Dredging a live oxidation ditch

[ch81pc]

Has anyone got any experience of cleaning a live oxidation ditch? Its the only one we have, we can not drain it or reduce the flow below 90 ls. Its an extended aeartion tyoe ditch with mechanical aearators. It has a large build up of grit and rag to be removed. As yet I have not been able to find a single company that can carry out the work? Any ideas or comments please let me know!!

 

[civilperson]

Build a parallel extra ditch and shift the flow for the rehabitation duration.

 

[bimr]

Using civilperson recommendation, you can rent tanks from Baker or Rain for Rent to make a temporary oxidation ditch.

http://www.bakercorp.com/tanks-steel.asp

 

[FLPE]

Try

settledsolids.net

What part of the world are you in?

 

[FLPE]

Let me explain a little further...

Removing sand & grit without taking the ditch off line is no problem; that's what they specialize in.
The rags on the other hand is a different story. It is very expense and depends on how big, how deep, what are attached to, etc.

 

[StoneCold]

Maybe you just need to get some really big gloves on and a rope with a bunch of fishing lures on it. Or maybe a grapling hook would work and you could "dredge" the rags out with that. If there are really a lot of them maybe you need to put it on the wench on a truck. Nasty but the rags would be out of the way.

Regards
StoneCold

 

[semo]

First of all make sure you get a screen installed in the headworks to prevent any additional rags from entering the ditch.

Just a thought on removing existing rags and I'm assuming they aren't all chopped up so they will be fairly large:

Lower the ditch operating level to provide freeboard.
Construct a temporary screen (aluminum or fiberglass grating with 2" openings?). Make it so it is a few feet long (1/3 of the ditch depth?)
Temporarily install the grate all the way across the ditch (at an angle) so that it can be removed daily/hourly/etc.

Do this prior to the grit removal so you stir up the rags and get them floating.

Then you can remove the screen as needed to remove the rags from it and prevent excessive build up slowing the flow in the ditch.

You might also permanently install the screen with a walkway across the ditch at the top of the grating for a short period of time and just rake the rags from it as they build up. Once the rags are removed, you remove the screen and walkway.

This won't be an instantaneous process; but, it should get the majority of the rags if you can get them suspended and moving around the ditch.

Just a thought.

 

[ch81pc]

Thanks for the suggestions.
I inherited this plant a year or so ago, its had a very poor inlet works for years, with poor screens and a grit plant that the operator of 15 years "only ever run on a Tuesday". I've got new screens and an automated grit plant now, so once I've got the ditch cleaned up it should stay like it for a while.
The plant is in the UK, it takes 198lds to treatment.
I've been trialing a hydraulic dredging pump with a modified impeller and pumping the material back to the head of the works for screening and grit removal. It seems to be working well so far.

 

[bimr]

ch81pc,

You are taking the correct approach. I would call it a sidestream treatment method. Cooling tower users use a similar treatment scheme. Over a short time period, your system will clean up.