Pilot-plant treatment of olive mill wastewater (OMW) by solar TiO2 photocatalysis and solar photo-Fenton

Olive mill wastewater (OMW), a highly polluted wastewater from the olive oil industry, was treated by solar photocatalysis and solar photo-Fenton. Among the tested systems the application of titanium dioxide alone was not successful. The addition of peroxydisulphate as an electron acceptor had only limited effect on degradation performance and led to high salt concentrations (30 g/l sulphate generated) and a pH value near zero. The photo-Fenton method successfully removed up to 85% COD and up to 100% of phenol index of OMW with different initial concentrations and from different sources. Two solar photocatalytic pilot-plant reactors were used; one of conventional CPC type and an open non-concentrating Falling Film Reactor. The latter, newly designed reactor worked properly and yielded comparable results to the CPC in terms of degradation rate referred to incident UV radiation energy per solution volume. The suspended solids in the OMW hinder light from entering the reactor. Therefore, flocculation induced by a commercial flocculation agent was successfully applied to remove suspended solids. Application of this pre-treatment led to considerable increase of degradation rates and decrease of hydrogen peroxide consumption

Techno-economical assessment of solar detoxification systems with compound parabolic collectors

This paper is focussed on a techno-economical analysis comparing TiO2-Persulfate and Photo-Fenton methods for Solar Detoxification of pesticides from an industrial point of view and considering the photocatalytic system coupled with a pesticide bottles recycling plant. The analysis is based on the experiments performed at PSA Solar Detox facility with 250 L of a mixture of 10 commercial pesticides, which have been treated with both photocatalytic methods in the same CPC-type reactor system. The initial TOC of the pollutants was 100 mg/L (considering not only the active ingredient but also the rest of the commercial formulation components) and the final TOC 10 mg/L (plant design parameters). Different experiments have been performed to optimize both treatments. In the experiments with Photo-Fenton 80% of the initial TOC were removed in 75 to 90 minutes and 90% in approximately 2 hours. In the experiment with TiO2-Persulfate, 80% of the TOC was removed in 3 hours and 90% of the TOC after 4 hours

Dynamic models for hydrogen peroxide control in solar photo-fenton systems

Simulations and real decomposition experiments with hydrogen peroxide induced by dissolved iron and solar illumination were performed in a solar pilot plant with compound parabolic collectors designed for photo-Fenton wastewater treatment. The structure of a gray-box linear model aimed at reproducing system dynamics with parameters dependent on operating conditions when operating around prescribed set-points is proposed. This simple model relates the changes in hydrogen peroxide concentration due to changes in hydrogen peroxide injection, dissolved iron, and solar illumination. Based on this model, control of the hydrogen peroxide concentration at set points between 200–900 mg/L±10 mg/L under dynamic conditions (simultaneous decomposition and addition of hydrogen peroxide by a dosage pump), was achieved. Different basic approaches for controller actuation upon the frequency of the dosage pump were tested, ranging from a simple PI controller to a PI controller plus antiwindup action and feedforward control. From these basic approaches, conclusions can be drawn about the process's behavior under closed-loop contro