Home > tanks and fields
Explore the differences between treating effluent vs simply getting rid of it ...
There are many different options for your septic tank. Concrete, fibreglass ...
Learn the options. Buried fields, mounds, at-grades, open discharges ...
Technology that takes treatment to the next level. Many options ...
Out of sight, out of mind? Eco-friendly development and responsible home and land owners should not think like this anymore. Properly designed systems will TREAT and CLEAN wastewater, while overloaded or improperly designed systems simply DISPOSE wastewater into the ground and contaminate and destroy soils and groundwater.
In the past, most acreage home owners (and installers) simply put a septic tank into the ground and then buried 100′ of weeping tile per bedroom, and this served as their “septic system”. Many are still operational today, but without first knowing the soils it is impossible to know if the system is properly sized and if proper treatment is happening.
Investigating and hand-texturing the soils on your site is vital to achieving proper treatment.
The industry has recognized that onsite soils are what dictate how much effluent waste we can distribute over an area. It is actually the soil and the microbes within the soil that clean our sewage. If we overload the onsite soil beyond its capacity, effluent can surface and cause ponding. This can “drown” the microbes, saturate and destroy the soils, and treatment will not occur. Each soil type is lab tested and we have values for each.
A properly designed system will remove almost 99% of contaminants (not pharmaceuticals and other chemicals, unfortunately), and return the water back to the environment in a safe and responsible way. Today’s regulations require each site to first have a site evaluation by a certified designer/installer. Test pits are dug and soil samples are analyzed and sent to the lab. (Note that perc tests are not accepted anymore in Alberta). A certified design is then created for your unique needs and lot requirements.
Domestic sewage (wastewater) includes:
1) “Black Water” – everything that goes down the toilet or urinal
2) “Greywater” – everything else; from sink, dishwasher, laundry, showers, etc.
There are also organics (proteins, organic material), nutrients (phosphorus, nitrogen,) and pathogens (bacteria, viruses, protozoa, helminths) in sewage. Properly designed soil-based treatment areas will treat and remove most of these elements.
Pharmaceuticals (medications) as well as household chemicals are very difficult to remove from domestic wastewater, and excess use therefore should be avoided whenever possible. Never throw old medications down the drain.
Domestic wastewater does not include, and these should not enter your system:
1) Ground Water
2) Water from weeping tile or roof gutters
3) Industrial waste (paint, fuel, other chemicals and cleaners)
Two-chambered septic tanks are common in Alberta. Proper sizing is critical.
Most designs today consist mainly of a septic tank and a soil-based final treatment area (FTA). Most septic tanks have two compartments. The first compartment (Working Chamber) catches all the sewage (from toilets, showers, sinks, dishwasher, etc) from the home, and must be sized correctly to give approx 24hrs of “quiet” time to allow solids (sludge) to sink and for fats, oils and grease (scum) to float. This is the first clarification of the water. This water (effluent) then passes into the second chamber (or Dose Chamber), where it waits to be sent to the field. It can be sent to the field via a syphon/gravity setup or a pump (pressurized) setup.
During the septic system design process, it is important to think about future plans for development. For example, if you are thinking about adding a future bedroom (home), or extra bathrooms or future capacity (office or commercial), it’s smart to design and size the septic tank(s) and treatment area to accommodate these future plans. It is much more economical than having to upgrade and add capacity to the system later on.
As you can see above, septic tanks slowly collect and fill with the sludge and scum that separates out from the rest of the effluent. A licensed vacuum truck needs to remove the sludge and scum on a regular basis (usually every 1-3 years). Some people call this “septic tank cleaning” or “septic tank pumping”.
Most septic tanks in Alberta are either concrete, fibreglass, or poly (plastic). Each type of septic tank material has advantages and disadvantages.
Regardless of the septic tank material, all tanks must be CSA certified.
Concrete septic tanks are quite popular in Alberta, especially in areas that are prone to Chinook winds that can make the ground heave and move regularly throughout the winter. Concrete tanks typically have deeper burial ratings, some up to 5m (~16ft). If your home or facility has a deep basement, a concrete tank might be the only option. Concrete tanks are heavy and need special equipment to install them. Concrete can also break down over time, but modern manufacturers mix special additives in the concrete that resists harsh soil and sewage conditions in and around the tank. Some manufacturers warranty their concrete tanks for up to 25 years. Concrete is robust and reliable and has been used for decades as a reliable tank product.
Concrete is popular in Alberta due to their extreme burial depth ratings
Fibreglass septic tanks also have excellent resiliency against the harsh conditions that sewage and alkaline soils present. They are not as porous as a concrete tank. A great advantage to a fibreglass tank is that it is lighter than concrete and is easier to transport and place. A disadvantage is usually the burial rating… unless extra reinforcement is added, most are only rated to around 2m (6ft) of burial depth. They are not recommended where high water tables exist.
Fibreglass tanks come in many different variations
The industry has evolved recently with stronger and better plastics. Poly (plastic) septic tanks are an excellent option where a shallow burial (6ft or less) is possible, and/or on lots where access is difficult for big machinery. They are normally light enough for a small backhoe or tractor to carry and install. Not all poly tanks are equal – most high quality poly tanks will be ribbed and/or roto-molded for strength. Poly tanks should outlast both concrete and fibreglass tanks due to the nature of the plastics involved. They are not recommended where high water tables exist.
Poly (plastic) septic tanks are light and easy to transport and install
“Septic Fields” can be used as a general term, as well as a specific term. As a general term, it means a soil-based treatment area where effluent is distributed and undergoes the final treatment processes. We also like to use the name ‘Final Treatment Area” or FTA to represent this. “Septic Fields” or “FTA’s” can include buried fields, treatment mounds, LFH at-grades, or open discharges. In Alberta, most treatment options (for residential and commercial facilities) require a FTA as part of the complete treatment process.
Example of a buried trench system with washed rock and 4″ piping
Example of a buried trench system with effluent chambers
Probably the most recognized system is the buried treatment field. In this system, several trenches are excavated to between 2ft – 3ft deep. A layer of washed rock is placed in the bottom of the trench and a 4″ perforated pipe is installed in the top few inches of the washed rock. The effluent is distributed by gravity through the pipe network, which exits the perforated pipe and travels through the washed rock before it enters the soil for final treatment.
Variations of a buried treatment field include using smaller diameter pipe (usually 1″ pipe with 1/8″ orifices) with a pump in the septic tank that will pressurize the effluent in the piping to help distribute the effluent more evenly throughout all the trenches.
Another variation includes using effluent chambers in place of the washed rock. Effluent chambers are a half-dome unit that creates a void space (like the washed rock) within the trenches to allow oxygen to be present as well as aid in the even distribution of the effluent in the trenches.
Although some people haven’t heard of sand treatment mounds before, they have been around for 30+ years or more. Sand treatment mounds are used where difficult soil conditions exist (ie. shallow restrictive layers or clayey type soils). They are an excellent (and less expensive) alternative to Advanced Treatment Units (ATU’s), and they produce the same high quality treatment and effluent.
Sand treatment mounds are built on top of the existing soil; this is why it’s important not to disturb or compact the soil in the potential area where it might be built. treat the effluent to a secondary treatment level before it enters the soil.
A layer of sand is placed directly on the existing ground, and then a layer of washed rock (or effluent chambers) is placed on top of the sand. Small diameter distribution piping (usually 1″) is installed on top of the gravel layer (or within the effluent chambers), and then this is all covered with a geo-tech fabric and then covered up with a sandy loam material. Mounds can be landscaped with grass and incorporated into your existing landscaping features. The grass needs to be mowed regularly and trees should not be planted on top of the mound as the roots can cause issues.
Mounds require pressure distribution via a pump. They cannot be fed using gravity distribution.
Mounds are very reliable. Some people question if they are more prone to freezing in the winter than a buried field. This may or may not be the case. All types of systems have the potential of freezing if they are not being used daily during periods of extreme cold weather. In our experience, mounds have no problems during the winter if they are sized properly and being used daily.
LFH At-grade requires effluent chambers
Chambers are completely covered in wood chips to help blend the system into the forest floor
Similar to a mound, the LFH At-grade is also built on top of the existing surface. However, there are a few extra requirements in order to qualify for the option of using this type of system.
LFH stands for different organic litter horizons found on a forested floor (like leaves, pine cones, grasses, etc)
L – the structures of the organic matter are easily recognized
F – the accumulated organic material is partly decomposed
H – the original structures of the organic matter are unrecognizable
First, this type of system must be located in an established, forested area. The LFH layer must be present and visible. Second, an Advanced Treatment Unit must be used to treat the effluent before it is sent to the LFH At-grade. Third, pressure distribution and effluent chambers must be used. The chambers are then completely covered in wood chips, helping it to blend into the forest floor.
This type of system provides excellent treatment, and is perfect for the land owner that does not want to cut down or disturb their treed or forested area.
A typical At-grade will perform at a rate 4.3 times better than any subsoil absorption method. Within 2 – 6 years, the entire area of the At-grade will become infiltrated by local flora and fauna, blending it in with the surrounding terrain. The efficiency of the At-grade is expected to improve as time passes, decomposition and growth in the area aid in the absorption/distribution of water. The vegetation in the forest provides the best infiltration available. Areas with sloping terrain are preferred, but level areas are also acceptable.
Open discharge systems are the very basic. An open discharge system discharges the effluent directly onto the ground. Because the effluent is not contained in a trench, there is a higher risk of human contact, and stricter setback requirements and restrictions. Some of the requirements are, but not limited to:
Generally you would need a parcel of at least 10-15 acres to meet the setback requirements, in addition to meeting all of the other restrictions, soil types, etc.
Advanced Treatment Units are basically additional technologies that provide additional treatment to the effluent. For example, septic tanks provide “primary” treatment. ATU’s provide “secondary” treatment.
Advanced Treatment Units are also known as “Aerobic Treatment Units” or “Packaged Treatment Plants”. In almost all situations, the ATU uses some form of aerated condition to promote aerobic bacteria and organisms to grow, thrive, and consume/clean the contaminants from the effluent.
ATU’s come in many configurations, but are commonly contained in a separate tank or “pod” that is installed somewhere in the treatment chain between the septic tank and the final treatment area.
Advanced Treatment Units are required in some counties, districts, and environmentally sensitive areas. Depending on the configuration, adding an ATU to your system might help reduce the required size of the final treatment area, which can be very helpful on small or restrictive lots.