Filtration medium to arrest 10 micron suspended solids

Is it absolutely necessary that suspended particles of marble dust larger that 10 microns be filtered out of water recycled to a marble sawing operation?

Have settling ponds been tried or at least considered?

Could centrifuge separators achieve the desired clarity and flow rates?

You can buy "Millipore" media but I would expect prohibitive cost factors.

Thanks for your suggestions. Please peruse following description, gives more idea about the problem.

The Indian stone industry is amongst top three in the world, but uses primitive open pits gravity sedimentation to circulate water. There are large number of stone processors having lesss than two / three sawing machines. These units can't efford complete auto system of twin verticle decanter towers, flocculant dozing, auto-filterpress etc. As a result these manufacturers use open pits only and feed grey water to sawing and polishing. A study shows that almost 50% of the solid soon again goes back to processing. This situation creates problems of slower processing speed, increased consumption of diamond tools, reduced water flow due to clogged lines. Besides, every time the pits are cleaned twice a month, very large quantity of fresh water is lost as the solid is pumped out in free flowing slurry form. The slurry discharge containing 100 metric ton of solid is unable to comply pollution control norms due to its free flowing state.

The mechanized system designed has to therefore, feed very clean water. The fresh water resource and cost of drawing being difficult, the quantity of water in circulation requires to be reduced from present levels of about 5,00,000 liters to say about 20,000 liters and provide easy method of solid disposal in relatively dry condition. Looking to these demands, the new system is designed to separate solid as it enters the system without it getting accumulated unlike gravity sedimentation.

The settling pits are already being used without much benefit due to rapid circulation and very high load of solids entering the system in a day. The solid generated and accumulating in the system every day is 3 metric ton. The system therefore, has to achieve required clarity in single stage filtration.

The solid as it is discarded now can not fetch any value. The marble dust has many applications. The dry ground marble powder fetches Rs.400 per metric ton locally. If the sawing waste is collected uncontaminated by mud or other air borne waste, it has good sell value. The point is: "The cost of using some costly filter medium can be compensated as the waste will generate additional income". However, the life of such filter medium must be longer.

I am now considering to use "Stainless Steel Woven Wire" having 12 to 14 micron absolute rating. The increased surface area requirement due to reduced flow rate can be arranged by nested frustum sieves having both sides suction, without increasing the overall size of the equipment. However, I fear if the results do not improve as the basic woven structure is the same as that of textile fabric.

"Millipore" in this situation can be considered. How do I get more info on this filter medium?

Plz. Contact me mikemahant@hotmail.com - I shall tell you how!

Your best bet is to install an on-line continuous Electro-Coagulator

Avoid all fitration and its headaches

I have never tried or used them myself but I have a gut feeling that a centrifugal separator as suggested by Stirling_Stan might be worth looking at. It dose mean additional equipment and you would probably need to clean it daily, but it would allow you to collect the suspended particles without contaminating them or having the problem of clogging like a filter has.

When the water circulation problem for stone industry was identified in the initial stages use of centrifugal separator was discarded due to following reasons.

1. The large motive power requirement for continuous operations 24x7.

2. Maintenance and part replacement due to large rotating bucket.

3. The very heavy solid load. Average 3 MT per day. May require frquent removal of filter fabric bag from the bucket stopping production. Water feeding to sawing must continue.

4. Auto solid discard continuous centrifuge cost not affordable.

These factors prompted for vaccum filtration. As no liquid recycler existed sustaining rate of continuous filtration, new design was evloved which being patented through WIPO.

It was only an idea and I wasn't sure it would work. Unfortunately I havn't got any other ideas but I hope you find a solution.

The weight of your particles makes a separator usable if you have a pump that will move the material through a rosedale separator Look to Rosedale.com in the SEP-xxx series of separator using a vortex to remove solids from the flowing fluid. We have begun using to remove fines from a drilling operation and are getting an improvement in the vacuum filter life. RIC

Thank you for the suggestion. You have confirmed our thoughts. A cyclone installation before or after vacuum filtration is felt necessary. The Rosedale catalogue is accessed. However, more details how you manage your things will help understand it clearly. Drilling & stone sawing do have similar processing activity. Mahess Desai

Your only technically feasible solution is by coagulation. try ODIS FILTRATION in Israel.

Wangito

Hi! Mr. Wangito, thanks for your reply and suggestion. The marble sawing units using only open pits gravity sedimentation have tried Synthetic Organic Polymer water flocculants. These water soluble flocculants are dozed in the channels leading to settling pits. However, even use of flocculant does not prevent the solid again going back to processing, only it is delayed by half an hour. The reason being very rapid rate of circulation not permitting enough time to get the soild settled. Normally two rows of pits are used. Once the first row is filled up by solid, the other row is used. A row of pits has about 6 pits in succession. Each pit measures 12' x 12' x 12' and holds 45,000 liters of water. Thus both rows togather requires 5,40,000 liters of water. If the number of pits are increased for more clear water, the total water requirement also increases which is difficult to manage.

When the marble sawing continues, I have observed that only the top floating portion of about one foot of the water column in the sedimentation pits circulates. A blown baloon put on the water surface in the circulating pits covered the distance from the first pit to the last pit only in 40 seconds.

Besides, the major problem is evacuating these pits. The solid is to be made free flowing by adding enough fresh water for the pump to lift it and transfer it out of the pits. Use of flocculant makes dislodging of solid more difficult and requires more water. Many units have now stopped using flocculants.

I did try flocculant in the filtration bowl. The immdiate result was good. Filtrate clarity was absolute. But as soon as the vaccum increased with more solid deposition, the clarity deteriorated as the solid again passed the filter fabric in large quantity.

The main problem after using flocculant and coagulation is how to remove the settled solid out of the way from the rapidly circulating water. The discharge of solid also has to avoid heavy loss of water from the total quantity in circulation.

I can't find information on Odis Filtration on any search engine. Do you have its ID?

Mahess Desai

http://www.odis.co.il/

Try my previous recommendation ODIS filtration in Israel look at their website especially refer to their SOLIQUAETOR. We have one system working at our packaging operation, flawlessly. flow rate is over 200L/Sec. with coagulation pond of over 300000 Liters., www.odis.co.il come visit us if you want to see it. If you want pix's let me have your e-mail.

Wangito.