Trisodium is a common hardware item, which is normally used as a cleaning agent or as a stain remover. If it is mixed with water it will have alkaline PH but it is not hazardous in any sense for humans. This is because it is not only used as a cleaning agent, it is also used as a food additive.
Whatever cannot be saved for recovery or recycling should be managed in an appropriate and approved waste disposal facility. Processing, use or contamination of this product may change the waste management options. State and local disposal regulations may differ from federal disposal regulations. Dispose of container and unused contents in accordance with federal, state and local requirements.