What is a concrete reclaimer, and how does it fit into a plant's overall environmental compliance picture? First, we need to consider exactly what a reclaimer does. A reclaimer does just that Û it reclaims something from something else. In this case, it reclaims aggregate (sand and stone) from returned, excess concrete at the plant (from brought-back concrete, rejected loads, etc.). Therefore, a reclaimer could be thought of first and foremost as a tool for concrete materials or solid materials at the concrete plant.
Generally, the value of the returned aggregate is, over time, a large part of the predetermined return on investment (ROI) provided by the reclaimer to the plant operator. And, the higher the value of the reclaimed aggregate, the better the ROI. But, while a reclaimer can be a very effective tool for dealing with solids management, it also can pay dividends by being an important part of a plant's process-water (or grey water) management system. While a bit more difficult to quantify relative to the ROI of a reclaimer, these benefits can be big when considering a concrete plant's overall environmental compliance level. In addition, it's important to realize that there are other cost benefits that affect the ROI of a reclaimer, such as reduction in fees associated with the off-site transport or disposal of concrete materials. Adding these up provides a true picture of the merit of a reclaimer at a concrete plant Û but what about the regulations?
As described above, a concrete reclaimer's first job is to manage returned concrete, which is a solids problem. For now, let's avoid the use of the phrase waste concrete, since, if it's going to be recycled, the industry ought to term this material recyclable concrete or something similar. Federal and State solid waste regulations should normally not affect the handling of returned concrete on a plant site, providing it's being done in a reasonable manner. This also includes fine concrete solids derived from a settling basin system. However, if this material piles up with no apparent plan for recycling, is used as fill on- or off-site in appropriate (unpermitted) settings, or is located near an environmentally sensitive area, then the material may raise the interest of solid-waste regulators (likely on a State or local level), who may wish to see a more formalized management plan in place for these materials.
In the worst-case scenario, a violation of applicable solid-waste regulations may be issued. So, the best way to avoid this is to have an appropriate program in place for regularly dealing with returned concrete and other concrete materials. Another word of caution here Û avoid references to fine concrete materials as sludge or residuals, since this carries a potential regulatory meaning that is best to be avoided. Instead, it might be better to refer to this material as fine recyclable concrete material, concrete fines, or concrete fill material Û any of which more accurately denote the intended manner of handling and ultimate end use.
Water-quality regulations may be a slightly different story. At concrete plants in the United States, stormwater discharges from the plant site are typically regulated under an NPDES (National Pollutant Discharge Elimination System) stormwater discharge permit (often a general permit), while process-water discharges are typically covered under another type of NPDES permit (often an individual permit written specifically for the concrete plant, although some states have combined stormwater/process-water discharge permits). Generally, NPDES permits for process water discharges are much more stringent than stormwater permits, require compliance with tough discharge limits for pollutants such as total suspended solids and pH, and are less commonly available to the concrete industry. In fact, many states in the United States will not even permit the discharge of process water.
On the NPDES stormwater permitting side, the mismanagement of concrete materials on a site could clearly be viewed as not following industry best management practices (BMPs), and therefore could lead to a violation of a facility's NPDES stormwater permit. This is fairly common, and should be easy to avoid with an appropriate concrete materials management program. It should also be noted that most states' NPDES stormwater discharge permits do not typically have strict discharge limits on stormwater discharges, which combined with large runoff volumes, usually mean it makes good sense to keep stormwater separated from process water to the highest degree possible (stormwater + process water = commingled process water), and to discharge this water when possible. Of course, when possible, it also makes sense to engage in stormwater harvesting to capture this water if a concrete plant has an intended use for it, which can also provide a cost savings over the use of public water from a municipality or electrical costs associated with well production.
On the NPDES process water side, nearly all aspects of concrete plant operation generate process water, principally from washing out mixer trucks, washing truck exteriors, and dealing with returned concrete materials Û all of which can generate a considerable volume daily of process water that must be dealt with. The use of a reclaimer to process returned concrete materials also generates a considerable volume of process water, however one of the greatest values of a well-designed and functional reclaimer system is that it should be able to utilize most, if not all, of the process water generated for further recycling efforts. When combined with a water storage system (usually an adjacent concrete-lined settling basin system) or other similar containment system, this water can be clarified to the point that it can remain closed in the recycling/reclaimer system, and not have to be discharged (under an appropriate NPDES permit, in those states which allow this type of discharge). Another way to utilize the process water generated is to return it to the concrete plant for further concrete batching, which also eliminates the need for discharge of this water. Since the large majority of process water at a concrete plant is typically involved with truck washout and returned concrete management, the use of a reclaimer can become a very effective tool towards an overall process water management strategy.
Presently, obtaining NPDES permits for the discharge of process water may not be an easy task, and it's likely to get harder in the future for the concrete industry and others. Since many states currently prohibit the discharge of process water at concrete plants, and others are considering it, the move towards a zero-discharge system for process water, along with concrete recycling, will not only benefit a concrete plant today, but will also provide a solid foundation for the future.
These can be a complex variable in the returned concrete/process water/stormwater management equation. Obviously, variables are best dealt with at the design stage of a new concrete plant, when they often can be used to make site permitting a lot easier. A proposed concrete plant with an integrated strategy for solids management, process water management, and sound stormwater management (hopefully built around the concepts of concrete recycling, zero process water discharge, and stormwater harvesting where appropriate) can truly be described to be the current state of the art in the United States, which should make site permitting and future operations a whole lot easier. If installing a reclaimer/process-water management system at an existing plant, things can be a lot trickier, but can be done and still can pay benefits. Either way, your best bet is to work with a qualified, knowledgeable expert in the field who can help with your integrated concrete materials/process water/stormwater program.
Financially, the positive benefits of a reclaimer are many Û returned aggregate value, reduced/eliminated costs of hauling returned concrete to off-site locations, elimination of disposal costs, reduced water costs, reduction of solid waste regulation liability and potential fines, possible elimination of NPDES process water permit and costs, elimination of process water discharge liability and potential fines, additional available space on the plant site, and others. When balanced against the additional cost for the reclaimer system (including adjacent settling basins if applicable) and maintenance and operating costs, a full evaluation of the ROI for a reclaimer typically justifies a very reasonable ROI in a relatively short period of time.
It's not to say that a reclaimer is the only way to deal with returned concrete and other concrete materials. Many facilities have highly successful programs built around concrete bin block creation, hardened concrete recycling, and other strategies. But, in terms of their ability to deal with both returned concrete and process water in an integrated fashion, reclaimers usually outperform all other options.
But, it's really the regulatory benefits where a reclaimer can shine. Reclaimers can be used to avoid solid waste regulatory issues, demonstrate the use of industry BMPs and state of the art practices, and be an integral tool in a plant's process-water management system, thereby greatly reducing liability under NPDES regulations.
CAN A CONCRETE RECLAIMER ACTUALLY PAY ITS OWN WAY?
Bibko dealer Mid Atlantic Concrete Equipment in Litiz, Pa., has developed a reclaimer payback spreadsheet with the help of engineers and customer-supplied data. It walks users through some basic math to help determine whether the investment of a reclaimer, including site prep costs, can be recouped within a reasonable period.
The sheet comes pre-loaded with sample values, making it easy to see how it works without entering a plant's actual figures. Entering those numbers for production, percent of material returned, cost of electricity, and labor rates, produces more relevant results.
Outputs include not only payback period in years (a very positive 2.15 years using the sample figures), but savings per cubic yard Û $1.51 in the example. Water savings would add additional savings but are not shown in this example. The spreadsheet calculator is available for free download at www.maconcrete.com/bibko-roi.
Doug Ruhlin is Principal Environmental Consultant and Owner of Resource Management Associates, environmental consultants to the ready mixed concrete and concrete industries worldwide. He can be reached for more information at Resource Management Associates at (609) 693-8301, or www.resourcemanagementassoc.com, or at firstname.lastname@example.org.