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Sewage (or domestic sewage, domestic wastewater, municipal wastewater) is a type of
wastewater Wastewater is generated after the use of fresh water Water (chemical formula H2O) is an inorganic, transparent, tasteless, odorless, and nearly colorless chemical substance, which is the main constituent of Earth's hydrosphere and the ...

wastewater
that is produced by a
community A community is a social unitThe term "level of analysis" is used in the social sciences to point to the location, size, or scale of a research target. "Level of analysis" is distinct from the term " unit of observation" in that the former refer ...

community
of people. It is typically transported through a
sewer system Sewerage is the infrastructure Infrastructure is the set of fundamental facilities and systems that support the sustainable functionality of households and firms. Serving a country, city, or other area, including the services and facilities nece ...
. 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 Greywater (or grey water, sullage, also spelled gray water in the United States) refers to domestic wastewater generated in households or office buildings from streams without fecal contamination, i.e., all streams except for the wastewater from ...
(from sinks, bathtubs, showers, dishwashers, and clothes washers) and
blackwaterBlackwater or Black Water may refer to: Health and ecology * Blackwater (coal), liquid waste from coal preparation * Blackwater (waste), wastewater containing feces, urine, and flushwater from flush toilets * Blackwater fever, an acute kidney diseas ...
(the water used to flush
toilet A toilet is a piece of hardware that collects human and , and sometimes , usually for disposal. use water, while do not. They can be designed for a sitting position popular in Europe and North America with a , with , or for a squatting po ...

toilet
s, combined with the
human waste Human waste (or human excreta) refers to the waste products of the human digestive system, menses, and human metabolism including urine Urine is a liquid by-product of metabolism in humans and in many other animals. Urine flows from the kid ...
that it flushes away). Sewage also contains soaps and detergents. Food waste may be present from
dishwashing Dishwashing, washing the dishes, doing the dishes, or washing up in Great Britain, is the process of wikt:cleaning, cleaning cooking utensils, Dish (food), dishes, cutlery and other items to prevent foodborne illness. This is either achieved by ...

dishwashing
, and food quantities may be increased where
garbage disposal unit A garbage disposal unit (also known as a waste disposal unit, garbage disposer, garburator etc.) is a device, usually electrically powered, installed under a sink, kitchen sink between the sink's drain (plumbing), drain and the trap (plumbing), t ...
s are used. In regions where
toilet paper Toilet paper (sometimes called toilet tissue) is a tissue paper product primarily used to clean the human anus, anus and surrounding anal region of feces after defecation, and to clean the perineum, perineal area and external genitalia of ur ...
is used rather than
bidet A bidet ( or ) is a bowl or receptacle designed to be sat on for the purpose of washing Washing is a method of cleaning Cleaning is the process of removing unwanted substances, such as dirt, infectious agents, and other impurities, from an o ...

bidet
s, that paper is also added to the sewage. Sewage contains macro-pollutants and micro-pollutants, and may also incorporate some
municipal solid waste Municipal solid waste (MSW), commonly known as trash or garbage in the American English, United States and rubbish in British English, Britain, is a List of waste types, waste type consisting of everyday items that are discarded by the public. ...
and pollutants from
industrial wastewater 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 (or effluent) may be reused or released to a sa ...
. Sewage usually travels from a building's
plumbing Plumbing is any system that conveys fluids for a wide range of applications. Plumbing uses pipes, valves, plumbing fixtures, tanks, and other apparatuses to convey fluids. Heating and cooling (HVAC), waste removal, and potable water delive ...

plumbing
either into a
sewer Sewer may refer to: * Part of sewerage, the infrastructure that conveys sewage *Sanitary sewer, a system of pipes used to transport sewage - several types of sanitary sewers can be distinguished *Storm drain, a collection and transportation system ...
, which will carry it elsewhere, or into an
onsite sewage facility 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. A septic tank ...
. Collection of sewage of several households together usually takes places in either sanitary sewers or
combined sewers (POTW). During large storms, the relief structure allows some of the combined stormwater and sewage to be discharged untreated to an adjacent water body. A combined sewer is a sewage collection system of pipes, tunnels, and bodies of water desig ...
. The former is designed to exclude
stormwater entering a storm drain A storm drain, storm sewer (United Kingdom The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom (UK) or Britain,Usage is mixed. The Guardian' and Telegraph' use Britain as a ...
flows whereas the latter is designed to also take stormwater. The production of sewage generally corresponds to the water consumption. A range of factors influence water consumption and hence the sewage flowrates per person. These include: Water availability (the opposite of
water scarcity Water scarcity (water stress or water crisis) is the lack of fresh water resources to meet the standard water demand. Humanity is facing a water crisis, due to unequal distribution (exacerbated by climate change Climate change inclu ...

water scarcity
),
water supply Water supply is the provision of water Water (chemical formula H2O) is an inorganic, transparent, tasteless, odorless, and nearly colorless chemical substance, which is the main constituent of Earth's hydrosphere and the fluids of al ...
options,
climate Climate is the long-term average of weather, typically averaged over a period of 30 years. More rigorously, it is the mean and variability of meteorological variables over a time spanning from months to millions of years. Some of the meteorologi ...

climate
(warmer climates may lead to greater water consumption), community size, economic level of the community, level of
industrialization Factories, refineries, mines, and agribusiness are all elements of industrialisation Industrialisation ( alternatively spelled industrialization) is the period of social and economic change that transforms a human group from an agrarian societ ...

industrialization
, metering of household consumption, water cost and water pressure. The main parameters in sewage that are measured to assess the sewage strength or quality as well as treatment options include: solids, indicators of organic matter, nitrogen, phosphorus, and indicators of fecal contamination. These can be considered to be the main macro-pollutants in sewage. Sewage contains
pathogens In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecular interactions, Physiology, physiological mechanisms, ...
which stem from
fecal matter Feces (American and British English spelling differences#ae and oe, or faeces) is the solid or semisolid remains of food that was not digested in the small intestine, and has been broken down by bacteria in the large intestine. Feces contains a ...

fecal matter
. The following four types of pathogens are found in sewage: pathogenic
bacteria Bacteria (; common noun bacteria, singular bacterium) are a type of biological cell The cell (from Latin ''cella'', meaning "small room") is the basic structural, functional, and biological unit of all known organisms. Cells are the sm ...

bacteria
,
viruses A virus is a submicroscopic infectious agent In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecul ...

viruses
,
protozoa Protozoa (singular protozoon or protozoan, plural protozoa or protozoans) is an informal term for a group of Unicellular organism, single-celled eukaryotes, either free-living or Parasitism, parasitic, that feed on organic matter such as other mi ...

protozoa
(in the form of cysts or oocysts) and
helminths Parasitic worms, also known as helminths, are large macroparasites; adults can generally be seen with the naked eye. Many are intestinal worms that are soil-transmitted and infect the gastrointestinal tract The gastrointestinal tract, (GI ...
(in the form of eggs).Andersson, K., Rosemarin, A., Lamizana, B., Kvarnström, E., McConville, J., Seidu, R., Dickin, S. and Trimmer, C. (2016)
Sanitation, Wastewater Management and Sustainability: from Waste Disposal to Resource Recovery
. Nairobi and Stockholm: United Nations Environment Programme and Stockholm Environment Institute. , p. 56
In order to quantify the organic matter, indirect methods are commonly used: mainly the
Biochemical Oxygen Demand Biochemical oxygen demand (BOD) is the amount of dissolved oxygen Oxygen saturation (symbol SO2) is a relative measure of the concentration of oxygen Oxygen is the chemical element with the chemical symbol, symbol O and atomic nu ...
(BOD) and the
Chemical Oxygen Demand In environmental chemistry Environmental chemistry is the scientific study of the chemical and biochemical phenomena that occur in natural places. It should not be confused with green chemistry, which seeks to reduce potential pollution at its so ...
(COD). Management of sewage includes collection and transport for release into the environment, after a treatment level that is compatible with the local requirements for discharge into water bodies, onto soil or for reuse applications. Disposal options include dilution (self-purification of water bodies, making use of their assimilative capacity if possible), marine outfalls, land disposal and sewage farms. All disposal options may run risks of causing
water pollution Water pollution (or aquatic pollution) is the contamination of , usually as a result of human activities, in such a manner that negatively affects its legitimate uses. Water pollution reduces the ability of the body of water to provide the tha ...

water pollution
.


Terminology


Sewage and wastewater

Sewage (or domestic wastewater) consists of
wastewater Wastewater is generated after the use of fresh water Water (chemical formula H2O) is an inorganic, transparent, tasteless, odorless, and nearly colorless chemical substance, which is the main constituent of Earth's hydrosphere and the ...

wastewater
discharged from residences and from commercial, institutional and public facilities that exist in the locality. Sewage is a mixture of water (from the community's
water supply Water supply is the provision of water Water (chemical formula H2O) is an inorganic, transparent, tasteless, odorless, and nearly colorless chemical substance, which is the main constituent of Earth's hydrosphere and the fluids of al ...
),
human excreta Human waste (or human excreta) refers to the waste products of the human digestive system, menses, and human metabolism including urine and Human feces, faeces. As part of a sanitation system that is in place, human waste is collected, transpor ...
(
feces Feces ( or faeces) is the solid or semi-solid remains of food that was not digested in the small intestine The small intestine or small bowel is an organ (anatomy), organ in the human gastrointestinal tract, gastrointestinal tract where mos ...

feces
and
urine Urine is a liquid by-product A by-product or byproduct is a secondary product derived from a production process, process or ; it is not the primary product or service being produced. A by-product can be useful and marketable or it can be cons ...

urine
), used water from , food preparation wastes, laundry wastewater, and other waste products of normal living. Sewage from municipalities contains wastewater from commercial activities and institutions, e.g. wastewater discharged from
restaurant A restaurant is a business Business is the activity of making one's living or making money by producing or buying and selling products (such as goods and services). Simply put, it is "any activity or enterprise entered into for profit." ...

restaurant
s, ,
hospital A hospital is a health care institution providing patient treatment with specialized Medical Science, health science and Allied Healthcare, auxiliary healthcare staff and medical equipment. The best-known type of hospital is the general hospit ...

hospital
s,
school A school is an educational institution An educational institution is a place where people of different ages gain an education, including preschools, childcare, primary-elementary schools, secondary-high schools, and universities. They p ...

school
s,
prison A prison, also known as a jail or gaol (dated, English language in England, standard English, Australian English, Australian, and Huron Historic Gaol, historically in Canada), penitentiary (American English and Canadian English), detention ...

prison
s,
office An office is a space where an Organization, organization's employees perform Business administration, administrative Work (human activity), work in order to support and realize objects and Goals, plans, action theory, goals of the organizatio ...

office
s, stores and establishments serving the local area of larger communities. Sewage can be distinguished into "untreated sewage" (also called "raw sewage") and "treated sewage" (also called "effluent" from a sewage treatment plant). The term "sewage" is nowadays often used interchangeably with "wastewater" – implying "municipal wastewater" – in many textbooks, policy documents and the literature. To be precise, wastewater is a broader term, because it refers to any
water Water (chemical formula H2O) is an Inorganic compound, inorganic, transparent, tasteless, odorless, and Color of water, nearly colorless chemical substance, which is the main constituent of Earth's hydrosphere and the fluids of all known li ...

water
after it has been used in a variety of applications. Thus it may also refer to “
industrial wastewater 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 (or effluent) may be reused or released to a sa ...
”, agricultural wastewater and other flows that are not related to household activities.


Blackwater


Greywater


Overall appearance

The overall appearance of sewage is as follows: The temperature tends to be slightly higher than in drinking water but is more stable than the ambient temperature. The color of fresh sewage is slightly grey, whereas older sewage (also called "septic sewage") is dark grey or black. The
odor An odor (American English American English (AmE, AE, AmEng, USEng, en-US), sometimes called United States English or U.S. English, is the set of variety (linguistics), varieties of the English language native to the United States. Cur ...
of fresh sewage is "oily" and relatively unpleasant, whereas older sewage has an unpleasant foul odor due to
hydrogen sulfide Hydrogen sulfide is a chemical compound A chemical compound is a chemical substance A chemical substance is a form of matter In classical physics and general chemistry, matter is any substance that has mass and takes up space by havi ...

hydrogen sulfide
gas and other decomposition by-products. Sewage can have high
turbidity Turbidity is the cloudiness or haziness of a fluid In physics, a fluid is a substance that continually Deformation (mechanics), deforms (flows) under an applied shear stress, or external force. Fluids are a Phase (matter), phase of matter ...

turbidity
from suspended solids. The
pH value In chemistry Chemistry is the scientific discipline involved with Chemical element, elements and chemical compound, compounds composed of atoms, molecules and ions: their composition, structure, properties, behavior and the changes they ...

pH value
of sewage is usually near neutral, and can be in the range of 6.7–8.0.


Pollutants

Sewage consists primarily of water and usually contains less than one part of solid matter per thousand parts of water. In other words, one can say that sewage is composed of around 99.9% pure water, and the remaining 0.1% are solids, which can be in the form of either dissolved solids or
suspended solids Suspended solids refers to small solid particles which remain in suspension Suspension or suspended may refer to: Science and engineering * Suspension (topology), in mathematics * Suspension (dynamical systems), in mathematics * Suspension of a ri ...
. The thousand-to-one ratio is an order of magnitude estimate rather than an exact percentage because, aside from variation caused by dilution, solids may be defined differently depending upon the mechanism used to separate those solids from the liquid fraction.
Sludge Sludge is a semi-solid slurry A slurry composed of glass beads in silicone oil flowing down an inclined plane A slurry is a mixture of solids denser than water suspended in liquid, usually water. The most common use of slurry is as a means of ...

Sludge
s of settleable solids removed by
settling Settling is the process by which particulates settle to the bottom of a liquid and form a sediment Sediment is a naturally occurring material that is broken down by processes of weathering and erosion, and is subsequently sediment transport, tr ...
or
suspended solids Suspended solids refers to small solid particles which remain in suspension Suspension or suspended may refer to: Science and engineering * Suspension (topology), in mathematics * Suspension (dynamical systems), in mathematics * Suspension of a ri ...
removed by
filtration Filtration is a physical separation process A separation process is a method that converts a mixture or solution of chemical substances into two or more distinct product mixtures. At least one of results of the separation is enriched in one or m ...
may contain significant amounts of entrained water, while dried solid material remaining after evaporation eliminates most of that water but includes dissolved minerals not captured by filtration or gravitational separation. The suspended and dissolved solids include organic and inorganic matter plus microorganisms. About one-third of this solid matter is suspended by
turbulence In fluid dynamics In physics Physics is the natural science that studies matter, its Elementary particle, fundamental constituents, its Motion (physics), motion and behavior through Spacetime, space and time, and the related entities o ...

turbulence
, while the remainder is dissolved or
colloid A colloid is a mixture In chemistry, a mixture is a material made up of two or more different chemical substances which are not chemically combined. A mixture is the physical combination of two or more substances in which the identities are r ...

colloid
al. For the situation in the United States in the 1950s it was estimated that the waste contained in domestic sewage is about half
organic Organic may refer to: * Organic, of or relating to an organism, a living entity * Organic, of or relating to an anatomical organ (anatomy), organ Chemistry * Organic matter, matter that has come from a once-living organism, is capable of decay or ...
and half
inorganic In chemistry Chemistry is the scientific discipline involved with Chemical element, elements and chemical compound, compounds composed of atoms, molecules and ions: their composition, structure, properties, behavior and the changes they under ...
.


Organic matter

The organic matter in sewage can be classified in terms of form and size: Suspended (particulate) or dissolved (soluble). Secondly, it can be classified in terms of
biodegradability Biodegradation is the breakdown of organic matter Organic matter, organic material, or natural organic matter refers to the large source of Carbon compounds, carbon-based compounds found within natural and engineered, terrestrial, and aquatic ...
: either inert or biodegradable. The organic matter in sewage consists of
protein Proteins are large biomolecule , showing alpha helices, represented by ribbons. This poten was the first to have its suckture solved by X-ray crystallography by Max Perutz and Sir John Cowdery Kendrew in 1958, for which they received a No ...

protein
compounds (about 40%),
carbohydrate A carbohydrate () is a biomolecule , showing alpha helices, represented by ribbons. This poten was the first to have its suckture solved by X-ray crystallography by Max Perutz and Sir John Cowdery Kendrew in 1958, for which they received a ...
s (about 25–50%), oils and grease (about 10%) and
urea Urea, also known as carbamide, is an organic compound In , organic compounds are generally any s that contain - . Due to carbon's ability to (form chains with other carbon s), millions of organic compounds are known. The study of the prop ...

urea
,
surfactant Surfactants are compounds that lower the surface tension Surface tension is the tendency of liquid surfaces at rest to shrink into the minimum surface area possible. Surface tension is what allows objects with a higher density than wate ...

surfactant
s,
phenols In organic chemistry, phenols, sometimes called phenolics, are a class of chemical compounds consisting of one or more hydroxyl Functional group, groups (—Oxygen, OHydrogen, H) Chemical bond, bonded directly to an aromatic hydrocarbon group. The s ...
,
pesticide Pesticides are substances that are meant to control pests Pest or The Pest may refer to: Science and medicine * Pest (organism), an animal or plant detrimental to humans or human concerns ** Weed, a plant considered undesirable * Infectious d ...
s and others (lower quantity). In order to quantify the organic matter content, it is common to use "indirect methods" which are based on the consumption of oxygen to oxidize the organic matter: mainly the
Biochemical Oxygen Demand Biochemical oxygen demand (BOD) is the amount of dissolved oxygen Oxygen saturation (symbol SO2) is a relative measure of the concentration of oxygen Oxygen is the chemical element with the chemical symbol, symbol O and atomic nu ...
(BOD) and the
Chemical Oxygen Demand In environmental chemistry Environmental chemistry is the scientific study of the chemical and biochemical phenomena that occur in natural places. It should not be confused with green chemistry, which seeks to reduce potential pollution at its so ...
(COD). These indirect methods are associated with the major impact of the discharge of organic matter into water bodies: the organic matter will be food for microorganisms, whose population will grow, and lead to the consumption of oxygen, which may then affect aquatic living organisms. The mass load of organic content is calculated as the sewage flowrate multiplied with the concentration of the organic matter in the sewage. Typical values for physical–chemical characteristics of raw sewage is provided further down below.


Nutrients

Apart from organic matter, sewage also contains nutrients. The major nutrients of interest are
nitrogen Nitrogen is the chemical element upright=1.0, 500px, The chemical elements ordered by link=Periodic table In chemistry Chemistry is the science, scientific study of the properties and behavior of matter. It is a natural science ...

nitrogen
and
phosphorus Phosphorus is a chemical element In chemistry, an element is a pure Chemical substance, substance consisting only of atoms that all have the same numbers of protons in their atomic nucleus, nuclei. Unlike chemical compounds, chemical el ...

phosphorus
. If sewage is discharged untreated, its nitrogen and phosphorus content can lead to pollution of lakes and reservoirs via a process called
eutrophication Eutrophication (from Greek ''eutrophos'', "well-nourished") is the process by which an entire body of water (Lysefjord) in Norway Norway, officially the Kingdom of Norway,Names in the official and recognised languages: Bokmål Bokm ...

eutrophication
. In raw sewage, nitrogen exists in the two forms of organic nitrogen or
ammonia Ammonia is a chemical compound, compound of nitrogen and hydrogen with the chemical formula, formula NH3. A Binary compounds of hydrogen, stable binary hydride, and the simplest pnictogen hydride, ammonia is a colourless gas with a distinct ch ...

ammonia
. The ammonia stems from the
urea Urea, also known as carbamide, is an organic compound In , organic compounds are generally any s that contain - . Due to carbon's ability to (form chains with other carbon s), millions of organic compounds are known. The study of the prop ...

urea
in
urine Urine is a liquid by-product A by-product or byproduct is a secondary product derived from a production process, process or ; it is not the primary product or service being produced. A by-product can be useful and marketable or it can be cons ...

urine
. Urea is rapidly hydrolyzed and therefore not usually found in raw sewage. Total phosphorus is mostly present in sewage in the form of
phosphate In chemistry, a phosphate is an anion, salt (chemistry), salt, functional group or ester derived from a phosphoric acids and phosphates, phosphoric acid. It most commonly means orthophosphate, a derivative of phosphoric acid, orthophosphoric a ...

phosphate
s.They are either inorganic (polyphosphates and orthophosphates) and their main source is from
detergent A detergent is a surfactant Surfactants are compounds that lower the (or interfacial tension) between two liquids, between a gas and a liquid, or between a liquid and a solid. Surfactants may act as s, agents, , s, or s. The word "surfact ...
s and other household chemical products. The other form is organic phosphorus, where the source is organic compounds to which the organic phosphorus is bound.


Pathogens

Human feces Human feces (or faeces in British English British English (BrE) is the standard dialect A standard language (also standard variety, standard dialect, and standard) is a language variety that has undergone substantial codification of gra ...

Human feces
in sewage may contain
pathogen In biology, a pathogen ( el, πάθος, "suffering", "passion" and , "producer of") in the oldest and broadest sense, is any organism that can produce disease. A pathogen may also be referred to as an infectious agent, or simply a Germ theory ...
s capable of transmitting diseases. The following four types of pathogens are found in sewage: *
Bacteria Bacteria (; common noun bacteria, singular bacterium) are ubiquitous, mostly free-living organisms often consisting of one Cell (biology), biological cell. They constitute a large domain (biology), domain of prokaryotic microorganisms. Typ ...

Bacteria
like ''
Salmonella ''Salmonella'' is a genus Genus /ˈdʒiː.nəs/ (plural genera /ˈdʒen.ər.ə/) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruse ...
'', ''
Shigella ''Shigella'' is a genus Genus (plural genera) is a taxonomic rank Taxonomy (general) is the practice and science of classification of things or concepts, including the principles that underlie such classification. The term may also refer to ...
'', ''
Campylobacter ''Campylobacter'' (meaning "curved bacteria") is a genus Genus (plural genera) is a taxonomic rank Taxonomy (general) is the practice and science of classification of things or concepts, including the principles that underlie such classificat ...

Campylobacter
'', or ''
Vibrio cholerae ''Vibrio cholerae'' is a species of Gram-negative Gram-negative bacteria are bacteria Bacteria (; common noun bacteria, singular bacterium) are a type of Cell (biology), biological cell. They constitute a large domain (biology), domain o ...

Vibrio cholerae
''; *
Virus A virus is a submicroscopic infectious agent In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecu ...

Virus
es like
hepatitis A Hepatitis A is an infectious disease of the liver The liver is an organ only found in vertebrates which detoxifies various metabolites, synthesizes proteins and produces biochemicals necessary for digestion and growth. In humans, it is l ...
,
rotavirus ''Rotavirus'' is a genus Genus /ˈdʒiː.nəs/ (plural genera /ˈdʒen.ər.ə/) is a taxonomic rank In biological classification In biology, taxonomy () is the scientific study of naming, defining (Circumscription (taxonomy), cir ...

rotavirus
,
coronavirus Coronaviruses are a group of related Orthornavirae, RNA viruses that cause diseases in mammals and birds. In humans and birds, they cause respiratory tract infections that can range from mild to lethal. Mild illnesses in humans include some ca ...

coronavirus
,
enteroviruses ''Enterovirus'' is a genus of positive-sense single-stranded RNA virus Ribonucleic acid (RNA) is a polymer A polymer (; Greek '' poly-'', "many" + '' -mer'', "part") is a substance or material consisting of very large molecule Fi ...
; *
Protozoa Protozoa (singular protozoon or protozoan, plural protozoa or protozoans) is an informal term for a group of Unicellular organism, single-celled eukaryotes, either free-living or Parasitism, parasitic, that feed on organic matter such as other mi ...

Protozoa
like ''
Entamoeba histolytica ''Entamoeba histolytica'' is an parasitic n, part of the '. Predominantly infecting humans and other primates causing , ''E. histolytica'' is estimated to infect about 35-50 million people worldwide. ''E. histolytica'' infection is estimated t ...

Entamoeba histolytica
'', ''
Giardia lamblia ''Giardia duodenalis'', also known as ''Giardia intestinalis'' and ''Giardia lamblia'', is a flagellate 's '' Artforms of Nature'', 1904 (''Giardia lamblia'') ('' Chlamydomonas'') A flagellate is a cell or organism with one or more whip-like ...

Giardia lamblia
'', ''
Cryptosporidium parvum ''Cryptosporidium parvum'' is one of several species that cause cryptosporidiosis, a parasitic disease A parasitic disease, also known as parasitosis, is an infectious disease An infection is the invasion of an organism's body Tissue (biology ...

Cryptosporidium parvum
''; and *
Helminths Parasitic worms, also known as helminths, are large macroparasites; adults can generally be seen with the naked eye. Many are intestinal worms that are soil-transmitted and infect the gastrointestinal tract The gastrointestinal tract, (GI ...
and their eggs including ''
Ascaris ''Ascaris'' is a genus of parasite, parasitic nematode worms known as the "small intestinal roundworms", which is a type of parasitic worm. One species, ''Ascaris lumbricoides'', affects humans and causes the disease ascariasis. Another species, ...

Ascaris
'' (roundworm), ''
Ancylostoma ''Ancylostoma'' is a genus Genus (plural genera) is a taxonomic rank Taxonomy (general) is the practice and science of classification of things or concepts, including the principles that underlie such classification. The term may also refer t ...
'' (hookworm), and '''' (whipworm) In most practical cases, pathogenic organisms are not directly investigated in laboratory analyses. An easier way to assess the presence of fecal contamination is by assessing the most probable numbers of
fecal coliforms A fecal coliform (British: faecal coliform) is a facultatively anaerobic, rod-shaped A bacillus (plural bacilli), or bacilliform bacterium, is a rod-shaped bacterium Bacteria (; common noun bacteria, singular bacterium) are a type of Cel ...
(called thermotolerant coliforms), especially ''
Escherichia coli ''Escherichia coli'' (),Wells, J. C. (2000) Longman Pronunciation Dictionary. Harlow ngland Pearson Education Ltd. also known as ''E. coli'' (), is a Gram-negative bacteria, Gram-negative, Facultative anaerobic organism, facultative anaer ...

Escherichia coli
''. ''Escherichia coli'' are intestinal bacteria excreted by all warm blooded animals, including human beings, and thus tracking their presence in sewage is easy, because of their substantially high concentrations (around 10 to 100 million per 100 mL).


Solid waste

The ability of a
flush toilet A flush toilet (also known as a flushing toilet, water closet (WC) – see also toilet names) is a toilet A toilet is a piece of sanitary hardware that collects human urine and Human feces, feces, and sometimes toilet paper, usually for d ...
to make things "disappear" is soon recognized by young children who may experiment with virtually anything they can carry to the toilet. Adults may be tempted to dispose of
toilet paper Toilet paper (sometimes called toilet tissue) is a tissue paper product primarily used to clean the human anus, anus and surrounding anal region of feces after defecation, and to clean the perineum, perineal area and external genitalia of ur ...
,
wet wipe A wet wipe, also known as a wet towel or a moist towelette, disinfecting wipe, or a baby wipe in specific circumstances, is a small to medium-sized moistened piece of plastic or cloth that often comes folded and individually wrapped for convenien ...
s,
diaper A diaper /ˈdaɪpə(r)/ (American American(s) may refer to: * American, something of, from, or related to the United States of America, commonly known as the United States The United States of America (USA), commonly known as the U ...

diaper
s,
sanitary napkin A sanitary napkin, sanitary towel, feminine napkin, sanitary pad, menstrual pad, or pad is an Absorption (chemistry), absorbent item worn by women in their Undergarment, underwear when menstruation, menstruating, lochia, bleeding after giving bi ...
s,
tampon A tampon is a menstrual product designed to absorb blood and vaginal secretions by insertion into the vagina In mammals, the vagina is the elastic, muscular part of the female genital tract. In humans, it extends from the Vulval vestibule ...
s, tampon applicators,
condom A condom is a sheath-shaped barrier device used during sexual intercourse Sexual intercourse (or coitus or copulation) is a sexual activity Human sexual activity, human sexual practice or human sexual behaviour is the manner in ...

condom
s, and expired
medication A medication (also called medicament, medicine, pharmaceutical drug, medicinal drug or simply drug) is a drug used to medical diagnosis, diagnose, cure, therapy, treat, or preventive medicine, prevent disease. Drug therapy (pharmacotherapy) ...

medication
s, even at the risk of causing blockages. The privacy of a toilet offers a clandestine means of removing embarrassing evidence by flushing such things as
drug paraphernalia "Drug paraphernalia" is a term to denote any equipment, product or accessory that is intended or modified for making, using or concealing drugs, typically for Recreational drug use, recreational purposes. Drugs such as Cannabis (drug), marijuana ...
,
pregnancy test A pregnancy test is used to determine whether a woman is pregnant Pregnancy, also known as gestation, is the time during which one or more offspring develops inside a woman. A multiple birth, multiple pregnancy involves more than one offspri ...

pregnancy test
kits,
combined oral contraceptive pill The combined oral contraceptive pill (COCP), often referred to as the birth control pill or colloquially as "the pill", is a type of birth control Birth control, also known as contraception, anticonception, and fertility control, is a meth ...
dispensers, and the packaging for those devices. There may be reluctance to retrieve items like children's toys or toothbrushes which accidentally fall into toilets, and items of clothing may be found in sewage from prisons or other locations where occupants may be careless. Trash and garbage in streets may be carried to combined sewers by stormwater runoff.


Micro-pollutants

Sewage contains
environmental persistent pharmaceutical pollutant The term Environmental persistent pharmaceutical pollutants (EPPP) was first suggested in the nomination in 2010 of pharmaceuticals and environment as an emerging issue in a Strategic Approach to International Chemicals Management ( SAICM) by the ...
s.
Trihalomethane Trihalomethanes (THMs) are chemical compound A chemical compound is a chemical substance composed of many identical molecules (or molecular entity, molecular entities) composed of atoms from more than one chemical element, element held together ...
s can also be present as a result of past
disinfection Disinfectants are chemical agents designed to inactivate or destroy microorganisms on inert surfaces. Disinfection does not necessarily kill all microorganisms, especially resistant bacterial spores An endospore is a dormant, tough, and no ...
. Sewage may contain
microplastics Microplastics are fragments of any type of plastic less than in length, according to the U.S. National Oceanic and Atmospheric Administration (NOAA) and the European Chemicals Agency. They cause pollution by entering natural ecosystems from a va ...

microplastics
such as polyethylene and polypropylene beads, or polyester and polyamide fragments from synthetic clothing and bedding fabrics abraded by wear and laundering, or from plastic packaging and
plastic-coated paperPlastic-coated paper is a coated or laminated composite material made of paper or paperboard with a plastic layer or treatment on a surface. This type of coated paper is most used in the food packaging, food and drink packaging industry. Function T ...
products disintegrated by lift station pumps.
Pharmaceuticals A medication (also called medicament, medicine, pharmaceutical drug, medicinal drug or simply drug) is a drug used to medical diagnosis, diagnose, cure, therapy, treat, or preventive medicine, prevent disease. Drug therapy (pharmacotherapy) ...
, endocrine disrupting compounds, and
hormone A hormone (from the Greek#REDIRECT Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the Hellenic Republic, is a country located in Southeast Europe. Its population is appr ...

hormone
s may be excreted in urine or feces if not
catabolized Catabolism () is the set of Metabolism, metabolic pathways that breaks down molecules into smaller units that are either oxidized to release energy or used in other anabolic reactions. Catabolism breaks down large molecules (such as polysaccharid ...
within the human body. Some residential users tend to pour unwanted liquids like used
cooking oil Cooking oil is plant, animal, or synthetic fat In nutrition Nutrition is the biochemical and physiological process by which an organism In biology, an organism (from Ancient Greek, Greek: ὀργανισμός, ''organismos'') ...
,
lubricant A lubricant is a substance that helps to reduce friction Friction is the force In physics Physics is the natural science that studies matter, its Elementary particle, fundamental constituents, its Motion (physics), motion and b ...
s,
adhesive Adhesive, also known as glue, cement, mucilage, or paste, is any non-metallic substance applied to one or both surfaces of two separate items that them together and resists their separation. The use of adhesives offers certain advantages over ...
s,
paint Paint is any pigmented liquid A liquid is a nearly incompressible In fluid mechanics Fluid mechanics is the branch of physics concerned with the mechanics Mechanics (Ancient Greek, Greek: ) is the area of physics concerned wi ...

paint
,
solvent A solvent (from the Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken in the area around Rome, known as Latium. Through the power of the ...

solvent
s,
detergent A detergent is a surfactant Surfactants are compounds that lower the (or interfacial tension) between two liquids, between a gas and a liquid, or between a liquid and a solid. Surfactants may act as s, agents, , s, or s. The word "surfact ...
s, and
disinfectant A disinfectant is a chemical A chemical substance is a form of matter In classical physics and general chemistry, matter is any substance that has mass and takes up space by having volume. All everyday objects that can be touched are ...
s into their sewer connections. This behavior can result in problems for the treatment plant operation and is thus discouraged.


Typical sewage composition


Factors that determine composition

The composition of sewage varies with climate, social and economic situation and population habits. In regions where water use is low, the strength of the sewage (or pollutant concentrations) is much higher than that in the United States where water use per person is high. Household income and diet also plays a role: For example, for the case of Brazil, it has been found that the higher the household income, the higher is the BOD load per person and the lower is the BOD concentration.


Concentrations and loads

Typical values for physical–chemical characteristics of raw sewage in
developing countries A developing country is a sovereign state with a less developed Industrial sector, industrial base and a low Human Development Index (HDI) relative to other countries. However, this definition is not universally agreed upon. There is also no ...
have been published as follows: 180 g/person/d for total solids (or 1100 mg/L when expressed as a concentration), 50 g/person/d for BOD (300 mg/L), 100 g/person/d for COD (600 mg/L), 8 g/person/d for total nitrogen (45 mg/L), 4.5 g/person/d for ammonia-N (25 mg/L) and 1.0 g/person/d for total phosphorus (7 mg/L). The typical ranges for these values are: 120–220 g/person/d for total solids (or 700–1350 mg/L when expressed as a concentration), 40–60 g/person/d for BOD (250–400 mg/L), 80–120 g/person/d for COD (450–800 mg/L), 6–10 g/person/d for total nitrogen (35–60 mg/L), 3.5–6 g/person/d for ammonia-N (20–35 mg/L) and 0.7–2.5 g/person/d for total phosphorus (4–15 mg/L). For high income countries, the "per person organic matter load" has been found to be approximately 60 gram of BOD per person per day. This is called the
population equivalentPopulation equivalent or unit per capita loading, (PE), in waste-water treatment is the number expressing the ratio of the sum of the pollution load produced during 24 hours by industrial facilities and services to the individual pollution load in ...
(PE) and is also used as a comparison parameter to express the strength of
industrial wastewater 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 (or effluent) may be reused or released to a sa ...
compared to sewage. Values for households in the United States have been published as follows, whereby the estimates are based on the assumption that 25% of the homes have kitchen waste-food grinders (sewage from such households contain more waste): 95 g/person/d for total
suspended solids Suspended solids refers to small solid particles which remain in suspension Suspension or suspended may refer to: Science and engineering * Suspension (topology), in mathematics * Suspension (dynamical systems), in mathematics * Suspension of a ri ...
(503 mg/L concentration), 85 g/person/d for BOD (450 mg/L), 198 g/person/d for COD (1050 mg/L), 13.3 g/person/d for the sum of organic nitrogen and ammonia nitrogen (70.4 mg/L), 7.8 g/person/d for ammonia-N (41.2 mg/L) and 3.28 g/person/d for total phosphorus (17.3 mg/L). The concentration values given here are based on a flowrate of 190 L per person per day. A United States source published in 1972 estimated that the daily dry weight of solid wastes
per capita ''Per capita'' is a Latin phrase literally meaning "by heads" or "for each head", and idiomatically used to mean "per person". The term is used in a wide variety of social sciences and statistical research contexts, including government statistic ...
in sewage is estimated as in feces, of dissolved solids in urine, of toilet paper, of greywater solids, of food solids (if
garbage disposal unit A garbage disposal unit (also known as a waste disposal unit, garbage disposer, garburator etc.) is a device, usually electrically powered, installed under a sink, kitchen sink between the sink's drain (plumbing), drain and the trap (plumbing), t ...
s are used), and varying amounts of dissolved minerals depending upon salinity of local water supplies, volume of water use per capita, and extent of
water softener Water softening is the removal of calcium Calcium is a chemical element with the Symbol (chemistry), symbol Ca and atomic number 20. As an alkaline earth metal, calcium is a reactive metal that forms a dark oxide-nitride layer when exposed to ...
use. Sewage contains urine and feces. The mass of feces varies with dietary fiber intake. An average person produces 128 grams of wet feces per day, or a median dry mass of 29 g/person/day. The median urine generation rate is about 1.42 L/person/day, as was determined by a global literature review.


Flowrates

The volume of domestic sewage produced per person (or "
per capita ''Per capita'' is a Latin phrase literally meaning "by heads" or "for each head", and idiomatically used to mean "per person". The term is used in a wide variety of social sciences and statistical research contexts, including government statistic ...
", abbreviated as "cap") varies with the water consumption in the respective locality. A range of factors influence water consumption and hence the sewage flowrates per person. These include: Water availability (the opposite of
water scarcity Water scarcity (water stress or water crisis) is the lack of fresh water resources to meet the standard water demand. Humanity is facing a water crisis, due to unequal distribution (exacerbated by climate change Climate change inclu ...

water scarcity
),
water supply Water supply is the provision of water Water (chemical formula H2O) is an inorganic, transparent, tasteless, odorless, and nearly colorless chemical substance, which is the main constituent of Earth's hydrosphere and the fluids of al ...
options,
climate Climate is the long-term average of weather, typically averaged over a period of 30 years. More rigorously, it is the mean and variability of meteorological variables over a time spanning from months to millions of years. Some of the meteorologi ...

climate
(warmer climates may lead to greater water consumption), community size, economic level of the community, level of
industrialization Factories, refineries, mines, and agribusiness are all elements of industrialisation Industrialisation ( alternatively spelled industrialization) is the period of social and economic change that transforms a human group from an agrarian societ ...

industrialization
, metering of household consumption, water cost and water pressure. The production of sewage generally corresponds to the water consumption. However water used for landscape irrigation will not enter the sewer system, while groundwater and
stormwater entering a storm drain A storm drain, storm sewer (United Kingdom The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom (UK) or Britain,Usage is mixed. The Guardian' and Telegraph' use Britain as a ...
may enter the sewer system in addition to sewage. There are usually two peak flowrates of sewage arriving at a treatment plant per day: One peak is at the beginning of the morning and another peak is at the beginning of the evening. With regards to water consumption, a design figure that can be regarded as "world average" is 35–90 L per person per day (data from 1992). The same publication listed the water consumption in China as 80 L per person per day, Africa as 15–35 L per person per day, Eastern Mediterranean in Europe as 40–85 L per person per day and Latin America and Caribbean as 70–190 L per person per day. Even inside a country, there may be large variations from one region to another due to the various factors that determine the water consumption as listed above. A flowrate value of 200 liters of sewage per person per day is often used as an estimate in World Bank high-income economy, high income countries, and is used for example in the design of sewage treatment plants. For comparison, typical sewage flowrates from urban residential sources in the United States are estimated as follows: 365 L/person/day (for one person households), 288 L/person/day (two person households), 200 L/person/day (four person households), 189 L/person/day (six person households). This means the overall range for this example would be .


Analytical methods


General quality indicators


Specific organisms and substances

Sewage can be monitored for both disease-causing and benign organisms with a variety of techniques. Traditional techniques involve filtering, staining, and examining samples under a microscope. Much more sensitive and specific testing can be accomplished with DNA sequencing, such as when looking for rare organisms, attempting Eradication of infectious diseases, eradication, testing specifically for drug-resistant strains, or discovering new species. Sequencing DNA from an environmental sample is known as metagenomics. Sewage has also been analyzed to determine relative rates of use of prescription and illegal drugs among municipal populations. General socioeconomic demographics may be inferred as well.


Collection

Sewage is commonly collected and transported in Gravity sewer, gravity sewers, either in a sanitary sewer or in a combined sewer. The latter also conveys urban runoff (
stormwater entering a storm drain A storm drain, storm sewer (United Kingdom The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom (UK) or Britain,Usage is mixed. The Guardian' and Telegraph' use Britain as a ...
) which means the sewage gets diluted during rain events.


Sanitary sewer


Combined sewer


Dilution in the sewer


Infiltration of groundwater into the sewerage system

Infiltration is groundwater entering sewer pipes through defective pipes, connections, joints or manholes. Contaminated or saline water, saline groundwater may introduce additional pollutants to the sewage. The amount of such infiltrated water depends on several parameters, such as the length of the collection network, pipeline diameters, drainage area, soil type, water table depth, topography and number of connections per unit area. Infiltration is increased by poor construction procedures, and tends to increase with the age of the sewer. The amount of infiltration varies with the depth of the sewer in comparison to the local groundwater table. Older sewer systems that are in need of rehabilitation may also exfiltrate sewage into groundwater from the leaking sewer joints and service connections. This can lead to groundwater pollution.


Stormwater

Combined sewers are designed to transport sewage and stormwater together, and therefore sewage becomes diluted during rainfall events. Inflow similarly dilutes sewage with water discharged from cellar and foundation drains, cooling-water discharges, and any direct stormwater runoff connections to the sanitary collection system. The "direct inflows" can result in peak sewage flowrates similar to combined sewers during wet weather events.


Industrial wastewater

Sewage from communities with industrial facilities may include some
industrial wastewater 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 (or effluent) may be reused or released to a sa ...
, generated by industrial processes such as the production or manufacture of goods. Volumes of industrial wastewater vary widely with the type of industry. Industrial wastewater may contain very different pollutants at much higher concentrations than what is typically found in sewage. Pollutants may be toxic or non-Biodegradation, biodegradable waste including pharmaceuticals, biocides, heavy metals, radionuclides, or thermal pollution. An industry may treat its wastewater and discharge it into the environment (or even use the treated wastewater for specific applications), or, in case it is located in the urban area, it may discharge the wastewater into the public sewerage system. In the latter case, industrial wastewater may receive pre-treatment at the factories to reduce the pollutant load. Mixing industrial wastewater with sewage does nothing to reduce the mass of pollutants to be treated, but the volume of sewage lowers the concentration of pollutants unique to industrial wastewater, and the volume of industrial wastewater lowers the concentration of pollutants unique to sewage.


Disposal and dilution


Assimilative capacity of receiving water bodies or land

When wastewater is discharged into a Surface water, water body (river, lakes, sea) or land, its relative impact will depend on the assimilative capacity of the water body or ecosystem. Water bodies have a self-purification capacity, so that the concentration of a pollutant may decrease along the distance from the discharge point. Furthermore, water bodies provide a dilution to the pollutants concentrations discharged, although it does not decrease their mass. In principle, the higher the dilution capacity (ratio of volume or flow of the receiving water and volume or flow of sewage discharged), the lower will be the concentration of pollutants in the receiving water, and probably the lower will be the negative impacts. But if the water body already arrives very polluted at the point of discharge, the dilution will be of limited value. In several cases, a community may treat partially its sewage, and still count on the assimilative capacity of the water body. However, this needs to be analyzed very carefully, taking into account the quality of the water in the receiving body before it receives the discharge of sewage, the resulting water quality after the discharge and the impact on the intended water uses after discharge. There are also specific legal requirements in each country. Different countries have different regulations regarding the specifications of the quality of the sewage being discharged and the quality to be maintained in the receiving water body.The combination of treatment and disposal must comply with existing local regulations. The assimilative capacity depends – among several factors – on the ability of the receiving water to sustain dissolved oxygen concentrations necessary to support organisms Catabolism, catabolizing organic waste. For example, fish may die if dissolved oxygen levels are depressed below 5 mg/l. Application of sewage to land can be considered as a form of final disposal or of treatment, or both. Land disposal alternatives require consideration of land availability, groundwater quality, and possible soil deterioration.


Other disposal methods

Sewage may be discharged to an evaporation or infiltration basin.. Groundwater recharge is used to reduce saltwater intrusion, or replenish aquifers used for agricultural irrigation. Treatment is usually required to sustain percolation capacity of infiltration basins, and more extensive treatment may be required for aquifers used as drinking water supplies.


Marine outfall


Global situation


Treatment

Sewage treatment is beneficial in reducing environmental pollution. Bar screens can remove large solid debris from sewage, and Sewage treatment#Primary treatment, primary treatment can remove floating and settleable matter. Primary treated sewage usually contains less than half of the original solids content and approximately two-thirds of the BOD in the form of
colloid A colloid is a mixture In chemistry, a mixture is a material made up of two or more different chemical substances which are not chemically combined. A mixture is the physical combination of two or more substances in which the identities are r ...

colloid
s and Solvation, dissolved organic compounds. Secondary treatment can reduce the BOD of organic waste in undiluted sewage, but is less effective for dilute sewage. Water disinfection may be attempted to kill pathogens prior to disposal, and is increasingly effective after more elements of the foregoing treatment sequence have been completed.


Reuse and reclamation

An alternative to discharge into the environment is to Reclaimed water, reuse the sewage in a productive way (for agricultural, urban or industrial uses), in compliance with local regulations and requirements for each specific reuse application. Public health risks of sewage reuse in agriculture can be minimized by following a "multiple barrier approach" according to guidelines by the World Health Organization.WHO (2006)
WHO Guidelines for the Safe Use of Wastewater, Excreta and Greywater – Volume IV: Excreta and greywater use in agriculture
World Health Organization (WHO), Geneva, Switzerland
There is also the possibility of resource recovery which could make Sustainable agriculture, agriculture more sustainable by using carbon,
nitrogen Nitrogen is the chemical element upright=1.0, 500px, The chemical elements ordered by link=Periodic table In chemistry Chemistry is the science, scientific study of the properties and behavior of matter. It is a natural science ...

nitrogen
,
phosphorus Phosphorus is a chemical element In chemistry, an element is a pure Chemical substance, substance consisting only of atoms that all have the same numbers of protons in their atomic nucleus, nuclei. Unlike chemical compounds, chemical el ...

phosphorus
,
water Water (chemical formula H2O) is an Inorganic compound, inorganic, transparent, tasteless, odorless, and Color of water, nearly colorless chemical substance, which is the main constituent of Earth's hydrosphere and the fluids of all known li ...

water
and energy recovered from sewage.Andersson, K., Rosemarin, A., Lamizana, B., Kvarnström, E., McConville, J., Seidu, R., Dickin, S. and Trimmer, C. (2016)
Sanitation, Wastewater Management and Sustainability: from Waste Disposal to Resource Recovery
Nairobi and Stockholm: United Nations Environment Programme and Stockholm Environment Institute.


Sewage farm


Regulations

Management of sewage includes collection and transport for release into the environment, after a treatment level that is compatible with the local requirements for discharge into water bodies, onto soil or for reuse applications. In most countries, uncontrolled discharges of wastewater to the environment are not permitted under law, and strict water quality requirements are to be met. For requirements in the United States, ''see Clean Water Act#Point sources, Clean Water Act.'' Sewage management regulations are often part of broader sanitation policies of a country. These may also include the management of human excreta (from Fecal sludge management, non-sewered collection systems), Municipal solid waste, solid waste and stormwater.


See also

* Fecal sludge management * History of water supply and sanitation * Reuse of human excreta * Urban Waste Water Treatment Directive * Wastewater-based epidemiology


References


External links


Sanitation and Wastewater Atlas of Africa
{{Authority control Anaerobic digestion Sewerage Sanitation Waste management Water pollution