so you can prevent damage when performing routine yard work or home maintenance. Avoid parking vehicles or structures over the drainage field or septic tank and pump station.
Sludge
A septic tank is designed to hold wastewater long enough for solid matter to undergo a process of separation. This allows grease, oils and fats to float to the top of the waste water layer, known as scum, while the heavier sediments sink to the bottom and form a dense sludge layer. Compartments and a T-shaped outlet prevent sludge and scum from exiting the tank, traveling through the drainfield, and polluting the soil and waterways.
A key part of septic system success is the bacteria that digest the sewage. Aerobic bacteria, which use oxygen, break down the scum layer in the tank. Bacteria in the sludge layer at the bottom of the septic tank decompose the rest of the sewage using anaerobic digestion, which doesn’t require oxygen. This process produces methane, carbon dioxide and hydrogen sulfide, which are the strong odors associated with septic systems.
Over time, the sludge layer grows thicker and denser as the bacteria decompose the organic material. When the sludge reaches a certain thickness, it becomes indigestible and is discharged from the septic tank through a second pipe called the drain field. The septic system’s drain field is an area of perforated pipes that filter out the remaining sewage into the soil.
It is essential that the septic tank be pumped out regularly to ensure the bacteria remain active and the sludge layer stays thin. If too much sludge builds up, it may reduce the tank’s effective volume and shorten the retention time. As a result, the septic tank may fail to separate solids from liquid wastewater before it is discharged into the drainfield, where solids can clog the drainfield’s piping or decrease the soil porosity and lead to failure of the system.
Keeping the septic tank clean is also essential to protect the health of household members and the surrounding environment. Avoid flushing non-biodegradable items, such as plastics, into the drains or toilets. Only flush “the 3Ps” – pee, paper and poop – down the toilet! Never dump chemicals into the septic tank, such as chemical cleaners and disinfectants, or bleach, as they can destroy or disrupt the bacteria populations in the septic tank and leach field.
Gases
A septic tank is a large, underground storage vessel that holds wastewater and solid waste. Its job is to filter the water before it enters groundwater, protecting the environment and preventing disease and contamination. A septic tank can also prevent overflowing sewage, which can cause damage to the environment and the surrounding area. When you notice strong sewage odors coming from your drains, it could be a sign that your septic tank is overflowing and needs to be emptied.
Aside from aerating the wastewater, the septic tank also separates the solid waste through both settling and flotation. Substances that are lighter than water float to the surface, where they form a scum layer. Aerobic bacteria digest these substances. The separated effluents flow into a second chamber. The septic tank must have adequate ventilation, because the decomposed organic matter in the septic tank produces toxic gases.
These gases include methane and hydrogen sulphide, which are produced by the anaerobic digestion of septage in the absence of oxygen. Methane is highly flammable, and it can explode in an oxygen-deficient space such as an enclosed septic tank. It is also a known greenhouse gas. Hydrogen sulphide, on the other hand, is poisonous and has a rotten egg smell. High concentrations of this gas can lead to respiratory irritation, vomiting, and even death.
Septic tanks are a cost-effective alternative to sewer systems in new construction. They are especially useful in rural areas where connecting to the sewer system would be too expensive. However, homeowners with septic tanks should consider the pros and cons of converting to a sewer system before making any major decisions.
In this study, the conditions inside septic tanks were monitored with sensors to measure the septage conditions in their first compartment. Sensor data were collected from 10 septic tanks (ST1-ST10) that received only blackwater from cistern-flush toilets. Sensor readings were taken on a daily basis for three months at each septic tank. A total of 12 parameters were correlated with the CH4 emissions from the first compartment, including ORP, biodegradable carbon mass, and temperature. Results showed that the conditions in the first compartment of the septic tank were diurnally stable.
Venting
Many people dream of moving to a rural area and living on a homestead. If that is the case with you and you are considering a home with a septic tank, there are some things to consider before making your move.
As wastewater goes through the septic tank, a process called anaerobic digestion takes place where solids are broken down. This process produces gases which must be released to prevent pressure buildup within the tank. Without the proper venting, these gases may travel through your plumbing system and cause slow drains or gurgling sounds in your toilets and sinks. Properly vented septic systems also allow the foul odors generated by the breakdown of waste materials to escape into the environment, rather than into your living spaces.
Venting is a critical part of septic systems, and it is important to keep them clear of obstructions, especially during winter when snow and ice can block the vent openings. In addition, septic tanks should be positioned in a way that is less likely to be covered by landscaping or other structures, which could also block the vent openings.
The septic system venting pipe is sometimes referred to as the “candy cane” pipe, and it is shaped like that to allow air into the leach field while keeping rain, snow, and small animals out. The size of this vent pipe is typically determined by local regulations. It should be the correct size to avoid any clogs or blockages.
A well-maintained septic tank can provide years of reliable service, but it must be inspected and pumped on a regular basis. A professional septic tank pumper can inspect the septic tank layers, determine the level of sludge in the septic tank and perform the necessary maintenance to ensure that the septic tank is working properly.
If you are thinking of buying a home with a septic system, you should make your offer contingent upon a septic inspection. It is a relatively inexpensive and easy step to take that can help to reduce the risk of buying a house with a failing septic tank system.
