Sewage

Sewage

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Sewage is water-carried waste, in solution or suspension, that is intended to be removed from a community. Also known as wastewater
Wastewater
Wastewater is any water that has been adversely affected in quality by anthropogenic influence. It comprises liquid waste discharged by domestic residences, commercial properties, industry, and/or agriculture and can encompass a wide range of potential contaminants and concentrations...

, it is more than 99% water and is characterized by volume
Volume
Volume is the quantity of three-dimensional space enclosed by some closed boundary, for example, the space that a substance or shape occupies or contains....

 or rate of flow, physical condition, chemical constituents and the bacteriological organisms that it contains. In loose American English
American English
American English is a set of dialects of the English language used mostly in the United States. Approximately two-thirds of the world's native speakers of English live in the United States....

 usage, the terms 'sewage' and 'sewerage
Sewerage
Sewerage refers to the infrastructure that conveys sewage. It encompasses receiving drains, manholes, pumping stations, storm overflows, screening chambers, etc. of the sanitary sewer...

' are sometimes interchanged. Both words are descended from Old French assewer, derived from the Latin exaquare, "to drain out (water)"

Categories


Classes of sewage include sanitary, commercial, industrial, agricultural and surface runoff
Surface runoff
Surface runoff is the water flow that occurs when soil is infiltrated to full capacity and excess water from rain, meltwater, or other sources flows over the land. This is a major component of the water cycle. Runoff that occurs on surfaces before reaching a channel is also called a nonpoint source...

. The spent water from residences and institutions, carrying body wastes, washing
Washing
Washing is one way of cleaning, namely with water and often some kind of soap or detergent. Washing is an essential part of good hygiene and health....

 water, food preparation wastes, laundry wastes, and other waste products of normal living, are classed as domestic or sanitary sewage. Liquid-carried wastes from stores and service establishments serving the immediate community, termed commercial wastes, are included in the sanitary or domestic sewage category if their characteristics are similar to household flows. Wastes that result from an industrial process or the production or manufacture of goods are classed as industrial wastewater. Their flows and strengths are usually more varied, intense, and concentrated than those of sanitary sewage. Surface runoff
Surface runoff
Surface runoff is the water flow that occurs when soil is infiltrated to full capacity and excess water from rain, meltwater, or other sources flows over the land. This is a major component of the water cycle. Runoff that occurs on surfaces before reaching a channel is also called a nonpoint source...

, also known as storm flow or overland flow, is that portion of precipitation
Precipitation (meteorology)
In meteorology, precipitation In meteorology, precipitation In meteorology, precipitation (also known as one of the classes of hydrometeors, which are atmospheric water phenomena is any product of the condensation of atmospheric water vapor that falls under gravity. The main forms of precipitation...

 that runs rapidly over the ground surface to a defined channel
Channel (geography)
In physical geography, a channel is the physical confine of a river, slough or ocean strait consisting of a bed and banks.A channel is also the natural or human-made deeper course through a reef, sand bar, bay, or any shallow body of water...

. Precipitation absorbs gases and particulates from the atmosphere
Atmosphere
An atmosphere is a layer of gases that may surround a material body of sufficient mass, and that is held in place by the gravity of the body. An atmosphere may be retained for a longer duration, if the gravity is high and the atmosphere's temperature is low...

, dissolves and leaches
Leaching (agriculture)
In agriculture, leaching refers to the loss of water-soluble plant nutrients from the soil, due to rain and irrigation. Soil structure, crop planting, type and application rates of fertilizers, and other factors are taken into account to avoid excessive nutrient loss.Leaching may also refer to ...

 materials from vegetation
Vegetation
Vegetation is a general term for the plant life of a region; it refers to the ground cover provided by plants. It is a general term, without specific reference to particular taxa, life forms, structure, spatial extent, or any other specific botanical or geographic characteristics. It is broader...

 and soil
Soil
Soil is a natural body consisting of layers of mineral constituents of variable thicknesses, which differ from the parent materials in their morphological, physical, chemical, and mineralogical characteristics...

, suspends matter from the land, washes spills
Spill containment
Spill containment is where spills of chemicals, oils, sewage etc are contained within a barrier or drainage system rather than being absorbed at the surface. One method is to use an inflatable stopper or pneumatic bladder which is inserted into the outflow of a drainage system to create a...

 and debris from urban streets and highways, and carries all these pollutants as wastes in its flow to a collection point
Waste collection
Waste collection is the component of waste management which results in the passage of a waste material from the source of production to either the point of treatment or final disposal...

.

Disease potential


All categories of sewage are likely to carry pathogenic organisms
Pathogen
A pathogen gignomai "I give birth to") or infectious agent — colloquially, a germ — is a microbe or microorganism such as a virus, bacterium, prion, or fungus that causes disease in its animal or plant host...

 that can transmit disease to humans and other animals; contain organic matter that can cause odor and nuisance problems; hold nutrients that may cause eutrophication
Eutrophication
Eutrophication or more precisely hypertrophication, is the movement of a body of water′s trophic status in the direction of increasing plant biomass, by the addition of artificial or natural substances, such as nitrates and phosphates, through fertilizers or sewage, to an aquatic system...

 of receiving water bodies; and can lead to ecotoxicity
Ecotoxicity
Ecotoxicity, the subject of study of the field of ecotoxicology refers to the potential for biological, chemical or physical stressors to affect ecosystems...

. Proper collection and safe, nuisance-free disposal of the liquid wastes of a community are legally recognized as a necessity in an urbanized, industrialized society. The reality is, however, that around 90% of wastewater produced globally remains untreated, causing widespread water pollution
Pollution
Pollution is the introduction of contaminants into a natural environment that causes instability, disorder, harm or discomfort to the ecosystem i.e. physical systems or living organisms. Pollution can take the form of chemical substances or energy, such as noise, heat or light...

, especially in low-income countries.

Increasingly, agriculture
Agriculture
Agriculture is the cultivation of animals, plants, fungi and other life forms for food, fiber, and other products used to sustain life. Agriculture was the key implement in the rise of sedentary human civilization, whereby farming of domesticated species created food surpluses that nurtured the...

 is using untreated wastewater for irrigation. Cities provide lucrative markets for fresh produce, so are attractive to farmers. However, because agriculture has to compete for increasingly scarce water resources with industry and municipal users, there is often no alternative for farmers but to use water polluted with urban waste, including sewage, directly to water their crops. There can be significant health hazards related to using water loaded with pathogens in this way, especially if people eat raw vegetables that have been irrigated with the polluted water.

The International Water Management Institute
International Water Management Institute
The International Water Management Institute is a non-profit research organisation with headquarters in Colombo, Sri Lanka, and offices across Africa and Asia...

 has worked in India, Pakistan, Vietnam, Ghana, Ethiopia, Mexico and other countries on various projects aimed at assessing and reducing risks of wastewater irrigation. They advocate a ‘multiple-barrier’ approach to wastewater use, where farmers are encouraged to adopt various risk-reducing behaviours. These include ceasing irrigation a few days before harvesting to allow pathogens to die off in the sunlight, applying water carefully so it does not contaminate leaves likely to be eaten raw, cleaning vegetables with disinfectant or allowing fecal sludge used in farming to dry before being used as a human manure. The World Health Organization
World Health Organization
The World Health Organization is a specialized agency of the United Nations that acts as a coordinating authority on international public health. Established on 7 April 1948, with headquarters in Geneva, Switzerland, the agency inherited the mandate and resources of its predecessor, the Health...

 has developed guidelines for safe water use.

Collection and disposal


A system of sewer
Sanitary sewer
A sanitary sewer is a separate underground carriage system specifically for transporting sewage from houses and commercial buildings to treatment or disposal. Sanitary sewers serving industrial areas also carry industrial wastewater...

 pipes (sewers) collects sewage and takes it for treatment or disposal. The system of sewers is called sewerage
Sanitary sewer
A sanitary sewer is a separate underground carriage system specifically for transporting sewage from houses and commercial buildings to treatment or disposal. Sanitary sewers serving industrial areas also carry industrial wastewater...

or sewerage system (see London sewerage system
London sewerage system
The London sewerage system is part of the water infrastructure serving London. The modern system was developed during the late 19th century, and as London has grown the system has been expanded.-History:...

) in British English and sewage system in American English. Where a main sewerage system has not been provided, sewage may be collected from homes by pipes into septic tank
Septic tank
A septic tank is a key component of the septic system, a small-scale sewage treatment system common in areas with no connection to main sewage pipes provided by local governments or private corporations...

s or cesspit
Cesspit
A cesspit, or cesspool is a pit, conservancy tank, or covered cistern, which can be used to dispose of urine and feces, and more generally of all sewage and refuse. It is a more antiquated solution than a sewer system. Traditionally, it was a deep cylindrical chamber dug into the earth, having...

s, where it may be treated or collected in vehicle
Vehicle
A vehicle is a device that is designed or used to transport people or cargo. Most often vehicles are manufactured, such as bicycles, cars, motorcycles, trains, ships, boats, and aircraft....

s and taken for treatment or disposal. Properly functioning septic tanks require emptying every 2–5 years depending on the load of the system.

Sewage and wastewater is also disposed of to rivers, streams and the sea in many parts of the world. Doing so can lead to serious pollution of the receiving water. This is common in third world countries and may still occur in some developed countries, where septic tank systems are too expensive.

Treatment



Sewage treatment
Sewage treatment
Sewage treatment, or domestic wastewater treatment, is the process of removing contaminants from wastewater and household sewage, both runoff and domestic. It includes physical, chemical, and biological processes to remove physical, chemical and biological contaminants...

 is the process of removing the contaminants from sewage to produce liquid and solid (sludge
Sludge
Sludge refers to the residual, semi-solid material left from industrial wastewater, or sewage treatment processes. It can also refer to the settled suspension obtained from conventional drinking water treatment, and numerous other industrial processes...

) suitable for discharge to the environment or for reuse. It is a form of waste management
Waste management
Waste management is the collection, transport, processing or disposal,managing and monitoring of waste materials. The term usually relates to materials produced by human activity, and the process is generally undertaken to reduce their effect on health, the environment or aesthetics...

. A septic tank or other on-site wastewater treatment system such as biofilters can be used to treat sewage close to where it is created.

Sewage water is a complex matrix, with many distinctive chemical characteristics. These include high concentrations of ammonium, nitrate, phosphorus, high conductivity (due to high dissolved solids), high alkalinity, with pH typically ranging between 7 and 8. Trihalomethanes are also likely to be present as a result of past disinfection.

In developed countries sewage collection and treatment is typically subject to local, state and federal regulations and standards.

Conversion to fertiliser


Sewage sludge can be collected through a sludge processing plant that automatically heats the matter and conveys it into fertiliser pellets (hereby removing possible contamination by chemical detergents, ...) This approach allows to eliminate seawater pollution by conveying the water directly to the sea without treatment (a practice which is still common in developing countries, despite environmental regulation). Sludge plants are useful in areas that have already set-up a sewage-system, but not in areas without such a system, as composting toilets are more efficient and do not require sewage pipes (which break over time).

Electricity


Power can also be obtained from sewage water. The technique uses Microbial fuel cell
Microbial fuel cell
A microbial fuel cell or biological fuel cell is a bio-electrochemical system that drives a current by mimicking bacterial interactions found in nature....

s.

See also

  • Blackwater (waste)
    Blackwater (waste)
    Blackwater is a term dating to at least the 1970s used to describe wastewater containing fecal matter and urine. It is also known as brown water, foul water, or sewage...

  • Chopper pumps
    Chopper pumps
    A chopper pump is a centrifugal pump, which is equipped with a cutting system to facilitate chopping/maceration of solids that are present in the pumped liquid. The main advantage of this type of pump is that it prevents clogging of the pump itself and of the adjacent piping, as all the solids and...

  • Cloaca Maxima
    Cloaca Maxima
    The Cloaca Maxima is one of the world's earliest sewage systems. Constructed in Ancient Rome in order to drain local marshes and remove the waste of one of the world's most populous cities, it carried an effluent to the River Tiber, which ran beside the city....

  • Directive on Urban Waste Water Treatment
  • Ecological sanitation
    Ecological sanitation
    Ecological sanitation, also known as ecosan or eco-san, are terms coined to describe a form of sanitation that usually involves urine diversion and the recycling of water and nutrients contained within human wastes back into the local environment....

  • Humanure
  • Sanitary sewer overflow
    Sanitary sewer overflow
    Sanitary sewer overflow is a condition whereby untreated sewage is discharged into the environment prior to reaching treatment facilities thereby escaping wastewater treatment. When caused by rainfall it is also known as wet weather overflow. It is primarily meaningful in developed countries,...

  • Sewage pumping
    Sewage pumping
    Sewage pumping is normally done by a submersible pump.This became popular in the early 1960s, when a guide-rail system was developed to lift the submersible pump out of the pump station for repair, and ended the dirty and sometimes dangerous task of sending people into the sewage or wet pit...

  • Sewerage
    Sewerage
    Sewerage refers to the infrastructure that conveys sewage. It encompasses receiving drains, manholes, pumping stations, storm overflows, screening chambers, etc. of the sanitary sewer...

  • Vacuum sewerage
    Vacuum sewerage
    A vacuum sewer system uses the differential pressure between atmospheric pressure and a partial vacuum maintained in the piping network and vacuum station collection vessel. This differential pressure allows a central vacuum station to collect the wastewater of several thousand individual homes,...

  • Waste management
    Waste management
    Waste management is the collection, transport, processing or disposal,managing and monitoring of waste materials. The term usually relates to materials produced by human activity, and the process is generally undertaken to reduce their effect on health, the environment or aesthetics...

  • wastewater
    Wastewater
    Wastewater is any water that has been adversely affected in quality by anthropogenic influence. It comprises liquid waste discharged by domestic residences, commercial properties, industry, and/or agriculture and can encompass a wide range of potential contaminants and concentrations...

  • Water quality
    Water quality
    Water quality is the physical, chemical and biological characteristics of water. It is a measure of the condition of water relative to the requirements of one or more biotic species and or to any human need or purpose. It is most frequently used by reference to a set of standards against which...


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