UC Irvine Saves with Microwave Medical Waste Unit

Municipal landfills are prohibited by state and local governments from accepting hospital contaminated wastes-"sharps" such as needles and razors, blood, and bandages--without their proper treatment.

The medical centers of the University of California at Irvine had used a steam autoclave to handle medical waste disposal requirements on-site. By disinfecting the waste, the centers avoided costly hazardous-waste disposal fees.

However, the waste retained its volume and odor, and "sharps" had to be contained in special boxes. Another drawback, employees had to operate the unit every hour of every day to keep pace with the waste being generated.

Southern California Edison introduced microwave disinfection to UCI in 1993 as a research-and-development demonstration project, contributing a grant toward the purchase of the equipment.

The Sanitec microwave disinfection system now in use combines shredding, steam injection, and microwave treatment to disinfect medical waste. The treatment reduces the waste to a moist, confetti-like residue acceptable to municipal landfills.

The system is housed in a 24-ft x 10-ft x 11-ft all-weather steel enclosure at the rear of the property. It takes 35 minutes to cycle on and can process more than 550 lb./h of waste.

A worker loads a cart of medical waste into the unit where it automatically empties into a hopper. There it is shredded and steam is injected to ensure uniform absorption of heat during treatment.

A screw conveyor then pushes the shredded waste through a chamber, where it is continually exposed to microwaves. The microwaves disinfect the waste by heating it to 203° to 212°F for 30 minutes. The treated material ships to a municipal landfill.

All this is done by one worker operating the unit five to six hours a day, three days a week--processing all of the centers' infectious waste-a ten-fold saving in worker and operating time.

The system's operator also has time to complete a checklist of preventive-maintenance items each time the system is run and on a monthly and yearly schedule. (Twice a year, the hospital conducts a microbiological test to confirm that the waste is being disinfected.)

The UC Irvine medical centers also attest to the following additional gains:

• no harmful air emissions, odors, liquid discharges, or ash products;
• reduced disposal fees because the shredder reduces the waste stream's volume by up to 90%;
• less likelihood of incomplete decontamination because material is heated both from within (microwave) and without (steam);
• reduced space requirements;
• reduced energy consumption (typically about 270 kWh per ton of waste); and
• no chemicals to add or dispose of.

Contact: Sanitec, Inc., 26 Fairfield Place, West Caldwell, NJ, 07006. Tel: 800-551-9897; Fax: 973-227-9048.

The previous case study was adapted from an environmental applications paper by Southern California Edison.