If the facility subcontracts a company to handle the sludge, and there are no employees that handle the sludge but the subcontractor does, the evidence of training for the subcontractor will be needed or employees must be trained whether they do not handle the sludge; the same for the sludge of the septic system, commonly this is handled by a subcontractor or 3rd party.
Training should be provided to all employees who handle wastewater sludge and the training should cover safe handling, storage, and disposal of sludge.