Parts of a Septic System
Differences between pretreatment and advanced pretreatment
Pretreatments prepare wastewater from the onsite system for its final treatment in the surrounding soil. A traditional pretreatment removes most solid waste from wastewater and prepares the wastewater for final treatment in the soil. Advanced treatment reduces organic strength, disinfects, and reduces nutrient content, which creates a cleaner effluent prior to final soil treatment. This provides additional treatment for soils that are receiving larger amount of organic compounds and waste in wastewater than pretreatment alone can handle. This is often utilized at sites with a higher risk of public or environmental health issues, like locations that provide public services or is close to a common water source.
Inlet and Outlet Baffles
Liquid enters the septic tank through an inlet baffle. Baffles keep the sludge, scum, and wastewater layers separate, which allows clarified wastewater to move into the soil treatment area. The water moving into the soil treatment area should have low solids content. The outlet baffle ensures only water from this “clarified” zone leaves the tank. Clarified wastewater is commonly called “septic tank effluent.” Wastewater entering the tank displaces an equal volume out of the tank, so the amount of septic tank effluent leaving the tank must be equal to the amount of waste water that enters. Outlet Baffles also prevent the scum layer from leaving the tank with the septic tank effluent.
Pump, Pump Tanks, Controls
A typical pump system consists of a pump tank, a dose pump, and controls. The pump tank collects wastewater until the next pump cycle. The pump will activate at a preset time or fluid level. It usually holds a two-day wastewater volume before the pump cycle changes. A pump tank must be accessible from the surface for maintenance and any repair needs. Dose pumps, most commonly submersible pumps, transfer the contents to the next component. It acts as a water lift, typically less than one horsepower, and uses a small amount of electricity. Dose pumps typically last 7 to 10 years. Controls, such as floats and timers, read the tank’s fluid level and activate or deactivate the pump as needed. Controls are accessed via a weatherproof control panel containing one of more float systems. Panels can provide information about pump operation, how to activate/deactivate the pump, and how to sound the alarm in case of emergency.
Effluent/Wastewater Dispersal
Blackwater vs Greywater
80% of the water brought into a dwelling leaves as wastewater. The two major types of wastewater encountered in most homes are blackwater and greywater. Blackwater is wastewater from toilets, kitchen sink, and dishwasher. It contains more pathogens and food waste than greywater. Greywater is wastewater from the laundry and shower, with higher concentrations of soap chemicals
Applying effluent to the soil
Soil-based wastewater treatment systems use 2-3 foot wide trenches partially backfilled with porous media to place effluent in the subsurface soil. This storage is necessary when the inflow of water to the trench is more significant than the outflow by infiltration into the soil. While gravel was the most common trench media, other materials, such as durable plastics, are becoming an increasingly common alternative.
Common dispersal methods
The most common ways of applying effluent into the soil after treatment are via gravity, pressurized, and combined treatment and dispersal. Gravity distribution systems are considered the conventional dispersal system. Gravity systems distribute effluent through the soil area via gravity. The effluent enters one end of the trench and moves to the other end on the opposite side, infiltrating the trench as it moves. It is considered to have poor distribution uniformity but takes the least amount of maintenance of all the dispersal systems.
Pressurized distribution provides good application uniformity but requires the installation of a pump tank, pump, electricity, and a control system. It is considered a low-pressure pipe system, with small perforations spaced consistently along the system, allowing for a more even distribution.
A combined treatment and dispersal system is often used in low permeability soils or shallow soils where organic matter from wastewater can further decrease permeability. These systems provide extra treatment to ensure organic matter removal from soils that are less capable of treating the water on its own.
Two noteworthy treatment-dispersal methods are via sand-lined trenches and mound systems. Sand-lined trenches act as trench media filters, providing additional treatment in the trench as air moves through the sand and creates an aerobic atmosphere allowing for bacterial growth. The bacteria remove more organic compounds, transform nutrients, and filter solids.
Mound systems were the first combined treatment dispersal system. They provide treatment by trickling effluent through media, which removes organic material and limits potential for soil clogging. Mound systems involve the creation of mounds that are coved with native soil and vegetation. These systems are often used in sites with very shallow soil.
Maintenance Overview (General Information)
Hiring a qualified professional
Every 1-5 years, depending on tank size and water use within the home, your septic system should be evaluated for cleaning/pumping. Inspections should be carried out annually if you have an advanced treatment system or a system with electrical components. This process is typically carried out via the services of a maintenance service provider. These individuals are licensed and trained to clean out tanks, service advanced treatment systems, make repairs to the tank, evaluate soil treatment areas, and report results to permitting authorities if required. After the evaluation, the provider should provide you with a septic tank cleaning report that includes the amount of sludge and scum, any tank leakage, or overall safety concerns with tank access, and troubleshooting or repairs needed/conducted. If the report is not provided, be sure to request one.
Additives
There is no third-party scientific research or evidence indicating that additives are required for septic system management. There is no quick-fix for maintenance and proper operation, as the system already has all the nutrients and bacterial requirements necessary naturally. Starters are unnecessary as the bacteria that exists in wastewater is already sufficient. Feeders are unnecessary as the material within wastewater acts as food for bacteria and cleaners are banned by some Indiana regulations as they run the risk of moving solids out of septic tanks that should be settled out on their own. The most recommended practice is allowing the septic system to operate as set up and establishing consistent evaluations, as suggested earlier, to ensure system functionality.
Maintenance Process
Septic Tank Maintenance
A licensed professional should perform septic tank maintenance to ensure practical evaluation and continued functionality. Solids must be removed from the septic tank to prevent overloading the pretreatment or soil treatment areas and backing wastewater up back into the home, which can result in surfacing. There are measuring devices utilized with septic systems to measure sludge and scum levels inside the tank. Tank cleaning becomes required when greater than 25% of the tank is storing sludge or scum. Backflushing and stirring are required to mix contents and get sludge off the bottom of the tank when cleaning. Pumping will leave a film on the tank walls, with a small amount of liquid visible on the tank floor. The bacteria within that liquid will regenerate the bacterial activity in the tank. The tank must be cleaned through a large maintenance hole cover approximately 20 inches wide. Be sure to have the contractor check for leaks or damage and ensure the baffles are in place. It may cost more initially to have the tank pumped through the maintenance hole, but it saves money in the long term. 4–6-inch inspection ports should not be used for cleaning.
Effluent screen cleaning
If your septic tank has an effluent screen, specifically on the outlet baffle, it should be cleaned according to screen size and use/condition. The effluent screen can be cleaned by either a septic professional or the owner of the septic tank; just be sure to clean it as prescribed by the manufacturer. The cleaning interval for the screen should be more frequent than complete tank cleaning, such as every six months. The screen should be washed off directly into the septic tank, with protective gloves on at all times. It is also recommended that the cleaning be done at the inlet end of the tank to protect against debris exiting the outlet end right away.
Typical maintenance of all soil treatment areas; professional will evaluate
During your service visit, the provider should evaluate the surfacing of effluent, signs of traffic over the system, depth of ponding in inspection ports, inappropriate vegetation growth on or near the system, and excessive surface water collecting over the system. It is also recommended that the property owner also note these conditions.
Typical maintenance with gravity distribution systems
For typical inspection, the distribution device (header, drop, or distribution boxes) should be opened, cleaned, and adjusted to ensure equalized flow to the various lines.
Typical maintenance of pressure soil treatment systems
The distribution system should be evaluated for uniform, even distribution of effluent across the soil treatment area. When cleanouts are available, the pipes are flushed and cleaned. The laterals may also need to be flushed to remove biosolids that may have accumulated.
Typical maintenance of pumps and controls
As maintenance is underway, confirm that the pump is working and set appropriately, accessible and replaceable, elevated, and alarmed. A tank with a pump may need cleaning if sludge is present. Run times and cycles on pumps should be recorded when available.
Private well
If you have a drinking water supply accessible by a private well, be sure to have the water tested regularly for contamination. Testing becomes even more important if young children are drinking from the well. Water should be tested for Coliform bacteria on a yearly basis, nitrate every other year, arsenic and lead at least once during the well’s lifespan, and manganese before a baby drinks from the water.