What is an Aerobic Septic System?
An aerobic septic system also known as an aerobic treatment system (ATS), is a small-scale sewage treatment system similar to a septic tank system, but which uses an aerobic method to digest sewages rather than just the anaerobic process used in septic systems.
An aerobic septic system works like a septic tank system, but the aerobic septic system uses an aerobic process instead of the anaerobic process.
These systems are often found in rural areas where there are no public sewers and can be used for a single residence or for a small group of houses.
Unlike the traditional septic system, the aerobic treatment system generates high-quality secondary wastewater that can be sterilized and used for surface irrigation. This allows much greater flexibility in the placement of the leach field, as well as cutting the required size of the leach field by as much as half.
Aerobic Treatment Units (ATUs) use many of the same processes as a municipal sewage plant but on a smaller scale. The aerobic system injects oxygen into the treatment tank.
The additional oxygen increases natural bacterial activity within the system which then provides additional treatment for nutrients in the effluent. Some aerobic systems may also have a pretreatment tank and a final treatment tank including disinfection to further reduce pathogen levels.
The benefits of this system are that it can be used in homes with smaller lots, inadequate soil conditions, in areas where the water table is too high, or for homes close to a surface water body sensitive to contamination by nutrients contained in wastewater effluent. Regular lifetime maintenance should be expected for ATUs.
How Does an Aerobic Septic System Work?
There are Convectional septic systems and then there are more complex aerobic septic systems. The difference is, in words: oxygen. While a Conventional septic system uses only the septic tank to separate solids, fats, and grease, an aerobic treatment unit (ATU) uses oxygen infusion for digestion rather than the anaerobic process.
Just as in the case of a conventional system, an aerobic septic system uses a natural process to treat wastewater. An oxygen-rich bacterial environment works to digest and break down sewage inside the Aerobic Treatment Unit.
This Treatment is Done in Stages:
- Pre-Treatment: this can mean having a septic tank staged in front of the ATU or an ATU can have a setting or Trash tank as part of the unit. This pre-treatment stage will separate the solids from the wastewater.
- Aeration Chamber: Forced air mixes with the wastewater either by an air compressor or a blower. This step supports aerobic bacterial growth that will aid in the digestion of solids in the wastewater.
- Disinfection: This step involves an additional treatment stipe to the effluent leaving the ATU. This can mean the use of chlorine or ultraviolet light.
- Final Treatment Disposal: The effluent leaving the ATU is discharged into a drain field, whether it be a sand filter, absorption field or an evapotranspiration bed.
What is an Aerobic treatment unit?
Aerobic units treat wastewater for homes and small businesses using the same process, only scaled-down, as our municipal wastewater treatment systems use. They remove 85 to 98 percent of the organic matter and solids from the wastewater, producing effluent as clean as that from municipal wastewater treatment plants, and cleaner than that from conventional septic tanks.
Aerobic units, which are certified as Class I aerobic systems, treat wastewater well enough to be used in conjunction with spray systems, which distribute treated wastewater over lawns. They are the most common way to treat wastewater for spray systems.
Components of Aerobic treatment unit
The aerobic treatment process includes four main components that work together to purify wastewater:
- A pretreatment tank is generally referred to as the “trash tank” because it removes materials that microorganisms (microbes) cannot degrade.
- An aeration chamber, where aerobic microbes decompose waste in the water. An aeration system consists of an air pump, piping, and diffusers that force air into the aeration chamber. The air pump, located near the aerobic tank, compresses air to flow into the aeration chamber. The diffuser forces the air into the water, dividing the air into bubbles that float to the surface. The oxygen in the air bubbles goes into the water for the microbes, while the rising bubbles mix with the water.
- A settling chamber, commonly called a clarifier, provides a place for the microbes that have treated the wastewater to settle out of the water.
- A land application system distributes the wastewater into the soil for final treatment and disposal/reuse. Aerobic treatment units usually disperse wastewater via spray distribution systems, which include a disinfection component for removing disease-causing microorganisms, a pump tank for dosing water, and spray heads for spreading the water over the ground.
How Does an Aerobic Treatment Unit Work?
Aerobic systems treat wastewater using natural processes that require oxygen. Bacteria that thrive in oxygen-rich environments break down and digest the wastewater inside the aerobic treatment unit as they are suspended in the liquid. Like most onsite systems, aerobic systems treat wastewater in stages.
By bubbling compressed air through liquid effluent in a tank, ATUs create a highly oxygenated (aerobic) environment for bacteria, which uses organic matter as an energy source. In another stage bacteria and solids settle out of the wastewater and the cleaner effluent is distributed to a soil treatment system.
ATUs are more complicated than septic tanks. In a septic tank, solids are constantly separated from the liquid. As individual bacterial cells grow, they sink to the bottom, along with less decomposed solids, to form a layer of sludge. Floating materials, such as fats and toilet paper, form a scum layer at the top of the tank.
In an ATU, the bubbler agitates the water so solids cannot settle out, and floating materials stay mixed in the liquid. Well-designed ATUs allow time and space for settling while providing oxygen to the bacteria and mixing the bacteria and its food source (sewage). Any settled bacteria must be returned to the aerobic portion of the tank for mixing and treatment.
How To Maintain Your Aerobic Septic System?
To remain effective, aerobic treatment unit components need regular maintenance. Poorly maintained systems may not produce water as clean as desired.
For the best care for an aerobic treatment unit, follow the manufacturer’s recommendations. Use these general guidelines as a basis for maintaining your system. They are divided into practices provided by a maintenance contractor, and those performed by the homeowner.
What To Do:
1. Regularly Inspect Your Septic System
While your aerobic system may be highly effective, it may require periodic inspections, septic tank cleaning, and emptying. Routine maintenance can help significantly increase the life service of your septic system. Gravity systems may require cleaning every three years, pressure distribution systems every year as do mound or sand filter systems.
2. Pump Out Whenever Necessary
As the septic company carries out its inspection, they may recommend pumping your septic tank. The frequency depends on several factors, including the size of the tanks, the amount of water used in the household, among others. Generally, residential septic systems require pumping after every three to five years.
3. Be Water-Wise
You may need to control water usage within the home. Too much water is a frequent factor in failed aerobic systems. It also causes your tank to fill up faster, requiring frequent pumping.
4. Use Licensed, Certified Companies
Your aerobic system should be repaired or maintained by certified maintenance providers. There’s a lot more to servicing a septic tank than adding chlorine tablets. Research and verify the experience of the maintenance team sent to our home.
What not To Do:
1. Flush Solids Down the Drains
Avoid putting just anything down the toilets or the drains. Solids and grease that flush down the septic pipes may require treatment and contribute to the sludge buildup. Your aerobic system is designed to treat domestic wastewater.
2. Pour Harsh Chemicals into Your Toilets
Chemicals destroy the bacteria in your aerobic system that are necessary to break down the solids. The chemicals are also corrosive, eating away at your drainage pipe. Find appropriate ways to dispose of the chemicals by contacting your local public health hazard waste line.
3. Park Cars or Trucks On Your Drain field Or Reserve Area
Heavy machinery resting over your septic tanks can pack down the soils over the aerobic system, leading to system failure. Additionally, you can prevent your pipes from breaking from the extra weight.
Additionally, avoid planting your flower garden over the septic tanks. Full tanks may require immediate attention, and you do not wish to hold back the septic company from destroying your flowers while your home is bubbling with waste.
4. Add Septic Tank Additives
Homeowners are often trying new products for their septic tank service, some which aren’t approved by the local Department of Health. The products may be harmful, adding extra solids to the system.
Additionally, the chemicals can pollute ground and surface water. This includes the use of swimming pool chlorine tablets as chlorinators. Only calcium hypochlorite tablets are approved for treating domestic wastewater.
Types Of Aerobic Treatment Systems
Small-scale aerobic systems generally use one of two designs, fixed-film systems, or continuous flow, suspended growth aerobic systems (CFSGAS). The pre-treatment and effluent handling are similar for both types of systems, and the difference lies in the aeration stage.
1. Fixed film systems
Fixed film systems use a porous medium that provides a bed to support the biomass film that digests the waste material in the wastewater. Designs for fixed film systems vary widely but fall into two basic categories.
The first is a system where the media is moved relative to the wastewater, alternately immersing the film and exposing it to air, while the second uses a stationary media, and varies the wastewater flow so the film is alternately submerged and exposed to air.
In both cases, the biomass must be exposed to both wastewater and air for aerobic digestion to occur. The film itself may be made of any suitable porous material, such as formed plastic or peat moss. Simple systems use stationary media and rely on intermittent, gravity-driven wastewater flow to provide periodic exposure to air and wastewater.
A common moving media system is the rotating biological contactor (RBC), which uses disks rotating slowly on a horizontal shaft. Nearly 40 percent of the disks are submerged at any given time, and the shaft rotates at a rate of one or two revolutions per minute.
2. Continuous flow, suspended growth aerobic systems
CFSGAS systems, as the name implies, are designed to handle continuous flow, and do not provide a bed for a bacterial film, relying rather on bacteria suspended in the wastewater.
The suspension and aeration are typically provided by an air pump, which pumps air through the aeration chamber, providing a constant stirring of the wastewater in addition to the oxygenation.
A medium to promote fixed film bacterial growth may be added to some systems designed to handle higher than normal levels of biomass in the wastewater.
3. Retrofit or portable aerobic systems
Another increasingly common use of aerobic treatment is for the remediation of failing or failed anaerobic septic systems, by retrofitting an existing system with an aerobic feature.
This class of product, known as aerobic remediation, is designed to remediate biologically failed and failing anaerobic distribution systems by significantly reducing the biochemical oxygen demand (BOD5) and total suspended solids (TSS) of the effluent.
The reduction of the BOD5 and TSS reverses the developed bio-mat. Further, effluent with high dissolved oxygen and aerobic bacteria flow to the distribution component and digest the bio-mat.
4. Composting toilets
Composting toilets are designed to treat only toilet waste, rather than general residential wastewater, and are typically used with water-free toilets rather than the flush toilets associated with the above types of aerobic treatment systems.
These systems treat the waste as a moist solid, rather than in liquid suspension, and therefore separate urine from feces during treatment to maintain the correct moisture content in the system.
An example of a composting toilet is the clivus multum (Latin for ‘inclined chamber’), which consists of an inclined chamber that separates urine and feces and a fan to provide positive ventilation and prevent odors from escaping through the toilet.
Within the chamber, the urine and feces are independently broken down not only by aerobic bacteria, but also by fungi, arthropods, and earthworms.
Treatment times are very long, with a minimum time between removals of solid waste of a year; during treatment, the volume of the solid waste is decreased by 90 percent, with most being converted into water vapor and carbon dioxide. Pathogens are eliminated from the waste by the long durations in inhospitable conditions in the treatment chamber.
What is a Conventional System?
A decentralized wastewater treatment system consisting of a septic tank and a trench or bed subsurface wastewater infiltration system (drain field). A conventional septic system is typically installed at a single-family home or small business.
The gravel/stone drain field is a design that has existed for decades. The name refers to the construction of the drain field. With this design, effluent is piped from the septic tank to a shallow underground trench of stone or gravel. A fabric or similar material is then placed on top of the trench so sand, dirt, and other contaminants do not enter the clean stone.
Effluent filters through the stone and is then further treated by microbes once it reaches the soil below the gravel/stone trench.
Gravel/stone systems are relatively large in overall footprint and may not be suitable for all residential sites or conditions.
How Much Does It Cost Aerobic Septic System?
Aerobic septic systems require aerobic bacteria (bacteria that like oxygen) as well as an air pump to aerate the septic tank and promote waste breakdown. Though costs vary depending on the size of the system, soil conditions, and location, aerobic setups are more complicated than their anaerobic counterparts and come at a higher price.
- Site evaluations and permits have an average cost between $200 and $400.
- An aerobic septic system has an average cost between $10,000 and $20,000.
- You need to have the system professionally inspected and pumped every one to three years, which has an average cost of $200.
- Aerobic systems may need motor & timer replacements from time to time. Motor replacements have an average cost between $500 & $600 and timers average $100.
How to Pick the Best Septic Air Pump?
The septic air pump is literally the lifeline of your aerobic system. The system cannot function the way it was designed without the air pump working. The actual purpose of the air pump is two-fold.
First, the air pump puts oxygen into the water allowing the formation and survival of Aerobic bacteria. These Aerobic bacteria are what eat up all of the waste in the tank. They are much larger and more efficient at processing waste as compared to the anaerobic bacteria found in a conventional septic system.
Secondly, the air pump creates an action in the tank that breaks down large solids into tiny particles, making it very easy for the bacteria to attach to and devour the waste.
If your air pump quits working on your aerobic system, over a period of about 2 weeks the system will begin to turn back anaerobic. The biggest problem with this happening is that there is no secondary treatment system behind your aerobic system, as you have in a conventional anaerobic septic system.
Once the aerobic system turns back anaerobic, instead of producing a clear odorless discharge the effluent will be closer to raw sewage.
As you may realize, raw sewage discharging into a ditch, lake, or pond, or being sprayed on your lawn is not a good thing. This is why it is important to your system for the air pump to be up and running.
7 Reasons Why You Need Aerobic Septic Systems on Your Property
Septic systems are a crucial part of many commercial and residential properties. Lack of a well-functioning septic system means that waste cannot be disposed of properly. Your home or building, as a result, will be a hazard to your health and that of your loved ones or clients.
If you want your septic tank to run properly, you must pump it on a regular basis. On average, you should ensure that your home septic tank is cleaned every three to five years.
When choosing a septic tank for your home or building you will have two options. One of these options is aerobic septic systems. Keep reading to find out why you should choose an aerobic septic system.
- Longevity: On average, a properly installed and well-maintained septic tank can last up to 40 years. Regular septic tank cleaning and inspection will keep your aerobic system functional for many years. Proper septic system installation is key to ensuring that your septic system lasts long.
- Requires Little Space: The size of a septic tank is determined by the number of occupants in your home or building. As such, some septic tanks require a lot of space. If you have limited space, this could be a problem. However, aerobic septic systems require little space.
- Provides Higher Level of Treatment: An aerobic septic system gives you cleaner treated effluent, so there is less likelihood of groundwater contamination. If your home is located in an area with a high-water table, it is advisable to install an aerobic septic system to avoid water pollution.
- Environmentally Friendly: With aerobic septic systems, water used for laundry or showers can be recycled to water your lawn. The water is moved through the system and treated, then recycled. If you are looking to go green and conserve the environment, an aerobic septic system is ideal for you.
- Breaks Down Household Waste Faster: Compared to its counterparts, an aerobic septic system breaks down solid wastes faster. As a result, the waste does not accumulate to alarming levels. You will, therefore, not need to pump your septic tank system frequently.
- Suitable In All Types of Land: One of the greatest benefits of aerobic septic systems is that they can be used in all types of land. Other septic systems cannot be used in land with high groundwater. No matter the type of soil you have, an aerobic septic system will be suitable. Aerobic septic systems are designed to work well and be compatible with all types of soil.
- Saves You Money: An aerobic septic system treats most of the wastewater inside the tank. As a result, the drain field does not require frequent repair. You get to save money that would have otherwise been used on drain field repair.
Advantages of Aerobic Septic Systems
- A higher level of effluent treatment
- Useable on poor soil types
- Used for challenging lot spaces and restrictive topography
- Used in setback constrictions to property lines, open water sources, aquifers
- Greener – utilizes smaller drain field footprints
- Proven to extend drain field life span
- Greatly reduces drain field clogging
- Great for water conservation, many states allow for irrigation
- Reduces nitrogen
- Offsets initial costs by extending overall system performance and longevity
Disadvantages of Aerobic Septic Systems
- Blower noise
- Slight smell if not vented properly
- Draws more power
- Maintenance is not an option
- Higher initial installation costs
- Poorly maintained systems can cause contamination
- Too much water can overburden the system
- Cold weather can have adverse effects, and must be insulated.