Pressure Sand Filter Media Options

[Vect]

Hello,

I've had a search through previous posts but they couldn't answer my questions.

I've been charged with solving our process water issues, which comes from a borehole full of iron-rich water. This has caused most of the front end water storage and pumping equipment to be coated in the brown slime typical of Iron Bacteria. (A water sample has been sent for analysis - but will take 2 weeks+ due to a worse than useless purchasing dept.) The specific problems caused are low level in the production line water tank (lack of throughput/blockage in pipe due to slime) and fluffy strands of bacteria blocking rotameters and water injectors.

My idea is to install a Pressure Sand Filter directly after the borehole pump. This should give the downstream equipment a fighting chance. But I'm struggling to find any concrete information on what type/types of filter media to use. The filtered water needs to be free of large contaminants (>~100um)and low in soluble Iron/Iron oxide which gave rise to the bacteria in the first place. I figure if their energy source is removed, they'll stop growing in such numbers.

So to summarise: What filter media options are available to reduce iron/iron oxide and also filter particles >100um?

Thanks

V

 

[semo]

The filter will not remove soluble iron from the water. You will have to get it out of solution so that the filter can remove those particles. Oxidation is typically performed with aeration, chlorination, permanganate, or a combination.

You really need your water analysis before you can do much.

Filters will work fine until the iron/manganese (yes you want to check for manganese levels too) are too high. Then the mass of the oxidized iron will limit the run times of the filters. High levels will cause you to have to backwash the filters more often. For these levels, a clarifier or other removal unit will be needed.

If you have manganese, you have to size your chemical feed and detention times to allow for its removal as well.

 

[Vect]

The equipment i'm looking at is rated at ~30 m3/h when really we only need 24 m3/h, so we have some extra capacity. The water contamination isn't too heavy, it looks relatively colourless (slight green/brown hue) when it jets out of the sample point and when it runs through the rotameters, but there is very noticeable brown slime in the pipes and tanks.

We are running a crystalisation process and we are vary wary of adding in additional chemicals. Chlorides are definitely out of the question, Potassium and manganese are also strictly limited.

So to open this out slightly, if you had a this problem (iron-rich water casing bacterial growth which clogs pipes and reduces pump throughout) what options would you consider?

Well cleaning is a lost cause, it would need to be done annually and it just wouldn't get done. (I'm in Brazil, the local team is a shambles - mainly due to short-sighted, close minded MD with a finance background)

 

[bimr]

In addition to Semo's comments.

Most sand or multimedia filters will remove particulates down to a particulate size of 20 microns.

You may have iron bacteria in your well. A more economical first step than installation of filters is probably to disinfect your well and water piping system.

Most of the iron removal methods involve oxidation of the iron in some manner. The most economical method of iron removal will depend somewhat on the elements present in your water analysis.

One would doubt that any of the basic water treatment chemicals would have any effect on a crystalizer. For example, chlorine would end up as 1-2 mg/l of chloride which is well within the parameters of most water supplies.

 

[Vect]

Ok, thanks for the comments. I'll report back when i have the water analysis

 

[Lan123]

What about considering a greensand filter?

 

[cremesti]

quick tip: u can take a water sample and add some bleach (Eau Du Javel, sodium hypochlorite) and see if any more iron comes from solution. this way u will know of u have Ferrous or Ferric only.

As for your theory of Bacteria, you have to prove that; the flocs may be just FeOH3. To check if the flocs are organic or inorganic, u have to burn them. if they are organic, the solid will burn away, if inorganic, it will not.

good luck

rami kremesti