Abstract: A fluid treatment chamber is provided for the deactivation of microorganisms in a fluid. The fluid treatment chamber comprises a housing and an electrode assembly. The housing comprises a fluid inlet for receiving fluid to be treated and a fluid outlet for allowing treated fluid to be retrieved. The electrode assembly is located within the housing and comprises at least two electrodes for generating an electric field there between. The electrodes have opposing convex electrode surface sections defining there between a biconcave treatment zone for treatment of the fluid by the most intense electric field generated by the electrode assembly. The treatment zone comprises a channel between the opposing convex electrode surface sections through which the fluid is to flow to receive treatment. The channel width tapers towards a vertical midsection of the channel due to the convex configuration of the opposing electrode surface sections.