Will Anthracite Coal from a Multimedia Bed Block Cartridge Filters?

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Very high differential pressure increase was detected across cartridge filters (1micron size). Differential pressure went from 10 kpa to 30-35kpa in the space of a week.

By taking off the cartridge filters, was noticed anthracite coal on the surface of the filter. Also SDIs were taken before (6.9) and after the multimedia filtration (4.9). SDIs are really high too and we have never seen anything like that before.

Asking for opinions and hopefully from experience. What will be my first root cause for the blockage, the anthracite coal or the high SDIs?

Thank you!

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19 Answers

  1. Yes, filter media (coal or sand) will definitely block cartridge filters.

    Did this facility re-fill any media filters recently? if new media is installed and fines are not washed out correctly during installation, it is possible that a load of fines clogged the cartridge filters when the filters came online for first time.

    The high SDIs and the particles probably are one and the same problem (SDI is just a measurement of how quickly a 0.45micron filter clogs).

    If the coal particles are big, they are most probably filter media espaping from a filter unit if the integrity of the filter floor has been compromised.

  2. Hi Maria, that happened to me before, after the inspection we founded that 1 or more nozzles were broken doing thea inspection before washing the MMF you can observe under the nozzle that is broke a small cone where the anthracite is going  to deposit, and some will be founded in the cartridge filters. The increase of the SDI could be caused by a preferencial way that the water founded ( probably the cause of the broken nozzles)  that can happen if the filter stays on service for to long and don’t have a proper backwash.

     I can send you some pictures so it’s easier for you to identify it. Just send me a email to   

    Joserafael1977@hotmail.com

  3. Hi Maria, that happened to me before, after the inspection we founded that 1 or more nozzles were broken doing thea inspection before washing the MMF you can observe under the nozzle that is broke a small cone where the anthracite is going  to deposit, and some will be founded in the cartridge filters. The increase of the SDI could be caused by a preferencial way that the water founded ( probably the cause of the broken nozzles)  that can happen if the filter stays on service for to long and don’t have a proper backwash.

     I can send you some pictures so it’s easier for you to identify it. Just send me a email to   

    Joserafael1977@hotmail.com

  4. I think that the answer to your problem lies in the multi media filter. The high SDI indicates that not all of the material that should be removed by the MMF  is being removed. This may be due to not adding a coagulant in the right amount for the conditions or by faults in the filter and its backwashing leading to cracks that permit both the anthracite particles and silt particles to break through. What is the size of the anthracite particles on the cartridge? If they are approaching the size of the sand and garnet then the problem is likely to be cracks or failed nozzles. Very fine and it is more likely to be coagulation. A sudden failure points more towards a filter fault.  

  5. what's specific flow rates in operation and in backwash mode? air sourcing specific flow? Did you change manufacturer, type of anthracite? Did you prewash and air-backwash before start up? I recommend for SDI removal a 4 to 6 BV. BTW SDI 15 minutes max. 6.666......

  6. Yes. Wear on the granules will form small particles that can flow through the multimedia filter. This particles then get trapped by the cartridge filter. If enough of the fine particles accumulate on the filter cartridge, it will clog up

  7. Dear Maria,
    Anthracite / Carbon get fragmented over a period of time and form the fine dust. This further gets trapped in the Cartridge filter. Please check the Multimedia filter for the fragmented anthracite.

    Rajendrakumar V Saraf

  8. Dear Researchers.

    It is needed to have a pre process filter.. is it done

    O&M practices to be followed.

    Do you have twin or more  sets of filters in service ie one working.. one on standby.. one on in-situ cleanup process.

    In certain in situ cleanup  process have - simple flush  with or with out air blow thro, back wash flush.. some vacuum at inlet to facilitate total back flush.

    At all these drains observe the matter getting released.

    This would tell you tale to shoot - trouble ..

    Well wishes.

    Prof Ajit Seshadri 

  10. New anthracite media has to be air scored  and back washed repeatedly till it is free from loose coal. High chlorine content may also may damage the anthracite media and give this problem. It is better to use graded sand and gravel which avoids the above problem.

    Any colloids/particles including powdered coal  increases SDI. 

  11. When selecting the anthracite media you must ensure that the manufacturer has used a product that is free of "fines" that will cross over the distribution plate, this frequently requires and extra step that isn't always followed in the attempt to increase production and reduce costs.

    1 Comment

    1. I agree that the premature fouling could be due to the anthracite accumulation. Perhaps a recent media replacement or a high flow upstream caused the media to be transported from the filter bed into the cartridge. I'd like to see the process flow.

  12. Check the following.

    . Pump pressure . May be very high distrurbin the flow.

    . CheCh if distribution plate is proper for flow distribution. 

    Input sdi 6.9 is very high. Should be around 4 preferably.

    . Check input Water turbidity as well and SS. .

    . 

     

  13. In multimedia filtration the delta P reaches high, the backwash performed if provision but cartridge have no facilities of backwash. Because the first layer of anthracite coal so there is observed that, generally the multimedia first layer of anthracite coal 2nd quartz and then Garnet and so on. Silica sand and anthracite are the most commonly used types. When silica is not suitable (e.g., in filters following a hot process softener where the treated water is intended for boiler feed), anthracite is usually used.

     However, is about cartridge-style filters rather than backwashing filters. Cartridges are for the most part disposable items. Except in rare cases, they are not backwashed. They are used until they stop up, then they are discarded. Certain cartridges can be cleaned and reused.

    Please check your input water quality or replaced the cartridge.

  14. Believe  your multi-media filter consists of antracite-sand and possibly garnet. Anthracite is normally with size 0.8 to 1.6mm or more. Unless your filter bed is seriously cracked (or has developed spiral holes) it is difficult for the particles to enter underdrain and then into filtered water outlet. If the Anthracite is not of requisite hardness then there is a possibility that crushed powder may have entered into filtered water outlet through the cracks.(A remote possibility is that underdrain nozzles have got damaged too). Best thing is to open the filters and have a physical inspection.    

    However normally it is inadequacies of pre-treatment which results in higher filtered water turbidity. This results in increased SDI. Need to check your feed turbidity & other parameters along with the chemical doses.(Is the pretreatment only limited to multimedia filters, what is the source of raw feed water?)

    You may eliminate the possibilities one by one. 

  15. These responses sound good.  It will help if you determine the amount of carbon in your inflow.  Any pretreatment design should know the carbon load and the form.

  16. One of the essential problems you are having is plugging of the cartridge pores by the anthracite.  One of the easiest solutions is to add a precoat material to the incoming stream.  A material such as diatomaceous earth or other light-weight material will form bridges in the anthracite and maintain the porosity you need to increase your filter life.  

    Alternatively, as was suggested, you could go to a prefilter such as a plate and frame or a sand filter. Either way you will have to backwash those filters, as you will with what I'm suggesting.

  17. Yes, I expect that the  anthracite coal from a multimedia bed blocked the cartridge filter. My suggestion is to use sand filter between anthracite coal from a multimedia bed and the cartridge ​filters. this sand filter can capture the anthracite  coal and act as protection stage and increase the durability of the cartridge. kindly, send to me your feed back.

  18. Hi Maria,

    Difficult to say with few information. The anthracite is relased from its filter that is for sure, the roots can be various.

    Maybe topics should be splited into 2 pieces : Particles clogging your cartridges :

    - Erosion/attrition during backwashed followed by a too short rinsing time ? Fines particles get through the nozzles of the media filter.

    - What about if one or more nozzles are damaged ?

    - The anthracite haven't just been replaced and has been badly rinsed at first start up ?

    SDI values :

    - Is there a risk the pretreatment is failing performing well ? raw water quality have changed ? 

    I assume, you do not face this since a major modification/maintenance/operation on your water treatment plant or is there a risk something has changed ?

    Best regards,

    Olivier