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Thread: Remove suspended clay particles from dam

  1. #1
    pibby is offline Master Silver Subscriber
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    Remove suspended clay particles from dam

    Got a dam I increased in size about 3 weeks ago. It's probably 25-30 metre diameter. The particles stirred up are not settling so I've lost my bath/swimming hole.

    Thought of putting a water tank say 5000l which ive got spare next to the dam and pumping into it then letting it drain out back into the dam via some sort of filter. I Imagine a filter fine enough to remove stuff will drain at a mightily slow rate. When I say filter it's something rudimentary like an old t shirt etc

    Any comments on feasibility of such or other method?

    This is the swimming season here now - the dam will often freeze over in winter and I ain't man enough to jump in then.

    Thanks

  2. #2
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    Back to the old chemistry...

    You could try some Calcium (i.e. gypsum = Calcium Sulphate) to make the clay particles stick together (flocculate) and drop out to the bottom of the dam
    Gypsum is fairly safe ..used on paddocks, lawns etc

    I also recall a product called Alum
    which uses Aluminium something to do the same - looked on Google and found an old flyer n it

    [ame]http://www.nowchem.com.au/wp-content/uploads/2013/03/aluminium_sulphate.pdf[/ame]

    Suggest you try a few grains of Gypsum into a glass jar of the clouded dam water ( leave another one without Gypsum as a control) and see what happens

    Before you scale up - get some advice!
    but often some Gypsum etc will do the trick

    cheers
    Nobby

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    Quote Originally Posted by NobbyTD5 View Post
    ...

    I also recall a product called Alum
    which uses Aluminium something to do the same -...
    Yes. Alum (Aluminium Sulphate) is very effective and used in all water treatment plants.

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    To clarify all of the water in the dam by filtration, you would need to pump all of the water through some sort of filter - this would take some time.

    A quicker option would be to use a flocculant. Simply set up a pump that draws water from the dam, and then pumps the water back into the dam. Put an injection line into the intake side of the pump (suction line) and inject a small quantity of flocculant into it. The flocculant will mix with the water / clay in the pump.

    It causes the clays to agglomerate together into larger particles, which will then settle out into the bottom of the dam. You will find that you only need to do this for a relatively short time, as the water / floc will mix with the rest of the water in the dam through turbulence. The floc will actually work better once it is in the dam and diluted throughout the water body.

    One warning though - if you have yabbies or similar life in the dam, don't do this as the floc will in the short term deplete the water of free oxygen, and any life in the dam will die.

    Not sure who you could get flocculant from in Tassie. Any decent size mining / industrial chemical supplier should be able to get it for you. Tell them that you want to settle oxides / clays (there are different flocs available for different minerals). Alternatively, if you know anyone working in any mines down there which have thickeners in the processing plants, they will have the stuff by the truckload. You would need less than a 25kg bag of powder to do a dam. Best to get it as a liquid if you can - much easier to inject into suction line, and the powder can be a bugger to mix if you don't have the right equipment (will go like jelly).

    No problems swimming in the dam afterwards - this stuff is virtually harmless to humans and animals, and will be so dilute once it is in the dam that you won't even know it is there. I've been swimming in dams / thickeners that have been treated with floc many times, and have copped a mouthful of treated water more than once. No harm so far ........................... I think.

    We did have someone throw some in a dam out near Karonie gold mine years back. They wanted a feed of yabbies without going to the effort of catching them in nets - all the yabbies in the dam died and floated to the surface. Not impressed !!!!!
    Cheers .........

    BMKAL


  5. #5
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    In the 70's when I worked with a Rural Supplies company, we sold hundredweight bags of Bluestone ( copper sulphate) for settling muddy dams.
    I tried googling it but no mention of dosages or whether livestock are affected. I recall it takes a few days to work.

  6. #6
    pibby is offline Master Silver Subscriber
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    Okay sounds like a few options.

    There's no yabbies but heaps of tadpoles, different frogs and things swimming in it I've got no idea what they are. My rule is if they don't bite/sting me then we can swim together. So I don't want to kill what's in there. My neighbour he just empties the dams of water first.

    Took couple bottles for testing and benchmarking.

    Will look into flocculants.

    Thanks.

  7. #7
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    Quote Originally Posted by pibby View Post
    Okay sounds like a few options.

    There's no yabbies but heaps of tadpoles, different frogs and things swimming in it I've got no idea what they are. My rule is if they don't bite/sting me then we can swim together. So I don't want to kill what's in there. My neighbour he just empties the dams of water first.

    Took couple bottles for testing and benchmarking.

    Will look into flocculants.

    Thanks.
    Alum (and all other flocculants mentioned above) will change the pH and may kill the life in your dam.

    This doc has lots of good info and lists some alternative organic flocculants which will have less of an effect on pH.
    [ame]http://www.wioa.org.au/conference_papers/06_qld/documents/petergebbie.pdf[/ame]

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    from the WA agri pages (sorry for some reason thought you were in the west


    No. 42/2004
    Replaces 11/86
    Clearing cloudy or coloured water
    By Officers of the Chemistry Centre of Western Australia

    Suspended material in cloudy (or turbid) water is generally clay, although sometimes organic matter and
    materials precipitated from solution, such as hydrated iron oxides, may be present. Water can be coloured by
    dissolved or suspended material. Changes to colour and quality of water usually occur after rainfall when runoff
    containing soil and organic debris is collected in the dam or tank. This is particularly evident if the rains have
    occurred after a long dry spell.

    Cloudiness or colour is mainly of concern where the water is used for household purposes. Only rarely is the
    cloudiness or colour present in such quantities that the water is unsuitable for livestock or irrigation.

    Chemicals required
    Cloudy and some coloured water comes from dispersed colloids or fines that are not removed by filtration. Certain
    chemicals can coagulate the colloids into particles large enough to settle or filter. Alum (also known as filter alum,
    hydrated aluminium sulphate), is the most commonly used clearing agent for the treatment of cloudy and
    coloured water. Other clearing agents such as lime, gypsum, iron sulphate and calcium chloride are suitable
    in some situations. Selecting a satisfactory treatment is a matter of practical testing.

    Since alum is acidic, many low alkalinity waters (for example, fresh surface water) require a preliminary
    treatment with soda ash (sodium carbonate) or builders lime (hydrolime or calcium hydroxide). Soda ash is
    preferred to builders lime because it can be dissolved and does not increase the hardness of the water.
    Filter alum and soda ash are available from swimming pool chemical suppliers; larger quantities are available
    from firms like Elders Pastoral. Builders lime is available from most hardware stores.

    Soda ash is the chemical recommended, but if you use builders lime the quantity required is two-thirds of the
    soda ash requirement; for example, a recommendation for 75 grams per cubic metre of soda ash is equivalent
    to 50 grams per cubic metre of builders lime.

    To clear water
    The four steps in the clearing of water are:
    ? Obtain a laboratory test to decide the level of treatment.
    ? Select a suitable vessel for the water treatment.
    ? Add and mix the chemicals.
    ? Allow settling of the suspended material and remove the clear, colourless water.

    Laboratory tests
    Small scale tests at home may adequately assess the required dosage, but because most cases need soda
    ash or builders lime it is safer and more accurate to have a laboratory assessment of the water.

    Advice can be obtained from the Chemistry Centre of Western Australia on (08) 9222 3177.

    Treatment vessel
    Tanks
    Batch treatment of the water using two tanks ? a treatment and a holding tank ? as illustrated in Figure
    1 is recommended.

    (refer to link for diagram)
    Add the correct amount of chemicals (as recommended in the laboratory report) to the treatment tank. The
    holding tank requires no treatment other than aeration of the water before entry.

    The water inlet to the treatment tank should be above the maximum water level to provide moderate aeration.
    Further aeration should be provided for the treated water as it is transferred to the holding tank. This is done by
    using a pump or adequate head differences between the two tanks to form a fine spray that travels one to two
    metres before entering the main water body.

    As well as the inlet being above the maximum water level, the treatment tank should have two outlets, one at
    the bottom so that the settled sludge can be flushed to waste, and the other about 100 to 200 millimetres above
    the bottom for removing the treated water. Alternatively, a floating take-off may be used.

    The treated water in the first tank is generally corrosive and fibreglass or concrete tanks should be used. If a
    galvanised tank is used it should be given a protective lining of cement or a plastic liner. Other coatings are
    rarely completely effective and may give a disagreeable taste to the water. A fibreglass lining can be used, but
    must be allowed sufficient time to cure.

    The second or holding tank requires no protective coating as efficient aeration makes the water noncorrosive.
    Only one outlet sited about 100 millimetres above the bottom is needed.

    Clarifiers
    Continuous flow clarifier units are available which incorporate chemical feed pumps that supply doses of
    soda ash and filter alum. The cost of these units is higher than the two tank treatment method.

    Dams

    Clearing or decolouring water in dams is not always satisfactory. The settled sludge from such treatment may
    be redispersed by slight disturbances of the water due to wind action. Further inflow of untreated water also
    counteracts the effect of earlier treatment. Where a dam is protected and further inflow can be diverted, treatment
    can be satisfactory, particularly if a floating take-off is used and the clear water is pumped and efficiently
    aerated into a holding tank.

    Addition and mixing of chemicals

    The amount of chemical required can be calculated from the dosage rates recommended and the capacity of the
    treatment vessel.

    Dissolve the chemicals into separate plastic buckets. DO NOT add soda ash and filter alum together in the same
    bucket as a reaction occurs which renders the clarification treatment useless. Builders lime cannot be
    dissolved but must be mixed into a uniform slurry.
    The treatment tank should be filled with the water to be treated and then the dissolved soda ash or builders lime
    slurry added and well mixed in. The dissolved filter alum should then be added and mixed in. The chemicals must
    be added after the tank is filled and must be vigorously mixed. In a tank of less than 20 cubic metres an oar used
    as a stirrer provides adequate mixing.

    For treatment of water in dams the plastic buckets can be replaced by small tanks such as those used for fire
    fighting. The soda ash and filter alum solutions should be separately sprayed over the surface of the water,
    spraying less near the edges because of the sloping sides of the dam. Ideally, the water should be well mixed
    after adding the soda ash and again after adding the filter alum. This can be achieved by driving a motor boat
    across the surface for an extended period or by dragging a branch of a tree or similar object repeatedly through the
    water. The small tanks and pump should be rinsed immediately after use as the filter alum solution is
    corrosive. The treated dam water is also corrosive and the clear water should be efficiently aerated into a
    holding tank before use.

    Settling of suspended material and recovery of clear water


    Settling time
    The time required for the treated suspended material to settle is not predictable; it may require from 2 to 24 hours.
    Generally, it is convenient to allow treated water to settle overnight.

    Recovery of clear water
    The volume occupied by the settled material will be variable ? it is usually from 2 to 10 per cent of the
    original volume but may be as high as 30 per cent for exceptionally cloudy water.

    The clear water is best removed by a floating take-off as indicated in the figure. This take-off can be made to
    always remain a certain distance above the bottom so that sludge is not picked up. A fixed outlet in the
    treatment tank as described earlier is also satisfactory.

    As soon as the clear water has been removed the sludge should be discharged to waste. Sludge left in the tank
    can prevent satisfactory treatment of the next fill.
    Where the treatment tank has only one outlet and this is at the bottom, it is possible to first flush the settled sludge
    to waste before collecting the clear water through the same outlet. However, with this method it is both difficult
    to remove all the settled sludge and wasteful to use clear water for flushing.

    http://archive.agric.wa.gov.au/objtw...004.pdf?noicon

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  9. #9
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    Homestar is offline Super Moderator & CA manager Gold Subscriber
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    I have wired up Alum plants in open cuts before and know first hand from commissioning the dosing units how effective it is, but as mentioned, it will kill pretty much everything in your dam, either by the PH change or by clogging the gills of fish, etc.

    It will clear naturally if it was clear before you started, but it could take a while.
    If you need to contact me please email homestarrunnerau@gmail.com - thanks - Gav.

  10. #10
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    The only downside of floc was get it on concrete with a bit of water and it turns into an ice rink. Just ask me I know as we used to have a floc plant to settle our thickeners in Nickel Production.


    Quote Originally Posted by BMKal View Post
    To clarify all of the water in the dam by filtration, you would need to pump all of the water through some sort of filter - this would take some time.

    A quicker option would be to use a flocculant. Simply set up a pump that draws water from the dam, and then pumps the water back into the dam. Put an injection line into the intake side of the pump (suction line) and inject a small quantity of flocculant into it. The flocculant will mix with the water / clay in the pump.

    It causes the clays to agglomerate together into larger particles, which will then settle out into the bottom of the dam. You will find that you only need to do this for a relatively short time, as the water / floc will mix with the rest of the water in the dam through turbulence. The floc will actually work better once it is in the dam and diluted throughout the water body.

    One warning though - if you have yabbies or similar life in the dam, don't do this as the floc will in the short term deplete the water of free oxygen, and any life in the dam will die.

    Not sure who you could get flocculant from in Tassie. Any decent size mining / industrial chemical supplier should be able to get it for you. Tell them that you want to settle oxides / clays (there are different flocs available for different minerals). Alternatively, if you know anyone working in any mines down there which have thickeners in the processing plants, they will have the stuff by the truckload. You would need less than a 25kg bag of powder to do a dam. Best to get it as a liquid if you can - much easier to inject into suction line, and the powder can be a bugger to mix if you don't have the right equipment (will go like jelly).

    No problems swimming in the dam afterwards - this stuff is virtually harmless to humans and animals, and will be so dilute once it is in the dam that you won't even know it is there. I've been swimming in dams / thickeners that have been treated with floc many times, and have copped a mouthful of treated water more than once. No harm so far ........................... I think.

    We did have someone throw some in a dam out near Karonie gold mine years back. They wanted a feed of yabbies without going to the effort of catching them in nets - all the yabbies in the dam died and floated to the surface. Not impressed !!!!!
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