![]() Types of Septic SystemsConventional SystemsGenerally there are two types of conventional septic systems: those that use gravel in the drainfield and those that use some form of chamber system. As its name suggests the older style gravelled system contains a layer of gravel in the drainfield. During construction, a drainfield ditch 1 to 3 feet below ground level is constructed. Its length is determined by the anticipated flow of effulent into the system from the home or rural office, as well as the soil's ability to absorb water. Washed gravel is poured into the bottom of the ditch, then over and around a perforated plastic pipe.![]()
Low-Pressure Dose SystemsLow-pressure dose systems (also known as low-pressure pipe systems) may offer an alternative where soil and topographical conditions do not permit placement of a conventional septic system. This is especially true where the topography requires the drainfield to be located up-hill from the the septic tanks or where there is uneven terrain that would otherwise preclude placement of a conventional system.Low-Pressure Dose Systems (LPDs) baiscally work like this: Beside the standard septic tank, an additional tank called a pumping chamber is installed. Under normal conditions, a low-pressure pump is turned on twice each day and forces wastewater in the pumping chamber to pass into the drainfield. Under an LPD application, the drainfield consists of small perforated pipes in shallow, gravel lined trenches 10" to 18" deep and 12" to 18" wide. Wastewater is pumped, or forced into the drainfield to the point where the entire field is saturated. Then the field is left to drain. This creates good aerobic conditions (aerated) thus promoting good bio-processing by bacteria and other parasites. Shallow placement also promotes evapo-transpiration, where evaporation and grass and other shallow rooted vegitation help eliminate wastewater. In an LPD system, the pumping chamber is designed to contain at least on extra day of effulent. More flow will cause alarms to be activated. With an LPD installation the drainfield is normally uphill from the septic tank to avoid the possibility of continuous distribution of effulent via gravity. When the drainfield are not located up-hill, the system will be designed is such a way that effulent will not leave the pumping chamber when the pump is turned off.
Evapotranspiration SystemsEvapotraspiration Systems (ETs) are typically feasible only in arid and semi-arid regions. Basically we are looking at climates where evaporation exceeds rainfall by at least 24" per year. The EP system relys on natural evaporation of wastewater through a sand barrier and simultaneous transpiration of water via the leaves of plants and grasses planted above the the drainfield.An ET system is similar to the systems described above except that the drainfield consists of a trench lined with an impervious barrier. At the bottom are perforated drainpipes surrounded by a layer of gravel. Above the gravel is a layer of sand that
is domed above the ground level.
Where the ground has some ability to absorb water, an ETA system may be employed. This is essentially the same system as an ET system with the exception that the drainfield is unsealed. This allows some of the water to perculate into the ground below the ETA beds. As a general rule, wastewater must be able to travel at least 2 to 4 feet of unsaturated soil before reaching ground water table. The advantage of an ETA over an ET system is the system's ability to operate in non-arid climates. In North Texas most permitting agencies require the construction of two fields and that the owner manually switch the wastewater flow between fields each month. Obviously, this requires a larger land area for evapotranspiration field, yet this system has no moving parts, electrical requirement and has less frequent maintenance demands than LPD or Aerobic Systems Aerobic Wastewater Treatment SystemsClearly aerobic septic systems are the one system that can be applied in almost any situation where septic systems are required. When you own an aerobic system you are basically the owner of a small version of a municipal sewage plant. That is, your aerobic system mirrors many of the steps and activities performed by an urban waste treatment plant. Aerobic systems are similar to septic systems in that both treat wastewater using natural processes. However, unlike the conventional septic system, the aerobic system injects oxygen via a pump into the tank. This increase in oxygen increases the natural bacterial consumption of waste within the system. The best aerobic systems provide a pretreatment tank as well as a final treatment tank with unstabilized chlorine. At this point the resulting discharge water is clean enough and pure enough to be discharged via sprinklers directly over the absorption field. This is a real plus to home owners who don't want to clear trees to create an absorption field and to other homeowners on lots close to a body of water that might otherwise be subject to potential polution.![]() Many permitting agencies, including those in North Texas, are now requiring aerobic system installation for new home
construction as well as for failed conventional, LPD and Evapotranspiration systems. The clear environmental advantages of an aerobic system suggest that it may be the required system at some point in the future. An inexpensive maintenance contract will reduce the need for homeowner intervention and care.
Aerobic systems work like this: Wastewater and effulent enter a pre-treatment tank where grease, oils, toilet paper, and other solids and foreign materials are captured. This helps to reduce the amount of solids entering the aerobic chamber. Too many solids can clog the system and cause malfunctions. Next, the wastewater enters the aerobic chamber where air is compressed and forced into the wastewater to increase the growth of beneficial bacteria that consume the solids. However, not all solids are consumed by the bacteria, so the mixture next enters a setting or clarifying chamber where any remaining solids can settle. Next the treated water moves to a pumping chamber where is receives a final treatment of unstabilized chlorine. This is not the same chlorine as you use to shock your pool, but rather a highly concentrated, tablet form of chlorine specifically designed for the treatment of wastewater. A float valve within the pump chamber will signal the pump to discharge the water to absorption field. This treated water is then piped to the field and dispersed via pop-up sprinklers. Typically aerobic systems cost little more than conventional septic systems to install and maintain. Systems are specially designed with alarms and control boxes to assure that they are functioning properly at all times. Usually they are less expensive to install than LPDs or Evapotranspiraton systems as there is no need to condition a drainfield with sand and/or gravel. Because you are basically running your own wastewater treatment plant, it is essential to secure the services of a qualified professional in order to obtain the periodic certification letters required by most permitting agencies. This maintenance contract will assure you that your plant is functioning within specifications at all times. Manufacturers provide a two-year waranty contract as a part of the purchase price. At the end of this time you will need to either renew your maintenance contract or obtain one from another waste water treatment professional. Septic Solutions of Texas offers three levels of aerobic system maintenance contracts for aerobic system owners in North Texas. Click here for details. Regardless of the type of system you would like to install, the starting place for determining your options is a soil analysis by a professional engineer. Without this analysis you cannot obtain a construction permit.
|