A leading aluminum producer manufactures high grade, low weight aluminum for use in the aerospace industry at its plant in the Midwest US. To prevent the buildup of oils, greases, and dirt on the produced billets during the quench process, installation of a filtration unit was required. The STiR filter was selected for its ability to effectively remove both suspended solids (TSS) and oils from the casting water.

The STiR filter is an automatic, backwashable filter which uses a crushed walnut shell bed instead of a disposable filter media. The walnut shell media in the STiR can remove up to 90% of free oil, and 95% of suspended solids at 5 micron. The bed is permanent, and does not need to be replaced over the life of the product.

Walnut shell filters were selected during design as the best available technology for the process, over induced gas flotation cells (IGFs) and other gravity separators. This is because walnut shell filters remove oils and greases more efficiently at lower concentrations (~50 ppm), and can continually provide clean water (<5 ppm="" oil="" to="" the="" casting="" process="" --5--="">