Harvesting Grey Water

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What methods can be used to harvest grey water flowing on the ground surface, for the purpose of purification for re-use for household and irrigation purposes?

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19 Answers

  1.  there are 2 low cost methods of harvesting grey water for household use

    1. by a ozonater which i have costing RS 5,000 connected by a pipe to a 20 liter plastic water jar which purifies this in 30 minutes-a bigger model could also be made

    2. a better method is to attach a UV  WATER FILTER connected to the kitchen tap the bulk purchase price of which is about US $ 10 EACH  but may retail at about US $ 30 which gives water @ 1 liter per second with zero e-coli with a optional porus filter if there are particles in the water 

     

  2. There are plenty of off the shelf solutions for urban / household grey water collection and reuse for garden watering and toilet flushing.

    A local authority in Western Australia - came very close to legislating that all new developments had to have grey water systems installed, it was narrowly defeated by 1 vote in the planning council.

  4. Harvesting Grey Water is very well known now a days. Simply to start you need an implementation plan from redesigning new building permits to existing building by adding separate network for collecting and distribution either for flushing toilet tanks, cooling system or irrigation usages.

    There are many good systems available in the market for just to bug in and starts…

    We have good system running in Sharjah City since 2003

  6. Hi dear Fungisai:

    The parameters of economic, level of pollution, land availability and most importantly the kind of consumption ( directly consumed by people or not) are the factors which determine the treatment approach.  But generally biological treatments (like aerated lagoons or wetlands) are preferred, because they are cheaper and enough efficient for decreasing the BOD5, COD and TSS. After that, with disinfection (preferably UV because of less byproducts) the grey water is ready to reuse. 

    But if the level of TDS is high yet, you should use membrane technologies which increase the costs, but it is inevitable.

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    1 Comment

    1. Thank you Iman. Very helpful input.

  7. I appreciate the question you asked. In India still this is a issue to use or not to use this grey water. However, as literature suggest a grey water can be directly used for irrigation if it collected from the healthy persons. Moreover, it has high nutrient content so of course it is good for the irrigation. 

    Regarding the question you asked, I think harvesting is better approach by proper treatment to grey water. So, as mentioned the water flowing onto ground so I will suggest to opt for wetland system as being low cost where land availability is not a issue. If land is the issue you can go with the bio filters for the treating grey water. Regarding household treatment, high TDS and colour could be major issue. the colour could be partially treated with filtration as mentioned earlier.

    however tertiary treatment with membrane filtration can be possible (costlier affair). 

  8. Hi Everyone, I have read most of the answers and have understood or used these methods. One problem I am facing right now is the Rain Harvested water has bed odour. Hence the system (ysed for toilet flushing only) has been temporarily been suspended. On water testing it is observed that apart from odour the water has above limit colour and turbity. I am planning to erect a filter cum dozing unit on the delivery pumping mains. Can someone suggest the type of filter cum dozing pump for a flow of 10m3/day.

  9. Fungisai, I presume that you are asking about the collection of the water not its treatment. This requires that you have a system of pipes which are connected to the source and carry the water where you want it to go. It could be done with open channels but that would be more problematical as regards maintenance. This is not too difficult if you have access to plastic pipes and, for grey water, they don't need to be too big as there should be no solids to pass - unlike sanitary sewers which are normally a minimum diameter of 100mm. As regards treatment - there are standards - but many rural communities use grey water for irrigation without any treatment.

    1 Comment

    1. Yes Peter the main emphasis was on how to collect the grey water in order to facilitate the necessary  treatment technologies.However I am grateful for the different responses I have received ,,they are all so helpful and will be a great contribution to my research.

  10. Dear Fungisai, for greywater treatment and reuse, if you have enough space, I suggest you to use constructed wetlands plus some disinfection unit if you are going to reuse treated greywater inside houses (e.g. WC flush tanks). They are cheap in O&M, and you can easily build them with local material. For an example, you can see this publication

    Masi F., El Hamouri B., Abdel Shafi H., Baban A., Ghrabi A., Regelsberger M. “Segregated black/grey domestic wastewater treatment by Constructed Wetlands in the Mediterranean basin: the Zer0-m experience”, Water Science & Technology , 61, 1, 97-105, 2010. doi:10.2166/wst.2010.780.

    For general information on possible greywater reuse, I suggest you the SSWM web site:

    https://www.sswm.info/category/implementation-tools/reuse-and-recharge

    1 Comment

    1. Thank you so much Anacleto,,very helpful indeed.

  11. Fungisal.  Greywater  (or graywater if you are an American) is typically defined as drainage from baths, showers, lavatories and laundry - where the soaps and detergents give the water a typically "grey" colour.  In some cases kitchen sink and dischwasher drainage  may also be considered greywater versus "blackwater" from toilets and urinals (i.e. sanitary sources).  I think you are referring to drainage from precipitation, which is often separated into two groups: 1)  drainage collected from elevated surfaces and roofs - "harvested rainwater"; and 2) drainage collected from ground surfaces, walkways, and road surfaces - "stormwater runoff".  Rainwater collected or harvested from elevated or surfaces are generally considered to have fewer sources of contamination than stormwater that has been collected after flowing over the ground or paved surfaces.   How you collect the water and the degree and method of treatment you apply  depends on the expected or potential level of contamination and the quality of the water required for the  application or use.  Rainwater harvested from roof areas is often drained into above ground or below ground storage tanks that can be made of any material that holds water without contaminating it.  Storage allows suspended solids to settle, and the water cane be used for either potable or non-potable applications - depending on the treatment provided.  Potable water treatment typically involves two-stage filtration followed by disinfection, as a minimum, but often includes granular activated carbon filtration to remove any metals or organic contaminants that may be present.  Treatment for non-potable applications - such as toilet/urinal flushing, vehicle washing, irrigation, laundry, etc. - generally involves filtration to prevent sedimentation and clogging of irrigation lines.  Stormwater is often collected in ponds, or other surface containment structures, and treatment also depends on the degree of contamination and the water use.  Collected stormwater may also be  a source of water for potable use following treatment, but the level of treatment is usually greater than for harvested rainwater.  Like water from a stream, river, or lake; stormwater treatment usually consists of a large sedimentation basin for suspended solids removal, followed by dual-media or membrane filtration - and sedimentation and /or filtration may also be chemically enhanced using coagulants and flocculants - particularly if there is a high degree of turbidity due to suspended colloidal particles. 

    Returning to your reference to greywater, greywater can also be used for non-potable purposes either directly (recycled) or following treatment (reused).   Using greywater to flush toilets, for example, can be a cost effective application that achieves significant water savings and reduces wastewater flows.  Because soap and detergent is biodegradable, they will likely result in biofilm growth that will require brushing periodically.  Because of this biodegradable material, if you need to store the greywater for more than about 24 hours, the biodegradable organic contaminants need to be removed - typically by bio-oxidation, followed by sedimentation and, in some cases, filtration to remove colloidal particles and improve disinfection.  While you will find some concern expressed in the literature regarding the use of greywater for landscape irrigation, due to the effect of soaps and detergents on soil structure - if the greywater is not the sole source of water applied to the soil (i.e. if there are seasonal rainfalls that can wash out accumulated salts from the soil) there should be no concerns.

    I trust the above helps.  The treatment technologies involved are very basic: 1) sedimentation to remove suspended solids; 2) aeration for biological oxidation of organic contaminants; 3) filtration to remove colloidal particles that could interfere with disinfection; 4) consideration for activated carbon filtration (for drinking water use) to remove residual organic contaminants and metals; and 5) disinfection to remove any pathogenic microorganisms that may be present (i.e. bacteria,parasites,and viruses).  The choice of treatment depends on the degree and types of contamination that may be present, and the water quality required for the desired water application/use.       

    1 Comment

    1. Extremely helpful and handy..Thank you.

  12. I would suggest what we call a septic tank.  I have attached a file.  The tees are important we call them baffles.  They will allow the FOG (fats, oils, grease) to form a scum on the water.  Settleable solids will form a sludge on the bottom of the tanks.  Measure your flow a provide enough detention time for two or three days.  The effluent can then be sent through a rock or sand filter.  This process will reduce the COD and BOD.  The water then should be good for irrigation or to flush toilets.  Much more treatment would be needed for potable use.

  15. Since the grey water is Flowing that means your new best friend is gravity. Pic a spot in that flow trench it out. (The length depends on how grey that water is) By using a combination of sand and mineral rocks (small chunks)  you have a inline filtering system. Down the line select a good spot for a drop off into a man made hole or a natural depression.  If you desire this water to be potable just add Archaea microbes. They will breakdown all compounds into elemental form and chelate any and all toxic materials into their non toxic state.  (depending on the volume multiple separate trenches leading to a main trench or the hole may be required.  The only factor that needs your attention is time and length of trench purifying system.  The black and grey water residential units have been designed and tested. Soon to hit the markets.  Forgot to mention all of this is free. Your local materials, your design, your hard work, your water. The Archaea microbes cost 6 cents a day to use for about 1,000 gallons of treating water.  All good ideas on this thread. Nice to have helpful options.

    1 Comment

    1. Thanks Guy.Very simple and straight forward method and cost effective too!I hope Archaea microbes are  readily available in the local markets in South Africa.I will definitely apply this method to a practical case study i will be busy with in the following few months.

      1 Comment reply

      1. They are not currently available in South Africa. They were used in the diamond and gold mining operations for many years.  The formula I work with is for agriculture.  In case you were interested. I have a complete off the grid program that is equally inexpensive. The grey water is only 10% of the overall program.  Never have to worry about clean water, food or energy ever again.  No magic. Just pure mother nature and taking the time to use what the lord has blessed us with.  If you wish my skype: guy_mcgowen email is biozomesales@biozome.com. Contact me any time.

  16. I agree with Tim Acland. It must be started with local specific conditions and available materials, if there is no infrastructure. Then start to build on site like disposable tranches from household toward the main channel (a bigger tranche) and a reservoir (a big hole in the ground). Have this first instance flow control, then it might be imaged next step as the use of the gray water, considering the biochemical charge and the costs (maybe for some irrigation is less costed than for human use, even if not potable). Of course the tranches and holes could be reinforced, if they are in good position and suitable for primary use/installation. Afterwards, all the technical solutions mentioned here might be considered at least like design ideas for local hand manufactured pieces of installation or, if enough money available, engineering infrastructure works and standard installations procured and mounted in.

  18. More details are required but initial considerations need to include how many point sources and local ground conditions. If porous ground then contain the discharges and aggregate them to be passed onto storage and/or treatment. If fairly impervious ground construct a ditch to collect discharges and pass to treatment. Treatment may include a settlement pond and/or a reed bed type biological cleaning stage prior to use for irrigation or recycling to home use.

  19. This is one of the easiest applications using bioremediation. I have done several with just grey water coming out of toilets (bathing area), wash basins and laundromats. 

    Ideally it is better to have black (sewage) water mixed with the grey.

    2 Comments

    1. I agree.  There is no justification from a health risk perspective, or treatment cost perspective, for segregating greywater from blackwater for the purpose of water reclamation and reuse.  The same technologies are used for both mixed wastewater and greywater, including the need for disinfection.    

    2. Excellent observation sir. The Bioremediation technology these days is quite remarkable. We have had more than 2500 cleanup projects over the last 16 years using Dr Oppenheimers Archaea microbes which he discovered back in the 1940,s. Not a single call back to date.  Still trying to get the info to India. The Political walls are very tall. The peoples needs are great. ( for those who are not aware. The black water has organic materials that can be consumed by the microbes and allows them to accelerate their activity level. In addition when Rna microbes reduce the organic material into their elemental state the water is tested and is declared potable. If so desired the electrons broken loose from the compound covalent bonds can be collected and used as electricity.  No sense letting anything go to waste. (biosolids make great compost materials).