Techno-economic assessment of surrogate-based real-time control and monitoring of secondary effluent ozonation at pilot scale

•A ΔUVA254-based surrogate model was implemented on pilot-scale.•A one-sensor approach reduces the fouling effect and required maintenance.•Ozone demand depends on the effluent matrix reactivity, less on the DOC content.•Differential control leads to less OPEX than load or flow proportional ozone dosing.•A feedback-feedforward concept might combine a high reliability and fast response.