Instruct: Given a question, retrieve documents that can help answer the question.
Query: How big is the average septic tank?
A septic tank consists of one or more concrete or plastic tanks of between 4000 and 7500 liters (1,000 and 2,000 gallons); one end is connected to an inlet wastewater pipe and the other to a septic drain field. Generally these pipe connections are made with a T pipe, allowing liquid to enter and exit without disturbing any crust on the surface. Today, the design of the tank usually incorporates two chambers, each equipped with a manhole cover, and separated by a dividing wall with openings located about midway between the floor and roof of the tank.
Services for de-sludging tend to empty a septic tank completely, i.e. take out all septage, while the actual requirement is removal of settled solids, it's left purposefully incomplete so as to leave at least some of the microbial populations in place to continue the anaerobic degradation processes that take place in a septic tank. An empty tank may be damaged by hydrostatic pressure causing the tank to partially "float" out of the ground, especially in flood situations or very wet ground conditions.[9]
A properly designed and normally operating septic system is odor-free and, besides periodic inspection and emptying of the septic tank, should last for decades with minimal maintenance.
Septic tanks also have a higher capital cost if they are being installed for new homes or if the existing septic tanks must be replaced. If there is a suitable septic tank in place, pumping the effluent from the tank is the lowest cost option for initial costs. Whether the septic tank is the lowest cost option over time depends on the cost of electricity in the area, how often the tank must be emptied and how much it costs to have the solids pumped out of the tank.
Additionally, a code of practice has been developed by the Environmental Protection Agency to regulate the planning and construction of new septic tanks, secondary treatment systems, septic drain fields and filter systems.[26] Direct discharge of septic tank effluent into groundwater is prohibited in Ireland, while the indirect discharge via unsaturated subsoil into groundwater, e.g. by means of a septic drain field, or the direct discharge into surface water is permissible in accordance with a Water Pollution Act license.[26] Registered septic tanks must be desludged by an authorized contractor at least once a year; the removed fecal sludge is disposed of, either to a managed municipal wastewater treatment facility or to agriculture provided that nutrient management regulations are met.[26]
In Australia, septic tank design and installation requirements are regulated by State Governments, through Departments of Health and Environmental Protection Agencies. Regulation may include Codes of Practice[31][32] and Legislation.[33] Regulatory requirements for the design and installation of septic tanks commonly references Australian Standards (1547 and 1546). Capacity requirements for septic tanks may be outlined within Codes of Practice, and can vary between states.
Weeping tile is used for the opposite reason in the septic drain fields for septic tanks. Clarified sewage from the septic tank is fed into weeping tiles buried shallowly in the drain field. The weeping tile spreads the liquid throughout the drain field.
The goal of percolation testing is to ensure the soil is permeable enough for septic tank effluent to percolate away from the drain field, but fine grained enough to filter out pathogenic bacteria and viruses before they travel far enough to reach a water well or surface water supply. Coarse soils – sand and gravel – can transmit wastewater away from the drain field before pathogens are destroyed. Silt and clay effectively filter out pathogens but allow very limited wastewater flow rates. Percolation tests measure the rate at which clean water disperses through a disposal trench into the soil. Several factors may reduce observed percolation rates when the drain field receives anoxic septic tank effluent:Just as the septic tank is sized to support a community of anaerobic organisms capable of liquifying anticipated amounts of putresible materials in wastewater, the drain field should be sized to support a community of aerobic soil microorganisms capable of decomposing the anaerobic septic tank's effluent into aerobic water. Hydrogen sulfide odors or iron bacteria may be observed in nearby wells or surface waters when effluent has not been completely oxidized prior to reaching those areas. The biofilm on the walls of the drain field trenches will use atmospheric oxygen in the trenches to catabolize organic compounds in septic tank effluent. Groundwater flow is laminar in the aquifer soils surrounding the drain field. Septic tank effluent with soluble organic compounds passing through the biofilm forms a mounded lens atop groundwater underlying the drain field. Molecular diffusion controls mixing of soluble organic compounds into groundwater and transport of oxygen from underlying groundwater or the capillary fringe of the groundwater surface to micro-organisms capable of catabolizing dissolved organic compounds remaining in the effluent plume.
The fermentation processes cause the contents of a septic tank to be anaerobic with a low redox potential, which keeps phosphates in a soluble and, thus, mobilized form. Phosphates discharged from a septic tank into the environment can trigger prolific plant growth including algal blooms, which can also include blooms of potentially toxic cyanobacteria.
Proponents claim the additives in wastewater can facilitate reduction in organic load and pathogen removal, leading to significant improvements in effluent quality. They also claim benefits relating to the rate of sludge build-up and odor reduction. One source claims that septic tank additives can reduce hydrogen sulphide and ammonia production. Their reasoning is that additives contain natural’ organisms that prevail over the rather less ‘natural’ organisms that would otherwise dominate conditions in the treatment unit, whether this be a septic tank or some form of aerobic treatment. They even claim that by overcoming the effects of ‘unnatural’ substances such as bleach and other disinfectants, the use of septic tank additives allows septic tanks and other treatment systems to function in conditions that would otherwise have resulted in their becoming ‘dead’ and non-functional.
Waste that is not decomposed by the anaerobic digestion must eventually be removed from the septic tank. Otherwise the septic tank fills up and wastewater containing undecomposed material discharges directly to the drainage field. Not only is this detrimental for the environment but, if the sludge overflows the septic tank into the leach field, it may clog the leach field piping or decrease the soil porosity itself, requiring expensive repairs.
Septic tank additives have been promoted by some manufacturers with the aim to improve the effluent quality from septic tanks, reduce sludge build-up and to reduce odors. However, these additives—which are commonly based on "effective microorganisms"—are usually costly in the longer term and fail to live up to expectations.[13] It has been estimated that in the U.S. more than 1,200 septic system additives were available on the market in 2011.[14] However, very little peer-reviewed and replicated field research exists regarding the efficacy of these biological septic tank additives.[14]
A septic tank is an underground chamber made of concrete, fiberglass or plastic through which domestic wastewater (sewage) flows for basic treatment.[1] Settling and anaerobic processes reduce solids and organics, but the treatment efficiency is only moderate (referred to as "primary treatment").[1] Septic tank systems are a type of simple onsite sewage facility (OSSF). They can be used in areas that are not connected to a sewerage system, such as rural areas. The treated liquid effluent is commonly disposed in a septic drain field which provides further treatment. However, groundwater pollution may occur and can be a problem.
Part 1 (EN 12566-1) is for septic tanks which are prefabricated or factory manufactured and made of polyethylene, glass reinforced polyester, polypropylene, PVC-U, steel or concrete. Part 4 (EN 12566-4) regulates septic tanks that are assembled in situ from prefabricated kits, generally of concrete construction. Certified septic tanks of both types must pass a standardized hydraulic test to assess their ability to retain suspended solids within the system. Additionally, their structural adequacy in relevant ground conditions is assessed in terms of water-tightness, treatment efficiency, and structural behaviour.[19]
The term "septic" refers to the anaerobic bacterial environment that develops in the tank which decomposes or mineralizes the waste discharged into the tank. Septic tanks can be coupled with other onsite wastewater treatment units such as biofilters or aerobic systems involving artificially forced aeration.[3]
In the United States, the 2007 American Housing Survey indicated that about 20 percent of all households rely on septic tanks, [17] and that the overwhelming majority of systems are located in rural (50%) and suburban (47%) areas.[17] Indianapolis is one example of a large city where many of the city's neighborhoods still rely on separate septic systems.[18] In Europe, septic systems are generally limited to rural areas.
The standard system is a tiled leach field combined with a septic tank. The basic idea is to provide a small system with primary sewage treatment. Sludge settles to the bottom of the septic tank, is partially reduced by anaerobic digestion, and fluid is dispersed in the leach field. The leach field is usually under a yard growing grass. Septic tanks can operate entirely by gravity, and if well managed, are reasonably safe.
Septage or "septic tank sludge" is partially treated sludge that is accumulated and stored in a septic tank or similar onsite sewage facility. Septage is a by-product from the pretreatment of household wastewater (sewage) in a septic tank. After a few years of accumulation, septage is usually pumped out of a septic tank by a vacuum truck. Septic tanks are receiving blackwater from flush toilets, as well as greywater. This means that septage only contains the kind of solid waste that can be flushed, such as toilet paper. Septage may also include "scum", which is material that floats at the top and contains fats, oil and grease as well as any floating solid waste. 
Septic tanks have to be pumped periodically by a vacuum truck to eliminate non reducing solids. Failure to pump a septic tank can cause overflow that damages the leach field, and contaminates ground water. Septic tanks may also require some lifestyle changes, such as not using garbage disposals, minimizing fluids flushed into the tank, and minimizing nondigestible solids flushed into the tank. For example, septic safe toilet paper is recommended.
While a properly maintained and located septic tank does not pose any more environmental problems than centralized municipal sewage treatment, certain problems can arise with septic tanks in unsuitable locations. Since septic systems require large drainfields, they are not suitable for densely built areas.
An Imhoff tank is a two-stage septic system where the sludge is digested in a separate tank. This avoids mixing digested sludge with incoming sewage. Also, some septic tank designs have a second stage where the effluent from the anaerobic first stage is aerated before it drains into the seepage field.
Most residents of Manila discharge their wastewater into an estimated 2.2 million septic tanks. The concessionaires are obliged to empty these septic tanks. Manila Water operates 60 desludging trucks that empty septic tanks free of charge. The sludge is brought to two septage treatment plants. Maynilad also operates desludging trucks, but so far does not have a septage treatment plant.
Ang Babae sa Septic Tank 2: Forever is Not Enough (; its subtitle stylized as #ForeverIsNotEnough) is a 2016 Filipino comedy film distributed by Quantum Films. It is the sequel to the 2011 film "Ang Babae Sa Septic Tank". The film was directed by Marlon Rivera, written by Chris Martinez, and stars Eugene Domingo, Jericho Rosales, Kean Cipriano (as film director Rainier de la Cuesta), Cai Cortez (as Rainier's line producer, Jocelyn), Khalil Ramos and Joel Torre. While the first film was a satire on the Philippine indie film industry and the dishonesty of Filipino filmmakers participating in foreign film festivals, "Ang Babae sa Septic Tank 2" satirizes the mainstream film industry.
A septic tank is part of a small scale sewage treatment system often referred to as a septic system. Septic systems are commonly used to treat wastewater from homes and small businesses in rural and suburban areas. It consists of the tank and a septic drain field. Waste water enters the tank where solids can settle and scum floats. Anaerobic digestion occurs on the settled solids, reducing the volume of solids. The water released by the system is normally absorbed by the drain field without needing any further treatment.
The United States Environmental Protection Agency (USEPA) produced a fact sheet on the use of pit additives to improve the performance of septic tank treatment systems. The fact sheet concludes that bacteria and extracellular enzymes do not appear to significantly enhance normal biological decomposition processes in septic tanks. They go on to say that ‘some biological additives have been found to degrade or dissipate septic tank scum and sludge. However, whether this relatively minor benefit is derived without compromising long-term viability of the soil infiltration system has not been demonstrated conclusively’. They noted that some studies suggest that material degraded by additives in the tank actually adds to the suspended solids and other contaminants in the otherwise clarified septic tank effluent.