Teresa Cristina Brazil de Paiva

Combined zero-valent iron and fenton processes for the treatment of Brazilian TNT industry wastewater.

The environmental impact caused by the production of explosives made from nitroaromatic compounds such as 2,4,6-trinitrotoluene (TNT) is currently a major concern, mainly due to their toxic nature, a fact that makes these compounds highly harmful. This work evaluated a continual system treatment reactor (CSTR) consisting of column zero-valent iron and a system to promote a fenton reaction in order to create possible definitive routines for treating effluents originating from the TNT production process. The spectrophotometric results demonstrated that this combination of processes was highly efficient in promoting the removal of all the absorbed species at 290 nm and the visible region of the specter. The results also revealed that the combination of treatments was significantly efficient in terms of correcting the effluents main parameters of relevance, mainly COD (95.5% reduction) and TNT concentration, whose total was converted into nitrous and phenolic compounds and, additionally, the acute toxicity was also significantly reduced (95%). These results indicate that the strategy can serve as an efficient option for effluent treatment, for release into the receiving body, or eventually for use as industrial reuse water.

Characterization of wastewater from the Brazilian TNT industry

The objective of this work was to characterize the effluent originating from a Brazilian TNT production industry. Analyses were performed using physical, chemical, spectroscopic and ecotoxicological assays, which demonstrated that the effluent had a significant pollution potential, mainly due to the low pH and high concentration of TNT (156+/-10mgL(-1)). The results also demonstrated that the effluent presented significant acute toxicity, and could cause countless damages if released into the receiving body without being adequately treated first. The observed pollution potential justifies studies to evaluate treatment technologies or recover the residue generated in the TNT industry.

Optimization of Brazilian TNT industry wastewater treatment using combined zero-valent iron and fenton processes

This work explores the optimization of combined zero-valent iron and fenton processes for the treatment of TNT industry wastewater, a residue with recognized polluting potential due to its high concentration of 2,4,6-trinitrotoluene and extremely acidic pH due of the nature of the product purification process. The results of the optimization study indicate that the most efficient condition for reducing the concentration of TNT also generates sufficient amounts of iron(II)for the subsequent oxidative treatment through the Fenton reaction. In general, it was observed that the treatment was highly efficient in terms of meeting the main associated environmental parameters, since it reduced acute toxicity, removed 100% of TNT, 100% of the organic nitrogen and 95.4% of the COD.

Combined photocatalytic and fungal processes for the treatment of nitrocellulose industry wastewater.

The objective of this work was to characterize the delignification effluent originating from the delignification industry and evaluate the combination of the fungus and photocatalytic process (TiO(2)/UV system) for the treatment of this effluent. The delignification effluent has proven harmful to the environment because it presents high color (3516 CU), total phenol (876 mg/L) and TOC (1599 mg/L) and is also highly toxic even in a low concentration. The results of photocatalysis were 11%, 25% and 13% higher for reductions in color, total phenol and TOC, respectively. The combined treatments presented benefits when compared to the non-combined treatments. Fungus and photocatalysis in combination proved to be the best treatment, reducing the color, total phenol, toxicity (inhibition of Escherichia coli growth) and TOC by 94.2%, 92.6%, 4.9% and 62%, respectively.

Ecotoxicological evaluation of wastewater from 2.4.6-TNT production.

During the manufacture of explosives, large amounts of water are used to remove unwanted by-products generated. This water in turn, ends up in wastewater treatment plants or water bodies. The aim of this study was to evaluate the toxic potential of effluent generated by 2.4.6-Trinitrotoluene (TNT) production, yellow water, red water and mixture of yellow and red water, produced from a plant located in the Paraíba Valley, São Paolo state, Brazil. Daphnia similis, Danio rerio, Escherichia coli, Pseudomonas putida and Pseudokircheneriella subcaptata were used as test organisms. Physicochemical parameters such as color, pH, conductivity, total dissolved solids, dissolved oxygen, chemical oxygen demand (COD) and biochemical oxygen demand (BOD) were evaluated. Effluent from 2.4.6-TNT production was extremely toxic to all test organisms. The physicochemical parameters evaluated showed high levels of conductivity (from 41.533 to 42.344 μS /cm) and chemical oxygen demand (COD of 8471 to 27.364 mg/L) for the effluents analyzed.

Caracterização física, química e ecotoxicológica de efluente da indústria de fabricação de explosivos

The production and use of nitroaromatic explosives have resulted in their dissemination into the environment, where their presence in waterways and soil represents an ecological and health hazard. The hazardous characteristics of these compounds need to be carefully studied, so that the impact of their discharge on the environment can be better evaluated. This work presents the characterization of wastewater from Brazilian TNT industry using as analytical techniques mass spectroscopy, chromatography, toxicity assays and other physico-chemical analyses.

Ecotoxicological evaluation of waste water from nitrocellulose production

The present study evaluated the toxic potential and physicochemical characteristics of waste water generated in nitrocellulose production, including effluents from delignification, bleaching, nitration and mixture (composed of these three effluents), from a plant in the Paraiba Valley, São Paulo, Brazil. The test organisms used for toxicity assays were Daphnia similis, Danio rerio, Escherichia coli, Pseudomonas putida and Pseudokircheneriella subcaptata. The results showed that the effluents analyzed present acute and chronic toxicity for the organisms tested. Nitration effluent was the least toxic, while delignification and bleaching effluents were the most toxic. The naturally occurring pollutants in wood fiber and cotton, like lignin, probably contributed to effluents toxicity, in addition to higher concentrations of total dissolved solids, which are in non-compliance with Brazilian legislation, conductivity, chemical oxygen demand and color. The discharge of nitrocellulose effluent into an aquatic environment should only occur after appropriate treatment, due to their toxic characteristics.

Degradação de espécies nitroaromáticas e remediação de efluentes da indústria de explosivos, utilizando-se processos redutivos-oxidativos fundamentados no uso de ferro metálico

In this work the potentiality of reductive-oxidative processes based on zero-valent iron was studied aiming the degradation of nitroaromatic compounds and the remediation of residues from the explosive industry. The reductive process was applied as a continuous treatment system, using steel-wool as zero-valent iron source. The process permitted an almost total degradation of nitrobenzene, nitrophenol, nitrotoluene, dinitrotoluene and trinitrotoluene, probably with generation of the respective amine-derivative. The yellow-water residue, containing soluble trinitrotoluene, was notably modified by the reductive process, a fact that permitted a substantial enhancement of its biodegradability. Furthermore, the subsequent photo-Fenton process allowed TOC removal of about 80%.

Bisphenol risk in fish exposed to a contamination gradient: Triggering of spatial avoidance

Bisphenol A (BPA) is an emerging contaminant widely used in various industrial products. Sublethal toxicity of BPA on aquatic organisms is expected to occur at a concentration of around 500 μg L-1, which is much higher than environmentally realistic concentrations found in water bodies (up to 0.41 μg L-1). However, there is no information concerning how a BPA contamination gradient could affect the spatial displacement of organisms. We hypothesized that fish might be able to detect an environmentally realistic BPA contamination gradient and avoid potential toxic effects due to continuous exposure. Therefore, the objectives of this work were: (i) to determine if BPA could trigger an avoidance response in the freshwater fish Poecilia reticulata; (ii) to assess whether BPA-driven avoidance occurs at environmentally relevant concentrations; and (iii) to estimate the population immediate decline (PID) at the local scale, considering avoidance and mortality as endpoints. Avoidance experiments were performed in a seven-compartment non-forced exposure system, in which a BPA contamination gradient was simulated. The results indicated that BPA triggered avoidance in P. reticulata. In a traditional forced acute toxicity test, lethal effects in 50% of the population occurred at a BPA concentration of 1660 μg L-1, while in the non-forced system with a BPA concentration gradient, avoidance of 50% of the population occurred at a concentration four orders of magnitude lower (0.20 μg L-1). At environmentally relevant BPA concentrations, PID was mainly determined by the avoidance response. Avoidance in P. reticulata populations is expected to occur at BPA concentrations below those that cause sublethal effects on fish and are considered safe by international agencies (≤1 μg L-1). The approach used in the present study represents a valuable tool for use in environmental risk assessment strategies, providing a novel and ecologically relevant response that is complementary to traditional ecotoxicological tests.

Acute toxicity and ecotoxicological risk assessment of rice pesticides to Lithobates catesbeianus tadpoles

The objective of this study was to determine the acute toxicity of some pesticides used in irrigated rice farming to Lithobates catesbeianus tadpoles. The LC50-96h for commercial formulations containing bentazon, penoxsulam, vegetable oil, permethrin and carbofuran, separately and their mixtures, were determined at the proportions commonly used in the field. The limits of risk concentrations of these products for the studied species were also established. The LC50-96h for tadpoles was 4,530 mg L−1 for bentazon; 7.52 mg L−1 for penoxsulam + 145.66 mg L−1 of vegetable oil; 81.57 mg L−1 for vegetable oil; 0.10 mg L−1 for permethrin; 29.90 mg L−1 for carbofuran (active ingredients), and 38.79 times the dose used in the field for the mixture of these products. The environmental risk was determined only for permethrin, and care should be taken when using the vegetable oil.