Recycling Service handles spent aluminum oxide.

With 100% closed loop recycling process, Washington Mills takes back spent aluminum oxide that would typically be put into landfills. Spent aluminum oxide is blended with new bauxite, and this mixture is fed into specially designed furnaces that melt and purify liquid abrasive.

[source: http://news.thomasnet.com/fullstory/Recycling-Service-handles-spent-aluminum-oxide-20039284]