The present invention is directed to processes for removing a contaminant from dental effluents and includes transporting a three-phase effluent through a suction line into a particle collection vessel, introducing a suction line cleaning solution which includes a reagent into the suction line, and introducing the three phase effluent and the line cleaning solution into the collection vessel, wherein the effluent separates into solid. liquid, and gas phases in the collection vessel and the reagent includes a flocculant and/or a precipitant. and removing the gaseous and liquid phases from the collection vessel. The contaminant includes mercury. lead. and arsenic.