Disclosed is a process for the treatment of a plant fluid effluent containing odor compounds including an alkyl mercaptan or an alkyl thiol, an amine compound, ammonia, hydrogen sulfide and mixtures thereof by contacting the plant effluent in either a counterflow or cocurrent flow process. In the process, the effluent is contacted with an aqueous solution comprising a peroxyacid compound and one or more essential oils. When contacted with the peroxyacid, odor compounds in the effluent are oxidized and converted from the gaseous phase into a chemically modified highly aqueous soluble phase in the aqueous treatment. In this way, odor removal from the gas is preferred and odor compounds are efficiently transferred into the aqueous treatment solution. The use of such a process produces a significant improvement in odor quality index as measured by a conventional process using an expert panel when compared to conventional treatment methods.