Challenge

The United States Environmental Protection Agency (EPA) has created the Environmental Technology Verification Program (ETV) to facilitate the deployment of innovative and improved environmental technologies through performance verification and dissemination of information. The ETV program has evaluated the performance of microfiltration technology for the recycling of alkaline cleaners. 

An ETV program was conducted on a Silverback® unit at Gates Rubber. Gates Rubber, in Versailles, Missouri, uses alkaline cleaning solutions at different times during manufacturing to remove oils, coolants and other metalworking fluids prior to electroplating. The verification test evaluated the ability of the Silverback® unit to remove oils and recover the alkaline cleaning chemistry.

Testing was conducted during two distinct 5-day test periods (Run 1 and Run 2):

• During Run 1, the Silverback® unit was operated at a typical oil and suspended solids loading rate.
• During Run 2, the Silverback® unit was operated at a significantly higher than normal oil and suspended solids loading rate.

Solution

The Silverback® Model 900 was used to recycle the alkaline cleaner. It uses microfiltration technology. The oils are removed from the alkaline cleaner by using a 0.2 micron ceramic membrane filter. This is a cross-flow application where the oil is rejected by the membrane and the cleaner is allowed to pass through the membrane and back to the cleaner bath. The Silverback® unit recovers 1.0 gpm of alkaline cleaner.

Results

The test results show that the Silverback® Model 900 provides an environmental benefit by extending the bath life of the alkaline cleaner, thereby reducing the amount of liquid and solid wastes produced by the cleaning operation without removing the cleaning constituents of the bath.

• The overall volume of concentrated waste generated from alkaline cleaning has been reduced 67.5% and the weight of total solids in the waste products has been reduced 58.9%.
• The O&M labor requirement for the equipment was observed to be 3.75 hrs/wk.
• The annual savings associated with the unit is $32,064, with a projected payback period of 1.3 years.