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Air & Water Filtration in the Stone Fabrication Industry

They might not be topics that readily come to mind when you think of the stone fabrication industry. But filtering air and water is a significant part of the stone fabrication process. Even if you are familiar with the importance of these particle removal techniques, you may be surprised at some of the most effective ways that these processes are performed. In this article we take a look at air filtration and water filtration in the stone fabrication industry. Along the way we will explore some of the different ways theat air and water are filtered as regards stone fabrication shops. We will also consider why these techniques are so important.

Stone Fabrication Generates Stone Dust Particles

For readers that are not already experienced fabrication or installation professionals, stone fabrication creates dust; and lots of it! This dust comes from several processes that take place in the fabrication shop.

The first process that generates stone dust in a fab shop that we will look at is cutting. Cutting the slab in any way will create dust.

Another dust creating action is shaping, or grinding stone. Grinders are used to remove various amounts of stone from the slab. Grind natural and engineered stone slabs is done to soften the edges, touch up angles, and smooth bowls and cutouts that are made by other tools.

A third task that creates dust is drilling. Diamond core bits are used for drilling holes in slabs so that the faucets, drains, and soap dispensers that are regularly found in countertops have mount points. The action of drilling causes dust particles.

Finally, the finishing phase of stone fabrication also is a creator of dust particulates. Whether the finish is a honed, antiqued, or leather-look finish using various abrasives, or if it is a smooth and shiny polished finish, there will be dust. Polishing pads and other abrasive tooling removes material in increments. As these tools remove stone, the result is dust. But how are air and water involved?

Why Stone Fabrication Air Needs Filtered

As we have seen from the processes we just mentioned, there is a tremendous amount of dust that is created during fabrication. Not all of the tasks we looked at are done on dry stone, but some of them can be, depending on what tools are used and in which environment they are used.

Polishing, grinding and shaping in a dry environment will inevitably generate a large amount of particulate matter. This dust is the reason that air filtration is important in stone fabrication. Why? Because many types of dust contain silica. In fact, various industries have requirements for controlling silica dust. Even construction dust is harmful due to the many materials that contain silica. The stone fabrication industry is no different. Natural and engineered materials alike contain respirable crystalline silica that can be hazardous. Therefore, air filtration is important.

Dry Dust Collection

Because air filtration is important to stone fabricators, many work stations use dust booths or dry dust cabins to draw air from the workbench. The air current carries the particles into the filters as the air moves through them. The filtered air then, is sent back into the shop without the particles. Dry dust cabins are only one of the air filtration systems used in the stone industry.

Another method for removing dust from stone fabrication shop air are dust benches. These machines, also called down draft tables, are designed to draw air downward toward the perimeter of the bench. The surface of the machine is used as a work table and slab operations are performed on the stone. Like the cabins mentioned earlier, the draft carries the generated dust particles into the machine where the air is filtered and set back into the shop.

Portable dust collection systems are another way of removing particulates form the work environment. These are smaller machines that use the same principles to filter dust from a moving air current. However, their small size and relatively light weight mea they are portable.

Wet Dust Collection

Even though water is mentioned here, we are still talking about air filtration and not water filtration. These machines also work with air currents. However, they use water to capture the dust particles. The particles are stored in a holding tank in the bottom of the unit and periodically emptied.

As we mentioned before there are down draft tables used for filtering the air around a workspace. Wet benches are one kind of down draft table. These are similar to the dry bench we talked about above, but they incorporate water into the process.

Air filtration plays a big part in the stone fabrication industry. Equipment is designed in all sorts of styles and is made to collect dust particles from the air to keep the work environment safe. And as we have seen water is even used in conjunction with air currents to filter dust form the air. But how does water filtration come into play?

Why Water Filtration is Needed

Not all stone fabrication equipment is designed to work in a dry environment. In fact, many machines require a steady stream of water to keep the stone and the tool from overheating. This stream of water must come from somewhere. It also has to go someplace after it is used. But it can't go just any place. Why not?

When fabricating, water is used to keep tools cool and capture dust that is generated. The water is run over the blade, bit, wheel, or polishing pad as the tool works. This is exactly where the material is being removed from the slab, so the water keeps the heat and the dust down right at the source. The particles that come off the slab are mixed with the water and together they make a slurry. This slurry cannot just be washed down the drain. Community sewer systems do not allow for this in many cases. On the other hand, filtering the water and controlling the mud that results from the filtration can be beneficial since the stone dust can be used for other purposes after it is removed. Notice what Science Daily said about reusing dust from stone fabrication and other processing methods:

"Using polymers and natural stone slurry waste, researchers are manufacturing environmentally friendly stone composites. These new composites are made of previously discarded materials left behind during the cutting of natural structural or ornamental blocks for buildings, construction supplies or monuments. While reusing the waste material of natural stone production is common in cement, tile and concrete, adding the stone slurry to polymers is a new and innovative idea..."

So then, it makes sense to think about water filtration and dust management in the stone fabrication shop. But what methods are used for water filtration and dust management?

Lamella Clarifiers

One of the ways that stone fabrication shops manage stone dust after accumulating it via fabricating in a wet environment is with lamella clarifiers, also called inclined plate settlers. The systems use gravity in combination with a specifically designed set of dividers placed at an incline to increase the rate at which the suspended solids separate from the water. With a lamella clarifier, gravity is your friend. Gravity works to pull the suspended particles to the bottom of the settling tank and it works again to pull the water through the sludge filtering bag where it can then flow into the clarified water holding tank. The image below Shows seven key parts to the lamella clarifier system:

Lamella Clarifier Process Illustrated

In the image above, 7 markers show how the lamella clarification system works. The seven labels are explained below:

  1. Inlet Channel - The inlet channel for "influent" facilitates the entering of water and particles into the clarification unit. Additionally, this water may or may not already have been put through the coagulation process.
  2. Lamella Plates - These plates sit at a precise angle and allow water to flow through them in an upward motion. They also, along with gravity, assist the particles in making their way to the bottom of the water clarifier.
  3. Sludge Reservoir - Particles fill the hopper as they settle by means of gravity. Hence, they collect at the bottom and an extraction process removes them from the hopper. For example, the above image shows an extraction pump at location number 5.
  4. Outlet Channel - The "effluent" (clarified water) exits the clarification system through the outlet channel. Afterward, the water clarification system either sends the processed water to a container for reuse in the shop, or passes it along as waste water.
  5. Sludge Extraction Pump - The mud extraction pump removes collected sludge from the clarification system. However, the sludge still contains water, so some additional filtering needs to takes place.
  6. Filter Bag Holder - Filter bags (shown in location 7) hold extracted sludge. Hence, this part of the system suspends the bags for this part of the clarification.
  7. Sludge Filtering Bag - Gravity extracts additional water from the sludge (or mud) pulled out of the system. Filter bags hang above a catch basin. As a result, gravity draws additional water out of the mud, thus leaving the extracted particles.

As you can see, the process relies on gravity to do most of the work and at a couple of points pumps are used to move partially processed slurry. Lamella clarifiers are an effective way to to accomplish water filtration. However, they are not the only way to reuse wastewater.

Compact Water Recycling Plants

Compact water recycling systems are another effective way to filter water used in a fabrication shop. These plants consist of a few more parts, but they yield great results. The water treatment plants continuously resupply the fabrication shop with clarified, reusable water that is reclaimed from the slurry produced in the fabrication processes of the shop. The following video is an animation that explains how one system works:

Wastewater treatment plants provide stone fabricators significant benefits that allow the shop to reduce costs while at the same time boosting productivity and therefore, profitability. By recycling the water after filtering it using water treatment plants, facilities can reduce wastewater disposal fees and the stone dust (in cake form) can be managed. In fact, water recycling is zero in water bills which can save hundreds of dollars each month in operating costs. And as science continues to come up with new ways to make use of what use to be merely a by product of stone fabrication, the opportunities for reusing the left over stone dust particles extracted from the wastewater will continue to grow.

As we have seen in this article, air and water filtration are very important to the stone fabrication process and deserve the attention of anyone wanting to start a fabrication shop or processing facility. One of the biggest reasons, if not the biggest reason is the dust that is inevitably generated when natural and engineered stone is fabricated. By making use of the equipment mentioned in this article and understanding how to set up a fabrication shop to operate efficiently, the endeavor you pursue will have the greatest chance for success.

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