Overview of Septic Systems

wastewater is generated by every home and business across our nation however not everyone who generates wastewater is served by a centralized wastewater treatment plant these users must rely on an on-site wastewater treatment system traditionally known as a septic system though septic systems have been considered a temporary solution for wastewater management that philosophy is changing today we see these systems as a permanent solution to waste water management in these systems wastewater will remain on the property because of that you have to carefully consider the amount and the type of wastewater generated in other words the land must be able to accept and treat the amount of wastewater you discharge if the system is too small problems can occur an on-site system is designed for a specific amount of water based on the size purpose and average use of the facility for a home this design is greatly affected by square footage and the number of rooms however there are many factors that are considered including the water use habits of the family such as the use of a garbage disposal or the number of water saving devices wastewater contains organic matter solids nutrients and pathogens the strength and concentration of these elements depends largely on the activities being conducted in a facility in general a home will have less contaminated waste than a business but home-based businesses like daycares or bakeries can dramatically affect the quality of the wastewater this wastewater will require additional treatment all contaminants must be removed before the water migrates through the soil to our groundwater supplies while soil can do an excellent job of removing contaminants and treating wastewater not all soils are equal in some situations we must pre-treat wastewater to place it in a contamination level the soil can handle the process of installing an on-site wastewater treatment system has several important steps during these next few minutes we will try to take you through the process and introduce you to several different systems however it’s important to continue to research a system before you begin the installation process it is equally important to speak with a professional like your county permitting authority to be sure that the system you choose is best for both the soils on your property and the regulations that govern wastewater treatment and dispersal a wastewater treatment system should be worked into the landscape to take advantage of natural vegetation topography and soils topography refers to the slope of the land and its natural drainage channels the ideal situation places the on-site system moving downslope from the residents and all water wells rainfall runoff should be diverted off the treatment field this keeps the field from being saturated and possible failure of the system the location of the treatment system is critical though a treatment system must be a minimum of five feet from the building it is usually placed further away to allow better access for operation and maintenance periodically you will need to have solids pumped from the treatment tank this is accomplished by a vacuum truck with a hose that extends down into the treatment tanks pre-planning on how this truck will be able to get to the tanks will assist further maintenance the treatment tanks should not be placed in a low area where rain water will collect and flood the system watertight risers should be placed on top of the treatment tanks to allow access to the tanks and prevent rainwater from entering the system the soil should be evaluated across the site soil profiles can be consistent across a given track of land or can vary greatly within just a few feet the evaluation of soil in the treatment area should reveal the most restrictive layer in the soil this layer will determine the quantity of water that can flow through the system as it limits the flow of water through the soil to find this layer you evaluate the soil below the bottom of the land application system presence of shallow groundwater will limit the ability of the site to treat the waste water carefully evaluate the ability of each

soil layer to transport water this is based on the soil type or texture the slowest of these transport rates is used to determine the wastewater loading rate of the soil this rate along with the quantity of wastewater generated in a home is used to determine the size of the treatment area another important consideration is to place the wastewater treatment system a safe distance from any water wells wastewater is cleansed as it moves through the soil but if this distance is too short the wastewater could still contain nutrients and pathogens when it reaches the well site if the well casing and native soils have not bonded well partially treated water can easily flow along the casing contaminating the groundwater below for this reason it’s important to note the location of any neighboring wells even those abandoned or not on your property wastewater is 99.9 percent water contaminated with a small amount of organic matter suspended and dissolved solids nutrients and pathogens these contaminants must be removed from the wastewater before it leaves the soil treatment area the goal of the onsite wastewater treatment system is to remove these contaminants protecting public health and the environment pre-treatment systems remove a sufficient quantity of the contaminants so the soil can provide final treatment and reuse of the waste water when selecting the pre-treatment system you must determine the treatment capability of the soils at the site whether you wish to reuse the water to irrigate your landscape and the type of land application system each land application system requires a particular quality of effluent for it to function properly and generally reusing wastewater requires the highest quality of water a septic tank is an enclosed water-tight container consisting of one or two compartments it collects wastewater and provides primary treatment by allowing floatable and settlable solids to separate from the water settleable solids accumulate at the bottom of the tank while floatables such as oils and greases rise to the top water should remain in the tank for at least 24 to 36 hours to provide optimal treatment as much as 50 percent of these solids remain in the tank and decompose the rest accumulates as sludge at the tank bottom and must be removed periodically still the majority of the organic matter solids nutrients and pathogens remain in the wastewater as it leaves the septic tank an effluent filter is used to assist in removing additional solids from the wastewater this keeps larger solids from clogging the soil absorption field this filter needs to be maintained periodically by removing it from the tank outlet to wash the solids off its surface and back into the tank an alarm system will alert the homeowner if the filter becomes plugged and the tank water level begins to rise most of the septic tanks are made of concrete however fiberglass and plastic polyethylene tanks are becoming more prevalent these are lightweight and ideal for hard to reach spots all tanks must be watertight to keep water from entering the system because excess water entering the system can saturate the soil absorption field the result is water flowing above the ground surface using a septic tank to pre-treat sewage allows secondary treatment systems to work more effectively the effluent emerging from a septic tank is mild consistent flows easily and is better treated by both aerobic and anaerobic processes aerobic treatment units for homes and small businesses are similar to municipal wastewater treatment systems just on a smaller scale the effluent these systems produce is as clean as that from a municipal system and cleaner than that from a conventional septic tank these treatment systems remove a large percentage of the organic matter and suspended solids from the waste water however water exiting the system can still contain organic matter solids nutrients and pathogens the aerobic treatment process contains four main components the first is a permanent tank generally referred to as the trash tank this stage removes materials that microbes cannot degrade second is an aeration chamber treatment in the aeration chamber is a biological process the air supplied by the air pump allows microbes to thrive the microbes consume the waste transforming it into a non-polluting cell mass non-degradable material and gases the chamber contains an aeration system including an air pump piping and

diffusers to force air in the third component is a settling chamber commonly called the clarifier this allows the microbes to settle out this clarifier also includes a method for returning the bacteria to the aeration chamber finally the land application system distributes the treated water into the soil it is important to maintain an active population of microbes for the system to effectively break down solids this population is a diverse society of aerobic microorganisms that decompose a variety of materials in the clarifier this mass of microbes cells and non-biodegradable materials settle from the effluent before it leaves the system aerobic treatment processes greatly lower biological oxygen demand which is a common measure of system performance it also reduces the amount of suspended solids in the effluent below that of simple sedimentation sand filtration is one of the oldest known wastewater treatment technologies in simple terms it is a lined watertight box filled with specific sand materials if properly designed constructed operated and maintained a sand filter produces a very high quality effluent a typical sand filter system consists of a septic tank dosing tank sand filter and land application system the sand filter box can be constructed of concrete or an excavated hole lined with plastic sand filters intermittently dose wastewater onto the sand bed the wastewater passes through the bed before entering the land application system sand filters generally have 24 to 36 inches of sand for treatment of the waste water the bed is underlined with a bed of grated gravel and a collection pipe sand filters can either be open to the surface or buried below ground surface filters called free access are typically built above ground with a lid allowing easy access to the system landscape design can help blend these systems into the surrounding landscape below ground systems are completely buried and therefore blend seamlessly into a landscape recirculating media filters consists of a septic tank recirculation tank media bed and land application system in these systems wastewater is pumped from the recirculation tank distributed onto the surface of the media bed this aerates the wastewater as it’s allowed to drain back into the tank this media may consist of sand gravel plastic peat foam or fabric the main difference among these filters is the size of the media and the amount of wastewater that can be treated by the media media filters are used to aerobically treat the wastewater with microbes growing on the media surface these filters remove large material absorb small and dissolved material onto the surface of the media and this waste material is decomposed by the microbes media filters reduce the quantity of organic matter solids nutrients and pathogens the quality of the effluent depends on the media size and how the water moves through the system a film of biological growth on the media feeds on the contaminants contained in the waste water as the film grows it will exceed its ability to hold on to the media pieces the biological growth will break off and fall back into the tank with the waste water for decomposition wastewater flows from the recirculation tank into the land application system a constructed wetland is designed to mimic nature’s own processes using plants and microbes to treat wastewater one major difference is that in a natural wetland water is generally visible in the system while in a residential constructed wetland the water flow is maintained at a subsurface level this system consists of a septic tank constructed wetland bed and land application system these systems are designed to blend into and even enhance a landscape design the wetland consists of a bed of grated stone with water flowing just below the surface aquatic plants are grown in this bed feeding on the nutrients organic matter suspended solids and pathogens in the effluent the bed is set in an earthen basin lined with compacted native clay bentonite clay concrete pvc or a similar water type substance plants in the wetland must be able to survive in a saturated medium though both hard and soft tissue plants can be used in the system some experts prefer hard tissue plants believing they provide a pathway for oxygen to enter the wetland during winter months and reduce maintenance however many homeowners prefer

colorful flowering soft tissue plants disinfection systems are used as an additional safeguard against pathogens in the waste water disinfection systems are placed between a secondary treatment unit and a land application system three methods of disinfection are available chlorine ultraviolet light and ozone chlorinators are the most common type of disinfection system this system relies on a monthly addition of chlorine tablets to ensure disinfection of the waste water soil acts as the final stage of treatment in these systems it’s nature’s own age-old system of cleaning water microbes that occur naturally in the soil remove the remaining organic matter solids nutrients and pathogens from the water the type of land application system you can use depends on your site conditions which were determined during the site evaluation the most critical information is the type and depth of soil you have for treatment of the waste water there are several options for moving wastewater from your pre-treatment system into the soil the first systems we will discuss use gravity or the ability of water to flow downhill to distribute the water throughout the drain field these systems generally can follow a septic tank pre-treatment device and require good soils at the site the next systems require a pump for pressurizing the wastewater and distributing it throughout the drained field the pressurized systems are used in areas with limited soil depth available for wastewater treatment this type of shallow soil can be in areas with seasonally high groundwater or bedrock near the soil surface the conventional drain field consists of perforated pipes surrounded by a media such as gravel effluent passes through the pipe and is stored by the gravel until it can be absorbed into the soil the microbes decomposing the waste form a biological mat at the surface of the soil and at the bottom of the drain field the mat tends to slow down water movement and helps avoid soil saturation microbes in the soil feed on the waste nutrients and pathogens remaining in the waste water grass growing on the soil surface then utilizes that water this is not a good option for soils with high clay content leaching chambers are an alternative to pipe and gravel systems a hard plastic dome serves as a reservoir holding waste water until it can be moved into the surrounding soil these chambers have greater storage capacity than gravel filled systems which provide only 35 percent of the trench volume for water storage in contrast the dome is completely open and 100 of its open volume can’t hold waste water leaching chambers can also serve as reservoirs for facilities with intermittent high volume use the components are available in a variety of sizes and have connectors to allow construction of trenches to follow the contour of a site however you should be aware that maintenance and soil requirements for this system are quite similar to that of the media filled trenches this too is not a good option for soils with high clay content graveless pipe is an option to mediafill trenches in this system an 8 to 10 inch corrugated polyethylene pipe is wrapped with a geotextile fabric and buried in a whale aerated soil the fabric acts as a wick evenly distributing wastewater around the circumference of the pipe it also works to prevent backfill from entering the discharge holes of the pipe the chief advantage of this type of system is that the pipe is flexible it may be placed in curved trenches fitting a specific elevation on a sloping site however it requires a well aerated soil to prevent buildup of the biological mat on the geotextile fabric wrap and cannot be installed in clay soils the evapotranspiration bed relies on the natural properties of soil to lose water both by evaporation and transpiration from plants growing on top of the bed an evapotranspiration bed is a bed of sand with trenches in the bottom four storing the water until it’s evaporated or transpired by the plants evapotranspiration beds are used in areas where soil will not properly treat wastewater before it reaches groundwater sources

or where soil will not allow water to move through it these systems are designed based on rainfall and expected evapotranspiration rates these beds can be either lined or unlined depending on the permeability of the surrounding soil gravelly sands and car soils require a liner this can be made of natural clays synthetic lining or concrete online bins are used for impermeable soils like clay plant cover is essential for the proper function of these systems grasses and other plants must be well maintained for them to work properly a low pressure dosing system requires a pump tank and a network of small diameter pipes placed in trenches the pump tank stores the waste water and the pump doses it into the drain field so that the trenches do not become saturated the pressurized system provides a relatively even distribution of the wastewater across the drain field the trenches accepting the wastewater can be media filled or constructed with leaching chambers these trenches serve the purpose of storing the water until it can be absorbed by the soil this system is generally used to move affluent from a treatment site that sits at a lower elevation than the application site and in soils with high clay contents it is also used in shallow soils where seasonal high groundwater and bedrock occur between three to four feet below the soil surface a mound system consists of a pump tank and mound land application system the mound has several layers including permeable fill material a wastewater distribution system a sandy loam cap and topsoil the mound system is ideal for areas with minimal soil between the surface and either groundwater or bedrock a drain field is created above the natural soil surface to allow final treatment of wastewater in essence this is a traditional low pressure dosing system built above ground level its layers work in combination with native soil to treat the wastewater like its traditional counterparts it relies on the soil microbes to provide the natural treatment process a subsurface drip dispersal system provides uniform application of wastewater across the application field the system consists of a pump tank filtration system subsurface drip tubing and controller the pump tank stores the wastewater until the controller turns the pump on to dose water into the soil the filtration system removes the large solids from the wastewater and flushes the solids back to the pre-treatment device the drip tubing is placed directly into the soil without the use of media filled trenches the system relies on drip tubing with emitters to reduce the water pressure before it enters the soil since the emitters in the line have the same emission rate wastewater is uniformly applied to the dispersal field the drip field is constructed to spread water across the landscape tubing is placed approximately two feet apart in the landscape so the emitters are on a grid pattern the drip lines are buried relatively shallow so the soil can provide treatment and landscape plants can use the nutrients and water the tubing can be placed within the existing landscape a spray dispersal system utilizes a pump tank pump and spray heads to distribute wastewater on the surface of the ground the pump tank stores the water until it is time to dose the water to the spray area the system can either be an on-demand system which sprays the water whenever the tank is full or night dosing system which holds the water until night and then the water is dispersed most residents prefer a night dosing system when the effluent will be sprayed in the landscape these systems distribute wastewater across the soil surface much like a traditional lawn irrigation system therefore the system requires the highest quality effluent from the pre-treatment system wastewater must also be disinfected the surface area must have vegetation and be landscaped to avoid runoff also low trajectory sprinklers are used to minimize drift from the spray area wastewater is an unavoidable part of our lives but onsite wastewater treatment systems are an effective and efficient way to deal with wastewater and its contaminants when the right combination of pre-treatment and land application systems are joined with the natural treatment of land itself these wastes are recycled

and become a benefit for all you