Septic 101

At Sewage Treatment Solutions Inc., we have been dealing with septic systems, and septic related issues, for more than 30 years. Throughout those years, we have seen many different types of systems, some that work, and some that don’t. In order for you to understand what we do, and the reasons why, please take a few minutes to read this article.

Basic Components – Not every septic system is the same, however as a general rule, they do follow the same basic conventional process.

Primary Treatment

Conventional Septic Tank (with and without pump)

In most cases the first component of a septic system is the septic tank. These can be made from; plastic (high density polyethylene), fiberglass, steel, or concrete. Concrete has been the most common type of tank utilized in North America, as it was one of first types to be manufactured.  For this reason many people still believe, that it is still, the only option.  Unlike other continents, Europe for example, plastic is much more common.  Septic tanks are commonly divided into two compartments.  Raw sewage gravity feeds via a pipe from the house into the septic tank .  The raw sewage separates with solids dropping to the bottom and a scum layer rising to the top of the liquid layer.  This scum layer or commonly referred to as FOG (fats, oils and greases) is an accumulation that builds up from the separation process in this compartment.

There is a solid baffle between the two compartments in the septic tank.  Designed within this baffle is either an elbow or a tee that draws the effluent from the middle of the first compartment emptying into the second compartment.  By removing liquid from the middle of the first compartment this would generally leave the FOG layer as well as the solids undisturbed in the first compartment.  In the second compartment the liquids will empty this compartment either by gravity or through a pump and  float which would usually be placed on or near the floor of this second compartment.  When a specific amount of effluent flows from the first compartment to the second compartment, the float is activated when the level in the second compartment reaches a certain height thereby engaging the pump and sending the effluent to another location.  In the case of a gravity system, when the effluent reaches a particular height it will then flow from this portal to either another compartment or to a septic field.

Advanced Treatment

In some systems, “Advanced Treatment Units” are used in place of, or combined with conventional septic tanks.  This is normally considered when increased treatment of the effluent is required or desired.

From the surface, most “Advanced Treatment Units” look similar in many respects to traditional septic tanks.  The difference however is what’s inside.  The main function of a treatment unit is to improve the conditions of the environment within the system, thereby enhancing the bacterial process of breaking down sewage.  There are many different manufactures of treatment plants, but there are really 4 basic processes involved for advanced treatment:

  • Attached Growth (Fixed Media) – A media for bacteria to attach themselves to inside the chambers of the treatment plant.  This technology increases the bacteria count thereby enhancing the bacterial process of breaking down sewage.  This media is in essence increasing the surface area for bacteria to live and thrive.
  • Rotational Biological Contactor (RBC) – This is very similar to the Attached Growth process, however, the media is fixed to a rotating drum.  This drum turns through the sewage and then back up into the air space above to introduce oxygen to the bacteria.
  • Fixed Activated – This again is very similar to Attached Growth, however this time oxygen is introduced into the system using some type of aeration process.
  • Suspended Growth – This system typically uses a “floating media” that is kept suspended in the sewage by means of aeration.

The vast majority of Advanced Treatment Units available today are using some combination of these types of systems.

Final Treatment

There are many different types and variations of final treatment systems, but they all work around 3 basic principles.

Open Discharge System

In Alberta this was one of the original systems utilized. The effluent from the second chamber is simply pumped away from the tank and then discharged to surface of the ground. This is a very simplistic discharge system, and it works fairly well, HOWEVER, from an environmental and health and safety perspective, this can be one of most unsafe ways to dispose of effluent. Please read Septic Related Health Issues for more information



Gravity flow field or mound

Basically, these systems are somewhat similar.  Effluent is pumped from the second compartment of the septic tank to a sub surface or buried header to either a stone and perforated pipe system, or a cavity type chamber, where it flows by gravity from the header throughout the buried chambers.

The premise is that the effluent is then absorbed by the soil; where the bacteria in the soils will continue to treat the effluent.  This type of system however has a high failure rate.  As the sewage leaves the header, its only method to move across the treatment area is gravity. Therefore, the design relies on the formation of biomat to move the effluent along the system. Of course, this bio-mat never goes away after the formation, and consequently the system progressively fails. Once the biomat is all the way across the distribution area, there is very little absorption into the soils.

Pressured Discharge to a field or mound

A pressurized field or mound is basically similar to a gravity field or mound. Instead of gravity from the header, there is a pipe in the cavity that is pressured directly from the pump in the septic tank. The pipe within the cavity is perforated at specific intervals to create even load distribution on the soils. Then the bacteria in the soils are required to treat the effluent.


Why Septic Systems Fail

There are obvious mechanical components of a septic system, such as; pumps, floats, alarms, etc. and as such from time to time these components may fail. These issues are what we would consider a basic general maintenance issue with respect to the septic system.  However, with a properly designed system, the failure of one of these components is significantly reduced.  What we at Sewage Treatment Solutions are mainly concerned with in this section is the failure of the individual major components of septic systems.  Let’s look at why septic systems fail.

 Failure of Septic Tanks 

H2S Damage to Concrete

As previously stated, the majority of septic tanks installed, are concrete. The utilization of concrete has resulted in some serious problems with respect to septic treatment.

Firstly one must realize that concrete is a porous material. This means that it will absorb any liquid or gas that it comes in contact with. This becomes a major concern with the issues of H2S gases that are regularly produced within a septic system. The H2S gas is absorbed by the concrete where the chemical reaction causes a bi-product of Sulfuric Acid.  Sulfuric acid eats away at the tank causing it to breakdown and basically crumbles apart over time.

Another major problem we see with concrete tanks is with the risers. Risers are typically constructed in 2 and 3 foot increments. Most concrete tanks however are usually buried 6 to 8 feet deep. That means that the risers need to be connected at least once if not twice before reaching grade level. In most cases these risers are connected using a sealant and the weight of the concrete to seal the riser tight. Settling of the soils and frost heaves causes the risers to shift ever so slightly. Because there is nothing physically holding the risers in place, the seal between the risers can break allowing groundwater to penetrate around the riser connection and leak into the tank. This will severely reduce the effluent residence time in the tank and consequently overload the discharge system.

Failure of Discharge Systems 

Discharge systems are the end of the line for septic systems. It is quite common for a septic discharge system to be the first indicator of a more serious problem. These problems can show as a “Break Out”, difference in vegetation from surrounding area, sewage backups into the home, or septic odours in the yard.


When biomat builds up within the septic field to the point that there is no place for the liquid to go a “break out” occurs. Regardless of a gravity septic system or a pressurized septic system, pressure from the effluent is forced into the septic field or septic mound.  If the effluent is hitting a proverbial “brick wall” or rather bio-mat the liquid will then come to surface and thus a “break out” has occurred.  Once this has occurred actions are required to replace the failed field.  This means taking a large portion of your existing yard and building a new discharge system. First of all this process is extremely expensive, and secondly and more importantly, in the majority of cases, the original problem causing the failure has yet to be addressed, thereby assuring future similar problems.

Over 30 years experience on the research and development in the septic industry has      clearly indicated that the majority of septic field or mound problems are directly related to the quality of effluent that is sent to them.

The lack or residence time is one the biggest issues as to why field s and mounds fail. Residence time is the length of time it takes for the sewage to travel from when it enters the tank to being discharged to the field or mound.  Conventional thinking is that all solids remain in the first compartment of the tank. It is well proven that this is not a fact.  There are suspended solids that will “float” from the first to the second compartment.  These suspended solids referred to as “grey water” have no choice but to be pumped out to the field or mound.


The Alberta Standards of Practice established guidelines and the majority of the septic industry base their beliefs on the fact that the soils within a field or mound should properly complete the treatment process of human organic waste matter.


Bio-Mat build-up within a septic field chamber will eventually plug off the entire chamber and create a “break out”

With a conventional two compartment tank without proper residence time, the organic waste leaving the tank will have a high suspended solid content.  This will create issues when this effluent is sent to the field or mound and left to be broken down by the bacteria in the soil. This bacterium produces a waste which will become part of the formation of biomat.  Biomat in a thin layer is healthy for your field or mound. This thin layer of biomat creates filtration eliminating

toxins and pathogens from getting to a fresh water supply. The problem however is that this layer of biomat becomes too thick and the effluent can no longer filter itself through this layer.  Once this excessive biomat begins to build a thicker layer in the field or mound it causes the effluent to no longer move downwards, thereby causing a horizontal movement of the effluent.  The biomat also moves with it and soon creates walls that cannot be penetrated by the effluent, which essentially creates a bathtub around the chamber giving the effluent nowhere to go.

Once the bio-mat has built up to a point, the system then “locks off”, and will not accept anymore effluent. However, the pump will still attempt to continue pumping effluent to the field or mound. As this point one of two things has to happen, either a backup of sewage into the home occurs as the pump fails due to over work, or the field or mound blows out.












Health Concerns Regarding Blown Out Systems and Open Discharges

Contaminated water is responsible for many diseases and health related issues. Discharge systems that are not working properly and surface discharge systems can easily contaminate our water system. We have seen discharges that are flowing directly into the water supply. If you follow the route of the sewage all it would take is a heavy rain or the spring runoff for the pathogens to get into our water supply.

Sewage Treatment Solutions Septic Tank Configuration which creates a 4300 Gallon Residence Time

How to Fix the System


At Sewage Treatment Solutions we have analyzed countless data that that has been accumulated over years and have come to the conclusion that residence time is the best thing that a system can have. When you have residence time, the breakdown of the sewage happens in the septic tank where it should, and the problem is not transported to the field.  If you send a septic field only water, the possibility of a failure is remote.  So when we design and implement our systems, we design them with a very long residence time, (several tanks).

If however you have an existing system, it is impractical at times to try to add more residence time. The next best solution is to increase the speed of which the system works. Please check out our biological dosing technology for more information on how we design systems.  Once you solve the basic problem with the residence time and convert your system from an anaerobic to an aerobic process the discharge system will take care of itself.