Who empties airplane septic tanks?

They may be called 'Rampers' if Ramp Service; 'Lav Guy' if Fleet Service or Utility personnel. It varies with the airline or if its at an FBO (Fixed Base Operator) for general aviation or corporate aircraft. Its not the worst job ever, however. That is probably the mechanic (A&P) that has to work on the system, like maybe change a flush pump, clean out under the dump valve, because its leaking down. Much better pay, but a very nasty job. If the 'ramper' is wearing his gloves and face shield, not a bad job at all.