Search

In this work, a pretreatment involving a combination of acidification, the Fenton method, and flocculation with polyelectrolytes was successfully applied to remove the suspended solids of Olive mill wastewater (OMW). This pretreatment strongly augmented the reaction rate in the following photo-Fenton treatment under solar irradiation in a Compound Parabolic Collector pilot-plant at Plataforma Solar de Almeria. The content in phenolic: substances could be degraded down to zero, while DOC was degraded down to about 25% of the initial value. In the work we describe different aspects concerning the process parameters of the pretreatment and the photo-Fenton treatment. Furthermore, decrease in phytotoxicity in the course of the treatment was monitored by germination tests with barley (hordeum vulgare L.). The results indicate that acute phytotoxicity can be substantially reduced by the application of the above mentioned pretreatment, enabling OMW to be used for ferti-irrigation in agriculture. [DOI: 10.1115/1.2391132]

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 [+ or -] 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 control. [DOI: 10.1115/1.2391014]

The technical feasibility and performance of photocatalytic Ti[O.sub.2] coatings in batch-process solar disinfection (SODIS) reactors to improve potability of drinking water in developing countries have been studied. Borosilicate glass and PET plastic SODIS reactors fitted with flexible plastic inserts coated with Ti[O.sub.2] powder were shown to be 20% and 25% more effective, respectively, than standard SODIS reactors for the inactivation of E. coli K12. Isopropanol at 100 ppm concentration levels was observed to be completely photodegraded after 24 h continuous exposure to 100 mW/[cm.sup.2] simulated sunlight in a similar solar photocatalytic disinfector (SPC-DIS) reactor. The technique for producing the Ti[O.sub.2]-coated plastic inserts is described and demonstrated to be an appropriate and affordable technology for developing countries. Keywords: Photocatalysis; Decontamination; Biological; Chemical; Drinking water

This paper compares three different collector shapes for the disinfection of water heavily contaminated with Escherichia coli (K-12). Tests were carried out in real sunlight using laboratory scale reactors to determine the performance of different reflector profiles. The reactors were constructed using Pyrex tubing and aluminium reflectors of compound parabolic, parabolic and V-groove profiles. Results have shown that the compound parabolic reflector promoted a more successful inactivation of E. coli than the parabolic and V-groove profiles. Tests were also carried out to assess the improvement to disinfection which could be achieved using Ti[O.sub.2] coated Pyrex rods fixed within the reactors. This technique, however, yielded a slight enhancement in the compound parabolic reactor but no benefit to overall disinfection performance in either the parabolic or V-groove reactors. These results show that the use of UV sunlight to disinfect contaminated drinking water in a full-scale continuous flow solar reactor is both promising and an appropriate technology for developing countries but that the inclusion of a fixed photocatalyst within the reactor tubes has yet to prove any significant improvement. Keywords: Solar photocatalysis; Parabolic reflector; Disinfection; E. coli

The objective of this work was to assess the effectiveness of using near UV light to disinfect water supplies for potential applications in developing countries. A pilot scale photoreactor comprised of non-tracking compound parabolic collectors installed at Plataforma Solar de Almeria was examined and a comparison of disinfection efficiency using E. coli K-12 was carried out with a reactor configuration of 3 and 1 [m.sup.2] illuminated area. Tests were also carried out using suspensions of titanium dioxide (Ti[O.sub.2]) at concentrations ranging from 0 to 9 mg/l. The removal of E. coli K-12 from initial concentrations of 1 x [10.sup.5] CFU/ml to below the limit of detection was achieved both with and without the use of Ti[O.sub.2]. Levels of inactivation in 351 of inoculated water of up to 4-log removal were achieved in under 30 min. The addition of Ti[O.sub.2] created an enhancement to the process only at the 3 mg/l dose. However, the results have also suggested the possibility that another disinfection mechanism, possibly governed by the frequency of intermittent UV light exposure, was regulating the overall inactivation kinetics of the trials. Keywords: Solar photocatalysis; Compound parabolic reflector; Disinfection, E. coli

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 constimption. Keywords: Olive mill wastewater; Photo-Fenton; Solar wastewater treatment