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Problem:
Metal products manufacturer needed to reduce fats, oils, and greases in its wastewater

Solution:
The company installed a membrane ultrafiltration system that saves it money on water, waste disposal and cleaners.

AMCO Engineering, a Schiller Park, Illinois, manufacturer of modular electronic enclosures for the computer industry and high-tech switching stations, needed to reduce fats, oils, and greases (FOG) in the 25.4-m (6700-gallon) first stage wash line. Metals fabricated at the company are washed, sealed, rinsed and painted: the FOG comes from rustproof coatings, says Ed Shook, formerly AMCO's environmental manager, now the company's purchasing manager.

For years, AMCO discharged this wastewater quarterly and replaced it with a fresh bath, Shook says. Although the company had used a wheel skimmer to remove FOG from the wastewater surface, he says, "We were getting awfully close to the [Metropolitan Reclamation District of Greater Chicago] standards of 250 [mg/L] for FOG." As a resulted AMCO decided to install more effective FOG controls before it had a compliance problem.

"The company considered several ultrafiltration (UF) systems," Shook says, and eventually chose one from Arbortech Corporation of McHenry, Illinois, which manufactures UF systems with semi-permeable polymeric membranes. "We chose the Arbortech unit because it worked best during a demo and was much cheaper than the other systems," Shook says.

In 1994, when the system was installed, AMCO spent less than $15,000; the same system today would range from $15,000 to $20,000, says Arbortech President, Ray Graffia Jr.  Cost is based in part on membrane square footage, materials of construction, and controls.

AMCO's UF unit features a semi-permeable membrane with openings that are smaller than 0.005 mm. "Bacteria, viruses, suspended solids, and macro molecules that are formed when the cleaner grabs onto the oil are way too large to pass through," Graffia says. Arbortech does not size its UF systems according to gallons per minute of permeate, he says, but by matching the rates of contaminant generation and flux. "If we oversize, the client may lose more of his cleaner than necessary, reducing payback," he says.

The unit also features programmable logic controls with pertinent operations' details built into help screens and a motor drive on the circulation pump to eliminate pressure-shocking membranes during starting and stopping, Graffia says. "No two systems we've ever built have been identical," he says.

According to Shook, AMCO "jazzed up" its system, by adding a heater "so we could heat the bath in the Arbortech unit [and added] surge and shunt protection to guard against power surge or power drop." The UF unit has saved AMCO money in several ways, he says.

The company uses less water and discharges 75% less wastewater than it did before installing the unit. Instead of draining, cleaning, and refilling the system every 3 months, Shook says, "now we only discharge it every year and a half and save about 6,000 gallons [23,000 L] of water every 3 months."

AMCO also saves money on oil-disposal fees because of the higher concentration of oil in haul-away, Shook says. The material that AMCO's skimmer had reclaimed was about 70% water and 30% oil, and had to be mixed as a fuel blend before it was burned, he says. "That was costing us around $400 or $500 per barrel," he says. The Arbortech system generates about 70% oil. "That costs us only about $200 per barrel to get rid of, and there are fewer barrels," he says.

Another unexpected benefit of the UF system, Shook says, is that "it saves us on chemical cleaners that we used to use to get rid of dirt and oils."

Arbortech tells customers to expect to spend less than 5 minutes per shift under normal operation to log pressures, temperature, and the flux rate, Graffia says.  Cleaning usually is necessary anywhere from once a week to twice a month, he says.

According to Shook, in the 5 years that the company has had the UF system, "we've replaced a valve and replaced the filter twice. The maintenance is minimal, and we've had no major problems. We're very happy with the system."