Factorial experimental design of winery wastewaters treatment by heterogeneous photo-Fenton process.

Winery wastewaters are difficult to treat by conventional biological processes because they are seasonal and experience a substantial flow variations. Photocatalytic advanced oxidation is a promising technology for wastewaters containing high amounts of organic matter. In this work, the photo-Fenton process in heterogeneous phase is presented as an alternative methodology for the treatment of winery wastewaters. As a consequence of the great number of existing variables, an experimental design methodology has been used in order to study the influence and interaction of various variables and to obtain a reduced empirical model which describes the organic matter degradation process. Applying photo-Fenton treatment in heterogeneous phase under energetic conditions for synthetic samples simulating winery wastewaters results in purification levels of up to 50% (measured as total organic carbon). Different reduced models are obtained and their utilization depends mainly on the degree of degradation of organic matter required.

Study of the presence of pesticides in surface waters in the Ebro river basin (Spain).

This work studies the presence of a total number of 44 substances found in waters of the Ebro river basin (Spain), all included in the Pesticides Control Network, whose purpose is to monitor diffuse pollution of surface waters caused by pesticides contained in some of the dangerous substances lists established in existing legislation and their high degree of use in the basin. Most of the pesticide sampling points are located in the sections of river that receive run-off waters from various agricultural areas shortly before opening out onto the main river (the Ebro), in areas of special agricultural importance. Water samples are subjected to a solid-liquid extraction as a previous step to their analysis by GC/MS (gas chromatography/mass spectrometry). Pesticides most frequently found and in greater concentrations in the waters of the Ebro river basin are 3,4-dichloroaniline, molinate, desethylatrazine, dimetoate, simazine, atrazine, metolachlor and chlorpyrifos. There are certain compounds that are not detected or their concentrations are below the quantification limit, such as 4-isopropylaniline, ametryn, beta-HCH, delta-HCH, aldrin, isodrin, dieldrin, heptachlor epoxide, endosulfan and endosulfan-sulfate. Diuron appears at specific points in some of the stations.

Characterization and photo-Fenton treatment of used tires leachate.

In this study the leachates derived from used tires were firstly characterized by means of the evaluation of their organic matter content. The leachate from tire powder presented a COD value of 508 mg O(2) l(-1) and a TOC of 214 mg Cl (-1). The main identified organic substances were constituents of the rubber structure: benzothiazole derivatives, phthalates, phenolic derivatives, hydrocarbons and fatty acids. The application of photo-Fenton treatment was investigated in order to obtain the maximum organic matter removal. When a solar chamber as light source was used (light intensity=500 Wm(-2)), the best operational conditions were the following: [H(2)O(2)]=3703 mg l(-1), [Fe(2+)]=92.1 mg l(-1), initial pH 2.7-3.0, reaction time=100 min. After the photo-Fenton treatment at optimum conditions, the reached COD and TOC reduction was 64% and 48%, respectively. The main initial organic substances were eliminated after the reaction and no significant by-products were identified. A complementary treatment consisted of coagulation-flocculation carried out with FeCl(3) x 6H(2)O at pH 12 produced a maximum organic matter removal of 43% as COD and 39% as TOC. A combination of photo-Fenton followed by coagulation-flocculation enhanced the organic matter removal: a reduction of 77% of COD and 64% of TOC was attained.

Study of the aromatic by-products formed from ozonation of anilines in aqueous solution.

Aqueous solutions of aniline and p-chloroaniline were treated with ozone in order to study the reaction and oxidation by-products. Aniline solutions were ozonated at low and high pH, so as to compare both molecular and hydroxyl free radical mechanisms, respectively. The main identified aromatic by-products were nitrobenzene and azobenzene when the experiment was carried out at acid pH. Formation of nitrobenzene, azobenzene, azoxybenzene and 2-pyridine-carboxylic was observed when the ozonation was carried out at basic pH. p-Chloroaniline was treated with ozone only at high pH and the identified by-products were in accordance with those obtained in the ozonation of aniline: p-chloronitrobenzene, 4,4'-dichloroazobenzene and 4-chloro-2-pyridine-carboxylic acid. All the aromatic by-products found were less toxic than the raw materials. The pseudo-first-order constants in aniline concentration were calculated, whilst kinetic in p-chloroaniline concentration could not be adjusted to a first-order reaction.