Inside the Plating Shop's Wastewater Treatment Plant
On any given day, the shelves and worktables of SLAC's Plating Shop are lined with pieces of metalfrom thumb-sized stainless steel pipes and rectangular lengths of copper to titanium jawsall destined for duty somewhere at SLAC. "About 90 percent of the equipment used at SLAC comes through our shop," says Ali Farvid, Metal Finishing Supervisor. The shop prepares the metal parts for use by cleaning, plating, or otherwise modifying them.
But along with useful equipment, the shop's processes produce wastewater that is either acidic or alkaline and contains small amounts of dissolved metals such as iron, copper, nickel, or silver. Regulations prohibit this wastewater from being released directly into the environment. Instead, it is diverted to an unremarkable-looking system of pipes and tanks adjacent to the shop. This system, however, is hardly unremarkable: it is the Plating Shop's award-winning wastewater treatment plant.
Over the past 15 years, Farvid and his staff have implemented innovative wastewater treatment processes and procedures that have reduced cost and waste generation, as well as enhanced safety.
As the shop's wastewater first arrives at the treatment plant, it is collected in a large holding tank. From there, an operator pumps it through two neutralization tanks, adding chemicals that make the wastewater more acidic or less acidic as needed. The change in acidity causes the dissolved metals within the wastewater to solidify so that they may be removed more easily.
Next, the operator transfers the wastewater to a clarifier tank, where a sticky substance known as polymer is added. The solid metal particles adhere to the polymer, forming a metal-laden sludge that slowly settles out of the water in a layer at the bottom of the clarifier. After settling, the clean water that remains is fit for release to the sanitary sewer system.
The treatment process doesn't stop there, however, because some water remains in the polymer-metal sludge. To remove it, the material is sent through a filter press and a drier. The water filtered out at this stage is transferred back to the holding tank and goes through the full treatment process again. The dried sludge, meanwhile, forms a solid "cake" that is hauled offsite for proper hazardous waste disposal. Using this process, the plant treats about 5,000 gallons of wastewater per day.
"Over the years, we've modified and optimized the system," says Farvid. Among the more recent changes is the installation of a redesigned filter press. The press is automated, reducing fumes and the potential for spills. In addition, Farvid and his staff replaced ferric chloride, a substance added to the neutralization tanks to help settle the sludge in the clarifier, with aluminum and iron. The switch helped to cut costs and reduced the amount of hazardous waste output from the system by nearly 50 percent over the past ten years.
The efforts of Farvid and his staff to constantly improve the treatment plant's performance have earned them awards from the California Water Pollution Control Association, the Department of Energy, and the Environmental Protection Agency.
Next, says Farvid, he and others at SLAC would like to explore the possibility of reusing the cleaned water on site, perhaps for irrigation. "We're always working to minimize waste and make the treatment system as efficient as possible," he says.
Above image: Ali Farvid and plant operator Oscar Zelaya stand at the control panel of the water treatment plant’s two neutralization tanks.