Types of Septic Systems
Due to a variety of reasons, septic system design and size might vary greatly from your neighbourhood to across the country. Household size, soil type, site slope, lot size, closeness to sensitive water bodies, weather conditions, and even municipal restrictions are all considerations to consider.
The 10 most popular types of septic systems are shown below.
- Septic Tank
- Conventional System
- Chamber System
- Drip Distribution System
- Aerobic Treatment Unit
- Mound Systems
- Recirculating Sand Filter System
- Evapotranspiration System
- Constructed Wetland System
- Cluster / Community System
Different Types of Septic Systems
Here, the different types of septic tank systems are as follows.
1. Septic Tank
The most typical small-scale decentralised treatment unit for grey and blackwater from cistern or pour-flush toilets is a septic tank. It essentially functions as a sedimentation tank. It might be rectangular or cylindrical in form.
Septic tanks are generally used for wastewater with a high proportion of settleable particles, such as household effluent, but they may also be used for other wastewater with comparable characteristics. Heavy particles sink to the bottom of the tank when liquid runs through it, while scum, primarily oil and grease, floats to the top.
Solids that sink to the bottom deteriorate anaerobically over time. However, because the rate of buildup outpaces the rate of decomposition, the collected sludge and scum must be removed on a regular basis. Septic tank effluent must be distributed using a Soak Pit, evapo-transpiration mound, or Leach Field, or transferred to another treatment technology using a Solids-Free Sewer, simplified sewer, or solids-free sewer.
Constructed wetlands with horizontal or vertical flow are ideal for secondary treatment, such as surface flow. Sludge must be emptied and treated on a regular basis in order to be safely disposed of or reused. It can be dried in settling or thickening ponds, as well as in planted or unplanted drying beds.
2. Conventional System
A septic tank plus a trench or bed subsurface wastewater infiltration system form a decentralised wastewater treatment system (drainfield). A single-family house or small company generally has a conventional septic system installed.
The gravel/stone drainfield is an old design that has been around for a long time. The term alludes to the drainfield’s creation.
The wastewater is routed from the septic tank to a shallow underground stone or gravel trench in this arrangement. The trench is subsequently covered with a geofabric or similar material to keep sand, dirt, and other pollutants out of the clean stone.
When the effluent reaches the soil below the gravel/stone trench, it filters through the stone and is treated further by bacteria. Gravel/stone systems have a big overall footprint and may not be appropriate for all types of residential sites or situations.
When space is at a premium, conventional sewage treatment systems (also known as mechanical treatment systems) are used. They are more expensive to develop and operate since they are mechanical, as opposed to natural treatment systems like lagoons, which require more acreage.
While conventional sewage treatment systems come in a variety of shapes and sizes, four of the most popular are described here. In South and Southeast Asia, each of the systems listed below may treat sewage to fulfil government discharge standards.
- Activated sludge
- Sequencing batch reactor
- Trickling filter
- Rotating biological contactor
3. Chamber System
Gravelless drainfields have been widely utilised in several states for over 30 years and have replaced gravel systems as a standard technology. Open-bottom chambers, fabric-wrapped tubes, and synthetic materials like expanded polystyrene media are just a few examples.
Gravelless systems may be made from of recycled materials, resulting in a considerable reduction in carbon emissions. The chamber system is an example of a gravelless system. As an alternative to the gravel/stone method, the chamber system can be used.
The major benefit of the chamber system is the simplicity with which it can be delivered and constructed. They’re also ideal for regions with high groundwater tables, where the amount of influent to the septic system varies, where gravel is rare, or where alternative technologies like plastic chambers are easily accessible.
This system is made up of a number of interconnected chambers. The earth is piled up around and above the rooms. Wastewater is transported from the septic tank to the chambers through pipes. The wastewater comes into touch with the soil in the chambers.
The wastewater is treated by microbes that live on or near the soil.
4. Drip Distribution System
Drip distribution is an effluent dispersal method that may be utilised in a variety of drain fields. Because the drip laterals are put into the top 6 to 12 inches of soil, the drip distribution system does not require a big mound of dirt. The drip distribution system’s drawback is that it necessitates the installation of a big dosage tank after the septic tank to facilitate the scheduled dose delivery of wastewater to the drip absorption region.
This method requires additional components, such as electrical power, which adds to the cost and requires more maintenance.
Pre-treated wastewater is sent to a soil treatment site through drip distribution, where it gives nutrients and moisture to plants. The pre-treated effluent “drips” from tubing at regular intervals, allowing a little amount of wastewater to irrigate a vast vegetative area with a small amount of wastewater.
Topsoil with plants is ideal because it optimises sewage treatment while reducing the danger of untreated water moving fast through the soil.
Drip distribution is frequently utilised in regions where traditional trenches are difficult to build, such as steep slopes and densely wooded areas. It’s also utilised in locations like resorts and golf courses that only function during the summer months.
After a pretreatment system, such as an aerobic treatment unit or a sand filter, drip distribution systems are frequently employed.
5. Aerobic Treatment Unit
Many of the same procedures as a municipal sewage plant are used in Aerobic Treatment Units (ATUs), although on a smaller scale. The oxygen is injected into the treatment tank via an aerobic system.
The increased oxygen boosts natural bacterial activity in the system, which helps to treat nutrients in the effluent further. To further minimise pathogen levels, some aerobic systems include a pre-treatment tank and a final treatment tank with disinfection.
The system has the advantage of being able to be employed in homes with smaller lots, poor soil conditions, places with a high water table, or homes located near a surface water body that is susceptible to contamination by nutrients in wastewater effluent. ATUs must be serviced on a regular basis during their lifetime.
6. Mound Systems
In regions with shallow soil depth, heavy groundwater, or shallow bedrock, mound systems are a possibility. A drainfield trench is built into the sand mound. The septic tank’s effluent runs to a pump chamber, where it is dosed and pushed to the mound.
The wastewater is treated as it flows into the trench and filters through the sand before being dispersed into the native soil. While mound systems might be a viable option for specific soil conditions, they can take up a lot of space and need to be maintained on a regular basis.
The primary goal of a mound system is to offer sufficient treatment to the natural environment in order to create effluent that is comparable to, or better than, that produced by a typical onsite disposal system. Mounds are sand filters that are pressure-dosed and discharge directly into natural soil. They are installed above the soil surface and are intended to overcome site constraints such as:
- Soils with low or high permeability.
- Over creviced or porous bedrock, a thin layer of soil is applied.
- The presence of a high water table
7. Recirculating Sand Filter System
Above-ground or below-ground sand filter systems are available. The septic tank’s effluent is pumped to a pump chamber. After that, it’s pumped to the sand filter. The sand filter is usually made of PVC or a concrete box filled with sand.
Effluent is pumped through the pipes at the top of the filter at a low pressure. As the wastewater leaves the pipelines and filters through the sand, it is treated. After that, the treated wastewater is dumped into a drainfield.
Sand filters provide a high level of nutrient treatment and are ideal for areas with high water tables or near proximity to bodies of water, but they are more expensive than a traditional septic system.
8. Evapotranspiration System
Drainfields in evapotranspiration systems are unique. A waterproof material is used to line the drainfield of the evapotranspiration system. After entering the drainfield, the effluent evaporates into the atmosphere.
The wastewater never filters into the soil and never reaches groundwater, unlike conventional septic system designs. Only certain climatic conditions make evapotranspiration systems useful. The climate must be arid, with plenty of heat and light.
9. Constructed Wetland System
The treatment mechanisms in a manmade wetland are similar to those seen in natural wetlands. The wetland cell receives waste water from the septic tank. The wastewater then flows into the media, where pathogens and nutrients are removed by bacteria, plants, and other media.
The wetland cell is normally made up of an impermeable liner, gravel and sand fill, and appropriate wetland plants that can survive in a constantly saturated environment. Gravity flow or pressure distribution can be used in a wetland system.
As wastewater travels through the wetland, it may escape and flow into a drainfield, where it will be treated further before being absorbed into the soil.
10. Cluster / Community System
A decentralised wastewater treatment system that gathers wastewater from two or more residences or buildings and transports it to a treatment and dispersal system installed on a suitable site near the dwellings or structures under some kind of shared ownership.
Cluster systems are widespread in regions like rural subdivisions. Cluster wastewater systems can handle anywhere from a few to a lot of connections. Smaller cluster systems that serve a few buildings resemble onsite systems, whereas big cluster systems that serve hundreds of buildings resemble centralised systems.
Although surface discharge or water reuse are also used, cluster systems primarily disperse wastewater through subsurface dispersal systems.
Health departments approve smaller cluster systems, whereas state environmental protection departments approve bigger cluster systems.