Most private septic tanks consist of two parts: the collection and digestion tanks and the dispersal field. [1] X reliable source U.S. Environmental Protection Agency Independent U.S. government agency responsible for promoting safe environmental practices Source When the first collection container fills, liquid waste is transferred to the second tank. As soon as the second tank fills with liquid, it spreads into the bottom below. The system presented here is a small system designed for limited use by two people without laundry. The tank is much smaller than required by building codes, and the design lacks some key elements such as internal baffles and a qualified site assessment. This system uses two 55 US gallon (210 L) drums, as opposed to the 1,000 to 2,000 US gallons (3,800 to 7,600 L) tanks used for a standard domestic septic tank. The system also has a propagation field that is about one-third of the field of a large house.
The design and size of a septic tank can vary greatly across the country due to a combination of factors. These factors include household size, soil type, site slope, plot size, proximity to sensitive waters, weather conditions, or even local regulations. Below are ten of the most commonly used septic tank types, followed by illustrations and descriptions of each system. The list is not exhaustive; There are many other types of septic tanks. Gravel and stone systems have a relatively large total area and may not be suitable for all residential locations or conditions. A built wetland mimics the treatment processes that take place in natural wetlands. Wastewater flows from the septic tank into the wet cell. The wastewater then passes through the medium and is treated by microbes, plants and other media that remove pathogens and nutrients. The wetland cell usually consists of an impermeable coating and filling of gravel and sand, as well as the plants of the corresponding wetlands that must be able to survive in a constantly saturated environment. Evapotranspiration systems are only useful under certain environmental conditions.
The climate should be dry and have enough heat and sunshine. These systems work well in flat soils; However, they may break down if it rains or snows too much. Hill systems are an option in areas with shallow soil, high groundwater, or shallow bedrock. The built sand mound contains a drainage ditch. Sewage from the septic tank flows into a pumping chamber, where it is pumped up to the hill at prescribed doses. Wastewater treatment occurs when it flows into the ditch and is filtered through the sand and then dispersed into the domestic soil. Drip distribution system is a type of wastewater distribution that can be used in many types of drainage fields. The main advantage of the drip distribution system is that there is no need for a large mound of earth because the drip sides are inserted into the first 6 to 12 inches of the soil. The disadvantage of the drip dispensing system is that after the septic tank, a large dose container is required to accommodate the timed administration of wastewater into the drip absorption zone. Additional components, such as power supply, are required for this system, which requires additional costs and increased maintenance. Homeowners planning a system similar to this should be aware that this system would not pass inspections by a U.S.
public health service and could fine the owner if the system was discovered in use. [2] X Research Source On the other hand, it is better to dispose of waste safely than not to do so. Today`s water-efficient toilets use less than two gallons per flush. This system will handle such a load. For people living in places without septic treatment, this could be a lifesaver. A wetland system can operate either by gravity or by pressure distribution. As wastewater passes through the wetland, it can leave the wetland and flow into a drainage field in the ground for subsequent wastewater treatment. An example of a gravel-free system is the chamber system. The chamber system serves as an alternative to the gravel system.
The main advantage of the chamber system is the increased ease of delivery and construction. They are also well suited to areas with high groundwater levels where the volume of inflow into the sewage system is variable (e.g. in a holiday home or seasonal hostel), in an area where gravel is scarce or in areas where other technologies such as plastic chambers are readily available. A conventional decentralized wastewater treatment system consists of a septic tank and an underground wastewater infiltration system called a drainage field. A conventional septic tank is usually installed in a single-family home or small business. Although hill systems can be a good solution for certain soil conditions, they require a lot of space and regular maintenance. Sand filter systems can be built above or below ground. Wastewater flows from the septic tank into a pumping chamber. It is then pumped to the sand filter. The sand filter is often lined with PVC or a concrete box filled with sand material. Wastewater is pumped under low pressure through the pipes at the top of the filter.
The wastewater leaves the pipes and is treated as it filters through the sand. The treated wastewater is then discharged into the sewer field. This type of system consists of a series of interconnected chambers. The area around and above the chambers is filled with earth. The pipes carry wastewater from the septic tank to the chambers. In the rooms, sewage comes into contact with the floor. Microbes on or near the ground treat wastewater. Sand filters provide a high level of nutrient treatment and are well suited for areas with high groundwater levels or near water bodies, but they are more expensive than a traditional septic tank. The advantages of this system are that it can be used in homes with smaller plots, insufficient soil conditions, in areas where groundwater levels are too high or in homes near a surface water body sensitive to contamination by nutrients in wastewater. ATUs can expect regular maintenance for life. Gravel-free drainage fields have been widely used in many states for over 30 years and have evolved into conventional technology that replaces gravel systems.
They come in many forms, including open-bottomed chambers, fabric-wrapped pipes, and synthetic materials such as expanded polystyrene supports. Gravel-free systems can be made with recycled materials and offer significant savings on carbon footprint. A decentralized wastewater treatment system (or municipality) is in some form of common ownership and collects wastewater from two or more apartments or buildings. It directs wastewater to a treatment and distribution system located in a suitable location near apartments or buildings. It is common to find cluster systems in places such as rural subdivisions. A septic tank is an underground and airtight septic tank designed and constructed to receive and partially treat raw domestic sanitary wastewater. Heavy solids settle to the bottom of the tank, while greases and lighter solids float upwards. The solids remain in the reservoir while the wastewater is discharged into the drainage field for further treatment and distribution. The gravel/stone drainage field is a design that has been around for decades. Wastewater is discharged from the septic tank into a shallow underground trench made of stone or gravel.
A geofabric or similar material is then placed on the trench so that sand, dirt and other impurities do not get into the clean stone. Aerobic treatment units (AWUs) use many of the same processes as a municipal wastewater treatment plant, but on a smaller scale. An aerobic system injects oxygen into the treatment tank. The supplemental oxygen increases the natural bacterial activity in the system, which then provides additional treatment for nutrients in the wastewater. Some aerobic systems may also have a pre-treatment tank and a final treatment tank that includes disinfection to further reduce pathogen levels. Below are illustrations and descriptions of different types of conventional and alternative septic tanks. More detailed information on specific technologies can be found in the fact sheets. Evapotranspiration systems have unique drainage fields. The base of the evapotranspiration system is lined with a waterproof material. Once the wastewater enters the drainage field, it evaporates into the air. Unlike other septic tank designs, wastewater never filters into the soil and never enters groundwater.
The wastewater filters through the stone and is then treated by microbes once it reaches the ground under the gravel/stone trench. This article was co-authored by wikiHow Staff. Our team of writers and researchers validates the accuracy and completeness of the articles.