The training regardless of whether sludge is hazardous or not should focus on the intent of the question:
"To ensure facilities have procedures in place to train all employees who handle wastewater sludge on practices to minimize environmental and health risks associated with sludge"
Sludge needs to be taken out of the tanks, and It also needs to be dewatered, and transported from the ETP/STP to a storage location, even though the sludge is not treated, employees within the facility would have some level of interaction with it, as such they need to be trained on how to handle it.
Unless there is a fully automated process within this facility that, collects the sludge from the WWTP, transports it from the WWTP to a storage location, bags or puts it into containers, and then it is directly collected by the external sludge disposer, or transporter from the gate or storage premises, with zero employee interaction, which is highly unlikely.
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