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Definition
Any domestic wastewater can be defined as Greywater, but it does not including blackwater(sewage). The main difference between greywater and blackwater is the organic loading. Comparing to Greywater, blackwater has a much larger organic loading..

Practical aspects
The Greywater reuse in toilet flushing and garden irrigation, both producing aerosols. These may transmit Legionella and bring a potential health risk for people. However, the result of the research shows that the health risk due to reuse Greywater either for garden irrigation or toilet flushing was not significantly higher than the risk associated with using clear water for the same activities.

Reuse
The global water resources are worsening. According to a report from United Nations states that 2.7 billion people will face the problem of water shortage by 2025, which means almost 1/2-1/3 of the total population of the world will affect by this problem. Reusing the wastewater become a good way to solve this problem, and wastewater reuse is also called recycled or reclaimed water.

Benefits
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, 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
Due to the limited purification technology, the treated grey water still contains some chemicals and bacteria, so some safety issues should be observed when using the treated grey water:

ground, reducing the risk of human-animal contact.
 * Untreated grey water can only be used for underground garden irrigation. In the prior art, sewer pipes were usually buried at least 1 meter below
 * Untreated grey water pipelines must have warning labels.
 * Use grey water immediately (or within 24 hours) and do not store untreated grey water at home as bacteria and other pathogens may be hazardous to human health.
 * If anyone at home has a gastrointestinal flu or other infectious disease, stop using grey water.
 * Do not use grey water containing bleach or dye.
 * Do not use untreated grey water to irrigate plants.
 * It is illegal to get grey water from home to home.

United States
In Arizona, Greywater is defined by BOD5 that must be less than 380 mg/L, TSS<430 and the Fats, Oil, and Grease (FOG) content should be less than 75 mg/L. Therefore, Arizona water department strongly recommends that people avoid direct contact with gray water, most Greywater are use underground drip irrigation, the government do not allow surface irrigation. Based on the actual situation, there are three types of gross weight 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 the following: (1) Avoid contact with Greywater and Greywater irrigated soils (2) Surface application of gray water may not be used to irrigate food plants, but citrus and nuts (3) The gross weight shall not contain hazardous chemicals obtained from the cleaning of automotive parts, the cleaning of greasy or greasy rags, the disposal of waste solutions from family photo labs, similar hobbyists or family occupational activities (4) Control of the use of gray water to minimize surface water (5) The option of gross direct discharge to major sewers should always be present (6) Cross-linking needs to be prevented; Greywater used for surface irrigation may not contain water used to clean diapers or similar contaminated or infectious clothes unless disinfected prior to irrigation (7) Irrigation is not permitted

United Kingdom
Until now, in UK, Greywater from single seweraged premises has the potential to be reused onsite for ornamental, garden and lawn irrigation, toilet flushing and ultimately for drinking water production.Interesting is the reuse criteria of Greywater in UK is similar to California standards, the apporach including: Horizontal flow reed bed (HFRB), Vertical flow reed bed (VFRB), Green roof water recycling system (GROW), Membrane bioreactor (MBR), Membrane chemical reactor (MCR).

Canada
Although Canada is a water-rich country, they also plan to reuse Grey water. This may be due to the large costs that often accrue to traditional large-scale waste treatment systems in big cities. However, at present, the standards for Greywater reuse are not strict compared with other countries in arid regions.

Australia
Household Grey water 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 Grey water 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 Grey water reuse. Therefore, they issued a few guidelines. Grey water converter must be designed and installed according to the following standards: (1) Greywater treatment must meet the requirements of the health department and remove all clogging and health risk factors (2) Each installation must only be applicable to single family homes (3) Only direct reuse is permitted (4) Minimum maintenance requirements must be specified (5) Greywater must pass through the filtration or sedimentation process (6) Greywater must be applied through underground systems (7) Disinfection Greywater can be applied by the ground system (8) The application should color and mark the area in the area (9) Greywater system must have an automatic overflow device (10) Ensure the soil is easily decomposed throughout the year (11) Greywater system installation, connections must be designed by authorized experts to prevent sewer gases entering from the property (12) All plumbing works must be carried out by plumbers licensed by the Water Co-ordination (Plumber's License) (13) The system of pumps and tanks (containers acting as reservoirs) must be connected according to all safety factors and it is acceptable to manually irrigate the absorbent soil with a bucket (eg： by dividing the wash bowl Greywater into a wash basin), as long as the relevant The health and safety conditions are respected

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 Grey water recycling systems.

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

Israel
Grey water Reuse System In Israel, private owners started installing their own private systems at the very outset without any rules or guidelines. They installed a Grey water reuse system to save on water bills. The new Grey water standard in Israel is now the standard document SI-6147 that was finally released after many meetings and discussions after the British standards (BS-8525-1, 2010 and BS-8525-2, 2011).

Grey water reuse is a natural process occurring in the early stages. The Grey water system consists of the following components: (1) Collection system There are many ways for Israeli families to collect gray water. In general, there must be a clear separation between conventional wastewater treatment and Grey water collection systems. To ensure a clear separation, a check valve is installed in the Grey water collection system to allow excess gross weight to pass through the central sewerage system.

(2) Treatment system Treatment systems typically consist of sedimentation elements, screening / filtering components and biological processes, which may also include membrane technology components or constructed wetland components. All of these are intended to treat Grey water and allow them to be used for hospital irrigation and / or toilet flushing. Disinfection elements (small UV lamps and / or chlorinated) are often included in the process.

(3) Storage of processed Grey water Before processing and before processing the Grey water, the original Grey water is stored and then "applied". Treated gross weight should not be detained for more than a few days. Tanks should be located on the ground or underground, but not at risk to local residents. Storage should be made from prefabricated materials on site.

(4) Pumping parts (collection system and distribution system) The size of the pumping equipment should be determined by the family size and flow rate. It should be located in a safe area to ensure that the health of residents is not compromised in the event of a spill and spill.

(5) System maintenance Maintenance is regulated by local authorities. It mainly refers to the normal operation of the reuse system without interfering with the private property of a single resident. Maintenance refers to the annual normal operation of the system. The disinfection system runs continuously and is monitored twice a year for proper system operation.

(6) Water quality The general stage of Grey water treatment is based on the following principles:

1) Filtering and precipitation.

2) Requires concentrations of BOD5 ( Biochemical Oxygen Demand ) and TSS not to exceed 20 mg / L and 30 mg / L, respectively.

3) Treated Grey water distribution system outside the house must be marked with a special symbol that the Grey water is flowing through the network (in Hebrew, Arabic and English).

4) Although it is highly recommended not to exceed 12 hours, the original gross weight can be kept for 24 hours. This is to prevent odor development and germ regeneration.

5) Treated Greywater can be stored for 7 days to prevent additional growth and development of bacteria under anaerobic conditions.

6) Care must be taken not to connect the Greywater to the main water supply.

7) The front of the system must be connected to the one-way flow valve to prevent mixing Greywater and clean tap water.

8) When chlorine disinfection (or equivalent) is used, the residual chlorine content at the remote outlet of the system must be 0.5 mg / L after a residence time of at least half an hour.

Related Greywater organization
Water Wise Group – Greywater Systems Distributor

Sustainable Earth Technologies

choice-WATER-SAVING WATER-GUIDE TO GREYWATER SYSTEMS

the Greywater Guide