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Concrete Producer turns to BIBKO Concrete Reclaimer to Focus on Zero Discharge-Zero Waste

Lititz, PA
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Rohrer's Quarry CON-E-CO concrete batch plant, Mid Atlantic Concrete Equipment
Concrete Producer turns to BIBKO Concrete Reclaimer to Focus on Zero Discharge-Zero Waste

Lititz, PA –While it might be difficult to get 100% consensus from ready mix producers on one particular issue, it is quite easy to get them to agree that returned concrete and the associated process water and slurry generated from cleaning out trucks is a pressing issue. Dealing with returned concrete has been a problem that the industry has wrestled with for decades. Increased federal and state Clean Water Act enforcement has also prompted producers to address the problem. The economy, the finite amount of natural resources, and increasing restrictions on how the ready mix concrete industry operates  are forcing producers to re-evaluate their processes and look to more economical and environmentally sustainable practices.  The easiest way to illustrate how producers are handling their processes and making changes is to follow one of them through their decision process.

Rohrer's Quarry, located in Lititz, Pennsylvania installed a new ready-mix concrete plant three years ago. The plant features three 200-ton cement silos, six compartments containing a total of 340 tons of aggregate, and a 430-foot vertical curve conveyer along with a 12 cu. yd. HRM (Horizontal Reversing Mixer).   Rohrer’s Quarry delivers ready-mix concrete to customers in surrounding Lancaster County, Pennsylvania using a fleet of 22 mixer trucks. 

Challenge
Like all concrete producers, at the end of each day’s production, each of Rohrer's Quarry’s mixer trucks needs to clean out their drums and prepare for the following day’s deliveries. The first option in addressing the returned concrete brought back as excess is the production of concrete blocks, a viable solution for some of the returned concrete.  Rohrer’s Quarry, like many other ready mix concrete producers, has been an advocate for the use of concrete blocks as a partial solution to returned concrete.

Like many other concrete producers, Rohrer's Quarry’s second option in addressing returned concrete has been windrowing, drying, and crushing of returned concrete. Rohrer’s analyzed this process and found that by the time the fill product was sold, the returned concrete was being re-handled up to six times; a significant drain on equipment, fuel, manpower and money.

The final step at the end of the day is to wash out and remove any left-over concrete from the truck mixer. Often, fresh water is used to wash out the barrel of a truck. The resulting accumulation of process water in settling ponds or weir pits can strain storage capacities. This process brings up three issues that surround concrete production; the traditional method of managing returned concrete reduces profits and takes up valuable space, while the water used to clean each mixer is left in a settling (retention) pond and is a housekeeping concern. These retention ponds build up a "muck" substance that will remain in a virtually unusable state when stored.

Solution
Rohrer’s Quarry’s solution began with the decision to incorporate returned concrete, process water and cementitious fines into the production of new concrete. The family-run ready mix concrete producer chose to purchase a BIBKO concrete reclaiming system.  BIBKO, a concrete reclaimer manufacturer based out of Germany, has installed more than 1,300 concrete reclaimers globally, with over 120 of these reclaimers in operation throughout North America. The BIBKO reclaimer gives today's ready mix concrete producer an environmentally compliant solution to the challenges associated with concrete production and process water.
The two most commonly accepted methods for reusing process water are a weir system (or open loop system) and a closed loop system. A weir system is most common, where water flows through several settling pits or ponds (up to 6) to the final clarified water pit. It can then be reused in new concrete production or truck washout. This method requires regular removal of the settled fines from each pit to be moved to a drying or storage area prior to disposal. This process is also hard on the equipment used to clean out the pits out.

BIBKO uses a closed loop system that makes the process water a resource that can be used to wash out trucks, reducing fresh water use and then reusing that same process water in the production of new concrete. ASTM part 94 has allowed the reuse of process water since 1978. ASTM C 1602 Standard Specification for Mixing Water Used in the Production of Hydraulic Cement Concrete addresses the requirements for water sources such as process water. In some cases up to 100% of the batching water can be process water.

Some concrete reclaimers allow the ready mix concrete producer to separate aggregates. These solids are then available for reuse in the production of new concrete.  The BIBKO system also addresses the issue of the process water. The water from the process water pits is pumped into the truck for the initial wash out of the barrel.  The trucks then empty the concrete and washout water from the barrel into the concrete reclaimer. The BIBKO concrete reclaiming system separates the suspended solids from water into different piles, and also de-waters the aggregate to an almost dry state. (It should be noted that washing out the residual concrete from a mixer truck will produce between 600 and 1100 pounds of solids.) The reclaimed aggregate can be added directly to existing stockpiles for use in future production. The water that is processed through the BIBKO concrete reclaimer is stored in concrete pits which have large rotating paddles that keep any cementitous fines from settling. The reuse of process water not only helps get rid of problematic retention ponds and cementitous fines that settle in those ponds, but drastically reduces the amount of potable water a producer uses by 25% to 38% by taking the place of potable water when batching or rinsing trucks.

Rohrer's Quarry, with the addition of the BIBKO concrete reclaiming system, will be able to rid their site of all returned concrete piles and retention ponds.  The reclaiming unit is enclosed in a 60 x 40 steel building. Water is pumped back up to the batch plant approximately 300 feet where it will be reused to produce fresh concrete. The system is tied into their existing plant automation software allowing proper percentages of process water to be blended into the batching process based on the specific gravity of the process water.  Turbidity meters are used to ensure accurate quantities of water and solids are maintained in the batch.

Result
Rohrer’s Quarry’s decision involved taking a long hard look at the resources they were using and a desire to achieve a higher level of sustainability.  At the end of the day Rohrer’s Quarry will reclaim the land used for storing and crushing concrete, significantly lower their fresh water consumption, use reclaimed aggregate in production.  They will also increase driver productivity, save man-hours, equipment and fuel expense previously used to crush returned concrete.

Crushed concrete, process water and slurry become a burden to the producer because it is often ignored until the problem demands attention. Returned concrete and the associated process water should be incorporated into the daily production cycle. The industry's ultimate sustainability objective should be zero discharge and zero waste. Today’s reclaimers are proving to be an asset that strengthens the producers’ bottom line, maintains environmental compliance and sustains the planet's resources. BIBKO North America has developed an easy-to-use ROI reclaiming calculator that can be found on their website at www.concretereclaiming.com.

BIBKO North America, established in January 2011, supports a network of distributors of BIBKO concrete reclaimers.  BIBKO North America is working with ready mix concrete producers across the United States and Canada to pinpoint challenges and identify and develop profitable and sustainable solutions for producers.
Inside the building that houses the BIBKO reclaimer
Looking down from the batch plant at the BIBKO 4000 system. The two open garage ports store sand and rock that have been reclaimed and screened.
A birds-eye view of the BIBKO 4000 concrete reclaiming system that shows how the footprint is minimized.
The 19-foot screw from the BIBKO 4000 discharges sand and stone onto an awaiting screen deck, where the deposited material is reused to make new concrete.
A close-up of the BIBKO's screen deck.
The BIBKO 4000 concrete reclaimer pump discharge conveyor allows dump trucks and pump trucks to wash out at ground level.
A BIBKO 4000 reclaimer awaits its enclosure prior to startup. The system is capable of processing 40 cubic yards per hour and storing up to 53,000 gallons of process (grey) water. A four inch diameter hose, 400 feet in length feeds grey water to the plant. This system reuses every drop of water, every grain of sand, and every piece of aggregate back into the production of new concrete. A zero discharge - zero waste solution.
The completed concrete reclaiming project.
Three BIBKO 4000 concrete reclaimer winches provide grey water to wash out mixer trucks.
A BIBKO 4000 concrete reclaimer, 54-inch diameter agitator paddle and 3 horsepower sump pump sit on top of 4-inch thick, steel-encased false bottoms that are used to circulate heated or chilled water.