Aerobic Septic System – Design & Installation


Aerobic septic systems are not the same as standard septic systems because they use aerobic bacteria where as standard septic systems use anaerobic bacteria. Aerobic bacteria require oxygen and can work much faster than anaerobic bacteria, which means that they can dispose of more effluent in less time and therefore require less space. Another difference between the two septic systems is that the aerobic system requires electricity and therefore requires regular maintenance and has more costs associated with it. The electricity is used to power a mechanism that introduces the air into the effluent which the bacteria use to help in their digestion of the waste materials. Aerobic septic systems are often brought in to replace aging or failing anaerobic septic systems. An Aerobic septic system is also an option if you have limited space as they do not require a large piece of land to install like a traditional septic system does. Just so you know, sometimes an aerobic septic system is referred to as an aerator septic tank.

Aerobic Septic Tank

Aerobic Septic System Installation

When installing these units you have the option of installing them above ground or below ground. Whatever you decide, keep in mind that they require electrical connections and easy access for regular maintenance. You will also have to install a pretreatment set up, which the manufacturer will provide to you.

Aerobic Septic System Benefits/Costs

The cost of an aerobic system varies based on location, installation, size, design, and maintenance requirements. A good rule of thumb is that aerobic septic tanks can cost two to three times as much as a traditional septic tank.

Savings created with an aerobic septic system are realized in a variety of ways. The aerobic units require less space and generally cause less groundwater pollution which is very important, especially if you live on well water. Savings can also be realized when the life of a drain fields is extended through the supplemental use of an aerobic system. If you’re drainage field ends up failing it can cost you tens of thousands of dollars to fix, so taking a load of the drainage field’s back can save you a lot.

One of the leading causes of septic system failure is lint from washing machines. For this reason all septic systems are required to have a washing machine (lint) filter. Having a lint filter is even more important with an aerobic septic system because they have tiny filters in them which are very easily clogged with lint. You will find that many manufacturers say that their systems do not require lint filters, but do not be fooled. They just do not want their system to look inferior compared to their competitor’s. If they are being honest, they will tell you that all septic systems require a lint filter. If they insist that you do not need a lint filter make sure that YOU insist upon one. At the end of the day it is your hard-earned money that you are investing in the septic system and you want it to last as long as possible.

Aerobic System Limitations

Aerobic septic systems require more upfront investment and more maintenance in the long term than a standard septic system. If you neglect your system or turn it off the treatment quality diminishes. If you pour harmful chemicals down the drain or the temperature in the aerobic tank is to low you will also be reducing the treatment quality. The aerobic bacteria will reduce the effluent’s ammonia contents but the nitrate content may be increased. So you may have to have a system that treats the effluent for nitrate.

Aerobic Septic System Codes and Regulations

Check with your local health department because aerobic systems are not allowed in all areas. Some areas do not want the drain field area to be reduced which will happen if you use an aerobic septic system; however, other jurisdictions do allow drain filed reduction or even its elimination as long as you have pre-treatment. You will find that in some areas aerobic systems are being used on a trial basis or only in the event of a failed standard septic system. NSF/ANSI 40 – 2000 Standard for Residential Water Treatment Systems documentation outlines the requirements and the approval process for aerobic septic systems. The approval for a aerobic units comes from local health departments or state authorities. Some requirements include alarms installed in the aerobic system to alert the homeowner of malfunctions and two years of manufacturer maintenance service.

Availability of Aerobic Systems

There are only a handful of aerobic treatment system manufacturers but the demand is increasing with the increasing demand for higher quality water treatment.

General information About Aerobic Systems

Generally an aerobic septic system is used when a standard septic system fails. There are times when a standard septic system with a drainage field cannot be installed because space requirements cannot be met. In that case an aerobic system is used in its place. Other situations in which aerobic treatment units are recommended include poor soil quality, bedrock or groundwater near the surface, large amounts of organic matter to be disposed of and the need for high quality water treatment in areas that are environmentally sensitive. Aerobic treatment systems provide higher-quality waste treatment because of the aerobic bacteria in conjunction with the air injection mechanisms.

Aerobic Septic System Designs

There are a variety of designs but they all have common features. These features include an aeration process, final disinfection/treatment, an area for suspended growth systems to operate, and pre-treatment to reduce the amount of clogging from solids. There are two main internal designs for aerobic systems, one is called “suspended growth” and the other is called “attached growth”. In the suspended growth design air is forced into the chamber which mixes with the liquids and the bacteria are suspended freely in the air/liquid solution. In the attached growth methods, the bacteria are attached to a surface that is alternately exposed to liquid and air.

Failing septic systems are a large concern because there is a heavy financial burden and environmental fallout associated with them. Throughout this country a large number of septic systems are failing and the financial costs as I said earlier can be in the tens of thousands of dollars. I am glad that you are doing your research into aerobic septic systems both for the benefits to the environment and the benefits for your bank account. There is one more thing you should know however, if you live in a house where the septic tank or septic tanks have failed you will not be able to sell the house until the septic systems are repaired and once again fully functional. In this case, it may be quicker, easier and cheaper to retrofit your failed system with an aerobic septic system if you are allowed to do so in your area. If you are not allowed, you may have to bite the bullet and pay up to have your system repaired and then sell your house.


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