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Sewage farms use sewage for
irrigation Irrigation (also referred to as watering) is the practice of applying controlled amounts of water to land to help grow crops, landscape plants, and lawns. Irrigation has been a key aspect of agriculture for over 5,000 years and has been devel ...
and fertilizing agricultural land. The practice is common in warm, arid climates where irrigation is valuable while sources of fresh water are scarce. Suspended solids may be converted to
humus In classical soil science, humus is the dark organic matter in soil that is formed by the decomposition of plant and animal matter. It is a kind of soil organic matter. It is rich in nutrients and retains moisture in the soil. Humus is the Latin ...
by microbes and bacteria in order to supply
nitrogen Nitrogen is the chemical element with the symbol N and atomic number 7. Nitrogen is a nonmetal and the lightest member of group 15 of the periodic table, often called the pnictogens. It is a common element in the universe, estimated at sevent ...
,
phosphorus Phosphorus is a chemical element with the symbol P and atomic number 15. Elemental phosphorus exists in two major forms, white phosphorus and red phosphorus, but because it is highly reactive, phosphorus is never found as a free element on Ea ...
and other plant nutrients for crop growth. Many
industrialized nations A developed country (or industrialized country, high-income country, more economically developed country (MEDC), advanced country) is a sovereign state that has a high quality of life, developed economy and advanced technological infrastruc ...
use conventional
sewage treatment Sewage treatment (or domestic wastewater treatment, municipal wastewater treatment) is a type of wastewater treatment which aims to remove contaminants from sewage to produce an effluent that is suitable for discharge to the surrounding en ...
plants nowadays instead of sewage farms. These reduce
vector Vector most often refers to: *Euclidean vector, a quantity with a magnitude and a direction *Vector (epidemiology), an agent that carries and transmits an infectious pathogen into another living organism Vector may also refer to: Mathematic ...
and
odor An odor (American English) or odour ( Commonwealth English; see spelling differences) is caused by one or more volatilized chemical compounds that are generally found in low concentrations that humans and animals can perceive via their sen ...
problems; but sewage farming remains a low-cost option for some
developing countries A developing country is a sovereign state with a lesser developed industrial base and a lower Human Development Index (HDI) relative to other countries. However, this definition is not universally agreed upon. There is also no clear agree ...
. Sewage farming should not be confused with sewage disposal through
infiltration basin An infiltration basin (or recharge basin) is a form of engineered sump or percolation pond that is used to manage stormwater runoff, prevent flooding and downstream erosion, and improve water quality in an adjacent river, stream, lake or bay. It i ...
s or subsurface drains.


Advantages

Sewage farming allows use for
irrigation Irrigation (also referred to as watering) is the practice of applying controlled amounts of water to land to help grow crops, landscape plants, and lawns. Irrigation has been a key aspect of agriculture for over 5,000 years and has been devel ...
of water which might otherwise be wasted. Some of the nutrients and organic solids in wastewater can be usefully incorporated into soil and agricultural products rather than fouling natural aquatic environments. Pumping to the point of application may be the only requirement if the village is not at a higher elevation than the sewage farm.


Disadvantages

Polluted runoff may occur from sewage irrigation of fields when entering wastewater and precipitation exceed evaporation and percolation capacity. Sewage is usually generated at a relatively constant rate, but irrigation is required only during dry weather, and is useful only while temperatures are high enough to promote plant growth. Over-irrigation causes soils to become septic, sour, or ''sewage-sick''. Arid climates may allow temporary storage of sewage in holding ponds while the soils dry out during non-growing seasons, but such storage may cause odor and aquatic insect problems, including mosquitoes. It may be impractical to protect the crops being grown from sewage contact. Even optimum situations like irrigating fruit trees with flow in surface ditches may involve some risk of pathogen transfer from the sewage to the edible fruit by birds, insects, and similar vectors. Pathogen transfer is more likely with ground crops, and practically unavoidable with spray irrigation.


Similar wastewater systems

Subsurface distribution piping is problematic since it is vulnerable to root blockage and to damage during soil cultivation. Also obstruction of distribution piping by sewage solids discourages sewage farming when wastewater is not pre-treated as it is typically the case in a septic drain field. Sewage farming should not be confused with wastewater disposal through
infiltration basin An infiltration basin (or recharge basin) is a form of engineered sump or percolation pond that is used to manage stormwater runoff, prevent flooding and downstream erosion, and improve water quality in an adjacent river, stream, lake or bay. It i ...
s or subsurface drains. Plows or harrows may be used to periodically break up vegetation mats which are slowing surface disposal. Subsurface disposal typically uses pipes placed deep enough to minimize root penetration and often manages overlying vegetation to avoid growth of plants with deep root systems.


History

As a predecessor to modern
sewage treatment Sewage treatment (or domestic wastewater treatment, municipal wastewater treatment) is a type of wastewater treatment which aims to remove contaminants from sewage to produce an effluent that is suitable for discharge to the surrounding en ...
systems, household sewage was collected from towns and cities and transported to nearby farm lands. During the Middle Ages this was accomplished with hand-carried buckets, but as local populations grew, during the
Industrial Revolution The Industrial Revolution was the transition to new manufacturing processes in Great Britain, continental Europe, and the United States, that occurred during the period from around 1760 to about 1820–1840. This transition included going f ...
sanitary sewer A sanitary sewer is an underground pipe or tunnel system for transporting sewage from houses and commercial buildings (but not stormwater) to a sewage treatment plant or disposal. Sanitary sewers are a type of gravity sewer and are part of an ...
systems were built. These used a network of pipes and pumps to transport sewage beyond the city boundaries to large rented grasslands, into which the sewage trickled down. Berlin once operated 20 sewage farms occupying about 10,000 hectares. In
Wales Wales ( cy, Cymru ) is a country that is part of the United Kingdom. It is bordered by England to the east, the Irish Sea to the north and west, the Celtic Sea to the south west and the Bristol Channel to the south. It had a population in ...
, it was the common means of sewage treatment when cess-pits became unusable as the population grew in towns during the industrial revolution. The initial response to overloaded local disposal was often a trunk sewer conveying sewage to the nearest river but as populations increased further, sewage farms were established. Some of these farms remained in use until the end of the 20th century, at which point it became apparent that as it was usually contaminated with infectious pathogens and sometimes with
industrial waste Industrial waste is the waste produced by industrial activity which includes any material that is rendered useless during a manufacturing process such as that of factories, mills, and mining operations. Types of industrial waste include dirt an ...
, sewage was not always suitable for use as a fertilizer. Therefore, sewage plants began to replace sewage farms. Modern sewage farms are usually combined with such plant, so that they irrigate the land with treated sewage (
reclaimed water Water reclamation (also called wastewater reuse, water reuse or water recycling) is the process of converting municipal wastewater (sewage) or industrial wastewater into water that can be reused for a variety of purposes. Types of reuse include ...
). Some types of untreated sewage can be used on a sewage farm, or filtered through a
constructed wetland 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 ...
.


Examples

* A small-scale example of a sewage farm exists at
Chester Zoo Chester Zoo is a zoo at Upton-by-Chester, Cheshire, England. Chester Zoo was opened in 1931 by George Mottershead and his family. It is one of the UK's largest zoos at . The zoo has a total land holding of approximately . Chester Zoo is oper ...
, where water fouled with elephant droppings and urine is filtered through a
reedbed A reedbed or reed bed is a natural habitat found in floodplains, waterlogged depressions and estuaries. Reedbeds are part of a succession from young reeds colonising open water or wet ground through a gradation of increasingly dry ground. As ...
. * Western Treatment Plant in
Melbourne Melbourne ( ; Boonwurrung/Woiwurrung: ''Narrm'' or ''Naarm'') is the capital and most populous city of the Australian state of Victoria, and the second-most populous city in both Australia and Oceania. Its name generally refers to a metr ...
.


See also

* On-site sewage system *
Reuse of excreta 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 ...


References

{{Authority control Sewerage infrastructure