Gray Water Sytems

What are Gray Water Systems?


Gray water is wastewater from all plumbing fixtures except the toilet and garbage disposal. A gray water system collects and treats gray water and then puts it to use somewhere purified water (white water or potable water) is not needed. These applications can include flushing the toilet and lawn or crop irrigation, among other things.
Gray water systems vary significantly in their complexity and size from small systems with very simple treatment to large systems with complex treatment processes. However, most include common features such as:
  • A tank for storing treated water
  • A pump
  • A treatment method
  • A distribution system for transporting the treated water to where it is needed
All systems that store gray water have to incorporate some level of treatment, as untreated gray water deteriorates rapidly in storage. This rapid deterioration occurs because gray water is often warm and rich in organic matter such as skin particles, hair, soap and detergents. This warm, nutrient-rich water provides ideal conditions for bacteria to multiply, resulting in odor problems and poor water quality. Gray water may also contain harmful bacteria that could present a health risk without adequate water treatment or with inappropriate use. The risk of inappropriate use is higher where children have access to the water.

Historical Development of Gray Water Systems:


In the early years of large cites, wastewater management became a major issue in the day-to-day lives of the city residents.[1] Dumping raw black and gray water straight into the street was not an acceptable method of removing waste from living areas. Feces borne diseases, terrible smells and general unsightliness were all problems with this method of removing waste water. Something had to be done to remove the waste more efficiently.
Some suggest that gathering of wastewater started as early as 10,000 BC for use in agricultural fields.[2] People would use this waste primarily for the nutrients suspended in the water. During this time, there was no real separation of gray water and black water - it was all used for agricultural applications.
Figure 1: Roman Aquaduct
Figure 1: Roman Aquaduct


During the apex of The Roman Empire, huge advances in wastewater systems were made. The Romans developed a maze of complex sewers and aqueducts to help carry freshwater into the cities and wastewater away from the capital city. The Romans had an exceptional system that collected and removed gray and black water, but there was still no real gray water recycling system.[3]


In 1865, T. Charles Lienur designed a system to remove wastewater from Castle Luxembourge in two pipes. One pipe was designed to carry black water while the other carried gray water.[4] The black water was sent to be dried and made into a natural fertilizer while the gray water emptied into the River Elz.[5] This system was successful in removing the two types of wastewater by themselves, but did not effectively recycle gray water.

In 1869, Santa Barbara was the first U.S. district to make the distinction between black water and gray water and legalize gray water in their building codes. [6] Over 100 years later, in 1991, Santa Barbara County published "How to Use Grey Water: Guidelines to the reuse of Grey Water in Santa Barbara County".[7] In February, 1992, Assembly Bill 3518 (AB3518) was written and passed in California. The bill required that a code be written for safe gray water use in California by July 1,1993.[8]

In 1997, the state of California approved gray water for commercial, industrial, and multi-family projects.[9] Before then, gray water could only be used in single-family homes because the sanitary levels were typically much higher than in public facilities.
Between 2001 and 2003, Arizona, Texas and New Mexico began issuing gray water permits to anyone who complied with a reasonable list of requirements. Montana and Nevada soon followed in 2007 and 2009, respectively. [10]

Some of the exact ways that gray water is recycled are talked about below. The basic design consists of a reservoir where gray is stored and filtered then pumped out and used.

Variations of Gray Water Systems:


Despite the huge variance between systems, there are two main methods of gray water recycling: with and without chemical treatment. There is very little difference in the collection and storage for the two types of systems. The true difference is in the quality water output by the two systems. Non-filtered systems produce non-potable water only good for watering grass, trees, etc; while filtered systems produce potable or near potable water good for showering, drinking and other similar domestic tasks.

Direct-Use Systems (No Treatment):

This is the most basic method of recycling gray water. Some systems are constructed so that shower or bathtub water is diverted out to where the gray water is to be used. The most simple direct-use systems transport cooled bath water out of a window using a garden hose and hand pump. Many frugal gardeners will use this type of recycling to keep their garden alive during periods of severe drought.[11]
beckson-pump.jpg
Figure 2: Direct Use Hand Pump

Advantages:
  • No storage tanks
  • Simple to construct
  • Very little maintenance
Disadvantages:
  • No water reserve capabilities
  • Low Volume

Short Retention Systems:

Short retention systems collect gray water for a short period of time and apply very basic treatment methods to increase water quality: i.e. skimming for debris and allowing particles settle to the bottom of the tank. Sand or fine gravel filters are typically used to strain out the larger suspended materials. This type of system requires slightly more complicated equipment but is still relatively simple. Collection methods for short retention systems are very similar to direct-use systems. The drains coming out of the sinks, bathtubs, showers, ect divert gray water though the basic treatment systems then deposit the water into a holding tank. [12]
Figure 3: Short Retention System
Figure 3: Short Retention System

Advantages:
  • Water reserve capabilities
  • Higher quality water than direct-use systems
  • Low maintenance
Disadvantages:
  • More mechanical parts which could fail
  • Low storage times in tank
  • Relatively low water quality

Basic Physical and Chemical Systems:

Some systems use a filter to remove debris from gray water before storing, and use chemical disinfectants like chlorine or bromine to stop bacterial growth during storage.This is one of the more complex systems due to the nature of filtering then adding chemicals in the right proportions. When working properly, these systems produce a much higher quality water, fit for showering/rinsing loads of laundry. These pumps seem to have more difficulty giving a consistent water quality, however. This is simply due the the mechanical part of this system. [13]

Advantages:
  • Higher quality water
  • Longer storage times
Disadvantages:
  • Lots of mechanical parts that can break
  • High maintenance costs

Applications in Construction:


Gray water systems fit today's construction methods well because they are a "green " way to reduce the amount of water going into the local septic system or the city sewer system. Due to the simplicity of the construction involved, most houses can be fitted with a gray water system.

Gray water systems can reduce energy costs by using gray water instead of white water for things like flushing toilets and irrigation. By decreasing the amount of freshwater needed, the water infrastructure leading up the building can be designed to handle less flow. This will also help reduce the cost and time in constructing a building.

Examples of Constructed Works:


Tsinghua University Eco-Sewerage System

An on-site eco-sewerage system for modern office buildings was constructed and implemented in a 10-story building at Beijing's Tsinghua University. At the time of its implementation, the sewerage system was the first of its kind in China.[14] VSSS (vacuum and source-seperation sewage system) combined the technologies of vacuum and source separation to separate and collect gray water, yellow water and black water at-source. Gray water was collected and then underwent coagulation, sand filtration and activated carbon adsorption processes at a compact water treatment facility. The reclaimed water was used for lawn irrigation. The system also collected and treated both yellow and black water. Ultimately, the eco-sewerage system saved approximately 40% of flushing water and was calculated to save around $5,300 per year.

Paul Mitchell Salon School

Every day, 270 students at the Paul Mitchell Salon School in Cosexternal image shampoo.jpgta Mesa send hundreds of gallons of soapy water down the drain and into the facility's gray water reclamation system. The system is designed to divert 400,000 gallons of water per year away from the sewer and into tanks that filter the water and reuse it in the school's toilets. [15] Wastewater is filtered through silica, anthracite coal and activated carbon.[16] Bacteria is treated by UV light and and a copper ionization process that does not require chemicals to be added to the water.[17] After gaining approval from the city of Costa Mesa for their treated gray water, the school plans to use excess water to irrigate the facility's landscaping.

Santa Monica Office Building

This 15,000 square foot office building was built in 1917 and renovated in 1975 with a plumbing system for gray water reclamation.[18] The building uses no potable water for outdoor purposes, but collects and treats shower and sink water for use in its landscape irrigation system. Waterless urinals and dual-flush toilets are other methods that this facility has incorporated to reuse and reclaim water. Rainwater is collected and filtered before being incorporated into the gray water system.

Financial Considerations


Factors that are considered when implementing a gray water system:
  • Capital cost
  • Project schedule
  • Maintenance costs
  • Payback time
  • Water conservation issues
  • Complexity of the system
  • Tax incentives
  • LEED credits[19]
Factors.png
Figure 4: Factors affecting the implementation of gray water reuse system


Research shows that, when considering implementation of a gray water system, a majority (76 percent in the figure) of design teams consider capital cost as a major factor in their decision.[20] Of the 66 projects studied, 33 considered LEED credits and the complexity of the system as factors that influenced whether or not they implemented a gray water system. Forty-eight percent listed maintenance costs as a deciding factor, 38 percent saw payback time as an important factor, and out of the 66 projects, 35 percent felt that tax incentives were a reason to consider a gray water system. Surprisingly, only nine percent of the projects studied listed the project schedule as a factor. Studies show that gray water systems rarely affect the length of time it takes to complete a project.

Future Improvement in the Sustainability of Gray Water Systems:


Future improvements in this field are almost endless. As technology increases and becomes "smarter," gray water systems will become more efficient and more reliable. When these systems become more consistent, they will increase the sustainability tremendously because the systems will be able to efficiently take dirty water and make clean water on location. Being able to make clean water on location is a huge step in sustainability for a building.

Ongoing Research:


Gray water systems continue to be a topic of interest to environmental scientists and engineers. Research is currently being conducted in several areas, a few of which are listed here. Follow the links below for more information.

1. How laundry gray water affects plant growth compared to tap water irrigation:
This study was concerned with sodium and surfactant build-up in soil from frequent gray water irrigation. A glasshouse experiment was conducted to study the effects of gray water irrigation on the growth, water and nutrient use of a tomato.
http://lscsproxy.lonestar.edu/login?url=http://search.ebscohost.com/login.aspx?direct=true&AuthType=ip,cpid&custid=s1088435&db=syh&AN=50361889&site=ehost-live

2. Reducing freshwater demand in third-world countries by the implementation of gray water irrigation system:
This study provides research on the benefits of gray water systems in Australia, Lebanon and Palestine and demonstrates how similar systems could be used in sub-Saharan Africa.
http://lscsproxy.lonestar.edu/login?url=http://search.ebscohost.com/login.aspx?direct=true&AuthType=ip,cpid&custid=s1088435&db=syh&AN=26584329&site=ehost-live

3. The effects of long-term gray water irrigation on groundwater sodium levels:
This study provides data on the impact of laundry gray water on non-swelling clay soil Soil samples were examined for their water retention, saturated hydraulic conductivity and sodium levels when exposed to gray water irrigation.
http://lscsproxy.lonestar.edu/login?url=http://search.ebscohost.com/login.aspx?direct=true&AuthType=ip,cpid&custid=s1088435&db=syh&AN=36567586&site=ehost-live

4. Graywater pollution variability and loadings:
Small, on-site gray water systems can have large fluctuations in flow (0-35L/min) and pollution levels (up to several orders of magnitude). This study focuses on how variation of flow and pollution levels in small gray water treatment plants can inform risk assessment and design processes.

http://lscsproxy.lonestar.edu/login?url=http://search.ebscohost.com/login.aspx?direct=true&AuthType=ip,cpid&custid=s1088435&db=syh&AN=38319798&site=ehost-live

Credible Experts


The journals that most frequently provide research and innovations in gray water systems are listed below:

1. Journal of Hydrology
http://www.journals.elsevier.com/journal-of-hydrology/

2. Journal of Environmental Engineering
http://ascelibrary.org/journal/joeedu

3. Ecological Engineering - Journal
http://www.journals.elsevier.com/ecological-engineering

Leading suppliers of gray water systems:

1. Ultra Clean Water Solutions, based in St. Petersburg, FL
http://www.environmental-expert.com/companies/ultra-clean-water-solutions-49395

2. Wahaso, Water Harvesting Solutions, based in Hinsdale, IL
http://www.environmental-expert.com/companies/wahaso-water-harvesting-solutions-37665

3. Clewer, North America, L.L.C., based in Bluffton, SC.
Provides bioreactors to recover and treat gray water.
http://www.environmental-expert.com/services/grey-water-solutions-193729
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    Bracken, P. (2007). "The Road Not Taken: How Traditional Excreta and Greywater Management may Point the way to a Sustainable Future." Stanford.edu, <http://www.stanford.edu/group/narratives/classes/08-09/CEE215/Projects/greendorm/water/GraywaterCD/graywater08/Research%20Articles/WS&T07GryWtrMgmt.pdf > (Dec. 3, 2013).
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    Bracken, P. (2007). "The Road Not Taken: How Traditional Excreta and Greywater Management may Point the way to a Sustainable Future." Stanford.edu, <http://www.stanford.edu/group/narratives/classes/08-09/CEE215/Projects/greendorm/water/GraywaterCD/graywater08/Research%20Articles/WS&T07GryWtrMgmt.pdf > (Dec. 3, 2013).
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    Hansen, R. "Water and Wastewater Systems in Imperial Rome." Waterhistory.org, <http://www.waterhistory.org/histories/rome/> (Dec. 3, 2013).
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    Bracken, P. (2007). "The Road Not Taken: How Traditional Excreta and Greywater Management may Point the way to a Sustainable Future." Stanford.edu, <http://www.stanford.edu/group/narratives/classes/08-09/CEE215/Projects/greendorm/water/GraywaterCD/graywater08/Research%20Articles/WS&T07GryWtrMgmt.pdf > (Dec. 3, 2013).
  5. ^ Bracken, P. (2007). "The Road Not Taken: How Traditional Excreta and Greywater Management may Point the way to a Sustainable Future." Stanford.edu, <http://www.stanford.edu/group/narratives/classes/08-09/CEE215/Projects/greendorm/water/GraywaterCD/graywater08/Research%20Articles/WS&T07GryWtrMgmt.pdf > (Dec. 3, 2013).
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    Ludwig, A. (2014). "History of Graywater Regulation." Oasis Design, <http://oasisdesign.net/greywater/law/history/#legalize> (Nov. 26, 2014).
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    Ludwig, A. (2014). "History of Graywater Regulation." Oasis Design, <http://oasisdesign.net/greywater/law/history/#legalize> (Nov. 26, 2014).
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    Ludwig, A. (2014). "History of Graywater Regulation." Oasis Design, <http://oasisdesign.net/greywater/law/history/#legalize> (Nov. 26, 2014).
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    Ludwig, A. (2014). "History of Graywater Regulation." Oasis Design, <http://oasisdesign.net/greywater/law/history/#legalize> (Nov. 26, 2014).
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    Multiple Unknown. (2013). "Greywater for domestic Users: An Information Guide." Enviroment-Agency.gov, <http://a0768b4a8a31e106d8b0-50dc802554eb38a24458b98ff72d550b.r19.cf3.rackcdn.com/geho0511btwc-e-e.pdf> (Dec. 3, 2013).
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    Multiple Unknown. (2013). "Greywater for domestic Users: An Information Guide." Enviroment-Agency.gov, <http://a0768b4a8a31e106d8b0-50dc802554eb38a24458b98ff72d550b.r19.cf3.rackcdn.com/geho0511btwc-e-e.pdf> (Dec. 3, 2013).
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    Multiple Unknown. (2013). "Greywater for domestic Users: An Information Guide." Enviroment-Agency.gov, <http://a0768b4a8a31e106d8b0-50dc802554eb38a24458b98ff72d550b.r19.cf3.rackcdn.com/geho0511btwc-e-e.pdf> (Dec. 3, 2013).
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    Xu, Kangning; Wang, Chengwen; Zheng, Min; Yuan, Xin. (2010).
    "Eco-sewerage System Design for Modern Office Buildings: based on Vacuum and Source-separation Technology." AIP Conference Proceedings,
    <web.b.ebscohost.com.> (Nov. 24, 2014).
  15. ^ Carpenter, S. (2010). "A new shade of gray: Paul Mitchell school starts recycling gray water." Los Angeles Times, <
    http://latimesblogs.latimes.com/alltherage/2010/12/new-paul-mitchell-school-recycles-water.html> (Nov. 29, 2014).
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    Carpenter, S. (2010). "A new shade of gray: Paul Mitchell school starts recycling gray water." Los Angeles Times, <
    http://latimesblogs.latimes.com/alltherage/2010/12/new-paul-mitchell-school-recycles-water.html> (Nov. 29, 2014).
  17. ^ Carpenter, S. (2010). "A new shade of gray: Paul Mitchell school starts recycling gray water." Los Angeles Times, <
    http://latimesblogs.latimes.com/alltherage/2010/12/new-paul-mitchell-school-recycles-water.html> (Nov. 29, 2014).
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    Varghese, Jeslin. (2007). "EFFECTS OF THE IMPLEMENTATION OF GREY WATER REUSE SYSTEMS ON CONSTRUCTION COST AND PROJECT SCHEDULE." Repository.tamu.edu, <http://repository.tamu.edu/bitstream/handle/1969.1/ETD-TAMU-1447/KADUVINAL-VARGHESE-THESIS.pdf> (Nov. 24, 2014).
  19. ^ Varghese, Jeslin. (2007). "EFFECTS OF THE IMPLEMENTATION OF GREY WATER REUSE SYSTEMS ON CONSTRUCTION COST AND PROJECT SCHEDULE." Repository.tamu.edu, <http://repository.tamu.edu/bitstream/handle/1969.1/ETD-TAMU-1447/KADUVINAL-VARGHESE-THESIS.pdf> (Nov. 24, 2014).
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    Varghese, Jeslin. (2007). "EFFECTS OF THE IMPLEMENTATION OF GREY WATER REUSE SYSTEMS ON CONSTRUCTION COST AND PROJECT SCHEDULE." Repository.tamu.edu, <http://repository.tamu.edu/bitstream/handle/1969.1/ETD-TAMU-1447/KADUVINAL-VARGHESE-THESIS.pdf> (Nov. 24, 2014).