Evaluation of biochemical and redox parameters in rats fed with corn grown in soil amended with urban sewage sludge

The increased production of urban sewage sludge requires alternative methods for final disposal. A very promising choice is the use of sewage sludge as a fertilizer in agriculture, since it is rich in organic matter, macro and micronutrients. However, urban sewage sludge may contain toxic substances that may cause deleterious effects on the biota, water and soil, and consequently on humans. There is a lack of studies evaluating how safe the consumption of food cultivated in soils containing urban sewage sludge is. Thus, the aim of this paper was to evaluate biochemical and redox parameters in rats fed with corn produced in a soil treated with urban sewage sludge for a long term. For these experiments, maize plants were grown in soil amended with sewage sludge (rates of 5, 10 and 20. t/ha) or not (control). Four different diets were prepared with the corn grains produced in the field experiment, and rats were fed with these diets for 1, 2, 4, 8 and 12 weeks. Biochemical parameters (glucose, total cholesterol and fractions, triglycerides, aspartate aminotransferase and alanine aminotransferase) as well the redox state biomarkers such as reduced glutathione (GSH), malondialdehyde (MDA), catalase, glutathione peroxidase and butyrylcholinesterase (BuChE) were assessed. Our results show no differences in the biomarkers over 1 or 2 weeks. However, at 4 weeks BuChE activity was inhibited in rats fed with corn grown in soil amended with sewage sludge (5, 10 and 20. t/ha), while MDA levels increased. Furthermore, prolonged exposure to corn cultivated in the highest amount per hectare of sewage sludge (8 and 12 weeks) was associated with an increase in MDA levels and a decrease in GSH levels, respectively. Our findings add new evidence of the risks of consuming food grown with urban sewage sludge. However, considering that the amount and type of toxic substances present in urban sewage sludge varies considerably among different sampling areas, further studies are needed to evaluate sludge samples collected from different sources and/or undergoing different types of treatment. © 2013 Elsevier Inc.

Uso do poli (tereftalato de etileno) no pós-tratamento de água para a remoção de fármacos residuais

Pós-graduação em Engenharia Civil - FEIS

Induction of suppressiveness to Fusarium wilt of chrysanthemum with composted sewage sludge

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Kinetic study of the co-firing of bagasse-sludge blends

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

CHEMICAL CHANGES AND ZINC PHYTOAVAILABILITY IN SEWAGE SLUDGE-AMENDED SOIL ESTIMATED BY THE ISOTOPIC METHOD

CHEMICAL CHANGES AND ZINC PHYTOAVAILABILITY IN SEWAGE SLUDGE-AMENDED SOIL ESTIMATED BY THE ISOTOPIC METHOD. Zn availability in Red Latossol (Rhodic Ferralsol) of different pH amended with different rates of sewage sludge was studied by the isotopic Zn-65 L value method. Soil chemical properties were found to be altered by SS addition. Zn concentration and Zn derived from SS (ZnpfSS) in plant, and Zn phytoavailability (L value), were increased with increasing SS rates. The linear correlation coefficient of plant Zn with SS rates and with L value was significant at 1% probability. The L value proved an efficient method for predicting Zn phytoavailability in sewage sludge-amended soil with different pH under the soil conditions studied.

Sewage sludge does not induce genotoxicity and carcinogenesis

Through a series of experiments, the genotoxic/mutagenic and carcinogenic potential of sewage sludge was assessed. Male Wistar rats were randomly assigned to four groups: Group 1 - negative control; Group 2 - liver carcinogenesis initiated by diethylnitrosamine (DEN; 200 mg/kg i.p.); Group 3 and G4-liver carcinogenesis initiated by DEN and fed 10,000 ppm or 50,000 ppm of sewage sludge. The animals were submitted to a 70% partial hepatectomy at the 3rd week. Livers were processed for routine histological analysis and immunohistochemistry, in order to detect glutathione S-transferase positive altered hepatocyte foci (GST-P+ AHF). Peripheral blood samples for the comet assay were obtained from the periorbital plexus immediately prior to sacrificing. Polychromatic erythrocytes (PCEs) were analyzed in femoral bone-marrow smears, and the frequencies of those micronucleated (MNPCEs) registered. There was no sewage-sludge-induced increase in frequency of either DNA damage in peripheral blood leucocytes, or MNPCEs in the femoral bone marrow. Also, there was no increase in the levels of DNA damage, in the frequency of MNPCEs, and in the development of GST-P AHF when compared with the respective control group.

NUTRITIONAL BALANCE, ESSENTIAL OIL AND WOOD PRODUCTION FROM Corymbia citriodora Hill & Johnson WITH SEWAGE SLUDGE AND MINERAL FERTILIZER APPLICATIONS

The Corymbia citriodora is one of the most important forest species in Brazil and the reason is the diversity of its use, because it produces good quality wood and the leaves may be used for essential oil production. Although, there are not many studies about species and the handling effect in the nutritional balance. This study aimed to evaluate the biomass production and nutrient balance in the conventional production of essential oil and wood of Corymbia citriodora with sewage sludge application. The experiment design established was the randomized blocks, with four replicates and two treatments: 1 - fertilization with 10 tons ha(-1) (dry mass) of sewage sludge, supplemented with K and B, and 2 - mineral fertilization. It was evaluated the aerial biomass production, the nutrient export of the leaves, the essential oil and wood production at four years old. The trees that received application of sewage sludge produced 20 % more leaves biomass than the trees with mineral fertilization, resulting in larger oil production. Besides, the trees with sewage sludge application produced 14.2 tons ha(-1) yr(-1) of woody biomass that was 27 % higher than the treatment with mineral fertilization. For both treatments the N balance was negative, but treatment with sewage sludge application (-45 kg ha(-1)) was four times lower than the observed on mineral fertilization treatment (-185 kg ha(-1)). It may be concluded in this paper that the application of sewage sludge benefits the production of leaves biomass, essential oil and wood, besides result better nutritional balance of the Corymbia citriodora production system.

Growth and nitrogen fixation in soybean treated with doses of composted sewage sludge

The use of sewage sludge is a highly promising practice for the development of sustainable agricultural systems. The objective of this study was to evaluate doses of sewage sludge composted with and without Rhizobium inoculation in leaf N content, nodule number, nodule dry weight and plant during flowering. The experiment was conducted in the greenhouse of the Department of Soil Science and Natural Resources College of Agricultural Sciences of Botucatu, using as substrate used in vessels of 30 liters a Red Yelow Latosol sandy texture with experimental design adopted was randomized blocks constituted for 10 treatments and five doses of composted sewage sludge (0, 10, 20, 30, 40 t ha(-1)) with or without inoculation Bradyrhizobium japonic with three replications. There was an increase in the number and dry weight of nodules and shoot dry mass of soybeans due to the increase of the dose of sludge up to a dose of 20 t ha(-1) and after this dose there was a decrease of these parameters. At a dose of 10 t ha(-1) sludge compost inoculated seeds showed higher for foliar concentrations of N and number of nodules compared with uninoculated seeds. At a dose of 30 t ha(-1) inoculated seeds were higher compared to uninoculated in all parameters.

A potential application of sludge-based catalysts for the anaerobic bio-decolorization of tartrazine dye.

Two highly efficient (K2CO3/sludge carbon and ZnCl2/sludge carbon) solids were prepared by chemical addition following carbonization at 800 °C and were tested for anaerobic reduction of tartrazine dye in a continuous upflow packed-bed biological reactor, and their performance was compared to that of commercial activated carbon (CAC). The chemical and structural information of the solids was subjected to various characterizations in order to understand the mechanism for anaerobic decolorization, and efficiency for SBCZN800 and SBCPC800 materials was 87% and 74%, respectively, at a short space time (τ) of 2.0 min. A first-order kinetic model fitted the experimental points and kinetic constants of 0.40, 0.92 and 1.46 min(-1) were obtained for SBCZN800, SBCPC800 and CAC, respectively. The experimental results revealed that performance of solids in the anaerobic reduction of tartrazine dye can depend on several factors including chemical agents, carbonization, microbial population, chemical groups and surface chemistry. The Langmuir and Freundlich models are successfully described in the batch adsorption data. Based on these observations, a cost-effective sludge-based catalyst can be produced from harmful sewage sludge for the treatment of industrial effluents.

Behaviour of dolomite, olivine and alumina as primary catalysts in air-steam gasification of sewage sludge

Sewage sludge gasification assays were performed in an atmospheric fluidised bed reactor using air and air–steam mixtures as the gasifying agents. Dolomite, olivine and alumina are three well known tar removal catalysts used in biomass gasification processing. However, little information is available regarding their performance in sewage sludge gasification. The aim of the current study was to learn about the influence of these three catalysts in the product distribution and tar production during sewage sludge gasification. To this end, a set of assays was performed in which the temperature (750–850 °C), the in-bed catalyst content (0, 10 and 15 wt.%) and the steam–biomass ratio (SB) in the range of 0–1 were varied with a constant equivalence ratio (ER) of 0.3. The results were compared to the results from gasification without a catalyst. We show that dolomite has the highest activity in tar elimination, followed by alumina and olivine. In addition to improving tar removal, the presence of water vapour and the catalysts increased the content of H2 in the gases by nearly 60%.

Sewage sludge gasification. Dolomite performance under different operating conditions

Gasification is a technology that can replace traditional management alternatives used up to date to deal with this waste (landfilling, composting and incineration) and which fulfils the social, environmental and legislative requirements. The main products of sewage sludge gasification are permanent gases (useful to generate energy or to be used as raw material in chemical synthesis processes), liquids (tars) and char. One of the main problems to be solved in gasification is tar production. Tars are organic impurities which can condense at relatively high temperatures making impossible to use the produced gases for most applications. This work deals with the effect of some primary tar removal processes (performed inside the gasifier) on sewage sludge gasification products. For this purpose, analysis of the gas composition, tar production, cold gas efficiency and carbon conversion were carried out. The tests were performed with air in a laboratory scale plant consisting mainly of a bubbling bed gasifier. No catalyzed and catalyzed (10% wt of dolomite in the bed and in the feeding) tests were carried out at different temperatures (750ºC, 800ºC and 850ºC) in order to know the effect of these parameters in the gasification products. As far as tars were concerned, qualitative and quantitative tar composition was determined. In all tests the Equivalence Ratio (ER) was kept at 0.3. Temperature is one of the most influential variables in sewage sludge gasification. Higher temperatures favoured hydrogen and CO production while CO2 content decreased, which might be partially explained by the effect of the cracking, Boudouard and CO2 reforming reactions. At 850ºC, cold gas efficiency and carbon conversion reached 49% and 76%, respectively. The presence of dolomite as catalyst increased the production of H2 reaching contents of 15.5% by volume at 850 °C. Similar behaviour was found for CO whereas CO2 and CnHm (light hydrocarbons) production decreased. In the presence of dolomite, a tar reduction of up to 51% was reached in comparison with no catalyzed tests, as well as improvements on cold gas efficiency and carbon conversion. Several assays were developed in order to test catalyst performance under more rough gasification conditions. For this purpose, the throughput value (TR), defined as kg sludge “as received” fed to the gasifier per hour and per m2 of cross sectional area of the gasifier, was modified. Specifically, the TR values used were 110 (reference value), 215 and 322 kg/h·m2. When TR increased, the H2, CO and CH4 production decreased while the CO2 and the CnHm production increased. Tar production increased drastically with TR during no catalysed tests what is related to the lower residence time of the gas inside the reactor. Nevertheless, even at TR=322 kg/h·m2, tar production decreased by nearly 50% with in-bed use of dolomite in comparison with no catalyzed assays under the same operating conditions. Regarding relative tar composition, there was an increase in benzene and naphthalene content when temperature increased while the content of the rest of compounds decreased. The dolomite seemed to be effective all over the range of molecular weight studied showing tar removal efficiencies between 35-55% in most cases. High values of the TR caused a significant increase in tar production but a slight effect on tar composition.

Characterization of spontaneous combustuion tendency of dried sewage sludge

The general purpose of this study was the determination of the safety conditions to avoid the presence of explosive atmospheres in the wastewater industry. Eight Spanish plants located in Madrid, Barcelona and Málaga were considered and several sludge samples were taken in different seasons. The base for the assessment of the spontaneous ignition behaviour of dust accumulations is the experimental determination of the self-ignition temperature under isothermal conditions. Self-ignition temperatures at four volumes were obtained for one sample of sewage sludge, allowing their extrapolation to large storage facilities. A simple test method, based also on an isothermal study of samples, is the UN classification of substances liable to spontaneous combustion. Two different samples were so tested, obtaining unlike results if transported in packages of different volumes. By means of thermogravimetric techniques it is possible to analyse the thermal susceptibility of dried sewage sludge. Apparent activation energy can be obtained from the rate of weight loss. It is also applied to the study of self-ignition susceptibility by modifying test conditions when oxygen stream is introduced. As a consequence of this oxidant contribution, sample behaviour can be very different during testing and a step drop or sudden loss of weight is observed at a characteristic temperature for every substance, associated to a rapid combustion. Plotting both the activation energy and the characteristic temperature, a map of self-ignition risk was obtained for 10 samples, showing different risk levels for samples taken in different locations and at different seasons. A prediction of the self-ignition risk level can be also determined.

Flammability properties of thermally dried sewage sludge

The treatment and disposal of sewage sludge is becoming an urgent need whereby different technologies were developed and integrated into the waste cycle all over the world. One of the most used technologies is the thermal drying of the sludge. Thermally dried sewage sludge has interesting properties that allow its use as an alternative fuel, but also needs some consideration from the point of view of its safe operation. The aim of this study was the research on the flammability properties of sewage sludge, including ignition sensitivity, explosion severity, thermal sensitivity and thermal stability. Furthermore relationships among those properties and composition parameters have been determined, added to the study of their variation depending on their origin or season. Finally, properties related to spontaneous combustion were determined. To study these relationships and characteristics sludge samples were selected from different locations in Spain and taken during different seasons.

Peri-conceptional changes in maternal exposure to sewage sludge chemicals disturbs fetal thyroid gland development in sheep

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