BACKGROUND The occurrence of pharmaceutical compounds in wastewater has become a major concern for human health and the environment. Therefore, it is an important challenge to improve conventional wastewater treatment to remove these compounds. Coupling biological treatment with advanced oxidation technology has been widely studied in the literature, but only sequential associations of the two processes have been used. This study proposes an innovative concept based on a real integration of the photocatalytic oxidation process in a continuous recycling loop on a membrane bioreactor. The role of the oxidation here is not to completely degrade pharmaceuticals, but instead to oxidize them moderately to increase their biodegradability so that they can be eliminated by the biological process. RESULTS Preliminary experiments on the oxidation process indicated that a flux density of 5 W m−2 was sufficient to increase biodegradability and decrease the toxicity of a cocktail of three pharmaceuticals. Then the performance of a 20‐L continuous membrane bioreactor treating wastewater with seven pharmaceuticals, without and with pre‐oxidation at 5 W m−2, were compared. Pre‐oxidation increased the global removal for some recalcitrant pharmaceuticals (from 3% to 47% for diclofenac and from 1% to 44% for furosemide) without affecting either the removal of carbon, nitrogen or phosphorous by activated sludge, or of already highly removed pharmaceuticals. CONCLUSION This work proves the feasibility of an innovative concept of a continuous hybrid process coupling a photocatalytic oxidation process and a membrane bioreactor for the treatment of pharmaceuticals in wastewater, with low cost and size. © 2020 Society of Chemical Industry (SCI)

Compared to more conventional techniques, advanced oxidation processes (AOP) hold significant promise in terms of elimination of organic (especially persistent) compounds and microorganisms (disinfection) in wastewater. If the objective is to power these processes using solar energy, we need to be able to manage the intermittency in the solar resource. This is an essential step for design and to ensure efficient operation of the treatment processes. As solar radiation is inherently variable due to day/night cycles, seasonal cycles, and weather meteorological conditions, solar AOP performances are difficult to establish using conventional measures. To address this gap, we carry out experimental campaigns under controlled conditions and develop modelling tools capable of describing dynamic-mode photocatalytic degradation. Here we develop a way to capture the responses of a photoreactor subjected to various stresses, including irradiation conditions, via an LED panel. Using a model that considers the influence of UV flux density and pollutant concentration made, it was possible to represent photoreactor responses under different irradiation conditions and feeds (concentration or flow at the input). The ultimate objective is to study the photocatalytic capacity of the photoreactor under irradiation conditions simulating a real day of sunshine.

This article aims to build a modeling and simulating tool of the operation of a continuous flow heterogeneous photocatalysis reactor. Continuous flow is well-known in reactor engineering for allowing advanced control of reactor and scaling-up with great confidence, but little research has addressed it's potential for this kind of application. In developing this model, particular attention was paid to the coupling which occurs at local scale between the radiative transfer and the reaction kinetics of advanced oxidation of a target organic micro-pollutant. The solution of the radiative transfer equation by Monte Carlo method was applied to a photocatalyst supported on a macroporous ceramic foam forming an efficient 3D support. After identification of the kinetic law of degradation, the dynamic simulation model was validated through comparison with a series of experiments performed for different but constant irradiations and for variable irradiations approaching, in term of intensity and dynamics, natural solar radiation.