Sand Filtration for Grey Water Treatment

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What are the practical problems using sand filters for greywater treatment for a community of 200 households to be discharged in inland waterbody?

Is it efficient for meeting the requirements or should the community go for an ETP?

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25 Answers

  1. in using this, you want a biofilm to develop.  basically you are feeding grey water to grow the geobacters in the soil.   otherwise the water coming out will still be dirty.   once it clogs, just rake it down.   to combat clogging just use the proper size of sand filter.  the larger the sand filter, the more time the microbes can clean the water.  a week long slow sand filter would have much less clogging than a 2 day sand filter.

    hope this helps.  good luck

     

     

  5. happy new year, everyone.

     

     slow sand filters would work really well.

    if you do an up flow one, it will also help denitrify.  

    you will need to back wash from time to time.  but you can use air to back wash.  the up flow ones

    so you will need two lines.

    also you want the biofilm.  and if it clogs, thats the time you till it in.  in a low wage country like india.  it should work out well.  ( this is the down flow one.)

    the biofilm can come in different colors.  from red, to yellow to green.  And sure in the down flow ones, you can see worms develop from helminth eggs.  but the water at the end will be clean.   sure, you will find all sorts of worms and insects feasting on the biolfilm.  

     

    for a small one, all you need is a rake to till it down.  kill the worms, its okay.  they are nematodes.  

     

    20 years ago, I built one for a city for their drinking water.  land was cheaper then.

     

    the main advantages is that, it world real well and opex is real low.  and its very good in disinfecting.  better than uv, chlorine or ozone.  

    disadvantage is it takes a lot more space.  there will be no odor.  

    one more thing.  you want large grains of sand.  more than 1 mm.

    and you may want a mix of pea  gravel and sand bed.  pea gravel is another wonderful medium.  

     

    good luck.

     

     

     

     

     

     

     

     

     

     

     

     

     

     

  6. Dear Mary Rose,

    I agree with Zaid and Anacleto: a constructed wetland is a more reliable solution to treat BOD and SS from grey waters than a sand filter. The latter is more likely to clog, due to microbial biofilm development.

    But I would rather advise a vertical flow constructed wetland (VFCW), with one or two stages, depending on the outlet requirements. A VFCW will accept raw water, after coarse screening. Biological clogging is avoided by constructing 2 or 3 beds for each stage. One bed is fed during 3-4 days, and then let for rest during 7 days while feeding the other beds. This way, biofilm remains under control. Of course granulometry of gravel or sand has nevertheless to be carefully selected.

    The surface of the beds is planted with macrophytes. Their role is to prevent SS clogging of the surface of the first stage, the layer trapped on the surface being continuously perforated by new sprouts. Species used is adapted to the geographical zone. The organic layer formed on the surface mineralizes with time, and need only be removed after several years.

    This process can accept reasonable amounts of grease, i.e. mainly what comes from dishwashing, and most of the products used for the washing, the kitchen, or the body.

    Standard outlet quality can be as low as 30 mg/l SS and 25 mg/l BOD. Lower levels can also be achieved with specific design.

    With sufficient water head, the process requires no energy.

    Feel free to ask me for more information: I would be glad to help you in dimensioning and designing your treatment.

    Sincerely yours,

    François

     

     

  7. Mary Rose.......Sand filters can be a good solution however, it is better to treat the water with biological enhancement product that is organic and biodegradable. before it enters the filters.

    This will have a secondary effect of keeping the sand filter clean and will initially remove fats, oils and grease and keep malodour to an absolute minimum.

    Hugh.

  9. I have quite a lot of experience with grey water treatment, and I agree with many of the comments below.

    First issue is what constitutes the grey water.  Does it include kitchen wastewater or not?  Does it include laundry wastewater or not?  The solids - lint, food waste, and FOG will create complexity and require proper removal before you would have any hope with a fixed media bed (sand or otherwise).

    I had a lot of success over several years with the following - treatment train:

    1. Inclined, curved slotted screen (sieve bend) with additional sprays for periodic cleaning

    2. Proprietary circulating bed biofilter, with automatic backwashing sequence based on bed pressure drop

    3.  Disinfection by UV and/or Hypochlorite depending on the re-use requirements.

    If you want to operate the system successfully in the long term, you need to have elements along the above lines or you will end up with a big mess.

    Another huge issue is protecting the microbiological population from the shock of flow/concentration, pH and temperature change, as well as nasty household cleaning materials....

    I'm happy to help if I can.

     

    Phil

  11. Hi Mary.

    Lots of input on this. I agree with Mathew Crowhurst. Whatever you choose, the design should include a settling chamber (e.g. septic tank). It will reduce the oils and grease and capture solids. If those get to the filter system it will require more frequent maintenance for the real treatment system. A one day and a half day retention time would be good for the settling chamber. After that, a sand filter or gravel wetland design could work fine. It really does depend on the media available. The finer the media (sand vs. gravel) the more maintenance and larger space. Whatever you use, it should be of fairly uniform size of gravel/sand so it does not plug. Everything should be covered (buried) if mosquitoes are a concern for public health reasons.

  12. I concur with all of the previous comments.  However there is an alternative to sand filtration, which is called AFM (Active filtration media).  It is a treated coating on recycled glass with particle sizes approximately the same size as sand.  The difference is that the media does not become clogged because bacteria do not grow on the surface of the media.  It is backwashed using water.  I have been using it for 15 years successfully.  The comments of COD from this grey water still stand, but this will remove suspended materials and a significant level of bacteria.

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    1 Comment

  13. Hi Mary

    I agree with some of the comments. Grey water has enough BOD to enhance biological growth in sand filter and you will face clogging in no time. You must use a conventional biological system to reduce BOD to levels that will not cause clogging, ie less than 10 mg/L. 

    If not possible forget sand filter, it won't work.

    Mehdi Borghei

  14. Hi Mary - I agree with the reservations regarding sand filters expressed by others.  Perhaps a different approach would be better, such as the geotextile-based filtration system used to clean stormwater by Urban Stormwater Technologies' Catch Basin Inserts - please see: www.urbanstormwater.com.au

    These systems may be easily adapted to suit a wastewater treatment application, and will not clog if they are properly maintained.

  15. depending on the licence release limits specifically nutrient loadings sand filtration would offer minimum reduction. 

     

  16. I always think of sand filters after after some treatment for solids and organics. I would think a membrane system would be a better choice. I have seen a small Kubota plate system where the air scour for the membranes provided enough dissolved oxygen for treatment.

  17. Hi Mary,

     

    As had been stated above concerning a sand filter, I think the media used is important and the ultimate discharge into the environment. The gray-water has a great resource capability to hydrate the outer landscape. A simple system can initially collect the water in basins with a preliminary "grease trap" and then infiltrate media for the different stages of water treatment. Ultimately this land surrounding the residential area could be your gated with such water for foo productions a perennial entry crops. Dividing up the households into districts also reduces the size of initial systems and may provide and easier management strategy as opposed to one large System needing to deal with the variable volume. I would advise many scaled Systems depending upon the size of your residential districts, and making them site specific as to their design.

  18. Hi Mary,

    I agree with ​Anacleto ​comment above, ​hence ​Constructed ​wetlands might ​be useful as ​alternative ​treatment ​techniques (low ​capital and ​operational ​costs and do ​not required ​qualified ​persons for ​operation and ​maintenance) ​

    Refereeing to ​your suggestion,​ as mentioned ​in some ​comments above, ​clogging of the ​sand filter ​will be the ​main problem, ​and therefore ​will required ​periodically ​backwashing. To ​minimize the ​backwashing ​frequency, I ​might suggest ​to fill the ​column with ​gravel at the ​bottom, coarse ​sand in the ​middle and fine ​sand at the top,​ once the ​clogging is ​occurred, you ​need to replace ​only the above ​layer of the ​fine sand with, ​in this way you ​will reduce the ​frequency of ​backwashing ​

    I will ​suggest first, ​that you need ​to determine ​the volume of ​the generated ​graywater from ​the households ​so may be one ​of our ​colleagues in ​this group can ​help you by the ​design of the ​system. ​

    Finally, I ​would remind ​you that if ​discharge from ​kitchens will ​be also ​included in the ​system, the ​household ​keepers must be ​aware to remove ​solids, as ​possible as ​they can, ​before start ​with washing ​and don’t ​discharge oil ​or fat to the ​gray water ​collection ​system ​

    Wish you good success

    Regards

    Zaid 

     REPLY (0)

     

  19. Sand filters can be used successfully for grey water treatment but depending on the solids content of the grey water, a primary settlement tank would most likely be needed.  The practical problems arising would be related to the type of sand filter design and the quality of the effluent required.  Do you have a discharge standard in mind?

  20. Good morning,

    First when you say grey water, you are talking about water from other sources in a household excluding toilet waste? Washing machines, sinks, and showers?

    There should be some type of bar screen, grit removal, primary clarification, or other types of pretreatment.

    What would be the discharge of this water? This would dictate the treatment post sand filter.

    You would definitely need to remove plastics, grit, and heavy materials.

    Sand filters are for removing suspended solids only.

    Hope this helps!

  22. Dear Mary,

    Sand filter is design for removal of Total Suspended Solid and not for removal of BOD/ COD. You have to go for Sewage Treatment Plant.  We are consider 135 liter/ Capita/ day sewage generation. The wastewater generation for 200 House Hold calculated as below:

    1 House- 5 people

    200 House- 1000 people

    Sewage Generation: 1000 x 135 liters/1000= 135 KLD

    Design Capacity of the STP by considering shock load and Future need is 150 KLD.

    There are many types of sewage Treatment Plant. Few are given below:

    1. Activated Sludge Process- MBBR or MBR: - Very Compact with clear treated water quality. Treated water can be reuse in garden and flushing. It can be safely discharge in Inland Water body

    2. Soil Immobilized Bio-technology (SIBT): required very large footprint area, but almost Zero Operating cost. You Can Develop SIBT as Garden and good looking landscape. Treated water can be safely discharge in inland waterbody.

    Please mail me or call me on climateventure4careu@gmail.com and Whatsapp +91 9376034476.

    Thanks

    Vimalesh Patel

  23. Hello

    The problem of a filter whatever it is is to clog up when it is used. As a result it loses immediately and gradually its effectiveness. How to solve this problem? Impossible.

    Greywater as all wastewaters contain dissolved pollution. In reality, the reality of all treatment proposals is to reject in the environment, a polluted liquid, making it appear that it has undergone a possible treatment of purification

    A filter will retain the suspended material but will not purify the dissolved pollution. 

    To date all wastewater is discharged into the environment with their dissolved pollution. 

    With biological sanitation one begins by preserving the characteristic of the water during its consumption, during its use.

    Therefore this waste water can be purified by a totally biological device that will reject a clean liquid. This liquid can then be used for the watering of plant biodiversity which it by absorbing the dissolved pollution purifies the soil.

  24. Dear Mary,

    having only Sandfilter as Greywater treatment is not practical at all.

     

    Greywater pollution is mostly made of COD and some TSS. Especially COD will create a lot of MLSS inside of the filter by bacterial growth, leading to frequent clogging of the filter and thus backwash. Furthermore, big material (food rests etc.) will clogg the filter and cannot be treated.

     

    For small communities,  better to make some lagoon or similar treatment. Please find some treatment option for decentralised/differenced wastewater treatment in the compendium of EAWAG. It is a real good ressource and best of all, softcopy is for free.

    http://www.eawag.ch/fileadmin/Domain1/Abteilungen/sandec/schwerpunkte/sesp/CLUES/Compendium_2nd_pdfs/Compendium_2nd_Ed_Lowres_1p.pdf

    They also did some classes on Coursera and uploaded the videos on youtube:

     https://www.youtube.com/channel/UCdDwnhvbqp2qMN1D4XyS8nA

     

    Best regards,

    Patrick

  25. Dear Mary. I cannot give you a detailed answer, but I'm thinking that you could have issues of clogging in your sand filter. If you have enough space, I suggest you to put plants and to build a constructed wetland :). Basically, it's not more complicated than sand filters to manage, and it has shown to be very efficient in treatment of greywater in comparison to other compact technologies, since CW works better for more dilluted greywaters. I suggest you to use gravel, if you have it, and to adopt the horizontal flow scheme, which is the simplest to be managed.

    You can find more information on greywater and CWs on the SSWM website (https://www.sswm.info/)

    1 Comment

    1. Hi Mary,

      I agree with Anacleto comment above, hence Constructed wetlands might be useful as alternative treatment techniques (low capital and operational costs and do not required qualified persons for operation and maintenance)

      Refereeing to your suggestion, as mentioned in some comments above, clogging of the sand filter will be the main problem, and therefore will required periodically backwashing. To minimize the backwashing frequency, I might suggest to fill the column with gravel at the bottom, coarse sand in the middle and fine sand at the top, once the clogging is occurred, you need to replace only the above layer of the fine sand with, in this way you will reduce the frequency of backwashing

      I will suggest first, that you need to determine the volume of the generated graywater from the households so may be one of our colleagues in this group can help you by the design of the system.

      Finally, I would remind you that if discharge from kitchens will be also included in the system, the household keepers must be aware to remove solids, as possible as they can, before start with washing and don’t discharge oil or fat to the gray water collection system

      Wish you good success

      Regards

      Zaid