J.L. Ovelleiro

Treatment of a wastewater resulting from dyes manufacturing with ozone and chemical coagulation

The degradation of the compounds present in a previously chlorinated wastewater resulting from the production of azoic dyes has been studied in this project. Towards this end, the first step developed was the characterization of the spillage water by GC/MS and GC/FID. Secondly, a combined ozone+Ca(OH)2 treatment was carried out, determining its efficiency on this wastewater. The majority of compounds found in the wastewater are aniline derivatives and azo compounds. Also, as a result of the chlorination treatment which is carried out by the factory, some organochloride compounds were identified, being the most important those which are subjected to legislative control, namely: chloroanilines, chloronitrobenzenes and chlorophenols. After ozonation, the concentration of the compounds present is reduced to good percentages. The by-products formed after this first treatment were, mainly, nitrobenzene derivatives and organic acid compounds. The following treatment with Ca(OH)2 leads to almost total elimination of the remaining compounds in the ozone treatment. However, aniline and chloroanilines are formed after chemical coagulation due to the strong basic medium at which the sample in this process is set. C.O.D. is reduced 25% after ozonation, while it decreased 50% after the complete treatment. T.O.C. remained constant during ozonation, but a 42% reduction was obtained after chemical coagulation. Color decreased gradually during ozonation reaction, and after the final treatment the reduction was 62%. The complete process of ozonation and chemical coagulation with Ca(OH)2 is, in general, very effective to treat this kind of wastewaters.

TiO2-CATALYSED OZONATION OF RAW EBRO RIVER WATER

Abstract This paper presents the results obtained with heterogeneous catalytic ozonation in which raw Ebro river (Spain) water is ozonated in the presence of titanium dioxide supported on alumina as a solid catalyst at two different O 3 :C weight basis ratios. The influence of catalytic ozonation on the trihalomethane (THM) formation during drinking-water treatment is also studied. It is shown that using this catalyst during ozonation of the natural water allowed reductions in THM formation. Characterization of the raw, ozonated and chlorinated water was made by concentrating the sample through liquid–liquid extraction, along with the gas chromatography/mass spectrometry (GC/MS). A total of 66 different organic compounds were identified, mainly carboxylic acids, aromatics, aldehydes, ketones and alcohols. The percentage of elimination or formation levels reached during ozonation and chlorination are discussed.

Study of the catalytic ozonation of humic substances in water and their ozonation byproducts

Abstract It is shown that using transition metals, especially Mn(II) and Ag(I), during ozonation of humic substances in water allows important reductions in the content of organic matter. Characterization of the organic compounds resulting from ozonation was made by concentrating the sample through liquid-liquid extraction or derivation with PFBOA.HCl, along with the GC/MS and GC/ECD techniques. In total, 110 different organic compounds were identified using GC/MS; mainly carboxylic acids, aromatics, hydrocarbons, aldehydes, ketones, and furan-carboxylic acids. The percentages of elimination or formation levels reached during ozonation are discussed.

Evaluation of trihalomethane formation potential in function of oxidation processes used during the drinking water production process.

The presence of natural organic matter (NOM) in both surface and groundwater supplies produces toxic by-products, mainly trihalomethanes (THMs), during oxidation steps in drinking water production. This research work shows the efficiency of different advanced oxidation processes (AOPs) based on ozone for the degradation of precursors of trihalomethanes in aqueous solutions. Completed treatments comprised different preoxidation processes (chlorination and AOP: O(3), O(3)/H(2)O(2), O(3)/TiO(2) and O(3)/H(2)O(2)/TiO(2)), adsorption with PAC (optional operation), coagulation-flocculation and final postchlorination applied to synthetic samples which were prepared by dilution of the soluble fraction of a humic solution. A direct chlorination of synthetic humic samples which display dissolved organic carbon close to 3 mg l(-1) produced a THM concentration of around 1600 microg CCl(3)l(-1) (measured as THMFP). Comparisons between the trihalomethane formation potential of initial synthetic samples and samples treated by prechlorination and coagulation-flocculation-decantation show that the main factor responsible for THM reduction is the coagulation-flocculation process since a decrease of 90% is achieved. Considering the various completed treatments studied, the most recommendable include preoxidation by ozonation, adsorption by PAC, coagulation-flocculation using aluminium sulphate followed by decantation and final postchlorination.

Degradation of organochloride compounds by O3 and O3H2O2

This paper presents the results obtained from oxidation with O3 and O3H2O2 of a residual water coming from the production of dicofol and tetradifon pesticides, where chlorobenzenes, DDTs and its metabolites and other organochloride compounds were found. The oxidation processes were carried out using ozone (O3) in basic medium (pH 9.4) at low dosage (0–1.5 g O3 g−1 initial TOC) and in the presence of hydrogen peroxide (H2O2), with a 0.5 H2O2O3 molar ratio. During the treatment, many compounds were removed (dichlorobenzophenone, tetradifon, chlorobenzene, trichlorobenzene) and their change in concentration at different ozonation contact time was monitored. Other compounds like DDE remained practically invariable. This study investigated the formation of first ozonation by-products (FOBPs) in the wastewater, specifically chlorophenols, by means of gas chromatography/mass spectrometry (GC/MS) and gas chromatography/electron capture detection (GC/ECD) analysis in terms of the amount of time the O3 has been in contact with the processed sample. o-Chlorophenol, p-chlorophenol, benzenemthanol, n-chlorohydroxibenzaldehyde, n-chlorobenzenemethanol, chlorobenzoic acid, etc., were formed during the treatment, due to the mechanism of fast and non-selective oxidation which ozone has through OH radicals, formed by the decomposition of the O3 molecule and accelerated by the presence of H2O2 in water

Heterogeneous Catalytic Ozonation with Supported Titanium Dioxide in Model and Natural Waters

Abstract This paper presents the results obtained with heterogeneous catalytic ozonation in which model and natural waters are ozonated in the presence of supported titanium dioxide (TiC2) as a solid catalyst. The conditions in preparing the supported catalyst are experimentally optimized. The efficiencies of three catalyst supports (attapulgyte, alumina and silica gel) for organic matter oxidation have been compared. The TiC2 supported in alumina calcined at 500[ddot]C compacted to granular form with a particle diameter about 2-4 mm is demonstrated to be the best catalyst on the removal total organic carbon (TOC) by ozone.

Sequential solar photo-fenton-biological system for the treatment of winery wastewaters.

In this study, winery wastewaters are considered for degradation using heterogeneous photo-Fenton as a preliminary step before biotreatment. The heterogeneous photo-Fenton process assisted by solar light is able to partially degrade the organic matter present in winery wastewaters. When an initial hydrogen peroxide concentration of 0.1 M is used over 24 h of treatment, a degradation yield of organic matter (measured as TOC) of around 50% is reached. The later treatment (activated sludge process) allows the elimination of 90% of the initial TOC present in pretreated winery wastewaters without producing nondesired side-effects, such as the bulking phenomenon, which is usually detected when this treatment is used alone. The final effluent contains a concentration of organic matter (measured as COD) of 128 mg O2/L. The coupled system comprising the heterogeneous photo-Fenton process and biological treatment based on activated sludge in simple stage is a real alternative for the treatment of winery wastewater.

Comparative Efficiency of the Systems O3/High pH And 03/catalyst for the Oxidation of Chlorobenzenes in Water

Abstract The objective of this study was to investigate the use of advanced oxidation processes to oxidize an industrial wastewater in which chlorobenzenes were found in the range of 1 mg/L to 5 mg/L and a solution of chlorobenzenes whose concentration was 0.03 mg/L, which was prepared from stock solutions. Ozone in a neutral medium (pH=7) was compared with ozone in presence of metallic ions, such as Fe (II), Fe(III) and Mn(II) at concentration of 610-5 M.

Mn(II)-CATALYSED OZONATION OF RAW EBRO RIVER WATER AND ITS OZONATION BY-PRODUCTS

Abstract It is shown that using Mn(II) as a catalyst during ozonation of raw Ebro river (Spain) water allows reductions in the content of organic matter. Characterization of the raw and ozonated water at two different O 3 :C weight basis ratios was made by concentrating the sample through liquid-liquid extraction or derivation with O -(2,3,4,5,6-pentafluorobenzyl)-hydroxylamine hydrochloride (PF-BOA.HCl), along with the gas-chromatography/mass-spectrometry (GC/MS) and electron capture detector (GC/ECD) techniques. A total of 88 different organic compounds were identified, mainly carboxylic acids, aromatics, aldehydes, ketones and alcohols. The percentage of elimination or formation levels reached during ozonation are discussed.

Wastewater from the manufacture of rubber vulcanization accelerators : characterization, downstream monitoring and chemical treatment

The content of wastewater resulting from the manufacture of rubber antioxidants and accelerators by a factory situated in the Ebro basin (Spain) has been determined using gas chromatography-mass spectrometry (GC-MS) and gas chromatography-flame ionization detection (GC-FID). The change in the pollutants was studied in the riverbed via two modules which continuously gathered pollutants on various solid supports (activated carbon and XAD-2 resins). These modules were located in Bocal Station, lying a further 100 km downstream from the factory, and from the Zaragoza water supply. Forty-six different compounds were identified at Bocal Station, the majority resulting from the production of rubber additives. Due to the immunity of different waste substances, and to the toxic nature of some, we studied their reaction when subjected to techniques of chemical oxidation using ozone.