Wastewater disinfection by ozone: main parameters for process design.

Wastewater disinfection by ozone was investigated at pilot scale on different wastewater effluents. Variations in operating conditions showed that a very low hydraulic retention time (2 min) was sufficient for efficient fecal coliform inactivation, provided a sufficient ozone dose was transferred to the effluent. Therefore, the transferred ozone dose appeared to be the critical parameter for the design of wastewater disinfection. As a consequence, the "Ct" approach commonly applied in drinking water treatment should not be used for wastewater ozonation. Design parameters of ozonation were proposed for two types of regulations, and for effluents of different qualities. It was demonstrated that only with an efficient filtration step one can meet stringent standards such as the California Title 22 criteria. In all cases, viruses were totally inactivated; consequently, viruses do not constitute a limiting factor in wastewater disinfection by ozone. The standard drinking water model failed to match the experimental data obtained on real wastewater effluents. A modified approach was successfully developed, based on the simultaneous consumption of ozone by the microorganisms and the organic matrix.

Hydrodinamics and mass transfer in ozonation reactors: use of CDF modelling

El diseño del proceso de desinfeccion del agua debe descansar en los fundamentos de la ingenieria quimica considerando los aspectos cineticos e hidrodinamicos. El objetivo del trabajo es brindar un panorama de la capacidad de las herramientas del CDF (un modelo de ecuaciones de movimiento de fluidos utilizando sistemas de computacion) para explicar los fenomenos fisicos y quimicos que tienen lugar en los distintos reactores para la ozonizacion. El diseño y el control de las condiciones optimas es de importancia fundamental para lograr la mayor eficiencia del proceso. Se explican las aplicaciones del modelo para la cloracion y la ozonizacion