Abstract: A system and method for removing hydrogen sulfide from natural gas using a triazine scavenger is described. The system includes a pre-treatment system that can be connected to an existing hydrogen sulfide removal system to more fully utilize the triazine scavenger. The pre-treatment system includes a contactor vessel in which sour natural gas is contacted with fresh and/or partially consumed scavenger to partially sweeten the sour gas by removing H2S. The partially sweetened gas then flows to the existing hydrogen sulfide removal system where it is fully sweetened.