Septic tank

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Septic tank
Septic tank Bolduc.jpg
A septic tank being installed in the ground
Position in sanitation chainCollection and storage/treatment (on-site) [1]
Application levelHousehold or neighborhood level (schools, hotels etc.) [1]
Management levelHousehold, public, shared (most common is household level) [1]
Inputs blackwater (waste), greywater, brownwater [1]
Outputs Fecal sludge, effluent [1]
TypesSingle tank or multi-chamber septic tanks (potentially with baffles) [1]
Environmental concerns Groundwater pollution, water pollution e.g. during floods [1]

A septic tank is an underground chamber made of concrete, fiberglass, or plastic through which domestic wastewater (sewage) flows for basic sewage treatment. [2] Settling and anaerobic digestion processes reduce solids and organics, but the treatment efficiency is only moderate (referred to as "primary treatment"). [2] Septic tank systems are a type of simple onsite sewage facility. 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. Nonetheless, groundwater pollution may occur and is a problem.

Contents

The term "septic" refers to the anaerobic bacterial environment that develops in the tank that 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]

The rate of accumulation of sludge—also called septage or fecal sludge—is faster than the rate of decomposition. [2] Therefore, the accumulated fecal sludge must be periodically removed, which is commonly done with a vacuum truck. [4]

Description

Schematic of a septic tank Schematic of a septic tank 2.png
Schematic of a septic tank
Septic tank and septic drain field Landpeople s cc8.PNG
Septic tank and septic drain field

A septic tank consists of one or more concrete or plastic tanks of between 4,500 and 7,500 litres (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 an access opening and cover, and separated by a dividing wall with openings located about midway between the floor and roof of the tank.

Wastewater enters the first chamber of the tank, allowing solids to settle and scum to float. The settled solids are anaerobically digested, reducing the volume of solids. The liquid component flows through the dividing wall into the second chamber, where further settlement takes place. The excess liquid, now in a generally clear condition, then drains from the outlet into the septic drain field, also referred to as a leach field, drain field or seepage field, depending upon locality. A percolation test is required prior to installation to ensure the porosity of the soil is adequate to serve as a drain field. [5] [6]

The remaining impurities are trapped and eliminated in the soil, with the excess water eliminated through percolation into the soil, through evaporation, and by uptake through the root system of plants and eventual transpiration or entering groundwater or surface water. A piping network, often laid in a stone-filled trench (see weeping tile), distributes the wastewater throughout the field with multiple drainage holes in the network. The size of the drain field is proportional to the volume of wastewater and inversely proportional to the porosity of the drainage field. The entire septic system can operate by gravity alone or, where topographic considerations require, with inclusion of a lift pump.

Certain septic tank designs include siphons or other devices to increase the volume and velocity of outflow to the drainage field. These help to fill the drainage pipe more evenly and extend the drainage field life by preventing premature clogging or bioclogging.

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.

A properly designed and normally operating septic system is odour-free. Besides periodic inspection and emptying, a septic tank should last for decades with minimal maintenance, with concrete, fibreglass, or plastic tanks lasting about 50 years. [7]

Emptying (desludging)

A vacuum truck used to empty septic tanks in Germany Emptying of a tank full with sewage by vacuum truck (2921521126).jpg
A vacuum truck used to empty septic tanks in Germany

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.

When a septic tank is emptied, the accumulated sludge (septage, also known as fecal sludge [8] ) is pumped out of the tank by a vacuum truck. How often the septic tank must be emptied depends on the volume of the tank relative to the input of solids, the amount of indigestible solids, and the ambient temperature (because anaerobic digestion occurs more efficiently at higher temperatures), as well as usage, system characteristics and the requirements of the relevant authority.

Some health authorities require tanks to be emptied at prescribed intervals, while others leave it up to the decision of an inspector. Some systems require pumping every few years or sooner, while others may be able to go 10–20 years between pumpings. An older system with an undersize tank that is being used by a large family will require much more frequent pumping than a new system used by only a few people. Anaerobic decomposition is rapidly restarted when the tank is refilled.

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]

Another option is "scheduled desludging" of septic tanks which has been initiated in several Asian countries including the Philippines, Malaysia, Vietnam, Indonesia, and India. [10] In this process, every property is covered along a defined route and the property occupiers are informed in advance about desludging that will take place.

Maintenance

The maintenance of a septic system is often the responsibility of the resident or property owner. Some forms of abuse or neglect include the following:

User's actions

Other factors

Septic tank additives

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. These additives—which are commonly based on "effective microorganisms"—are usually costly in the longer term and fail to live up to expectations. [14] It has been estimated that in the U.S. more than 1,200 septic system additives were available on the market in 2011. [15] Very little peer-reviewed and replicated field research exists regarding the efficacy of these biological septic tank additives. [15]

Environmental concerns

A septic tank before installation, with manhole cover on top Septic tank not in ground.jpg
A septic tank before installation, with manhole cover on top
The same tank partially installed in the ground Septic tank.jpg
The same tank partially installed in the ground

While a properly maintained and located septic tank poses no higher amount of environmental problems than centralized municipal sewage treatment, [16] certain problems could arise with a septic tank in an unsuitable location, and septic tank failures are typically more expensive to fix or replace than municipal sewer. [16] Since septic systems require large drainfields, they are unsuitable for densely built areas.

Odor and gas emissions

Some constituents of wastewater, especially sulfates, under the anaerobic conditions of septic tanks, are reduced to hydrogen sulfide, a pungent and toxic gas. Methane may also be released. Nitrates and organic nitrogen compounds can be reduced to ammonia. Because of the anaerobic conditions, fermentation processes take place, which may generate carbon dioxide and/or methane.[ citation needed ]

Nutrients in the effluent

Septic tanks by themselves are ineffective at removing nitrogen compounds that have potential to cause algal blooms in waterways into which affected water from a septic system finds its way. This can be remedied by using a nitrogen-reducing technology, [17] or by simply ensuring that the leach field is properly sited to prevent direct entry of effluent into bodies of water.[ citation needed ]

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.

The soil's capacity to retain phosphorus is usually large enough to handle the load through a normal residential septic tank. An exception occurs when septic drain fields are located in sandy or coarser soils on property adjacent to a water body. Because of limited particle surface area, these soils can become saturated with phosphates. Phosphates will progress beyond the treatment area, posing a threat of eutrophication to surface waters. [18]

Pathogens

Diseases extremely dangerous to human contact such as E. coli and other coliform bacteria are often reported following failures of septic tanks. [19]

A properly functioning septic system, on the other hand, provides significant reduction of pathogens compared to direct discharge due to settling (in the tank) and soil absorption (in the drain field). Log reductions of 48 for coliform bacteria, 02 for viruses are achieved in the effluent. Parasitic worm eggs are also removed. Additional filters may be added to improve removal performance although they will need to be replaced periodically. [20]

Groundwater pollution

In areas with high population density, groundwater pollution beyond acceptable limits may occur. Some small towns experience the costs of building very expensive centralized wastewater treatment systems because of this problem, due to the high cost of extended collection systems. To reduce residential development that might increase the demand to construct an expensive centralized sewerage system, building moratoriums and limitations on the subdivision of property are often imposed. Ensuring existing septic tanks are functioning properly can also be helpful for a limited time, but becomes less effective as a primary remediation strategy as population density increases.

Surface water pollution

In areas adjacent to water bodies with fish or shellfish intended for human consumption, improperly maintained and failing septic systems contribute to pollution levels that can force harvest restrictions and/or commercial or recreational harvest closures.

Use

In the United States, the 2008 American Housing Survey indicated that about 20 percent of all households rely on septic tanks, [21] and that the overwhelming majority of systems are located in rural (50%) and suburban (47%) areas. [21] Indianapolis is one example of a large city where many of the city's neighborhoods still rely on separate septic systems. [22] In Europe, septic systems are generally limited to rural areas.[ citation needed ]

Regulations

European Union

In the European Union the EN 12566 standard provides the general requirements for packaged and site assembled treatment plants used for domestic wastewater treatment.

Part 1 (EN 12566-1) is for septic tanks that 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 on site 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. [23]

France

In France, about 4 million households (or 20% of the population) are using on-site wastewater disposal systems (l’assainissement non collectif), [24] including septic tanks (fosse septique). The legal framework for regulating the construction and maintenance of septic systems was introduced in 1992 and updated in 2009 and 2012 with the intent to establish the technical requirements applicable to individual sewerage systems. [25] Septic tanks in France are subject to inspection by SPANC (Service Public d’Assainissement Non Collectif), a professional body appointed by the respective local authorities to enforce wastewater collection laws, at least once in four years. Following the introduction of EN 12566, the discharge of effluent directly into ditches or watercourses is prohibited, unless the effluent meets prescribed standards. [26]

Ireland

According to the Census of Ireland 2011, 27.5% of Irish households (i.e. about 440,000 households), with the majority in rural areas, use an individual septic tank. [27]

Following a European Court of Justice judgment made against Ireland in 2009 that deemed the country non-compliant with the Waste Framework Directive in relation to domestic wastewaters disposed of in the countryside, the Water Services (Amendment) Act 2012 was passed in order to regulate wastewater discharges from domestic sources that are not connected to the public sewer network and to provide arrangements for registration and inspection of existing individual domestic wastewater treatment systems. [28] [29]

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. [30] 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. [30] 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. [30]

United Kingdom

Since 2015, only certain property owners in England and Wales with septic tanks or small packaged sewage treatment systems need to register their systems, and either apply for a permit or qualify for an exemption with the Environment Agency. [31] Permits need to be granted to systems that discharge more than a certain volume of effluent in a given time or that discharge effluent directly into sensitive areas (e.g., some groundwater protection zones). [32] In general, permits are not granted for new septic tanks that discharge directly into surface waters. A septic tank discharging into a watercourse must be replaced or upgraded by 1 January 2020 to a Sewage Treatment Plant (also called an Onsite sewage facility), or sooner if the property is sold before this date, or if the Environment Agency (EA) finds that it is causing pollution.

In Northern Ireland, the Department of the Environment must give permission for all wastewater discharges where it is proposed that the discharge will go to a waterway or soil infiltration system. The discharge consent will outline conditions relating to the quality and quantity of the discharge in order to ensure the receiving waterway or the underground aquifer can absorb the discharge. [33]

The Water Environment Regulations 2011 regulate the registration of septic tank systems in Scotland. Proof of registration is required when new properties are being developed or existing properties change ownership. [34]

Australia

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 [35] [36] and Legislation. [37] 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.

Mainly because of water leaching from the effluent drains of a lot of closely spaced septic systems, [38] many council districts (e.g. Sunshine Coast, Queensland) have banned septic systems, and require them to be replaced with much more expensive small-scale sewage treatment systems that actively pump air into the tank, producing an aerobic environment.[ citation needed ] Septic systems have to be replaced as part of any new building applications, regardless of how well the old system performed.[ citation needed ]

United States

According to the US Environmental Protection Agency, in the United States it is the home owners' responsibility to maintain their septic systems. [39] Anyone who ignores this requirement will eventually experience costly repairs when solids escape the tank and clog the clarified liquid effluent disposal system.

In Washington, for example, a "shellfish protection district" or "clean water district" is a geographic service area designated by a county to protect water quality and tideland resources. The district provides a mechanism to generate local funds for water quality services to control non-point sources of pollution, such as septic system maintenance. The district also serves as an educational resource, calling attention to the pollution sources that threaten shellfish growing waters. [40]

Slang usage

The term "septic tank", or more usually "septic", is used in some parts of Britain as a slang term to refer to Americans, [41] from Cockney rhyming slang septic tank equalling yank. [42] This is sometimes further shortened to "seppo" by Australians . [43]

See also

Related Research Articles

<span class="mw-page-title-main">Sewage sludge</span> Semi-solid material that is produced as a by-product during sewage treatment

Sewage sludge is the residual, semi-solid material that is produced as a by-product during sewage treatment of industrial or municipal wastewater. The term "septage" also refers to sludge from simple wastewater treatment but is connected to simple on-site sanitation systems, such as septic tanks.

<span class="mw-page-title-main">Sanitary sewer</span> Underground pipe for transporting sewage

A sanitary sewer is an underground pipe or tunnel system for transporting sewage from houses and commercial buildings to a sewage treatment plant or disposal. Sanitary sewers are a type of gravity sewer and are part of an overall system called a "sewage system" or sewerage. Sanitary sewers serving industrial areas may also carry industrial wastewater. In municipalities served by sanitary sewers, separate storm drains may convey surface runoff directly to surface waters. An advantage of sanitary sewer systems is that they avoid combined sewer overflows. Sanitary sewers are typically much smaller in diameter than combined sewers which also transport urban runoff. Backups of raw sewage can occur if excessive stormwater inflow or groundwater infiltration occurs due to leaking joints, defective pipes etc. in aging infrastructure.

<span class="mw-page-title-main">Wastewater treatment</span> Converting wastewater into an effluent for return to the water cycle

Wastewater treatment is a process which removes and eliminates contaminants from wastewater and converts this into an effluent that can be returned to the water cycle. Once returned to the water cycle, the effluent creates an acceptable impact on the environment or is reused for various purposes. The treatment process takes place in a wastewater treatment plant. There are several kinds of wastewater which are treated at the appropriate type of wastewater treatment plant. For domestic wastewater, the treatment plant is called a Sewage Treatment. For industrial wastewater, treatment either takes place in a separate Industrial wastewater treatment, or in a sewage treatment plant. Further types of wastewater treatment plants include Agricultural wastewater treatment and leachate treatment plants.

<span class="mw-page-title-main">Composting toilet</span> Type of toilet that treats human excreta by a biological process called composting

A composting toilet is a type of dry toilet that treats human waste by a biological process called composting. This process leads to the decomposition of organic matter and turns human waste into compost-like material. Composting is carried out by microorganisms under controlled aerobic conditions. Most composting toilets use no water for flushing and are therefore called "dry toilets".

Human waste refers to the waste products of the human digestive system, menses, and human metabolism including urine and feces. As part of a sanitation system that is in place, human waste is collected, transported, treated and disposed of or reused by one method or another, depending on the type of toilet being used, ability by the users to pay for services and other factors. Fecal sludge management is used to deal with fecal matter collected in on-site sanitation systems such as pit latrines and septic tanks.

<span class="mw-page-title-main">Cesspit</span> Underground holding tank or soak pit

Cesspit, cesspool and soak pit in some contexts are terms with various meanings: they are used to describe either an underground holding tank or a soak pit. A cesspit can be used for the temporary collection and storage of feces, excreta or fecal sludge as part of an on-site sanitation system and has some similarities with septic tanks or with soak pits. Traditionally, it was a deep cylindrical chamber dug into the ground, having approximate dimensions of 1 metre (3') diameter and 2–3 metres depth. Their appearance was similar to that of a hand-dug water well.

<span class="mw-page-title-main">Constructed wetland</span> Artificial wetland to treat municipal or industrial wastewater, greywater or stormwater runoff

A constructed wetland is an artificial wetland to treat sewage, greywater, stormwater runoff or industrial wastewater. It may also be designed for land reclamation after mining, or as a mitigation step for natural areas lost to land development. Constructed wetlands are engineered systems that use the natural functions of vegetation, soil, and organisms to provide secondary treatment to wastewater. The design of the constructed wetland has to be adjusted according to the type of wastewater to be treated. Constructed wetlands have been used in both centralized and decentralized wastewater systems. Primary treatment is recommended when there is a large amount of suspended solids or soluble organic matter.

<span class="mw-page-title-main">Agricultural wastewater treatment</span> Farm management for controlling pollution from confined animal operations and surface runoff

Agricultural wastewater treatment is a farm management agenda for controlling pollution from confined animal operations and from surface runoff that may be contaminated by chemicals in fertilizer, pesticides, animal slurry, crop residues or irrigation water. Agricultural wastewater treatment is required for continuous confined animal operations like milk and egg production. It may be performed in plants using mechanized treatment units similar to those used for industrial wastewater. Where land is available for ponds, settling basins and facultative lagoons may have lower operational costs for seasonal use conditions from breeding or harvest cycles. Animal slurries are usually treated by containment in anaerobic lagoons before disposal by spray or trickle application to grassland. Constructed wetlands are sometimes used to facilitate treatment of animal wastes.

<span class="mw-page-title-main">Industrial wastewater treatment</span> Processes used for treating wastewater that is produced by industries as an undesirable by-product

Industrial wastewater treatment describes the processes used for treating wastewater that is produced by industries as an undesirable by-product. After treatment, the treated industrial wastewater may be reused or released to a sanitary sewer or to a surface water in the environment. Some industrial facilities generate wastewater that can be treated in sewage treatment plants. Most industrial processes, such as petroleum refineries, chemical and petrochemical plants have their own specialized facilities to treat their wastewaters so that the pollutant concentrations in the treated wastewater comply with the regulations regarding disposal of wastewaters into sewers or into rivers, lakes or oceans. This applies to industries that generate wastewater with high concentrations of organic matter, toxic pollutants or nutrients such as ammonia. Some industries install a pre-treatment system to remove some pollutants, and then discharge the partially treated wastewater to the municipal sewer system.

<span class="mw-page-title-main">Septic drain field</span> Type of subsurface wastewater disposal facility

Septic drain fields, also called leach fields or leach drains, are subsurface wastewater disposal facilities used to remove contaminants and impurities from the liquid that emerges after anaerobic digestion in a septic tank. Organic materials in the liquid are catabolized by a microbial ecosystem.

Onsite sewage facilities (OSSF), also called septic systems, are wastewater systems designed to treat and dispose of effluent on the same property that produces the wastewater, in areas not served by public sewage infrastructure.

An aerobic treatment system (ATS), often called an aerobic septic system, is a small scale sewage treatment system similar to a septic tank system, but which uses an aerobic process for digestion rather than just the anaerobic process used in septic systems. These systems are commonly found in rural areas where public sewers are not available, and may be used for a single residence or for a small group of homes.

<span class="mw-page-title-main">Sewage treatment</span> Process of removing contaminants from municipal wastewater

Sewage treatment is a type of wastewater treatment which aims to remove contaminants from sewage to produce an effluent that is suitable to discharge to the surrounding environment or an intended reuse application, thereby preventing water pollution from raw sewage discharges. Sewage contains wastewater from households and businesses and possibly pre-treated industrial wastewater. There are a high number of sewage treatment processes to choose from. These can range from decentralized systems to large centralized systems involving a network of pipes and pump stations which convey the sewage to a treatment plant. For cities that have a combined sewer, the sewers will also carry urban runoff (stormwater) to the sewage treatment plant. Sewage treatment often involves two main stages, called primary and secondary treatment, while advanced treatment also incorporates a tertiary treatment stage with polishing processes and nutrient removal. Secondary treatment can reduce organic matter from sewage,  using aerobic or anaerobic biological processes. A so-called quarternary treatment step can also be added for the removal of organic micropollutants, such as pharmaceuticals. This has been implemented in full-scale for example in Sweden.

<span class="mw-page-title-main">Sewage</span> Wastewater that is produced by a community of people

Sewage is a type of wastewater that is produced by a community of people. It is typically transported through a sewer system. Sewage consists of wastewater discharged from residences and from commercial, institutional and public facilities that exist in the locality. Sub-types of sewage are greywater and blackwater. Sewage also contains soaps and detergents. Food waste may be present from dishwashing, and food quantities may be increased where garbage disposal units are used. In regions where toilet paper is used rather than bidets, that paper is also added to the sewage. Sewage contains macro-pollutants and micro-pollutants, and may also incorporate some municipal solid waste and pollutants from industrial wastewater.

<span class="mw-page-title-main">Reuse of human excreta</span> Safe, beneficial use of human excreta mainly in agriculture (after treatment)

Reuse of human excreta is the safe, beneficial use of treated human excreta after applying suitable treatment steps and risk management approaches that are customized for the intended reuse application. Beneficial uses of the treated excreta may focus on using the plant-available nutrients that are contained in the treated excreta. They may also make use of the organic matter and energy contained in the excreta. To a lesser extent, reuse of the excreta's water content might also take place, although this is better known as water reclamation from municipal wastewater. The intended reuse applications for the nutrient content may include: soil conditioner or fertilizer in agriculture or horticultural activities. Other reuse applications, which focus more on the organic matter content of the excreta, include use as a fuel source or as an energy source in the form of biogas.

<span class="mw-page-title-main">Fecal sludge management</span> Collection, transport, and treatment of fecal sludge from onsite sanitation systems

Fecal sludge management (FSM) is the storage, collection, transport, treatment and safe end use or disposal of fecal sludge. Together, the collection, transport, treatment and end use of fecal sludge constitute the "value chain" or "service chain" of fecal sludge management. Fecal sludge is defined very broadly as what accumulates in onsite sanitation systems and specifically is not transported through a sewer. It is composed of human excreta, but also anything else that may go into an onsite containment technology, such as flushwater, cleansing materials, menstrual hygiene products, grey water, and solid waste. Fecal sludge that is removed from septic tanks is called septage.

<span class="mw-page-title-main">Pit additive</span> Material to reduce fecal sludge build-up

Pit additives is a commercially-produced material that aims to reduce fecal sludge build-up and control odor in pit latrines, septic tanks and wastewater treatment plants. Manufacturers claim to use effective microorganisms (EM) in their products. Current scientific evidence does not back up most claims made by manufacturers about the benefits. Removing sludge continues to be a problem in pit latrines and septic tanks.

<span class="mw-page-title-main">Vermifilter</span> Aerobic treatment system, consisting of a biological reactor containing media

A vermifilter is an aerobic treatment system, consisting of a biological reactor containing media that filters organic material from wastewater. The media also provides a habitat for aerobic bacteria and composting earthworms that purify the wastewater by removing pathogens and oxygen demand. The "trickling action" of the wastewater through the media dissolves oxygen into the wastewater, ensuring the treatment environment is aerobic for rapid decomposition of organic substances.

<span class="mw-page-title-main">Decentralized wastewater system</span> Processes to convey, treat and dispose or reuse wastewater from small communities and alike

Decentralized wastewater systems convey, treat and dispose or reuse wastewater from small and low-density communities, buildings and dwellings in remote areas, individual public or private properties. Wastewater flow is generated when appropriate water supply is available within the buildings or close to them.

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