Wausau Tile takes pride in being a green company. The precast producer, based in Rothschild, Wis., makes concrete pavers, planters, bollards, benches, and recreation equipment. The company services customers nationwide, including major commercial and retail chains. With a diverse product line, demanding clientele, and high environmental standards, the producer can't afford to waste time, money, or materials.
To meet these internal and external expectations, Wausau promotes a “green initiative” as part of its core business. The management team has adopted energy-saving measures such as installing high efficiency lighting, and incorporating recycled steel, plastic, rubber, and glass into its products.
As part of its environmentally-friendly operations, Wausau installed a filter press water treatment system at its main plant several years ago. The system removed solids from water used in the casting process. However, the producer began to wonder if the environmental benefit came at too high a price.
With the filter press system, water flowed through a series of cloth filters which effectively collected any solid material. But the waste water quickly clogged the filters, especially when returned fresh concrete was introduced into the system. Filters had to be cleaned once a day. The build-up was so severe that the filters were being replaced every week. With Wausau's high volume of wastewater – about 30,000 gallons a day - the filter replacements cost the producer $1200 a week, in addition to non-productive repair and maintenance time.
A clear solution
The producer needed an efficient and cost-effective method to handle gray water, while staying true to its environmental goals. Wausau contacted Alar Corp., in Mokena, Ill., a manufacturer of water pollution control equipment. To eliminate the filter binding, Alar suggested the Auto-Vac wastewater treatment system. It has successfully solved similar problems at more than 100 precast and ready-mix plants.
The Auto-Vac filters concrete wash water using a rotating drum under a vacuum. The drum is pre-coated with a filter media called diatomaceous earth. After the pre-coat is complete in 10-20 minutes, gray water is pumped into a pan where the drum is rotating. The vacuum pulls clean water through the drum, and solids larger than .5 micron are trapped on its surface. After the drum surface is blinded, a variable speed blade removes the solids from the drum and leaves a clean layer of filter media.
After testing a pilot unit for several weeks, the precasters were impressed. “The Alar system does a much better job at handling live cement than our other system,” says Rodney Dombrowski, Wausau vice president. “We end up with a cleaner product, with particles of about 3 microns, that we can put to a beneficial use.” Wausau worked with Alar to select the correct size unit for their volume of wastewater.
In addition to processing wastewater more efficiently, Wausau wanted to recycle its concrete by recovering coarse and fine aggregate. The Liebherr LRS606 reclaimer offered a solution. The compact LRS recycling system uses a screw design to wash out residual concrete. Its paddles break down the material, and a discharge hopper prevents overfilling as the concrete flows through. Once the reclaimer separates the coarse and fine aggregate, the residual gray water flows to an underground agitated pit and is then pumped to the Alar unit.
The clarified water from the filter unit is pumped to a pH adjustment tank to neutralize its alkalinity. Wausau also up- instead graded this process by using CO2 of acid. While acid is a common way to reduce alkalinity, it corrodes equipment, and becomes an environmental hazard if it spills. When CO2 is injected into the tank, it is used up in the process of neutralizing the water's pH level, and is not harmful if there is a leak. And the CO2 system saves the producer $1000 a month, according to Dombrowski.
Reusing and recycling
With the new wastewater management and reclamation system, Wausau Tile has reinforced its green reputation. Now, the producer reuses all of its recovered sand and aggregates. Its processed wastewater is used for washouts and to run automated grinding equipment.
Wausau once paid to haul away its waste. Now the producer reuses and recycles more material, and even sells a byproduct to a new market. All of the fine solid waste extracted by the Auto-Vac unit is now sold to local farming cooperatives. “The solid waste is primarily lime, so the farmers are using it as agricultural fertilizer,” explains Dombrowski.