Abstract: Apparatus and methods for sanitizing sewage effluent comprising supporting a plurality of solid members in a conduit in fluid-flow intercepting relationship to sewage effluent flowing therethrough, the said solid members being soluble in the effluent to release a bactericidal agent at a relatively constant rate at least in part as a function of the mass rate of effluent flow thereover and the surface area of said members exposed to effluent flow, the said solid members being supported in the conduit by means such as a rack in which the solid members are positioned generally in a row extending along the path of effluent flow, each solid member extending across a substantial portion of the flow-responsive, varying depth of effluent in the conduit such that the surface area of said member exposed to effluent flow is at least in part a function of the mass-rate of effluent flow in the conduit such that the quantity of bactericidal agent released varies at least in part as a function of the mass rate of effluent f