The modular and offsite construction industries build a lot of single-family homes that are placed in the ground without access to public sewer systems and require the home to be serviced by an on-site septic system.
Septic systems are miniature sewage treatment systems that treat and dispose of household wastewater by separating solid and liquid waste. They are widely used in areas without centralized sewer systems. In the US, there are several types of septic systems that can be installed for new homes, depending on the specific needs of the site, soil conditions, groundwater level, and local regulations.
Recently a friend told me they had a Recirculating Sand Filter System put in when they built their modular home a few years ago. I had to admit that was a new type I had never heard of before, so I decided to look a little closer into the business of poo disposal.
Here is my Primer on the main types along with their individual Pros and Cons.
Gravity System:
As the name suggests, it uses gravity to move wastewater from the house to the septic tank and then to the drain field or leach field. It’s the simplest type of system and relies on a suitable slope and favorable soil conditions.
Pressure Distribution System: This system uses a pump to ensure uniform distribution of the effluent over the drain field. It’s often used when conditions aren’t favorable for a gravity system.
Pros:
Gravity septic systems are relatively inexpensive to install and maintain and are relatively easy to service and repair. They are very reliable and can last for many years with proper maintenance, other than pumping the septic tank every few years.
They are also environmentally friendly because they do not release wastewater into the environment.
Cons:
Gravity septic systems can be affected by ground shifts, which can damage the pipes or the drainfield and can clog if the drain field becomes saturated or if the septic tank is not pumped regularly. Gravity septic systems are not as efficient as some other types of septic systems, such as aerobic septic systems.
Chamber System:
Uses large chambers instead of traditional stone and pipe. It requires less land area than conventional systems and allows for better aeration.
Pros:
Chamber septic systems are more efficient than single-chamber septic systems because they allow for better treatment of wastewater and can last longer than single-chamber septic systems because they are less likely to clog and require less maintenance than single-chamber septic systems.
Chamber systems are more environmentally friendly than single-chamber septic systems because they release less wastewater into the environment.
Cons:
Chamber septic systems are more expensive to install than single-chamber septic systems and require a larger footprint than single-chamber septic systems They are more complex than single-chamber septic systems and may require more specialized maintenance.
Aerobic Treatment Unit (ATU):
Adds oxygen to the treatment process, which promotes a high rate of waste digestion by bacteria. The treated wastewater is typically cleaner than that from conventional systems. These systems often require electricity and more maintenance.
Pros:
ATUs are more efficient than traditional septic systems because they use oxygen to break down wastewater. This results in cleaner effluent that can be discharged into the environment making them more friendly than traditional septic systems because they release less pollutants.
ATUs can be used in areas with poor soil, such as clay or sand because they do not rely on the soil to filter the wastewater and have a smaller footprint than traditional septic systems because they do not need as much space for a drain fields a traditional septic systems because they are less likely to clog.
Cons:
ATUs are more expensive to install than traditional septic systems and require electricity to operate the aerators, which can add to the cost of ownership. They are more complex than traditional septic systems and may require more specialized maintenance.
Overall, ATUs are a good option for homes that need a more efficient and environmentally friendly septic system. However, they are more expensive to install and require more specialized maintenance.
Sand Mound System:
Sand Mound Systems are used in areas where the soil is shallow over porous bedrock or groundwater is close to the surface. It involves placing a mound of sandy fill material on top of the native soil and then installing the drain field in the mound.
Pros:
Sand mound septic systems can be used in areas with shallow water tables because the mound is located above the water table and/or in poor soil because the sand provides a good filtering medium. They require less maintenance than traditional septic systems because the sand helps to filter the wastewater.
Sand mound septic systems are more efficient than traditional septic systems because the sand helps to remove more pollutants from the wastewater making them more environmentally friendly than traditional septic systems.
Cons:
Once again, sand mound septic systems are more expensive to install than traditional septic systems and require a larger footprint than traditional septic systems.
More complex: Sand mound septic systems are more complex than traditional septic systems and may be unsightly and may not be suitable for all properties.
Drip Distribution System:
Uses a pump to deliver effluent to a series of shallow underground drip lines. This is often used in areas with shallow soil.
Pros:
Drip distribution septic systems are more efficient than traditional septic systems because they allow for a more controlled and even distribution of wastewater. This can help to prevent clogging and improve the treatment of wastewater. They can be used in areas with poor soil because the emitters allow for a more even distribution of wastewater. This can help to prevent the wastewater from clogging the soil.
They also require less maintenance than traditional septic systems because the emitters, which are buried in the ground, make them visually discreet.
Cons:
Drip distribution septic systems require more specialized maintenance than traditional septic systems. This is because the emitters can clog and need to be cleaned regularly, plus they may not be suitable for all sites. This is because the soil type and slope of the land must be suitable for the installation of the emitters.
Recirculating Sand Filter System:
Effluent flows from the septic tank to a pump chamber where it’s then pumped to the sand filter. The sand filter removes solids and treats the effluent with bacteria before it’s discharged to a drain field.
Pros:
Recirculating sand filter systems are effective at removing pollutants from wastewater, including bacteria, viruses, and suspended solids. It uses a recirculating sand filter system that is relatively low-maintenance. The sand needs to be back-washed periodically to remove the accumulated pollutants, but this is a relatively simple process.
Recirculating sand filter systems are relatively compact, making them suitable for small spaces. This system can be used in a variety of applications, including aquaculture, industrial wastewater treatment, and swimming pool filtration.
Cons:
Recirculating sand filter systems can be expensive to install, depending on the size and complexity of the system, and require electricity to operate the pumps. The pumps can be noisy, depending on the size and type of pump. The sand in a recirculating sand filter system can be corrosive, so the system needs to be made of materials that are resistant to corrosion.
Constructed Wetland System:
Designed to mimic natural wetland processes. Wastewater flows into a bed filled with plants and the plants, bacteria, and other organisms treat the wastewater before it’s discharged.
Pros:
Constructed wetland septic systems use natural processes to treat wastewater, which is more environmentally friendly than traditional septic systems. They are effective at removing pollutants from wastewater, including bacteria, viruses, and suspended solids and are relatively low-maintenance. The wetland needs to be monitored and the plants may need to be trimmed occasionally, but this is a relatively simple process.
Constructed wetland septic systems can be used in a variety of settings, including rural and urban areas where it can help to improve water quality by removing pollutants from the wastewater.
Cons:
Constructed wetland septic systems can be expensive to install, depending on the size and complexity of the system, and require a large area of land, which may not be available in all areas. They can be unsightly, depending on the design, and can be susceptible to flooding, which can damage the system.
Evapotranspiration System (ET):
Used in very dry regions. Wastewater is stored in a basin and then evaporated into the air or taken up by plants. There’s no discharge to the ground with this system.
Pros:
Constructed ET systems use natural processes to treat wastewater, which is more environmentally friendly than traditional septic systems. It is effective at removing pollutants from wastewater, including bacteria, viruses, and suspended solids. These systems are relatively low-maintenance. The plants and soil need to be monitored and the system may need to be adjusted occasionally, but this is a relatively simple process.
Constructed ET systems can be used in a variety of settings, including rural and urban areas to help to improve water quality by removing pollutants from the wastewater and can be aesthetically pleasing, as they can be designed to look like a garden or landscaped area.
Cons:
Constructed ET systems can be very expensive to install, depending on the size and complexity of the system. They require a large area of land, which may not be available in all areas. These systems can be susceptible to flooding, which can damage the system and may not be as effective in cold climates, as the plants may not be able to grow as well.
Cluster/Community Systems:
Serves multiple homes or a community. Wastewater from several homes flows to a central septic system where it’s treated before being released into the ground.
Local regulations, site evaluations, and soil tests are critical when determining the most suitable septic system for a new home. It’s always important to work with professionals who are familiar with local conditions and requirements.
Pros:
Cluster/community systems can be more efficient than individual septic systems because they can treat a larger volume of wastewater with less land and they can be less expensive than individual septic systems because they can be shared by multiple homes or businesses. These systems can be used in areas with limited space, such as on small lots or in urban areas.
The Cluster/community system can be used in areas with poor soil conditions, such as areas with clay or sandy soil. The community systems can be more environmentally friendly than individual septic systems because they can treat wastewater more effectively and can reduce the amount of wastewater that is discharged into the environment.
Cons:
Cluster/community systems can be more complex than individual septic systems, which can make them more difficult to design, install, and maintain and may require more land than individual septic systems, which can be a problem in areas with limited space. Obviously, these systems may require more permits than individual septic systems, which can add to the cost of installation. Maintenance of this shared system can add to the cost of ownership.
I really hope you enjoyed this trip through the most popular on-site poo disposal systems.
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With over 9,000 published articles on modular and offsite construction, Gary Fleisher remains one of the most trusted voices in the industry.
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