NC Division of Highways - Equipment Depot

Year Submitted: 2007

Process: Parts Cleaning

Industry: Automotive Maintenance

Wastes Reduced: Solvent

Location: Raleigh NC

Contact: Tom Martin

Phone: (919) 733-3535

Description:

The North Carolina Division of Highways Equipment Depot provides routine maintenance to off-road vehicles. To assist in the maintenance operations, the facility had 12 parts washers serviced by Safety-Kleen on site. As part of a statewide effort to reduce off-site transfers of hazardous solvent waste and associated management costs, the facility sought to replace some of the traditional mineralbased solvents with non-hazardous solvents and to extend solvent life to reduce solvent waste.

P2 Application:

Filters To extend the working life of traditional mineral-based solvents, the facility installed filters on the parts washers. The filters supplied by Gulf Coast cost approximately $70 each and utilize a disposable paper towel filter media that removes fine contaminant particles down to approximately 2 microns in size. The paper filter media is replaced after approximately 2 months of use. To date these filters have been installed on 6 parts washers.
Biological Solvent The facility installed a new parts washer that utilizes a biological solvent. An emulsifier transfers oil and hydrocarbon contaminants from the parts to the solution, and microbes in the solvent then feed on the contaminants. Oil is converted harmlessly to water and carbon dioxide. However, the facility has found that the solvent is effective in removing thin films of oil but struggles with more heavily greased parts. Also, the solvent will not remove synthetic lubricants.

Details of Reductions

• Solvent
  Comments: The filters installed on the mineral spirit parts washers have significantly reduced waste solvent management costs. Previously, the facility replaced 6.5 gallons of solvent for every gallon of parts washer capacity each year. Since the introduction of the filters, solvent life has been extended to approximately 1 year. Currently, the facility is adding only 2 gallons of solvent for every gallon of parts washer capacity annually to replace for evaporative losses. The total costs have declined 39%, from $18 per gallon of capacity per year for virgin solvent and waste management costs, to $10.96 per gallon of capacity per year in solvent costs for only evaporative losses. By adding filters and modifying parts washers to extend solvent life, the facility has been able to virtually eliminate its hazardous waste generation, and thus terminate the Safety-Kleen Contract, as well as reduce the total number of parts washers on site. Since the filters are keeping the solvent clean and extending solvent life, the waste generated is expected to be a small amount of solid filtrate material, potentially less than 1 drum per year. The liquid loss is expected to be almost all evaporation. The reductions in solvent consumption from the parts washer modifications resulted in the facility being reclassified from a large quantity generator to a small quantity generator for RCRA hazardous waste management.

Additional Information :

The reductions in solvent consumption from the parts washer modifications resulted in the facility being reclassified from a large quantity generator to a small quantity generator for RCRA hazardous waste management.
Biological Solvent Due to the nature of the parts to be cleaned (heavily soiled and often synthetic oils), the facility has decided not to purchase additional biological parts washers. The parts washers effectively clean lightly oiled parts and would be more suited to a specialty automotive shop dealing with these types of parts.