Train-ing Day

Lorton, Va.-based Davis Industries has been providing ferrous and nonferrous metals recycling for more than 70 years to peddlers, salvage companies and other scrap dealers within a 100-mile radius of its scrap yard. The company processes a range of metals, including aluminum, mixed steel, copper and brass, appliances and junked automobiles, as well as other scrap material from consumer and industrial sources.

An auto shredder and downstream sorting system are among the processing equipment the company operates at its 23-acre scrap yard, which also includes a shear and a nonferrous baling system. Additionally, Davis Industries operates a variety of material handling equipment, including seven cranes and numerous forklifts and skid steers to assist in loading and unloading scrap material.

Davis Industries’ yard operates under a National Pollution Discharge Elimination System (NPDES) permit and must file a Storm Water Pollution Prevention Plan with the commonwealth of Virginia. The company says it was concerned about meeting facility discharge parameters for metals and suspended solids in its stormwater runoff. After testing the scrap yard’s stormwater discharge, Davis Industries says it realized additional stormwater best management practices (BMPs) would need to be implemented to meet the company’s NPDES permit requirements.
 

Making Improvements
Among the BMPs Davis Industries would need to adopt was the augmentation of its settling pond using a more robust stormwater filtration system, the company found. The new filtration system would need to remove dirt, sediment, fine particulates, hydrocarbons and dissolved metals from the stormwater runoff.

“We are always looking for ways to improve the efficiency and sustainability of our operations,” Bill Bukevicz, executive vice president of Davis Industries, says, “and making sure we have the best stormwater treatment equipment is part of that commitment.”

The company began investigating available stormwater treatment system options. Davis Industries says it wanted an option that was not complicated and that could meet its water quality goals without the use of chemicals.

This requirement led the company to select StormwateRx (www.stormwaterx.com), Portland, Ore. Davis Industries says it found that most designs from other vendors used chemical treatments to remove concentrations to the required benchmark levels, while StormwateRx instead relied on physical treatment. The company says StormwaterRx also offered the capability to quickly and easily retrofit the required equipment into its existing structures.

The StormwateRx treatment train uses a Retenu™ basic stormwater filtration system to remove dirt and concentrate solids, an Aquip® enhanced stormwater filtration system to condition the water and remove hydrocarbons and a Purus® advanced stormwater polishing system to remove fine particulates and dissolved metals. According to the companies, this system has enabled Davis Industries to meet stringent environmental permit requirements and protect local waterways from pollution.

According to StormwateRx, Davis Industries also uses “synergistic water reclamation processes” that allow the company to save water by recycling it for use in washing and cooling its automobile shredder.

“The installation of a StormwateRx treatment train at Davis Industries sets another example for the scrap metal industry and demonstrates the company’s commitment to clean water,” says Calvin Noling, president and CEO of StormwateRx. “It is the most extensive StormwateRx treatment train installed in the eastern region.”

Bukevicz adds, “The StormwateRx treatment train has put Davis Industries at the forefront of environmental technology for the scrap metal recycling industry, and we are proud to own one of the most environmentally protective systems on the East Coast.”

Filtering Down
The StormwateRx system at Davis Industries begins with the Retenu chemical-free treatment process. According to StormwateRx, “The Retenu is a basic industrial stormwater filtration system for high-sediment loading applications and can be used stand-alone or, as in the case of Davis Industries, as a pre-treatment to the Aquip enhanced stormwater filtration system and Purus advanced stormwater polishing system.”

The company says Retenu’s treatment process uses filtered stormwater for backwashing, flushing out accumulated dirt and concentrating pollutants, which are sent back to the stormwater sedimentation pond. This process is designed to reduce the concentration of particulates in the effluent by removing solid metals and other pollutants before the enhanced filtration process, according to StormwateRx.

The second stage in the process is the Aquip. “This stormwater treatment BMP is an efficient, yet simple and easy-to-use, system that provides the treatment needed to meet most stormwater quality standards,” according to StormwateRx.

The Aquip is designed to provide removal of stormwater pollutants, including oils; suspended solids; turbidity (a measure of water clarity determined by how much the material suspended in water decreases the passage of light through the water); organics; nutrients, such as ammonia and phosphorus; and heavy metals, such as copper, zinc, iron, lead, aluminum, nickel and cadmium, according to StormwateRx.

The final step in Davis Industries’ stormwater treatment system is the Purus stormwater polishing system. According to StormwateRx, the Purus “provides the most advanced level of stormwater treatment and is designed for challenging stormwater conditions and/or targeted pollutant removal.” In the Davis Industries’ system, the Purus is designed to provide additional removal of dissolved metals to meet Virginia’s water quality standards.

According to StormwateRx, “The high level of pollutant removal provided by the Purus system is ideal for facilities such as scrap metal yards, where higher concentrations of total and dissolved metals are unavoidable and/or where more stringent or watershed-specific water quality standards apply.”

The company adds that the Purus system is designed to remove fine particulates and turbidity to single-digit nephelometric turbidity units (NTU) standards and dissolved metals to the parts-per-billion range.

Fine-Tuning Process
Construction and installation of the systems were completed in early September 2011 under the management of Rocky Hall of StormwateRx.

Following the installation, the companies performed testing and fine-tuning during the first series of rains at the site. Davis Industries says it monitored seven rain storms, finding a 76 to 96 percent reduction in the monitored parameters for discharges.

Additional fine-tuning has occurred since that time. Bukevicz says the filtration media used in the Purus has had to be changed to help the company meet is discharge parameters for zinc and mercury and to deal with organics in the runoff. Additionally, some valves and pumps have required adjustment, he says. These types of adjustments are typical, Bukevicz says.

Davis Industries’ StormwateRx treatment train continually captures 85 to 95 percent of the heavy metals present in the stormwater runoff at the site and requires little in the way of maintenance, which has been largely automated, Bukevicz says. The system’s filtering beds need to be changed with every 5 million gallons of water processed, he says, and the filtration media will need to be replenished over time as its efficiency decreases.

The company performs sampling at the time of discharge. In the drier summer season to avoid stagnation, Bukevicz says Davis Industries plans to discharge its stormwater system after each rain if a number of days are going to pass between rains.

Bukevicz says he has been happy with the stormwater treatment train’s performance overall. “We have a lot of confidence in the system,” he says. “It has worked well and met our requirements.”

The author is managing editor of Recycling Today and can be contacted at dtoto@gie.net.