Tired of storing and hauling used synthetic air-compressor lubricant, managers at Sikorsky Aircraft Corp.  (Stratford, Connecticut), which designs and manufactures helicopters, began searching for a low-maintenance system that could process the highly corrosive lubricant onsite.

After an extensive search, operators chose Arbortech Corp. (McHenry, Illinois) to custom design a corrosion-resistant ultrafiltration system. "We build aircraft, not run pollution-control equipment," says Walter Joseph, the Sikorsky engineer in charge of selecting the new system. "We needed to work with a company that could understand our focus and design a system with enough automation to suit our requirements."

Using an ultrafiltration system to treat a single-source condensate like the lubricant may seem simple, but in this case, the condensate was highly corrosive to plastics, explains Arbortech President, Ray Graffia Jr.

Arbortech engineers designed a totally stainless steel ultrafiltration system, replacing even the most minute plastic parts that would contact wastewater. 

Converting the entire system to stainless steel was not the only modification, adds Tom Huemann, Arbortech's Vice President of Engineering. The system was installed in the basement of the plant, but Joseph wanted to be able to monitor operations from the first floor, where employees spend most of their time. To satisfy this need, Arbortech constructed a second operator interface terminal in the control room that allows all non-manual operations to be performed from the main floor.

The capacity of the system, which discharges to the municipal wastewater treatment plant, is 5677 L/d (1500 gal/d). The nominal capacity of similar systems treating spent coolant probably would be about 1900 L/d (500 gal/d), Graffia says. However, he says, lighter-duty applications, like compressor condensate, often run two to three times as fast because the streams are cleaner to begin with than most industrial wastewater processes. 

The ultrafiltration system operates in modified batch mode, Huemann says, and routine maintenance is limited to cleaning between batches. Thus far, Sikorsky officials are pleased with the system, which cost a little less than $40,000, Graffia says.