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The standard waste water system w/ soil absorption system is the most cost efficient method available to treat residential waste water. But for it to work properly, you need to choose the right kind of septic system for your household size and soil type, and you need to maintain it regularly.
This type of waste treatment system has two components: a septic tank and a soil absorption system. The Septic Tank is an enclosed watertight container that collects and provides primary treatment of waste water by separating the solids from the waste water. It removes the solids by holding waste water in the tank and allowing the settleable solids to settle to the bottom of the tank while the floatable solids (oil and greases) rise to the top. To provide time for the solids to settle, the tank should hold the waste water for at least 24 hours. Some of the solids are removed from the water, some ore digested, and some are stored in the tank. Up to 50 percent of the solids retained in the tank decompose; the rest accumulate as sludge at the tank bottom and need to be removed periodically by pumping the tank. There are three main types of septic tanks for on-site waste water treatment:
1. Concrete septic tanks-the most common
2. Fiberglass tanks-used more often because they are easy to carry to “hard to get to” locations
3. Polyethylene/plastic tanks-which come in many different sizes and shapes. Like fiberglass tanks, these are light, one-piece tanks that can be carried to “hard to get to” locations.
All tanks must be water tight to prevent water from entering as well as leaving the system. Water entering the system can saturate the soil absorption field, resulting in a failed system. From the septic tank, the wastewater passes through the outlet of the tank and enters the soil absorption field. The most common outlet is a tee fitting connected to the pipe going to the soil absorption field. However, an effluent filter can be placed in the outlet tee for additional filtering of the wastewater. The effluent filter removes additional solids from the wastewater and keeps them from clogging the absorption field and causing it to fail prematurely.
The Soil Absorption Field provides final treatment and distribution of the wastewater. A conventional system consists of perforated pipes surrounded by such media as gravel and chipped tires, covered with geo-textile fabric and loamy soil. To treat wastewater, this system relies heavily on the soil, where microorganisms help remove the organic matter, solids, and nutrients left in the water. As effluent continually flows into the soil, the microbes eating the components of the wastewater form a biological mat. The mat slows the water’s movement through the soil and helps keep the area below the mat from becoming saturated. The water must travel into unsaturated soil so that the microbes there and in the mat can feed on the waste and nutrients in the effluent. The grass covering the soil absorption system also uses the nutrients and water to grow.
If the Treatment is used properly, the septic tank and soil absorption system works well. It reduces two ratios commonly used to measure pollution: biological oxygen demand, which is lowered by more than 65%; and total suspended solids, which are cut by more tan 70%. Oil and grease are typically reduced by 70% to 80%. Using a septic tank to pre-treat sewage also makes other secondary treatment systems more effective. The effluent from the septic tank is mild, consistent, easy to convey and easily treated by either aerobic (with free oxygen) or anaerobic (without free oxygen) processes.
For the Design of a septic tank to perform successfully, the tank must be a watertight, stable structure including the proper size and construction. The size of the septic tank you need depends on the number of bedrooms in the home, number of people living there, the home’s square footage and whether or not water saving fixtures are used. For example, a three-bedroom house, assuming four people live there and it has no water saving fixtures, would require a 1,000-gallon tank. A key factor in the septic tank’s design is the relationships between how much surface area it has, how much sewage the tank can store, how much waste water is discharged and how fast it exits. All affect the tank’s efficiency and the amount of sludge it retains. The greater the liquid surface area, the more sewage the tank can collect. As more solids collect in the tank, the water there becomes shallower, which requires that the discharge be slower to allow more time to separate the sludge and scum. A key to maintaining a septic tank is placing risers on the tank openings. If a tank is buried more than 12 inches below the soil surface, a riser must be used on the openings to bring the lid to within 6 inches of the soil surface. Generally, the riser can be extended to the ground surface and protected with a good lid. These risers really make it easy to perform maintenance on the tank.
An Aerobic Septic or Aerobic Waste Water system is a system that contains aerobic bacteria, which is completely different than septic bacteria.
Here at Texas Septic Solutions we install both Standard and Aerobic systems. We believe both setups are effective when installed correctly. Here's some general information on both systems to give you an idea on how these two setups function:
Aerobic bacteria require constant air movement to exist and stay alive. Unlike septic bacteria, it is a veracious eater and eats bacteria very quickly. It eats up disease causing pathogens more rapidly than a septic system. Therefore causing no odor.
The water should stay in the system for 24 hours, for correct treatment of the waste. It then goes into a pump tank. It is dispersed from the pump tank, through pipes to a subsurface drip irrigation system.This drip irrigation system will then irrigate your yard.
Most Aerobic Systems are constructed of three tanks: a holding tank for solids, a treatment tank and a pump tank. Aerobic systems are designed according to the size of the home and the size of the family to use the system at the time of construction.
In situations where a family expects to entertain multiple persons, in the future at one time, it is suggested to over build the system accordingly. Overloading the system with excessive use will cause it to malfunction.
The Soil Texture can differ in many ways. There are three textures of soil: sand, silt, and clay. Soil texture affects how fast the waste water filters into the soil (called hydraulic conductivity) and how big of an absorption field you need. Sand transmits water faster than silt, which is faster than clay. Texas regulations divide these three soil textures into five soil types (Ia, Ib, II, III, IV). Sandy soils are in soil type I and clay soils are in soil type IV. A standard drain field cannot be used in a clay soil.
Also important to the design is the Hydraulic Loading, which is the amount of effluent applied per square foot of trench surface. Because water filters through clay soils more slowly than through sand or silt, the hydraulic loading rate is lower for clay than for sand. Because clay soils have a low conductivity, only nonstandard drain fields can be used in clay.
The size of the Absorption Field needed is also determined by how much wastewater goes into the system each day. Divide the wastewater flow by the hydraulic loading for the soil type in which the field will be built.
To Keep Your System Working and treating sewage efficiently, you need to have the tank pumped periodically. As the septic system is used, sludge accumulates in the bottom of the septic tank. As sludge level increases, waste water spends less time in the tank, and solids are more likely to escape into the absorption area. If sludge accumulates too long, no settling occurs, the sewage goes directly to the soil absorption area, and little is treated. Properly sized tanks generally have enough space to accumulate sludge for at least 3 years. In Texas, a 1,000-gallon septic tank is used for homes with three bedrooms without water saving devices. If four people live in that three-bedroom house, the tank should be pumped every 2.6 years (see table 2). If the same system serves a family of two in a three-bedroom house, the tank should be pumped every 5.9 years. It is important to know that the soil absorption field will not fail immediately if you don’t pump your tank. However, the septic tank is no longer protecting the soil absorption field from solids. If you neglect the tank for long, you may have to replace the soil absorption field. Another maintenance task you need to do periodically to keep the system from backing up is to clean the effluent filter. Clean it periodically by spraying it with a hose directly into the septic tank, or have your maintenance provider clean the filter. Soil absorption fields need to be protected from solids and rainfall. If you don’t pump the tank, solids can enter the field. Rainfall running off roofs or concrete areas should be drained around the soil absorption field to prevent the field from filling with water. Fields that are saturated with rainwater are unable to accept waste water. Planting cool-season grasses over the soil absorption field in winter can help remove water from the soil and help keep the system working properly.