Aerobic Septic Systems: Cost, Maintenance and How They Work

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Aerobic Septic Systems: How do they work, how do you maintain them and how much do they cost?

Aerobic Septic Systems Let’s Talk About Them: How does an aerobic septic system work? How do you maintain an aerobic septic system? And how much does an aerobic septic system cost?

“So… what type of septic system do you have, or what would you need if you were building a new home or renovating?


No, it’s not exactly the sort of question that would get conversation bubbling around the water-cooler. But it is an important question to ask because not all septic system types are created equal and, in certain locations and situations, some work better than others.


How does an aerobic septic system work?

There are conventional septic systems and then there are the more complex aerobic septic systems. The difference being, in a word: 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.

Aerobic Septic system

Just as in the case of conventional (or standard) systems, an aerobic septic system uses natural processes to treat wastewater.

An oxygen-rich bacterial environments work to digest and breakdown sewage inside the ATU (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 settling 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 the aerobic bacterial growth that will aid in the digestion of solids in the wastewater.


  • Disinfection – This step involves an additional treatment stip 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.


Why do we need an Aerobic Septic System?

Let’s say you want to purchase an amazing property for a cottage, right by the lake of course.  Now let’s say that the lot space is rather small, but it will suit your needs just fine for what you have in mind.  

Well…a conventional septic system may not work for this type of lot, let’s see why:

Being near a water body could mean that there will be a high water table just below the surface or at least seasonally.  This would mean a conventional gravity system would malfunction immediately and you would start to have sewage back.

Now if we introduce an aerobic treatment unit, the wastewater leaving the system is what is called a type 2.  This wastewater effluent is now treated to a higher degree… with?… Yes, you know it, Oxygen!

This allows system designers to come up with a good solution for your property where alternatively a conventional gravity septic system would not work or be allowed as part of our standards.


10 Advantages Of An Aerobic Septic System & Negatives

The Benefits

  • 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
  • More green – 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

The Negatives

  • 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, must be insulated.


So… say you have a conventional system


In this kind of system, solid waste enters your septic tank and settles at the bottom. This, over time, turns into sludge. Meanwhile, the liquid waste that ends up inside your septic tank rises to the top.


Enter your little buddies, the anaerobic microbes that live inside your tank. These tiny fellas get to work and help break down the liquid and solid waste in a process that produces wastewater. (In some cases, this wastewater passes through a final treatment tank).


But overall, that’s it – the work of your conventional septic tank is just about done. All that needs to happen now is for the wastewater to be directed to a drain field that you’ve prepared earlier and with much caution. You will have had to ensure the soil is permeable, that the wastewater will not saturate nearby water tables and that the absorption of the wastewater into the soil will not be blocked or deviated by restrictions such as bedrock.

septic tank installation

Now let’s say you have traded in your standard system for an aerobic system.


As mentioned, aerobic septic systems differ from conventional systems because the aerobic treatment process requires air to be injected and circulated inside the treatment tank. Hence, your aerobic septic system is made up of a greater number of parts than a conventional system, including electrical components and extra tanks. Specifically, your system will have a trash tank (got one), an aerobic treatment unit (tick) and a pump tank (yep, there it is).  An air compressor infuses the treatment unit with air through diffusers in the tank and the cycle begins.


aerobic septic system

Ready? Let’s go. Solid waste and liquid waste enter the trash tank where, like in a standard septic tank, the waste separates into solids at the bottom and liquids at the top. And it is here, inside the trash tank, where the similarities between your new aerobic septic system and your old conventional system end.

What is now wastewater flows from the trash tank and into the aerobic treatment unit. It is here that most of the treatment occurs (or, reworded for the informal aerobic septic system owner: here is where the cool stuff happens). While aerobic treatment units come in many different designs, their job is simple: to house an aerator that circulates oxygen bubbles through the wastewater in a similar fashion to a fish tank pump. This additional oxygen provides a stable environment for aerobic microbes.

aerobic septic system


Now, if anaerobic microbes were your buddies, aerobic microbes are your comrades – the kind that would come to your aid in battle if there was indeed a battle going on and they were slight… larger. You are very fond of your comrades, these aerobic microbes because they break down the effluent a lot faster and more effectively than even the strongest anaerobic microbe could.


Once your comrades have done their work, the liquids flow into the pump tank. If you are using drip irrigation, the pump tank can start emitting the water straight away. If you are dispensing the water as a spray, a final treatment is performed before the water enters the pump tank(commonly with a tablet or liquid chlorinators) or an individual tank just prior to the pump tank for the water chlorination, to eliminate any remaining pathogens. The now environmentally-safe water passes into the pump tank, where the pump gets to work and directs the water to spray heads around your lawn or vegetation.

sub surface drip


As a final step, the water is absorbed into the soil.



Aerobic septic system maintenance: what’s involved?


Aerobic Septic systems are one of the most complex and advanced systems for treating waste – and now we know how it works and how it compares to a conventional septic system. But what’s involved in maintaining an aerobic septic system?


First, it’s important to know how to access your system to make the proper checks.


The access ports to your system will usually be within 10 feet of your home, at ground level. The lids to your access ports should be screwed shut. If they are cracked or discoloured, it’s a good sign that it’s time to have them replaced. 


Unscrew and open the lids with caution – septic systems produce hydrogen sulfide gas, which can be harmful if inhaled. So make sure you let the gas clear before checking the tank.


Most systems are equipped with an alarm light that signals an issue.


Keep an eye on this, because finding and fixing a problem while it is still minor is definitely more ideal than neglecting your system and letting a problem fester for long enough to damage the equipment.


Add chlorine to your tank.


This is something you can easily do yourself, so long as you have checked the frequency and dosages specified in the owner’s manual accompanying your particular system. Do not use pool chlorine as this will not disinfect the wastewater. It will, however, kill your grass or vegetation.


Remove the lid to your aerobic septic system, add the recommended amount of septic-friendly chlorine, then screw the lid back into place.


Keep an eye on the spray fields.


Again, it’s about noticing the minor problems before they become major. Spray heads that are broken or not spraying correctly should be replaced with proper septic spray heads. Do not use irrigation sprinkler heads as these are not compatible with the operation of a septic system.


If the spray heads are constantly on, if you notice puddles of water or if there is a foul odour coming from your septic system, it might be time to call a maintenance expert.


A great way to keep track of your entire aerobic septic system, from the access ports all the way to the spray heads, is to have a map of the system and the spray field. This will help you locate faulty or missing spray heads and make safe decisions if you’re planning home renovations or extensions.


Keep a maintenance record.


Having on hand the model name, capacity, state license and the date that your system was installed will help you identify which system you have and the maintenance requirements specific to your system. And documenting the dates of all services and tests performed on your system will help you keep track of what happened when. For instance, you will know precisely the type and date of any repairs, when to add chlorine, the results of the free chlorine residual and clarity tests and when to have the trash tank and the aerobic treatment unit pumped.


Make sure that at least every six months: the free chlorine residual of the effluent in the pump tank is tested and recorded; the depth of the sludge in the trash tank is measured and recorded; the volume of the sludge in the aerobic treatment unit is measured and recorded, and; a clarity test is conducted and the results of this test (pass or fail) are recorded.


And remember: if it goes down the drain, it will end up in your septic tank.


Some unfortunate things that make their way into septic systems via household toilets include dental floss, bandages, condoms, female hygiene products, cigarette butts and kitty litter. None of these things is healthy for the operation of an aerobic septic system.

baby wipes for septic


Be mindful that you have your comrades down there: pouring poisonous chemicals and cleaners down the drain can kill the microbes and bacteria that live inside your system and treat your wastewater. These chemicals will also make their way through your septic system and out onto the drain field, where people or animals may come into contact with the poisons. So don’t pour liquids like drain cleaners, pesticides, varnishes, thinners or paints down the drain.


When it comes to garbage disposal units, check with your supplier or with a maintenance professional as to whether your aerobic septic system can accommodate this additional waste.


Lastly, know when to call a maintenance professional.


Aerobic septic system maintenance is not the best place to start if you are testing out your do-it-yourself skills. A well-functioning septic system keeps your home running smoothly and keeps your family healthy.


The most effective and efficient way to maintain your aerobic septic system is to have the details of your maintenance provider on hand for emergencies and to have a professional make the appropriate system checks and cleans as regularly as the maintenance schedule recommends. 



How much does an aerobic septic system cost?


Aerobic septic systems are more complex than standard systems because of this they are also more costly. The value lies in the speed and the advanced level of treatment that you can expect from an aerobic septic system.


Here’s a breakdown of the estimated costs for our systems and services:    

Here in British Columbia, Canada we can estimate costs based on a few systems:

Type 2 Septic System costs using an ATU with aeration and drain field:

  • Gravity or conventional septic systems or using a uniform distribution along with using drain field technology used to achieve a type 2 system can cost between $20,000 – $30,000.
  • Using an ATU (Aeration Treatment Unit) septic system installation to achieve a type 2 can range from $25,000 – $35,000
  • Using an ATU with a subsurface drip line can range from $25,000 – $35,000 depending on the topography
  • Using an ATU with an Evotranspiration bed can cost between $25,000 –  $40,000 depending on the home

When using an engineer to design a Type 3 septic system, which requires an added disinfection to the aeration unit we can approximate an added cost from $10,000 – $15,000 more than the above-evaluated cost points.

Here is more information on how a septic system cost is evaluated: Costing a Septic System


Design Services are typical $2000 for Type 1 Gravity systems and $2500 for Type 2 Gravity systems and Pressure systems.

Summary Video


Please note these costs will vary, depending on the region of British Columbia and the accessibility of supplies. For a quote specific to your location and situation, call 250-768-0056 to speak with one of our maintenance experts. Or leave your details here :

 and one of our experts will be in touch with you soon.

groundstone wastewater

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