Triethylene glycol? The hydraulic fluid is water-based. I expect (do I remember having observed it?) that it doesn't mix with oil. Anyway, the density differs a lot, like 1050-1150 for polyglycol lube, and 800-900 for dense mineral lube oil.
Waste recycling would like them separated.
Both contain additives that may pass from one into the other, but as waste it's a small worry.
If your TEG is a real lube, with all due additives, a pump will accept it easily.