Treatment of Sludge from Tannery Efluent

[CBRoberts]

Hi,

I am involved in the treatment of tannery effluent from a leather dying plant and have been asked to install a belt press to dewater sludge. I am doubtful if this will work as the sludge is very sloppy and fine. At present the sludge is collected in a set of flat sludge beds consisting of a layer of filter sand about 200mm thick over a sheet of geotextile. This works well but we are running out of space and the factory is expanding. Has anyone got experience in this sort of operation who can help?

 

[whoislee]

Why don't you consider installing a hydrocyclone to remove water?

Water removed can be recycled back to your plant....savings.

Depending on the waste characterisitics, there are plenty of ways to dewater tannery waste. However, if your management/boss decision is to install a belt filter, there is not much considerations you have to make.

Email me if you need more info.

There are 2 sides of a coin
One is to give, one is to take
Give until it hurts with a smile

 

[ischgl99]

I haven't done that particular process, but the factors in dewatering municipal sludge should be similar.

You mention the solids are very fine, this can cause problems with capture efficiency. Very fine particles may seep through the belt instead of being captured and dewatered. Also, you need to be able to displace the water, polymer is normally used to do this. If enough water is not displaced, the solids do not dewater, and it will squeeze out of the belt and make a big mess. If you haven't already, have a local polymer rep do some jar testing to see how your sludge reacts. You are looking for flocculation of the solids. If it doesn't flocculate, then it probably will not work.

Another possiblity is a centrifuge. These get better results then belt presses, but also cost more. The fine solids can also be a problem here unless the flow rate is very low. To test this, use a test tube centrifuge and spin it for a couple minutes and see what the sample looks like. If you have nicely dewatered solids on the bottom and clean supernate, then the centrifuge should work well.

Another thing to consider, neither will removed soluable solids.

I think you should have a pilot test before making a decision. This will give you a much better idea of what is possible. If you want some names of people/companies to contact, feel free to email me.

Mike Bensema

http://www.dutchmenservices.com

 

[CBRoberts]

To whoilsee (petrolium) and Mike Bensema,

Thank you for your prompt responses and information.
I have managed to arrange for tests to be done on the sludge and am awaiting results. I suspected that it wasn't as simple as the belt press salesman described and judging by your suggestions I was right.

By the way, I am writing from Port Elizabeth in South Africa.

Regards

Chris Roberts

 

[sklone]

Belt Press requires a fairly large volume of clean water for belt washing which may need treatment. I do not think that belt press is a good idea. Belt Press would be good for a paper mill fibrous sludge.

Conditioning of the sludge with polymer/Lime/Diatomaceous Earth (increase sludge volume), etc. followed by a rotary thickener before the belt press should help.


We in Malaysia seem to prefer filter press.

Regards,

Sklone

 

[bimr]

If you buy a quality belt filter press, it will work fine. I am not affiliated with Ashbrook, but I know that Ashbrook has belt filter press installations on tannery wastes. You should buy a high quality press made of stainless steel to avoid maintenance problems.

http://www.ashbrookcorp.com

I am personally familiar with an operation in Missouri USA that runs well. The solids are land applied after dewatering. The tannery is responsible for the land application as well as the dewatering.

Flyash is commonly used as a sludge conditioning material.

Not clear from your post what you are doing. Usually, a tannery has significant quantities of solids to be disposed of. Doesn't make sense that you are using sludge beds with the expected amount of solids from a tannery. Sludge beds are generally only used for small applications or rural applications and the weather must be appropriate for sludge beds to work.

 

[CBRoberts]

To sklone and bimr,
Thanks for your responses. It seems that filter presses are also favoured in the Italian tanning industry and we are looking into this here.

Re the sludge beds, the plant we are dealing with started out quite small and the beds were the best option then. They have worked very well so far but the plant is expanding and space is now becoming a problem, hence the move to more efficient systems.

Regards
Chris Roberts