Replacement of Sand Media with Activated Filter Media

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Hello Everyone,

Suggestions are invited on replacement of sand media with AFM in Rapid Sand filter. We are facing problems of Rapid Sand filter clogging, mud ball formation, and turbid water after filtration.

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29 Answers

  2. Hello

    The filter clogging is due to the formation of mud balls in that case, which increases the pressure on the filter that's what cause a salting-out of the particles previously retained on the filter which will rise the turbidity after filtration.

    That turbidity after filtration could be also due to a bad backwach of the filter or a saturation of the media if it has been used for a long time.

    And also if there is no pretreatment i think that coagulation floculation followed by a decantation could be a solution to reduce the mud ball formation and consequently a less rapid clogging of the filter which lead at the end to a good quality after filtration in terms of turbidity.

  4. I had the problem of mud ball formation filtering water coming from one artificial reservoir preliminary treated in one DAF plant for algae removal.

    The filter is double layer anthracite plus sand.

    The problem was solved increasing the air+water backwash and decreasing the polymer dosage in the DAF.

    The high turbidity in the treated water is symptom of some preferential way in the filter probably related with low backwash efficiency.

    Also the quick clogging can be related with low backwash efficiency but also with the filter solid loading, incorrect sand size and suspended solid characteristic.

    You can try to follow the suggestions of Mr Derek French and to do some pilot plant test(always the best way to follow) as suggested by Mr Coronado.  

  5. Turbidity of feed water plays  a very important role in filtration. If Turbidity is more then Head loss increases & needs frequent back washing.

    Type of turbidity also plays an important role. Compressible particle reduces filtration rate

    Mud ball formation is a typical phenomenon associated with amount and characteristics of turbidity.

    Please improve the turbidity removal in sedimentation tank

    Rajendrakumar V Saraf

  9. Is there any pretreatment process prior to sand filtration? What quantity of solids are being removed e.g. TSS & Turbidity? There is not enough information to provide. Is this water for drinking, RO feed, boiler use etc????

  10. I agree with Michael Chipps, Amirtharajah's does conclude that a sub fluidized backwash with air is the best way to backwash a filter. The difficulty is that the media will be highly fluidized and may backwash out of a pressure vessel (not sure if this is gravity filter or pressure vessel). Air scour prior to backwash will help, if you don't have it you may need to install it. Simply changing the media will not solve the problem Media that is backwashed without an air scour cycle does not change size or change shape, be definition "fluidization"  in water only means the filter grains don't touch during backwash. You need to make sure you getting full fluidization (use ~30% expansion as a guideline) and make sure your backwash is long enough. Pull grabs from the backwash waste and backwash until the waste effluent is  < 50 ntu (closer to 25 would be better) and this will tell you if your backwash is long enough. 

  11. Hello Ashish Yadav,

    we can provide you with a hard coal, which has excellent filtration characteristics and also adsorption characteristics. This coal has a BET-surface of 500 m²/cm. With a sandfilter you have a surface filtration. Due to the granulation of our material, you have a deep bed filtration instead. Allowing you to increase the lifetime of the filtration process as well as the amount of solids and suspended particles. Furthermore we could investigate, whether an ultrafiltration might lead to a better process or might be required. We will need more data to give you an excellent solution for the problems you are facing.

    Should you be intrested, just let me know and I am pleased to help you in this matter.

    Kind regards,

    Jan-Peter Kiel

  13. Hi Ashish,

    I suggest you;

    (1). Test/analyze your turbid treated water to ascertain the contaminant responsible for the turbidity and then target that in your filter packing/recharge.

    (2). Check if your sand is very smooth, then use fine grade on coarse grade after your under-drain gravel, at the bottom.

    (3). The analysis of the "turbid treated water" will indicate if you need to include activated carbon, ion exchange resins, etc in your recharge.

    (4). Control your backwash flow rate, it is not too good to be very high or very low.

    (5). A good filter packing/recharge and on-time/proper backwashing will solve the clogging problems.

    Regards.

    Justin (MACJAMES - www.macjamesglobal.com)

  16. Apparently you used silicate sand.
    General advices:
    1. Replace silicate sand on activated glass.
    2. Use two fractions of activated glass (large and small)
    3. Provide  back-washing washing of the glass with water.  At the same time, the glass is recharged
    4. Observe the recommended work criteria.
     

  19. I hate to be the one to tell you. But you actually have 2 problems.  First you are using sand and mechanical filters. You may be partially cleaning the water but the residue will be in concentrate and be dumped somewhere.  Searching for a process  that augments a failed way of doing things makes no sense. Most of which you speak was 1950,s technology. Since  the late 70's microbial cleaning of waste and waste water is the preferred method and at 1% of the old technology's cost.  The major benefits are:  all waste is reduced into its elemental/nutritional form, there is zero residue to flush into rivers to the ocean, 40 years of monthly testing's had no pathogens, chlorine is no longer needed, all heavy metals are chelated into their elemental form. Lastly and most important the cleaned water is potable.  Not the answer you were looking for. But best solutions need to be at the top of your options list.  G'day mate.

  20. From experience of a project where this was tried it won't do any good for improving the problems that you describe. You would be far better advised to address the issues causing this which are likely to be inadequate air scour or backwashing, possibly poor distribution of air and backwash. I wouldn't go much on their claims of removing specific substances either. Converting to a combined air scour and backwash would be more likely to work. 

  21. As granular media is backwashed repeatedly it 'tumbles' and loses its sharp edges, essentially going off-spec. Then media starts getting washed out and there is less in place, accelerating the problems. Inspect the grains using microscope or magnifying glass. If they are rounded off you could have a sieve-size test conducted to verify but if it has been in service for several years just replace it. I suggest replacing it all at once not adding-to. Assuming the ongoing operations include monitor and adjust backwash rate and duration, carefully control coagulant dose and regularly look for underdrain problems.

    1 Comment

  22. We already had that problem.

    You sould review the back wash flow rate and eventually the back wash parameters. 

  23. Sounds like your water supply has gotten higher in suspended solids, especially clay particles. Addition of a  flocculant like Alum, deeper sand bed layers and more frequent and longer duration backwash possibly at higher pressure should do a better job of suspended solids removal. Do you know if your turbidity after filtration is being caused by suspended solids or dissolved salts/organics?   

  24. Dear Ashish,

     

    As I suppose, in both cases you will have the same suspended solids, and maybe you could continue with the same cogging period in both media if both media have the same particle size.

    Other gestion could be that you use a multimedia filtration system in which you could use a larger size antracite layer over the sand filter to retain the higher particles over, and the smaller particles down in the sand layer.

    Whatever case, it will be good that you do a pilot test with all this technologies before exchance the media.

    We can help with an innovative containerized technolgy that can be used to filtrate drinking water repleacing clarifiers and sand filtratio in one equimpent, and in just one container you can filtrate from 20 to 100 l/s, depending the inlet parameters savign area and chemicals.

     

    Regards,

     

    Orlando D. Gutiérrez Coronado

  25. Please check stepwise 

    Inlet water characteristic changed from the designed one?

    System feed pumps are adequately designed or changed recently from previously installed or their VFD are not working 

    Air release valve on Sand filters are working?

    How old is the Sand media and what are the layers you have placed I.e. at least 4 layers of media are there properly 

    Check the strainers are not loosen due to pressure built up and if these are tightened properly or not.

    If media filter vessels are sized properly according to flow rate?

    I think one by one you need to look into this aspect and solve the problem. 

     

    Also check if the feed water quakltiy is worsen then you may need any coagulation flocculation pipe Flocculator sedimentation prior to sand filters.... 

    Do not jump to simply change this to Carbon Filter.  

    1 Comment

    1. Great suggestion! The plant was designed in 1992 and sand media hasn't been changed since then. 6 Layers of media with gravels and different grading sand is used. Flocculator is also being used prior to sand filters and we are using Alum. But i  will also try and check the other things you suggested. Thanks

      1 Comment reply

  27. AFM is used to removed specific substance, perhaps the substances cause this issue when it adheres to media surface. You also have to look into the backwash flow rate and perform air scrubbing as recovery.