unsalable waste--not suitable even for regrind.
Time for a risk assessment!
HDPE melt temperatures normally well exceed 100ºC, so you have little biological concerns in using this stuff for regrind. So what are the other hazards that could be introduced from the floor?
Chemical hazards?
Physical hazards or contamination that will pollute your resin stream and cause holes in bottles?
Honestly if I was running an HDPE facility I would keep the floors reasonably clean and free of dust/debris and very much consider that product for regrind. There's practically zero microbiological concerns and the only other "unknowns" would have to come from my floor, which I can control. There may be other hazards in your facility so approach cautiously, but go through a risk assessment and see what could possibly go wrong. If you can put controls in place to address those concerns then full sail ahead.