Study of Evolution of Microbiological Properties in Sewage Sludge-Amended Soils: A Pilot Experience.

Large amounts of sewage sludge are generated in urban wastewater treatment plants and used as fertilizer in agriculture due to its characteristics. They can contain contaminants such as heavy metals and pathogenic microorganisms. The objective of this research work is to study, in real conditions, the evolution of microbial concentration in agricultural soils fertilized by biologically treated sewage sludge. The sludge (6.25 tons Ha-1) was applied in two agricultural soils with different textures and crops. A microbiological (total coliforms, Escherichia coli, Staphylococcus aureus, Enterococcus sp., Pseudomonas sp., Salmonella sp. and total mesophylls) and physical-chemical characterization of the sludge, soils and irrigation water were carried out. The evolution of these parameters during sowing, growth and harvesting of crops was studied. Initially, sewage sludge had a higher concentration of microorganisms than soils. Irrigation water also contained microorganisms, fewer than sewage sludge amendment but not negligible. After amendment, there were no differences in the microbiological evolution in the two types of soil. In general, bacterial concentrations after crop harvest were lower than bacterial concentrations detected before sewage sludge amendment. Consequently, the application of sludge from water treatment processes did not worsen the microbiological quality of agricultural soil in this study at real conditions.

Influence of Composition on the Environmental Impact of a Cast Aluminum Alloy.

The influence of alloy composition on the environmental impact of the production of six aluminum casting alloys (Al Si12Cu1(Fe), Al Si5Mg, Al Si9Cu3Zn3Fe, Al Si10Mg(Fe), Al Si9Cu3(Fe)(Zn) and Al Si9) has been analyzed. In order to perform a more precise environmental impact calculation, Life Cycle Assessment (LCA) with ReCiPe Endpoint methodology has been used, with the EcoInvent v3 AlMg3 aluminum alloy dataset as a reference. This dataset has been updated with the material composition ranges of the mentioned alloys. The balanced, maximum and minimum environmental impact values have been obtained. In general, the overall impact of the studied aluminum alloys varies from 5.98 × 10-1 pts to 1.09 pts per kg, depending on the alloy composition. In the analysis of maximum and minimum environmental impact, the alloy that has the highest uncertainty is AlSi9Cu3(Fe)(Zn), with a range of ±9%. The elements that contribute the most to increase its impact are Copper and Tin. The environmental impact of a specific case, an LED luminaire housing made out of an Al Si12Cu1(Fe) cast alloy, has been studied, showing the importance of considering the composition. Significant differences with the standard datasets that are currently available in EcoInvent v3 have been found.

Study of the biodisintegration of a bioplastic material waste.

The aim of this work was to study the biodisintegration degree of different pieces made of a biodegradable thermoplastic material, the polylactic acid (PLA) with and without corn in its composition, is studied. The pieces of different shapes and thicknesses were obtained by both injection and extrusion processes, where also a specific foaming additive of polystyrene was added. The PLA and PLA-corn manufactured pieces were subjected to aerobic degradation at a constant temperature of 58+/-2 degrees C for 90 days, following EN 14806 and ISO 20200:2004 Norms. It was found that the pieces made of PLA and PLA with foaming agent had an average biodisintegration degree of 63.6%. With regard to the pieces made of PLA-corn, an average biodisintegration degree of 79.7% was obtained. In this case, the percentage of non degraded material was independent of the size, shape and thickness of the original pieces.

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.

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.