Greywater Samples Before And After Treatment In A VFB (5547295000)
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Greywater (or grey water, sullage, also spelled gray water in the United States) refers to
domestic wastewater Sewage (or domestic sewage, domestic wastewater, municipal wastewater) 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 residen ...
generated in households or office buildings from streams without fecal contamination, i.e., all streams except for the wastewater from toilets. Sources of greywater include
sinks A sink is a bowl-shaped plumbing fixture for washing hands, dishwashing, and other purposes. Sinks have a tap (faucet) that supply hot and cold water and may include a spray feature to be used for faster rinsing. They also include a drain to ...
,
shower A shower is a place in which a person bathes under a spray of typically warm or hot water. Indoors, there is a drain in the floor. Most showers have temperature, spray pressure and adjustable showerhead nozzle. The simplest showers have a ...
s, baths, washing machines or
dishwashers A dishwasher is a machine that is used to clean dishware Tableware is any dish or dishware used for setting a table, serving food, and dining. It includes cutlery, glassware, serving dishes, and other items for practical as well as dec ...
. As greywater contains fewer pathogens than
blackwater Blackwater 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 disea ...
, it is generally safer to handle and easier to treat and
reuse Reuse is the action or practice of using an item, whether for its original purpose (conventional reuse) or to fulfill a different function ( creative reuse or repurposing). It should be distinguished from recycling, which is the breaking down of u ...
onsite for
toilet flushing A flush toilet (also known as a flushing toilet, water closet (WC) – see also toilet names) is a toilet that disposes of human waste (principally urine and feces) by using the force of water to ''flush'' it through a drainpipe to another loca ...
, landscape or crop irrigation, and other non- potable uses. Greywater may still have some pathogen content from laundering soiled clothing or cleaning the anal area in the shower or bath. The application of greywater reuse in urban water systems provides substantial benefits for both the water supply subsystem, by reducing the demand for fresh
clean water Drinking water is water that is used in drink or food preparation; potable water is water that is safe to be used as drinking water. The amount of drinking water required to maintain good health varies, and depends on physical activity level, ag ...
, and the wastewater subsystems by reducing the amount of conveyed and treated wastewater. Treated greywater has many uses, such as toilet flushing or irrigation.


Overview


Quality

Greywater usually contains some traces of
human waste Human waste (or human excreta) refers to the waste products of the human digestive system, menses, and human metabolism including urine and faeces. As part of a sanitation system that is in place, human waste is collected, transported, treated a ...
and is therefore not free of pathogens. The excreta come from washing the anal area in the bath and shower or from the laundry (washing underwear and diapers). The quality of greywater can deteriorate rapidly during storage because it is often warm and contains some nutrients and organic matter (e.g. dead skin cells), as well as pathogens. Stored greywater also leads to odour nuisances for the same reason.


Quantity

In households with conventional flush toilets, greywater makes up about 65% of the total wastewater produced by that household. It may be a good source of water for reuse because there is a close relationship between the production of greywater and the potential demand for toilet flushing water.


Practical aspects

Misconnections of pipes can cause greywater tanks to contain a percentage of blackwater. The small traces of
feces Feces ( or faeces), known colloquially and in slang as poo and poop, are the solid or semi-solid remains of food that was not digested in the small intestine, and has been broken down by bacteria in the large intestine. Feces contain a relati ...
that enter the greywater stream via
effluent Effluent is wastewater from sewers or industrial outfalls that flows directly into surface waters either untreated or after being treated at a facility. The term has slightly different meanings in certain contexts, and may contain various pollut ...
from the shower, sink, or washing machine do not pose practical hazards under normal conditions, as long as the greywater is used correctly (for example, percolated from a dry well or used correctly in farming irrigation).


Treatment processes

The separate treatment of greywater falls under the concept of source separation, which is one principle commonly applied in
ecological sanitation Ecological sanitation, commonly abbreviated as ecosan (also spelled eco-san or EcoSan), is an approach to sanitation provision which aims to safely reuse excreta in agriculture. It is an approach, rather than a technology or a device which is ch ...
approaches. The main advantage of keeping greywater separate from toilet wastewater is that the pathogen load is greatly reduced, and the greywater is therefore easier to treat and reuse. When greywater is mixed with toilet wastewater, it is called sewage or
blackwater Blackwater 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 disea ...
and should be treated in sewage treatment plants or an onsite sewage facility, which is often a septic system. Greywater from kitchen sinks contains fats, oils and grease, and high loads of organic matter. It should undergo preliminary treatment to remove these substances before discharge into a greywater tank. If this is difficult to apply, it could be directed to the sewage system or to an existing sewer. Most greywater is easier to treat and recycle than sewage because of lower levels of contaminants. If collected using a separate plumbing system from blackwater, domestic greywater can be
recycled Recycling is the process of converting waste materials into new materials and objects. The recovery of energy from waste materials is often included in this concept. The recyclability of a material depends on its ability to reacquire the p ...
directly within the home, garden or company and used either immediately or processed and stored. If stored, it must be used within a very short time or it will begin to putrefy due to the organic solids in the water. Recycled greywater of this kind is never safe to drink, but a number of treatment steps can be used to provide water for washing or flushing toilets. The treatment processes that can be used are in principle the same as those used for sewage treatment, except that they are usually installed on a smaller scale (decentralized level), often at household or building level: * Biological systems such as constructed wetlands or living walls and more natural 'backyard' small scale systems, such as small ponds or biodiverse landscapes that naturally purify greywater. *Bioreactors or more compact systems such as membrane bioreactors which are a variation of the activated sludge process and is also used to treat sewage. * Mechanical systems ( sand filtration, lava filter systems and systems based on UV radiation) In constructed wetlands, the plants use contaminants of greywater, such as food particles, as nutrients in their growth. Salt and soap residues can be toxic to microbial and plant life alike, but can be absorbed and degraded through
constructed wetlands 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. ...
and aquatic plants such as sedges, rushes, and grasses.


Reuse

Global water resource supplies are shrinking. According to a report from the United Nations, water shortages will affect 2.7 billion people by 2025, which means 1 out of every 3 people in the world will be affected by this problem. Reusing greywater has become a good way to solve this problem, and wastewater reuse is also called recycled or
reclaimed water Water reclamation (also called wastewater reuse, water reuse or water recycling) is the process of converting municipal wastewater Sewage (or domestic sewage, domestic wastewater, municipal wastewater) is a type of wastewater that is produce ...
.


Benefits

Demand on conventional water supplies and pressure on sewage treatment systems is reduced by the use of greywater. Re-using greywater also reduces the volume of sewage effluent entering watercourses which can be ecologically beneficial. In times of drought, especially in urban areas, greywater use in irrigation or toilet systems helps to achieve some of the goals of ecologically sustainable development. The potential ecological benefits of greywater recycling include: * Reduced freshwater extraction from rivers and aquifers * Less impact from septic tank and
treatment plant Water treatment is any process that improves the quality of water to make it appropriate for a specific end-use. The end use may be drinking, industrial water supply, irrigation, river flow maintenance, water recreation or many other uses, includ ...
infrastructure * Reduced energy use and chemical pollution from treatment * Groundwater recharge * Reclamation of nutrients * Greater quality of surface and ground water when preserved by the natural purification in the top layers of soil than generated water treatment processes In the U.S. Southwest and the Middle East where available water supplies are limited, especially in view of a rapidly growing population, a strong imperative exists for adoption of alternative water technologies. The potential economic benefits of greywater recycling include: * Can reduce the demand for
fresh water Fresh water or freshwater is any naturally occurring liquid or frozen water containing low concentrations of dissolved salts and other total dissolved solids. Although the term specifically excludes seawater and brackish water, it does include ...
, and when people reduce the use of fresh water, the cost of domestic water consumption is significantly reduced, while alleviating the pressure of global water resources. * Can reduce the amount of wastewater entering the sewer or on-site treatment system.


Safety

Greywater use for irrigation appears to be a safe practice. A 2015 epidemiological study found no additional burden of disease among greywater users irrigating arid regions. The safety of reuse of greywater as potable water has also been studied. A few organic micropollutants including benzene were found in greywater in significant concentrations but most pollutants were in very low concentrations. Fecal contamination, peripheral pathogens (e.g., skin and mucous tissue), and food-derived pathogens are the three major sources of pathogens in greywater. Greywater reuse in toilet flushing and garden irrigation may produce
aerosol An aerosol is a suspension (chemistry), suspension of fine solid particles or liquid Drop (liquid), droplets in air or another gas. Aerosols can be natural or Human impact on the environment, anthropogenic. Examples of natural aerosols are fog o ...
s. These could transmit legionella disease and bring a potential health risk for people. However, the result of the research shows that the health risk due to reuse of greywater either for garden irrigation or toilet flushing was not significantly higher than the risk associated with using clear water for the same activities.


Irrigation

Most greywater should be assumed to have some blackwater-type components, including pathogens. Greywater should be applied below the surface where possible (e.g., via drip line on top of the soil, under mulch; or in mulch-filled trenches) and not sprayed, as there is a danger of inhaling the water as an
aerosol An aerosol is a suspension (chemistry), suspension of fine solid particles or liquid Drop (liquid), droplets in air or another gas. Aerosols can be natural or Human impact on the environment, anthropogenic. Examples of natural aerosols are fog o ...
. In any greywater system, it is important to avoid toxic materials such as bleaches, bath salts, artificial dyes, chlorine-based cleansers, strong acids/
alkali In chemistry, an alkali (; from ar, القلوي, al-qaly, lit=ashes of the saltwort) is a basic, ionic salt of an alkali metal or an alkaline earth metal. An alkali can also be defined as a base that dissolves in water. A solution of a ...
,
solvents A solvent (s) (from the Latin '' solvō'', "loosen, untie, solve") is a substance that dissolves a solute, resulting in a solution. A solvent is usually a liquid but can also be a solid, a gas, or a supercritical fluid. Water is a solvent for p ...
, and products containing
boron Boron is a chemical element with the symbol B and atomic number 5. In its crystalline form it is a brittle, dark, lustrous metalloid; in its amorphous form it is a brown powder. As the lightest element of the ''boron group'' it has th ...
, which is toxic to plants at high levels. Most cleaning agents contain sodium salts, which can cause excessive soil alkalinity, inhibit seed germination, and destroy the structure of soils by dispersing clay. Soils watered with greywater systems can be amended with gypsum ( calcium sulfate) to reduce pH. Cleaning products containing ammonia are safe to use, as plants can use it to obtain nitrogen. A 2010 study of greywater irrigation found no major health effects on plants, and suggests sodium buildup is largely dependent on the degree to which greywater migrates vertically through the soil. Some greywater may be applied directly from the sink to the garden or container field, receiving further treatment from soil life and plant roots. The use of non-toxic and low-sodium soap and personal care products is recommended to protect vegetation when reusing greywater for irrigation purposes.


Indoor reuse

Recycled greywater from showers and bathtubs can be used for flushing toilets in most European and Australian jurisdictions and in United States jurisdictions that have adopted the
International Plumbing Code The International Plumbing Code is a plumbing code and standard that sets minimum requirements for plumbing systems in their design and function, and which sets out rules for the acceptance of new plumbing-related technologies. It is published by th ...
. Such a system could provide an estimated 30% reduction in water use for the average household. The danger of
biological contamination A biological hazard, or biohazard, is a biological substance that poses a threat to the health of living organisms, primarily humans. This could include a sample of a microorganism, virus or toxin that can adversely affect human health. A bioh ...
is avoided by using: * A cleaning tank, to eliminate floating and sinking items * An intelligent control mechanism that flushes the collected water if it has been stored long enough to be hazardous; this completely avoids the problems of filtration and chemical treatment Greywater recycling without treatment is used in certain
dwellings In law, a dwelling (also known as a residence or an abode) is a self-contained unit of accommodation used by one or more households as a home - such as a house, apartment, mobile home, houseboat, vehicle, or other "substantial" structure. The ...
for applications where potable water is not required (e.g., garden and land irrigation,
toilet flushing A flush toilet (also known as a flushing toilet, water closet (WC) – see also toilet names) is a toilet that disposes of human waste (principally urine and feces) by using the force of water to ''flush'' it through a drainpipe to another loca ...
). It may also be used in dwellings when the greywater (e.g., from rainwater) is already fairly clean to begin with and/or has not been polluted with non-degradable chemicals such as non-natural soaps (thus using natural cleaning products instead). It is not recommended to use water that has been in the greywater filtration system for more than 24 hours as bacteria builds up, affecting the water that is being reused. Due to the limited treatment technology, the treated greywater still contains some chemicals and bacteria, so some safety issues should be observed when using the treated greywater around the home. A clothes washer grey water system is sized to recycle the grey water of a one or two family home using the reclaimed water of a washing machine (produces 15 gallons per person per day). It relies on either the pump from the washing machine or gravity to irrigate. This particular system is the most common and least restricted system. In most states with in the United States, this system does not require construction permits. This system is often characterized as Laundry to Landscape (L2L). The system relies on valves, draining to a mulch basin, or the area of irrigation for certain landscape features (a mulch basin for a tree requires 12.6 ft2). The drip system must be calibrated to avoid uneven distribution of grey water or overloading. Recycled grey water from domestic appliances also can be used to flush toilet. Its application is based on standards set by plumbing codes. Indoor grey water reuse requires an efficient cleaning tank for insoluble waste, as well as a well regulated control mechanism. The Uniform Plumbing Code, adopted in some U.S. jurisdictions, prohibits greywater use indoors. However, the California Plumbing Code, derived from the UPC, permits it.


Heat reclamation

Devices are currently available that capture heat from residential and industrial greywater through a process called drain water heat recovery, greywater heat recovery, or hot
water heat recycling Water heat recycling (also known as drain water heat recovery, waste water heat recovery, greywater heat recovery, or sometimes shower water heat recovery) is the use of a heat exchanger to recover energy and reuse heat from drain water from vario ...
. Rather than flowing directly into a water heating device, incoming cold water flows first through a heat exchanger where it is pre-warmed by heat from greywater flowing out from such activities as dish washing or showering. Typical household devices receiving greywater from a shower can recover up to 60% of the heat that would otherwise go to waste.


Regulations


United States

Government regulation governing domestic greywater use for landscape irrigation (diversion for reuse) is still a developing area and continues to gain wider support as the actual risks and benefits are considered and put into clearer perspective. "Greywater" (by pure legal definition) is considered in some jurisdictions to be "sewage" (all wastewater including greywater and toilet waste), but in the U.S. states that adopt the ''International Plumbing Code'', it can be used for subsurface irrigation and for toilet flushing, and in states that adopt the '' Uniform Plumbing Code'', it can be used in underground disposal fields that are akin to shallow sewage disposal fields. Wyoming allows surface and subsurface irrigation and other non-specific use of greywater under a Department of Environmental Quality policy enacted in March 2010. California, Utah, New Mexico and some other states allow true subsurface drip irrigation with greywater. Where greywater is still considered sewage, it is bound by the same regulatory procedures enacted to ensure properly engineered septic tank and effluent disposal systems are installed for long system life and to control spread of disease and pollution. In such regulatory jurisdictions, this has commonly meant domestic greywater diversion for landscape irrigation was either not permitted or was discouraged by expensive and complex sewage system approval requirements. Wider legitimate community greywater diversion for landscape irrigation has subsequently been handicapped and resulted in greywater reuse continuing to still be widely undertaken by householders outside of and in preference to the legal avenues. However, with water conservation becoming a necessity in a growing number of jurisdictions, business, political and community pressure has made regulators seriously reconsider the actual risks against actual benefits. It is now recognized and accepted by an increasing number of regulators that the microbiological risks of greywater reuse at the single dwelling level where inhabitants already had intimate knowledge of that greywater are in reality an insignificant risk, when properly managed without the need for onerous approval processes. This is reflected in the New South Wales Government Department of Water and Energy's newly released greywater diversion rules, and the recent passage of greywater legislation in Montana. 2007 grey water legislation in Montana In the 2009 Legislative Session, the state of Montana passed a bill expanding greywater use into multi-family and commercial buildings. The Department of Environmental Quality has already drafted rules and design guidelines for greywater re-use systems in all these applications. Existing staff would review systems proposed for new subdivisions in conjunction with review of all other wastewater system components. Strict permit requirements in Austin, Texas, led to issuance of only one residential graywater permit since 2010. A working group formed to streamline the permitting process, and in 2013, the city created new code that has eased the requirements, resulting in four more permits. In California, a push has been made in recent years to address greywater in connection with the State's greenhouse gas reduction goals (see
AB 32 The Global Warming Solutions Act of 2006, or Assembly Bill (AB) 32, is a California State Law that fights global warming by establishing a comprehensive program to reduce greenhouse gas emissions from all sources throughout the state. AB32 was c ...
). As a large amount of energy (electricity) is used for pumping, treating and transporting potable water within the state, water conservation has been identified as one of several ways California is seeking to reduce greenhouse gas emissions. In July 2009, the California Building Standards Commission (CBSC) approved the addition of Chapter 16A "Non-potable Water Reuse Systems" to the 2007 California Plumbing Code. Emergency regulations allowing greywater reuse systems were subsequently filed with the
California Secretary of State The secretary of state of California is the chief clerk of the U.S. state of California, overseeing a department of 500 people. The secretary of state is elected for four year terms, like the state's other constitutional officers; the officeho ...
August 2009 and became effective immediately upon filing. Assembly Bill 371 (Goldberg 2006) and Senate Bill 283 (DeSaulnier 2009) directed the California Department of Water Resources (DWR), in consultation with the State Department of Health Services, to adopt and submit to the CBSC regulations for a State version of Appendix J (renamed Chapter 16 Part 2) of the Uniform Plumbing Code to provide design standards to safely plumb buildings with both potable and recycled water systems. November 2009 the CBSC unanimously voted to approve the California Dual Plumbing Code that establishes statewide standards for potable and recycled water plumbing systems in commercial, retail and office buildings, theaters, auditoriums, condominiums, schools, hotels, apartments, barracks, dormitories, jails, prisons and reformatories. In addition, the California Department of Housing and Community Development has greywater standards and DWR has also proposed dual plumbing design standards. In Arizona, greywater is defined as water with a BOD5 less than 380 mg/L, TSS<430 and the Fats, Oil, and Grease (FOG) content should be less than 75 mg/L. The Arizona water has issued advice that people should avoid direct contact with greywater. Most greywater use is by underground drip irrigation since surface irrigation is not permitted. There are three types of use in Arizona: up to a quota of 400 gpd per family (close to 1500 L per day) no permission is required for greywater use, between 400 and 3000 gpd (1500 and 11,355 L per day, respectively) permission is required and above 3000 gpd (>11,355 L per day) it is considered as conventional wastewater venture. Other limitations include restrictions on contact, restrictions on use on herbaceous food plants, exclusion of hazardous materials and effective separation from surface water run-off. The Uniform Plumbing Code, adopted in some U.S. jurisdictions, prohibits gray water use indoors.


United Kingdom

Greywater recycling is relatively uncommon in the UK, largely because the financial cost and environmental impact of mains water is very low. Greywater systems should comply with BS8525 and the Water Supply (Water Fittings) Regulations in order to avoid risks to health. Greywater from single sewered premises has the potential to be reused on site for ornamental, garden and lawn irrigation, toilet flushing. The reuse options include Horizontal flow reed bed (HFRB), Vertical flow reed bed (VFRB), Green roof water recycling system (GROW), Membrane bioreactor (MBR) and Membrane chemical reactor (MCR).


Canada

Although Canada is a water-rich country, the center of the country freezes in the winter and droughts happen some summers. There are locations where watering outdoors is restricted in the dry season, some water must be transported from an outside source, or on-site costs are high. At present, the standards for greywater reuse are not strict compared with other countries. The National Plumbing Code, which is adopted in whole or in part by the provinces, indicates that non-potable water systems should only be used to supply toilets and underground irrigation systems, collecting rainwater with roof gutters is included as a form of greywater. Health Canada has published a guideline to use greywater for toilet flushing and British Columbia's building code includes subsurface irrigation with greywater. In Alberta "Reclaimed wastewater from any source cannot be used domestically unless it is approved and meets water quality testing and monitoring by the local municipality." Saskatchewan also treats greywater as sewage.


Australia

Household greywater from a single contaminated site may be reused on-site at the ornamental garden and lawn watering, toilet flushing and laundry uses, depending on the type of greywater and treatment level. Some people wisely re-use the gross weight, but others use it even worse (without any treatment), such as bathing in the bath or simply transferring laundry water to the lawn where children and pets may be exposed directly. The Department of Health and Community Services (DHCS) focuses on protecting public health and then takes action to control and minimize the public health risks associated with greywater reuse.


Cyprus

The government of Cyprus has implemented four water-saving subsidies: drilling installations, drilling with lavatories, installation of hot water circulation systems and installation of greywater recycling systems.


Jordan

The emphasis on the use of greywater in Jordan has two main purposes: water conservation and socioeconomic aspects. The Amman Islamic Water Development and Management Network (INWRDAM) in Jordan promoted research on gray water reuse in Jordan. At present, greywater research in Jordan is funded mainly by the International Development Research Center (IDRC) in Ottawa, Canada, to install and use greywater systems based on the establishment of small wetland systems in private households. The cost of this system is about 500 US dollars per household.


See also

*
Potable water Drinking water is water that is used in drink or food preparation; potable water is water that is safe to be used as drinking water. The amount of drinking water required to maintain good health varies, and depends on physical activity level, ag ...
* Rainwater harvesting * Water conservation * Water purification


References

{{Authority control Water supply Water pollution Water conservation