Switch in wastewater treatment chemistry pays an estimated $25K in dividends for Duncan Aviation
Duncan Aviation is one of those companies that succeed by treating the by-products of their enterprise with the same care normally lavished on profit centers. The result is not only meaningful recognition, but also more cost-efficient operating budgets.
A case in point: Duncan Aviation’s pretreatment- and finishing-oriented wastewater treatment, sludge dewatering and disposal of dry filter cake. Previously, the treatment utilized four dusty, malodorous chemicals they blended onsite. Today, they use specialized proprietary formulations from Chemetall Oakite.
The business of business aircraft
Headquartered in Lincoln, Neb., Duncan Aviation is an aircraft support services supplier for the most popular business aircraft in use today—including Falcons, Hawkers, Challengers, Gulfstreams, Astra-G100s/Westwinds, Citations and Learjets.
They perform a wide variety of aviation services at their major service centers in Lincoln and Battle Creek, Mich., and at 21 satellite avionics facilities throughout the U.S. These aviation services include:
- Airframe maintenance;
- Engine maintenance;
- Avionics installations;
- Aircraft modifications;
- Completions design;
- Paint and interior completions;
- Avionics/instrument repair and overhaul; and
- Accessory repair and overhaul.
Duncan Aviation is one of only a few service centers qualified to perform 12-year Learjet inspections and similar milestone inspections on Falcons, Hawkers, Westwinds, Jetstars and Citations. It is a factory-authorized service center for Cessna Citation, Cessna Propjet, Falcon, and Learjet airframes; and is factory authorized to work on many different business aircraft engines.
It is exacting, cutting-edge work that nevertheless generates significant hazardous waste volume: 203,521 lb in 2003.
“We are a very environmentally conscious organization,” said Kelly Becker, Duncan Aviation environmental director. “Working with our suppliers, we have been able to have a huge impact on safety and the health of our employees, reducing hazardous waste while also passing savings through to our bottom line.”
For the past year, for example, Becker has been able to achieve 10% savings on his environmental budget. The hazardous waste stream has been reduced thus far in 2003 by 44,149 lb.
Duncan Aviation has achieved this by taking a number of environmental initiatives including recycling and conservation in addition to purchasing more environmentally acceptable chemical products and adjusting in wastewater disposal procedures.
The payoff was not only budgetary savings, but recognition as well. In the last two years, Duncan Aviation has won several prestigious environmental awards including:
- The Environmental Clean Your Files Week Award, presented by the Lincoln/Lancaster, Nebraska Chamber of Commerce in April, 2003;
- A Certificate of Recognition for the Development of the Industrial WasteWater Certification in May, 2003, presented by the Nebraska Industrial Council on the Environment;
- The Engineering Excellence Honor Award for Air Emission Management and Tracking System, presented by ACED in April 2002; and
- The Environmental Leadership Excellence Award presented in May 2001 by the Nebraska Safety Council.
Safer, environmentally friendly chemicals
This is a remarkable record for a company engaged in paint stripping, paint finishing, and specialized treating operations that require state-of-the-art water treatment and effluent disposal.
Specialists strip old paint from fuselages and aircraft interiors, then repaint. They remove flight soils from engine, propulsion and airframe components. They preclean and deoxidize aviation aluminum, and pretreat it with chromate conversion coatings that condition the metal substrates for finishing and protect the surfaces during service life.
These operations produce spent solutions and effluent streams that contain suspended solids and solutions of chemicals that by regulations must be removed from process water and hauled away—an expensive proposition.
Water used for cleaning, deoxidizing and chromate conversion coating of aircraft before repainting, for instance, contains metal hydroxides, as well as ferrous and aluminum sulfates that require charge neutralization, coagulation, flocculation and solid’s dewatering. Duncan Aviation’s treatment utilizes chemical treatment of the water plus a Sperry filter press to produce the dry cake from the dewater sludge. In essence, heavy metals in 3,500-gal batches of water are clumped together and dropped out of suspension. Water is then pressed out of the sludge, and filtered. Dry cake is hauled away in 55-gal HAZMAT drums costing approximately $2,000 per shipment.
Prior to 2002, the chemical treatment utilized a combination of four raw chemicals—ferrous sulfate, caustic soda, aluminum sulfate and sodium hypochlorite.
Workers were experiencing problems with this approach. When feeding the powdery chemicals, operators had to be constantly aware of the need for respiratory protection. Odor was a problem, too—especially from the sulfate-based compound. Too often the operators would literally take that reminder of their work home with them.
A better way
“During the past few years, Duncan Aviation has introduced safer and more environmentally friendly chemicals for employees and the work environment,” said Becker. “We continue to strive to reduce the amount of hazardous waste and are always looking for new products and processes.”
In this case, Becker turned to chemical supplier Chemetall Oakite, based in Berkeley Heights, N.J. Oakite supplies many of the chemistries that handle Duncan Aviation’s conditioning and refurbishing operations, so they were experienced in the treatment of spent solutions, including the trace metals that must be removed from paint spray booth washout and spent cleaning/treatment solutions.
Working with Becker, Chemetall Oakite’s Account Manager Doug Van Duyne installed a new water treatment process. The process involves neutralizing waste solids with Enprox 8412, a proprietary, reacted aluminum/calcium treatment coagulant, and Enprox 8440, an anionic polyelectrolyte in hydrated form, designed to quickly flocculate the waste solids and precipitate them from the water solution.
Following lab analysis of the wastewater, each 3,500-gal batch is treated in four steps:
- Addition of Enprox 8412 at 5,000 ppm (six gallons);
- Adjustment of pH to between 9.5 to 10 standard units with caustic soda;
- Addition of Enprox 8440 at 100 ppm (588 mills); and
- Allow floc to settle.
The formed metal hydroxide sludge is then run through the press and the water, now hazy-clear, is recirculated.
In this process, waste solids are settled out of the water quickly. Initial analyses showed significant removal of metallic solids.
“Chemetall Oakite’s service was wonderful,” reported Becker, “and their follow-through excellent. Representatives were here in the shop at least every other week to fine-tune the new treatment process until we had it running smoothly.”
Savings year-to-year have been remarkable, too. Using the Enprox Treatment System, only 68 HAZMAT drums of dry cake were shipped, compared to 161 drums using the previous system. During the same periods, Duncan Aviation reduced shipments of dry cake from water-wash paint spray booths from 42 drums to 10.
In a very real sense for Duncan Aviation, the $25,000 or so in projected annual savings achieved by the switch is secondary to other benefits such as worker productivity and health, job satisfaction, and the enhancement of environmental responsibility.
“When I first approached top management with the idea of achieving those benefits plus the annual savings by switching from the old chemical approach to the proprietary treatments from Chemetall Oakite,” said Becker, “the initial cost of the new chemicals was viewed as a drawback. But they approved the switch, and we are all believers now. Once again, environmental responsibility has paid for us.”