Dissertations / Theses on the topic 'Tannery effluents'

The considerable volume of chromium-bearing wastes generated during the process of leather tanning, exacerbated by the potential for trivalent chromium in the wastes to be oxidised to the toxic hexavalent state, has created a major waste disposal dilemma for the tanning industry. While methods are available for the safe and effective treatment of residual chrome-tanning liquors, little has been done to address the issue of the chrome-bearing solid wastes. Given the increasingly stringent environmental compliance standards facing tanneries, unless an appropriate treatment process is developed in the immediate future, the continued use of chromium as a tanning agent could be compromised. Recent investigations have demonstrated the potential of heated alkaline conditions for dechroming these solid wastes. This study expanded upon these considerations and examined the feasibility of utilising the highly alkaline tannery waste effluents as cost-effective, substitute alkaline media. The three effluents considered in this study, classed as lime sulphide liquors, were shown to be capable of dechroming wet blue shavings, with resultant separation of the solid wastes into a protein and a concentrated chromium product. The solubilised protein product contained low chromium concentrations which comply with legal discharge limits. The precipitated chromium product offers opportunity for reutilisation in the tannery. A novel industrial-scale treatment process, based on these investigations, indicated the process to be capable of treating the quantity of shavings produced on a daily basis by a medium to large scale tannery. Application of this method for the dechroming of other chrome-tanned solid wastes was also shown to be feasible.

The problems of waste disposal in the tanning industry are unique in that the effluents are highly saline, have a high organic loading and contain heavy metals. Methods are available for the safe treatment and disposal of the latter two components, but the saline component requires the expensive outlay of evaporation ponds. This study has identified a possible use for the saline effluents, turning a problematic waste product into a potentially valuable by-product. A range of tannery effluents were identified and tested for their suitability for the mass cultivation of Dunaliella salina (bardawil strain). The bardawil strain was preferred over a local isolate because of its higher production of β-carotene. Ponded tannery effluents and combined processes effluent proved unsuitable for realistic propagation of the alga. Anaerobic digestion of combined processes effluent did not improve its suitability significantly. Anaerobic digestion of hide-soak effluent may remove persistent antimicrobial agents which influence algal growth, but its contribution to enhancing algal growth is equivocal. Undigested hide-soak effluent lacking in persistent antimicrobial agents was found to be an ideal culture medium, as no additional nutrients needed to be added. Significantly higher biomass was obtained in this effluent compared to chemically defined media. Induction of β-carotene was achieved in nitrogen-deficient defined media after culture in tannery effluent. This suggests that a two-stage system using hide-soak effluent for cell propagation and nitrogen deficient media for β-carotene induction, could be possible for the mass cultivation of D. salina for β-carotene production.

Chromium and other heavy metals are known to cause issues related to human and environmental health when they occur in high concentrations in ecosystems. Chromium poses a particularly large threat if it occurs in its hexavalent form, Cr(VI), as it is highly reactive and carcinogenic. The aim of this project was to investigate the wastewater emitted from a tannery in Liwonde, Malawi, with respect to the metals Cr, Al, Cd, Cu, Fe, Mn, Pb and Zn, and to reduce the concentrations using locally available materials. A particular emphasis was put on chromium.   Wastewater collected from the tannery was analysed to determine the total and dissolved concentrations of the metals using a Microwave Plasma-Atomic Emission Spectrometer (MP-AES). The wastewater was then mixed with various dosages of peeled and unpeeled Moringa Oleifera seed powder as well as pure Moringa Oleifera shell powder and sand collected from river Shire. Thereafter, the remaining concentrations of metals were analysed. Additional analyses of various contact times were performed for the removal agent that had shown the best results.     The analyses showed a total chromium concentration of 2.25 ppm and a dissolved chromium concentration of 0.251 ppm in the wastewater discharged from the tannery. Both concentrations were lower than what had initially been expected but still above both the WHO guideline value for chromium in drinking water and the Swedish threshold value for chromium in industrial wastewater (0.05 ppm). No other metals were found in concentrations above trace levels. All of the investigated removal agents, except for pure shell powder, showed positive results for chromium removal. The highest removal observed for dissolved chromium was 72 % and occurred with a removal agent mixture of 5.0 g of river sand and 2.0 g of unpeeled Moringa Oleifera seed powder to 100 mL of wastewater. The reduction of total chromium was 97 % for the same removal agent mixture. However, lower dosages of the removal agents also gave a chromium removal of similar size. Due to resource limitations, no analysis of whether the wastewater contained Cr(III) and Cr(VI) could be performed.   Considering the low initial concentrations of metals emitted from the tannery, there is no urgent need for further treatment of the wastewater. This study has however substantiated the theory that Moringa Oleifera seeds can be used as a low-cost chromium remediation agent in wastewater, a result that can be of use to improve the water quality in other industries and applications.
Det har länge varit känt att krom och andra tungmetaller kan orsaka hälso- och miljöproblem när de förekommer i höga koncentrationer i ekosystem. Krom utgör ett särskilt stort hot om det förekommer i sin sexvärda form, Cr(VI), eftersom det är mycket reaktivt och cancerogent. Syftet med detta projekt var att undersöka avloppsvattnet från ett garveri i Liwonde, Malawi, med avseende på metallerna Cr, Al, Cd, Cu, Fe, Mn, Pb och Zn, samt att minska koncentrationerna med hjälp av lokalt tillgängliga material. En särskilt tonvikt lades på krom.   Avloppsvatten som inhämtats från garveriet analyserades med hjälp av en mikrovågsplasma-atomemissionsspektrometer (MP-AES) för bestämning av total samt löst koncentration av metallerna. Avloppsvattnet blandades sedan med olika doser av pulver från skalade och oskalade Moringa Oleifera-frön, liksom med pulver från skal av Moringa Oleifera-frön och sand från Shire-floden. Därefter analyserades proverna med avseende på återstående metallkoncentrationer. Ytterligare undersökningar genomfördes med olika kontakttider för det inbindningsmedel som visat bäst resultat.   Analyserna visade en total kromkoncentration på 2,25 ppm och en löst kromkoncentration på 0,251 ppm i det avloppsvatten som släpptes ut från garveriet. Båda koncentrationerna var lägre än vad som ursprungligen hade förväntats, men ändå över både WHOs riktlinjer för krom i dricksvatten och det svenska gränsvärdet för krom i industriellt avloppsvatten (0,05 ppm). Inga andra metaller påvisades i betydande koncentrationer. Alla undersökta inbindningsmedel, med undantag av Moringa Oleifera-skal, visade positiva resultat för kromrening. Den största observerade reningen för löst krom var  72 %, och uppmättes för en blandning av 5,0 g sand och 2,0 g pulver av oskalade Moringa Oleifera-frön till 100 mL avloppsvatten. Reduktionen av totalt krom var 97 % för samma blandning. Även lägre doser gav dock en nästan lika hög reningsgrad. På grund av resursbegränsningar kunde ingen analys av huruvida avloppsvattnet innehöll Cr(III) eller Cr(VI) genomföras.   Då avloppsvattnet från garveriet endast innehöll låga koncentrationer av metaller finns inget akut behov av ytterligare rening. Denna studie har dock styrkt tesen att Moringa Oleifera-frön kan användas som ett lågkostnadsalternativ för rening av krom i avloppsvatten. Detta resultat kan vara användbart för att förbättra vattenkvaliteten vid andra industrier och tillämpningar.

L’électrocoagulation est une technique de traitement des eaux usées basée sur la dissolution d’anode sacrificielle de fer ou d’aluminium. Ces métaux se dissolvent sous formes de cations Fe2+ puis Fe3+ et Al3+ qui vont former des hydroxydes de métal qui entraînent par adsorption les impuretés de l’effluent en diminuant le potentiel Zêta de ces impuretés. Le réacteur électrochimique utilisé est constitué de deux électrodes métalliques (Fe ou Al) planes et parallèles qui laissent passer entre elles l’effluent à traiter. Des densités de courant de 50 à 200 A/m2 ont été appliquées pour traiter les trois effluents. L’un est un effluent directement issu d’une usine textile (effluent « usine »). Un second provient du flux d’entrée de la station d’épuration du site qui collecte les effluents de plusieurs usines (effluent « station »). Le troisième est un effluent artificiel de tannerie, créé en ajoutant 200 ppm de chrome VI à l’effluent « station ». Pour chaque expérience, la densité de courant et le temps de traitement vont déterminer la charge électrique et la concentration en métal dissous atteinte. L’influence de ces quatre paramètres sur l’élimination de la DCO, de l’absorbance, de la turbidité, du COT et du chrome hexavalent a été étudiée. L’évolution au cours du temps d’autres paramètres de l’EC tels que le pH, la tension, le rendement faradique et la dissolution métallique ont été étudiés afin de comprendre leur rôle dans le procédé. Le traitement a permis d’avoir un abattement maximal de DCO de 82% et 80% pour l’effluent « station » traité respectivement avec les électrodes de fer et d’aluminium ; 75 et 67% pour l’effluent « usine » traité respectivement avec les électrodes de fer et d’aluminium. L’abattement du chrome est de 100% avec les électrodes de fer mais tombe à 70% avec celles en aluminium. Des modèles d’élimination de la DCO et de l’absorbance ont été établis pour chaque matériau d’électrode utilisé. Le modèle d’élimination du chrome VI a été établi à partir du traitement avec les électrodes de fer. Une étude de la spéciation des espèces a permis de déterminer les pH optimaux de coagulation-floculation pour chaque métal impliqué (Al, Fe, Cr). La compétitivité entre l’abattement de la pollution organique et du Chrome a aussi été étudiée pour chaque type d’électrode
Electrocoagulation (EC) is a water treatment technology that relies on the electrochemical sacrificial anodes (in Fe or Al) dissolution. This metal dissolve themselves in Al3+ and Fe2+ cations that later oxidise to Fe3+ ions. These cations form metal hydroxides that adsorb the impurities of the effluent while decreasing the zeta potential. The electrochemical reactor used consists on two plane parallel metal electrodes with recirculation of the effluent to be treated between them. Current densities from 50 to 200 A/m2 were imposed to treat each effluent. Three effluents were used in this study. The first one is an effluent sampled at the outlet of a textile plant (« plant »). The second one is a mixture of several effluents coming from different plant and collected at the inlet of the wastewater treatment (« treatment plant »). The last one is a wastewater tannery plant simulated by addition of 200 ppm Chromium VI in the treatment plant effluent. For each experience the current density and the time of treatment rule the electrical charge and the concentration in dissolved metal reached. The influence of these four parameters on the elimination of COD, absorbance, turbidity, COT and hexavalent chromium content has been studied. Parameters e.g. potential, faradic yield, metal dissolution and pH have also been continuously monitored to better understand their role on EC process. The results show that DCO abatement reached 80 and 82% for treatment plant effluent, respectively with iron and aluminium electrodes; and 75 and 67% for plant effluent, respectively with iron and aluminium electrodes. The chromium treatment yields 100 % abatement with Fe electrodes whereas it is only 70% using Al electrodes. Models have been developed for COD and absorbance removal for the two electrode materials. Model for chromium (VI) treatment has been established considering all reactions occurring for iron EC. Metal speciation study allowed us to determine the optimal pH of coagulation –flocculation for each metal involved in the treatment (Al, Fe, Cr). Competition between organic pollution removal and chromium elimination has been also investigated for each electrode material

Content: Wastewater from tanneries besides having toxic compounds also contain nutrients such as carbon, phosphorus, and nitrogen, which facilitate the rapid multiplication of microalgae. Currently, many types of researches search microalgae capable of growing in industrial effluents, exploiting the advantages of removing the nutrients present in these waters and producing biomass with high value- added. The liquid effluents produced in tanneries for finished leather have essential nutrients for the growth of microalgae, but also some compounds that may restrict or hinder the growth of microalgae in this medium. Therefore, the present work has the objective to evaluate the growth of a microalgae consortium (collected in a wastewater treatment plant of a beamhouse tannery) for the removal of phosphorus and ammonia from wastewater streams of a tannery (processing wet-blue to finished leather) with different photoperiods. Microalgae consortium was cultivated at two different compositions of mixtures of raw wastewater (R) and wastewater after secondary biological treatment (B): 50% of R + 50% of B, (50R50B) and 75% of R + 25% of B, (75R25B), in photoperiod of 24 hours and 12 hours of light, temperature of 25 °C and constant aeration. The growth of microalgae in the effluent and the removal of phosphorus and ammonia were monitored throughout the cultivation. The microalgae consortium presented maximum biomass concentrations in the 75R25B effluent (1.40 g L-1) and phosphorus removal (97.64% for the 50R50B and 95.54% for the 75R25B) effluent and ammonia removal (100%) for both effluent with 24-hour photoperiod light. Take-Away: In this study, it was found that the microalgae consortium can survive in wastewater from tanneries (processing wet-blue to finished leather) and exhibit removals of phosphorus and ammonia from the medium. The 24-hour light photoperiod presented better microalgae growth and nutrient removal results.

Content: Sustainable tannery effluent treatment system in achieving required discharge standards including Total Dissolved Solids (TDS) is one of the major challenges faced by the World Leather Industry. Conventional treatment system reduces Biochemical Oxygen Demand (BOD), Chemical Oxygen Demand (COD), Suspended Solids (SS), heavy metals etc. and not the TDS and salinity. To achieve the TDS level, the tanneries in South India were forced to adopt Zero Liquid Discharge (ZLD) system by incorporating Reverse Osmosis (RO) system and Multiple Effect Evaporator (MEE). Though recovery of water is beneficial to certain extend in adopting ZLD system, the major challenges are high energy consumption, huge operation & maintenance cost and no safe disposal method for large quantity of mixed/contaminated salt generated from MEE. In view of the challenges faced in adoption of ZLD system, sustainable major technological developments have been made to control more than 50% of TDS in the effluent by adopting cleaner tanning process, segregation of saline streams, treatment and recovery of chromium and salt for reuse by the member units. The balance composited waste stream with low TDS is further treated and taken for mixing/dilution with treated domestic sewage to achieve all discharge standards including TDS. This development is being implemented in many tannery clusters in India such as Pallavaram in South India and Jajmau, Unnao, Banthar, etc. in North India. The Common Effluent Treatment Plants (CETPs) are being upgraded with financial support from Govt. of India and respective State Governments. Take-Away: Improved Chrome Recovery System for Reuse, Recovery of Salt from Saline Stream and Reuse, Sustainable TDS Management

Nitrification realisable simultanement a l'epuration carbonee par le procede des boues activees. Une etude sur pilote a permis, en s'appuyant sur les caracteristiques de cette microflore nitrifiante, de degager des consignes de gestion et de dimensionnement pour que la nitrification soit possible

Os efluentes líquidos de curtumes apresentam altas cargas orgânicas e de poluentes que devem ser tratados corretamente para atingir os padrões legais para seu descarte, evitando a eutrofização de corpos hídricos e poluição das águas. O acabamento do couro é o estágio final da produção, onde o couro recebe as características desejadas de acordo com os produtos e artigos que serão produzidos. Os efluentes das etapas de processamento para acabamento do couro são responsáveis por conterem poluentes químicos devido ao uso de corantes, surfactantes, metais tóxicos, agentes emulsificantes, recurtentes, óleos, pigmentos, resinas, entre outros produtos químicos adicionados. As microalgas têm sido alvo de vários estudos no âmbito de tratamento de efluentes, devido à sua capacidade de remover diversos nutrientes, matéria orgânica do meio e por serem formas mais limpas e econômicas de tratar os poluentes. Diante disto, o objetivo deste trabalho foi avaliar o emprego de um consórcio de microalgas para tratamento de efluentes de um curtume e analisar a capacidade de remoção de poluentes que são nutrientes para estes microrganismos. Os efluentes foram caracterizados ao longo dos ensaios com o consórcio de microalgas por meio de Nitrogênio Total (NT), Amônia (NH3), Fósforo (P-PO4), Carbono total (CT), Carbono Orgânico Total (COT), Carbono inorgânico (CI), DQO e Demanda Biológica de Oxigênio (DBO) e foi acompanhado o crescimento das microalgas. Para os experimentos foram coletados efluentes em três estágios distintos em uma estação de tratamento: efluente bruto (B), efluente após tratamento primário de coagulação/floculação (P) e efluente após ao tratamento biológico secundário (S). Os resultados com concentração de efluente de 50%, diluídos em água destilada (A), após 16 dias de cultivo, mostraram que houve crescimento do consórcio nos três efluentes com um crescimento máximo de 1,77 g L-1 no efluente Bruto (50B50A). Na sequência, foi testado o cultivo em efluente bruto (100B) e em efluentes compostos nas seguintes proporções: 50% efluente bruto + 50% efluente após tratamento biológico (50B50S) e 25% efluente bruto + 75% efluente após tratamento biológico (25B75S). Foi possível cultivar o consórcio no efluente bruto sem diluição, entretanto os resultados foram ruins, pois o mesmo apresentou baixo crescimento e, consequentemente, baixos níveis de remoção de nutrientes. Com o efluente composto 25B75S percebeu-se morte rápida das microalgas, uma vez que o efluente apresentava baixas concentrações de nutrientes. Em contrapartida, no efluente 50B50S foram atingidos valores efetivos de crescimento e remoção de nutrientes. Em cultivos fotoautotrófico, mixotrófico e heterotrófico de efluente composto 50B50S e de 75% efluente bruto + 25% efluente após tratamento biológico (75B25S), os melhores resultados foram atingidos no efluente 75B25S no cultivo fotoautotrófico, crescendo até 1,42 g L-1 e atingindo valores de remoção de NNH3, Nitrogênio Total (NT), DQO, carbono orgânico total (TOC) e demanda biológica de oxigênio (DBO5), de 99,90%, 74,89%, 56,70%, 58,18% e 20,68%, respectivamente. Ao obter a microalga isolada Tetraselmis sp. predominante no consórcio foi analisado os parâmetros anteriores em cultivo fotoautotrófico, além disso foi verificada a quantidade de lipídio presente na biomassa. A microalga Tetraselmis sp. apresentou um crescimento notório no cultivo fotoautotrófico com remoções eficientes dos parâmetros e 5,0% de lipídio no peso seco.
Liquid effluents from tanneries present high organic and pollutant loads and must be treated correctly to meet the legal standards for effluent disposal and to avoid eutrophication of water bodies and water pollution. The leather finish is the final stage of production, where the leather receives the desired characteristics according to leather goods and articles. The effluents from the processing steps for leather finishing are responsible for containing chemical pollutants due to the use of dyes, surfactants, toxic metals, emulsifying agents, retanning agents, oils, pigments, resins, among other chemicals added. Microalgae have been the subject of several studies in the field of effluent treatment due to their ability to remove various nutrients, organic matter from the environment and to be cleaner and more economical ways to treat pollutants. In this work, the growth of a microalgae consortium for the treatment of effluents from a tannery was analyzed and the capacity of removal of Total Nitrogen (NT), Ammonia (NH3), Phosphorus (P-PO4), Total Carbon ), Total Organic Carbon (COD), COD and Biological Oxygen Demand (DBO), as well as the growth of microalgae biomass in these effluents. The effluents were characterized before and after the trials with the microalgae consortium. Effluents were collected in three distinct stages at a treatment plant: crude effluent (B), effluent after primary coagulation / flocculation (P) treatment and effluent after secondary biological treatment (S). The results with 50% effluent concentration, diluted in distilled water (A) after 16 days of cultivation, showed that there was a consortium growth in the three effluents with a maximum growth of 1.77 g L-1 in the crude effluent (50P50A). (50B50S) and 25% crude effluent + 75% effluent after biological treatment (25B75S) were tested in the following proportions: 50% crude effluent + 50% effluent after biological treatment (50B50S). It was not possible to cultivate the consortium in pure crude effluent, since it presented low growth and, consequently, low levels of nutrient removal. With the compound effluent 25B75S it was observed rapid death of the microalgae, since the effluent presented low concentrations of nutrients. On the other hand, in the effluent 50B50S, effective values of growth and nutrient removal were achieved. In photoautotrophic, mixotrophic and heterotrophic cultures of 50B50S effluent and 75% crude effluent + 25% effluent after biological treatment (75B25S), the best results were reached in the effluent 75B25S in photoautotrophic cultivation, growing up to 1.42 g L-1 and reaching values of removal of N-NH3, total nitrogen (NT), (DQO), total organic carbon (COT) and biological oxygen demand (DBO), of 99.90%, 74.89%, 56.70%, 58.18% and 20.68%, respectively. By obtaining the isolated microalgae Tetraselmis sp., predominant in the consortium and analyzed and the previous parameters in photoautotrophic cultivation, in addition to being verified the amount of lipid present in the biomass. The microalgae Tetraselmis sp. showed a notable growth in photoautotrophic cultivation with efficient removal of the parameters and 5.0% of lipid in dry weight.

FundaÃÃo de Amparo à Pesquisa do Estado do CearÃ
A dissertaÃÃo teve como objetivo analisar a estabilidade e eficiÃncia do processo anaerÃbio de reduÃÃo de sulfato aplicado ao tratamento de efluente de um curtume. Utilizaram-se dois reatores anaerÃbios de manta de lodo e fluxo ascendente (UASB-Upflow Anaerobic Sludge Blanket), com capacidade de 3,0 litros, temperatura constante de 29+2ÂC e tempo de detenÃÃo hidrÃulica de 12 e 24 horas. Os reatores operaram com afluente sintÃtico e em seguida com afluente real. Inicialmente, com afluente sintÃtico, foram estudadas as relaÃÃes de DQO/SO4-2 de 1,4; 0,8 e 0,5. Os resultados obtidos demonstraram que a relaÃÃo DQO/SO4-2 de 0,8 apresentou a melhor eficiÃncia na remoÃÃo de DQO (87,8%) e remoÃÃo de sulfato (38,7%). Em seguida, o reator foi alimentado com afluente real e as remoÃÃes de DQO variaram de 20,4 a 58,5% e Sulfato de 39,4 a 73,9%, nas diferentes fases deste estudo. O sulfeto formado dentro do reator foi responsÃvel pela remoÃÃo de 39,7 a 77,6% do cromo presente no afluente real. Em todos os ensaios o reator apresentou estabilidade na produÃÃo de alcalinidade total e a concentraÃÃo de Ãcidos graxos volÃteis se manteve em nÃveis adequados. Os resultados obtidos permitiram concluir que a utilizaÃÃo do processo de reduÃÃo de sulfato em reatores UASB apresenta-se como a alternativa promissora ao prÃ-tratamento de efluentes de curtume, visando a atender os limites de lanÃamento impostos pelos ÃrgÃos ambientais.
The research aimed to analyze the stability and efficiency of the anaerobic sulfate reduction applied to the treatment of effluent from a tannery. It was used two anaerobic reactors upflow anaerobic sludge blanket (UASB), with capacity of 3.0 liters, constant temperature of 29 + 2ÂC and hydraulic detention times of 12 and 24 hours. The reactors were operated with synthetic influent and then with real influent. First, synthetic influent was studied using DQO/SO4-2 ratio of 1.4, 0.8 and 0.5. The results showed that DQO/SO4-2 ratio of 0.8 showed the best removal efficiency of COD (87,8%) and removal of sulfate (38,7%). After, the reactor was fed with real influent and removals of COD ranged from 20.4 to 58.5% and removal of sulfate from 39.4 to 73.9% in the different phases of this study. The sulfide formed inside the reactor helped remove chromium present in the real influent from 39.7 to 77.6%. In all experiments the reactor was stable in the production of alkalinity and total volatile fatty acid concentration was maintained at adequate levels. The results showed that the use of the process of sulfate reduction in UASB reactors is presented as a promising alternative to pretreat effluents from tannery, to meet the release limits imposed by environmental agencies.

This study investigated the application of advanced oxidative processes for the homogeneous and heterogeneous degradation of a tanning effluent. The catalytic activity of a solid oxide containing manganese was evaluated in the heterogeneous systems. The experiments were performed in a photocatalytic batch reactor in laboratory scale. The solid used was the commercial product Birm®, consisting mainly of crystalline silica, silicate, aluminum and manganese dioxide. The adsorption results using Birm® in synthetic sewage adjusted to the models of Langmuir and Freundlich and established that the adsorption capacity of the Birm ® is low. The synthetic and real tannery effluents were assessed by the degradation kinetics of photochemical homogeneous (H2O2/UV) processes and heterogeneous (UV/H2O2/Birm®) at different pH, concentration of H2O2 and catalyst. The degradation kinetics of the ES followed in law and kinetics order of pseudofirst showing that the Birm® presented no catalytic activity in appreciable color degradation of the synthetic effluent. But when the solid was evaluated for the degradation of the real tannery effluent, it proved to be active, with kinetics of degradation occurring more efficiently than the homogeneous system (H2O2/UV) one. In both effluents there was a catalytic decomposition of hydrogen peroxide. However, the decomposition in ES resulted in inactive products for the catalytic oxidation or free radicals, which possibly were disabled in difusional ways and didn t react with the effluent. The increasing of the concentration of nitrate and sulfate also demonstrated a good the treatment of tanning effluent.
Este estudo investigou a aplicação de processos oxidativos avançados, homogêneos e heterogêneos, na degradação de efluentes líquidos industriais de couro sintético e real. O efluente sintético é uma solução aquosa do corante de couros Acid Orange G. O efluente real é oriundo da indústria de processamento de couro, coletado após o decantador secundário do tratamento por lodos ativados. Os experimentos foram realizados em reator fotocatalítico descontínuo em escala de laboratório. O sólido utilizado como catalisador heterogêneo é um composto comercial denominado Birm®, constituído principalmente de sílica cristalina, silicato de alumínio e dióxido de manganês. A adsorção do efluente sintético sobre o Birm® ajustou-se aos modelos de Langmuir e de Freundlich e, o sólido apresentou baixa capacidade adsortiva. As cinéticas de degradação dos efluentes pelos processos fotoquímicos homogêneo (H2O2/UV) e heterogêneo (UV/H2O2/Birm®) foram avaliadas em diferentes valores de pH, concentração de H2O2 e de catalisador. Os resultados estabeleceram o modelo cinético de pseudoprimeira ordem para a degradação do efluente sintético. O Birm® apresentou atividade catalítica apenas para o efluente de curtume, apesar de a decomposição catalítica do peróxido de hidrogênio ter ocorrido em ambos efluentes. Supõe-se que essa atividade foi potencializada pela diversidade de compostos orgânicos presentes no efluente de curtume. A degradação deste efluente também foi comprovada pelo aumento das concentrações de sulfato e nitrato.

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Pollution is a currently environmental problem of world concern. There are many events such as the discharging of untreated effluents in watercourses that cause the eutrophization of water bodies and bad water quality, as well as an inefficiency or lack of a current environmental law. The main goal of this dissertation was the application of solar and artificial-based photo-Fenton processes and aluminum electrodes-based electrocoagulation method in non coupled mode and in an integrated mode for the tannery effluent treatment. These effluent treatments were carried out in lab-scale reactors. In order to evaluate the performance of the reactor experimental conditions of photo-Fenton reactor, a 33 complete experimental design was performed. The lab scale EC reactor was operated at the 4 A electrical current, 4 cm electrode distance and 3 initial pH optimized values, according to the previous results obtained in another work, while the electrolysis time was varied from 5 to 120 min. For EC and photo-Fenton reactors, their performance was evaluated on the removal values of chemical oxygem demand (COD), color, turbidity, total solids (TS), total fixed solids (TFS), total volatile solids (TVS) and metal concentration. Measurements of physico-chemical parameters for untreated and treated effluent samples were performed applying the Standard Method for water analysis, while metal concentrations were determined by the Synchrotron radiation total Reflexion X-ray Fluorescence technique at Brazilian Light Synchrotron Laboratory. By an optimized photon-Fenton process at 0.5 g Fe2+ L-1, 30 g H2O2 L-1, 3 initial pH, and 120 min reaction time, tannery effluent was treated achieving a high performance in pollutant removal as reported by 98.1, 96.4, 98.8, 71.8, 32.1 and 98.5 percent removal for COD, color, turbidity, TS, TFS, and TVS, respectively. As a primer treatment stage, electrocoagulation technique was not achieved a well successful result based on the physico-chemical parameter values reduction as compared with photo-Fenton process. However, an integrated solar irradiation-based photo-Fenton and Al electrodes-based electrocoagulation with 15 min electrolysis time has achieved recommended values by the Brazilian environmental law for Cr concentration (0.24 mg Cr L-1) and DQO (107 mg O2 L-1). Considering both the costs of electrical energy and material and the generated sludge discharging, one m3 of tannery effluent should cost R$ 56.30 for a treatment system based on an integrated and optimized photo Fenton and electrocoagulation processes. Finally, the integrated solar-based photo Fenton and electrocoagulation method is suggested as an efficient one, instead to apply a unique process.
A poluição ambiental é um dos grandes problemas nos países desenvolvidos e em desenvolvimento. Isto é decorrente de uma série de fatores, como o despejo de efluentes não tratados em corpos hídricos e a ineficiência e/ou a falta de legislação ambiental vigente. O objetivo principal deste trabalho é aplicar os processos foto-Fenton com irradiação solar e/ou artificial, a técnica da eletrofloculação e a integração destes processos no tratamento de efluente de curtume. Ambos os processos de tratamento do foto-Fenton e da eletrofloculação foram conduzidos em reatores a escala laboratorial. Para a técnica da eletrofloculação foi utilizado um par de placas de alumínio como eletrodos no reator de eletrofloculação. Para avaliar as melhores condições de processo do sistema foto-Fenton, foi aplicado um planejamento experimental 33 completo. Para a técnica da eletrofloculação manteve-se constante a intensidade de corrente, pH inicial do efluente bruto e distância entre os eletrodos, variando-se o tempo de eletrólise de 5 à 120 min. A eficiência de ambos os processos foram avaliadas com base na redução de Demanda química de oxigênio (DQO), cor, turbidez, sólidos totais (ST), sólidos totais fixos (STF), sólidos totais voláteis (STV). Para a técnica da eletrofloculação e dos processos integrados também foram avaliados a redução da concentração dos metais pesados. Todas as medidas dos parâmetros físico-químicos foram realizadas aplicando os métodos padrões do Standard Methods for the Examination of Water and Wastewater para amostra não tratada e tratada. As concentrações dos metais pesados foram determinadas usando a técnica de fluorescência de raio X por reflexão total, na linha de Luz (D09-XRF) do Laboratório Nacional de Luz Synchrotron. A maior eficiência na redução dos poluentes verificada no processo foto-Fenton foi de 98,1, 96,4, 98,8, 71,8, 32,1 e 98,5 para valores da DQO, cor, turbidez, ST, STF e STV, respectivamente, nas condições operacionais do reator: concentração de ferro de 0,5 gL-1, concentração de peróxido de hidrogênio de 30 gL-1, pH inicial 3 e tempo reacional de 120 min. No entanto a técnica da eletrofloculação não apresentou boa redução nos valores dos parâmetros físico-químicos. Após a aplicação dos processos integrados do foto-Fenton com irradiação solar e da eletrofloculação em tempo de eletrólise de 15 min, foi alcançado valores mínimos de Cr e DQO no efluente tratado, contendo 0,24 mg Cr L-1 e 107 mg O2 L-1 da DQO. O custo do tratamento do efluente e da disposição final do lodo gerado no processo integrado FFs→EF foi de R$ 56,30 m3 do efluente de curtume tratado. Este processo integrado reduziu as concentrações de cromo, ferro e DQO, a níveis permitidos pelas legislações ambientais. Baseada na redução da matéria orgânica e inorgânica, o método integrado FFs→EF pode ser recomendado como uma substituição eficiente ao método individual.

Tannery wastewater is highly complex and contains high concentrations of organics and other toxic chemicals, such as sulfide and chromium, which inhibit the activity of microorganisms during biological oxidations and are not removed completely from wastewater. Since the biological processes are not able to fully depollute tannery effluents, other technologies, such as electrochemical oxidation processes, are being studied for the treatment of aqueous wastewaters. In this work, the study of the electrochemical oxidation of samples from tannery wastewater, clarified or not, was carried out. Assays were run under galvanostatic conditions, with different current densities, in electrochemical reactors equipped with anodes based on metal oxides, Ti/Pt/PbO2 and Ti/Pt/SnO2-Sb2O4, and of boron-doped diamond (BDD). For the pretreatment by clarification, chemical coagulation (with iron and aluminum ions) and electrocoagulation (with iron and aluminum consumable anodes) were used. The performance of each assay was followed by variations observed in the concentrations of COD, DIC, DOC, TDC, TKN,TN, N-NH4 +, N-NH3, NO3 -, NO2 -, S2- and SO4 2-. The kinetics of the conversion of S2- into SO4 2- , in aqueous solutions of S2- (60 mM), by electro-oxidation using a BDD electrode was also investigated. For the conversion of S2- to SO4 2-, assays were run at current densities from 10 to 60 mA cm-2, with a duration varying from 10 to 42 h. The results showed that the electrochemical conversion occurs in steps, via intermediate production of other sulfur species (S2- Sx 2- SnOm y-, with x, n, m and y integers) and the oxidation rate of the sulfide ion is dependent on its concentration and current density. The reaction order strongly varies with the applied current intensity, being order 2 for the lower applied current density. For higher applied current densities, where the current control is less important, the reaction order varies from 0.15 to 0.44 for the applied current densities of 20 and 60 mA cm-2, respectively. For the formation of SO4 2- from S2- electro-oxidation, the reaction order with respect to sulfide varied from 0.35 to 0.05 when the applied current densities changed from 10 to 60 mA cm-2. The electrochemical oxidation for unclarified effluent samples under a current density of 30 mA cm-2 and in a batch with stirring (100 rpm) during 8 h assays showed the best performance for BDD electrode in the removal of COD and TDC. The others two tested electrode presented similar behavior in the DOC removal; Ti/Pt/SnO2-Sb2O4 was the least efficient in the oxidation of nitrogen to NO3 -, despite providing considerable production of gaseous nitrogen compounds, which reduces the total nitrogen load present in the final samples; removal of S2- was more intense at BDD, although the other electrodes presented similar behavior. Ti/Pt/SnO2-Sb2O4 electrode was more effective to form SO4 2-. Regarding specific charge consumption, BDD showed the lowest consumption, 2.70 C g-1 of COD removed, against 3.25 and 3.21 C g-1 of COD for the Ti/Pt/PbO2 and Ti/Pt/SnO2-Sb2O4 electrodes, respectively. In all clarifications assays the best performance was verified for chemical coagulation. This appears be derived from a better operational control in chemical coagulation than in electrocoagulation. In addition, iron cation was more efficient than aluminum cation. This is important because the clarification by iron avoids the presence of aluminum in the final sludge In the case of anodic oxidation (8 h assays, current density of 30 mA cm-2 and constant stirring at a rate of 100 rpm) for effluent samples (400 mL), previously clarified by chemical coagulation or electrocoagulation by aluminum, the clarification stage strongly influenced the anodic oxidation processes and showed that electrodegradation by Ti/Pt/PbO2 and Ti/Pt/SnO2-Sb2O4 electrodes can be used as effluent polishing step. BDD electrode generally showed better performance in the removal of contaminants from the not clarified samples and was very efficient in the S2- removal but not in its conversion to SO4 2-. On the contrary, Ti/Pt/SnO2-Sb2O4 electrode showed better performance in the production of SO4 2- from intermediate sulfur species. The energy consumption of the anodic oxidation processes performed with Ti/Pt/PbO2 and Ti/Pt/SnO2-Sb2O4 anodes is strongly influenced by the contaminant concentrations. The combined process, chemical coagulation followed by anodic oxidation with metal oxide electrodes, proved to be a good alternative to the BDD electrodes for wastewater treatment. The same situation was observed in the anodic oxidation of samples previously clarified by chemical coagulation or electrocoagulation using iron cation. Finally, in the last stage, clarified samples by Fe3+ ion, 0.25 g L-1, were submitted to anodic oxidation (8 h) in two different sets with recirculation system: set A composed by Ti/Pt/SnO2- Sb2O4 + Ti/Pt/PbO2 electrodes, and set B with BDD only. The current densities in each set were 20 mA cm-2 and 40 mA cm-2 for Ti/Pt/SnO2-Sb2O4 and Ti/Pt/PbO2, respectively, in set A; and 60 mA cm-2, for BDD, set B. Both the tested sets showed similar behavior in the removal of COD, TC, DOC, TKN and ammonia nitrogen, showing the feasibility of metal oxides as electrodes in replacement to BDD electrode in anodic oxidation systems; set A was the least efficient in the oxidation of nitrogen to NO3 -, despite show similar behavior to the set B for production of gaseous nitrogen compounds, which reduces the total nitrogen load present in the final samples; the COD concentration worked as an important inhibiting factor for TKN removal. Regarding energy consumption, in a general way, the set B showed the lowest consumption.
Os efluentes das indústrias de couro são altamente complexos e contêm concentrações elevadas de produtos orgânicos, sais e outros produtos químicos tóxicos que inibem a atividade de micro-organismos durante as oxidações biológicas, nomeadamente, sulfuretos e crómio. Assim, os processos biológicos não são capazes de depurar totalmente as águas residuais provenientes desta indústria. Como alternativa à utilização dos processos biológicos para o tratamento de águas residuais com cargas poluentes elevadas tem sido estudada a aplicação de processos de oxidação eletroquímica no tratamento de resíduos aquosos. Neste trabalho estudou-se a aplicação da oxidação eletroquímica no tratamento de amostras de efluentes provenientes da indústria dos curtumes, clarificadas ou não. Os ensaios de oxidação eletroquímica foram realizados sob condições galvanostáticas num reator eletroquímico equipado com ânodos de óxidos metálicos, Ti/Pt/PbO2 e Ti/Pt/SnO2-Sb2O4, e de diamante dopado com boro (BDD), utilizando diferentes densidades de corrente. A clarificação das amostras foi realizada por coagulação química (com iões de ferro ou alumínio) ou eletrocoagulação (com elétrodos de ferro ou alumínio). Para além disso, estudou-se a cinética da conversão do S2- em SO4 2-, com soluções aquosas de S2- (60 mM), por eletro-oxidação, utilizando ânodos de BDD. Para o estudo da cinética da conversão de S2- em SO4 2- foram realizados ensaios a diferentes densidades de corrente, que variaram entre 10 e 60 mA cm-2. A duração dos ensaios variou com a densidade de corrente aplicada, tendo sido de 42 h para 10 mA cm-2 e de 10 h para 60 mA cm-2. Os resultados mostraram que a conversão eletroquímica ocorre em etapas, através da produção de outras espécies intermediárias de enxofre (S2- Sx 2- SnOm y-, com x, n, m e y inteiros). A taxa de oxidação, para além de variar com a concentração de sulfureto, varia fortemente com a intensidade de corrente aplicada, sendo de ordem 2 para a densidade de corrente mais baixa, 10 mA cm-2. Para densidades de corrente mais elevadas, em que o controlo de corrente é menos importante, a ordem de reação varia entre 0,15 e 0,44 para as densidades de corrente aplicadas de 20 e 60 mA cm-2, respetivamente. Para a formação de SO4 2-, a ordem da reação em relação à concentração de S2- é sempre zero para todas as densidades de corrente aplicadas. Nos estudos de remoção de contaminantes de efluentes da indústria dos curtumes, os desempenhos de cada ensaio de oxidação anódica foram verificados por meio de variações observadas nas concentrações de carência química de oxigénio, carbono inorgânico dissolvido, carbono orgânico dissolvido, carbono total dissolvido, azoto total Kjeldhal, azoto total, NNH4 +, N-NH3, NO3 -, NO2 -, S2- e SO4 2-. Para a oxidação eletroquímica de amostras de efluente não clarificadas (400 mL), os ensaios foram realizados com densidade de corrente de 30 mA cm-2, agitação (100 rpm) e duração dos ensaios de 8 h. O elétrodo de BDD apresentou o melhor desempenho na remoção de carbono orgânico dissolvido e de carbono total dissolvido. Os outros dois elétrodos testados apresentaram comportamentos semelhantes nas remoções do carbono orgânico dissolvido; Ti/Pt/SnO2-Sb2O4 foi o menos eficiente na oxidação do azoto a NO3 -, tendo levado à produção de formas de azoto gasoso, o que reduz a carga total de azoto presente nas amostras finais; o elétrodo de BDD removeu mais intensamente o S2-, apesar dos outros elétrodos apresentarem um comportamento semelhante. O elétrodo de Ti/Pt/SnO2-Sb2O4 foi mais eficaz na formação do SO4 2-. Em relação ao consumo específico de carga, o BDD mostrou o menor consumo, 2,70 C/(g de CQO removida), contra 3,25 e 3,21 C/(g de CQO removida) para os elétrodos de Ti/Pt/PbO2 e de Ti/Pt/SnO2-Sb2O4, respetivamente. Foram também realizados ensaios de oxidação anódica ao efluente clarificado e não clarificado. Para todos os ensaios de pré-tratamento por clarificação, o melhor desempenho foi verificado para a coagulação química. Isto parece ser devido ao melhor controlo operacional na coagulação química face à eletrocoagulação. Além disso, os catiões de ferro foram mais eficientes do que os catiões de alumínio. Isto é importante porque a clarificação por ferro evita a presença de alumínio no lodo final. As oxidações anódicas das amostras (400 mL), clarificadas previamente por coagulação química ou eletrocoagulação por alumínio, foram processadas por 8 h com densidade de corrente de 30 mA cm-2 e agitação contínua (100 rpm). Foram realizados ensaios idênticos de eletro-oxidação para amostras não clarificadas. Neste sentido, a etapa de clarificação influenciou fortemente os processos de oxidação anódica e mostrou que a eletrodegradação com elétrodos de Ti/Pt/PbO2 e Ti/Pt/SnO2-Sb2O4 pode ser usada como etapa de polimento no tratamento de efluentes. O elétrodo de BDD, em geral, mostrou melhor desempenho na remoção de contaminantes a partir das amostras não clarificadas e foi muito eficiente na remoção S2-, mas não na sua conversão em SO4 2-. Pelo contrário, o elétrodo de Ti/Pt/SnO2- Sb2O4 mostrou excelente desempenho para produção de SO4 2- a partir de espécies intermediárias sulfuradas, uma vez que, para estes elétrodos, a formação de SO4 2- foi maior do que a esperada. O consumo de energia dos processos de oxidação anódica realizados com ânodos de Ti/Pt/PbO2 e de Ti/Pt/SnO2-Sb2O4 é fortemente influenciado pelas concentrações de contaminantes. O processo combinado, coagulação química seguido por oxidação anódica com elétrodos de óxidos metálicos, provou ser uma boa alternativa aos elétrodos de BDD para tratamento de águas residuais. Um processo similar foi efetuado para amostras clarificadas, ou não, com catiões de ferro. Os resultados dos ensaios de oxidação anódica mostraram ser semelhantes aos observados quando a clarificação foi realizada por alumínio. Tendo em vista os resultados anteriormente descritos, na última fase do trabalho efetuou-se a eletrooxidação, durante 8 h, de amostras clarificadas por catiões ferro, 0,25 g L-1, com volume total de 2 L, em dois sistemas diferentes, dotados de recirculação: um sistema de eletrooxidação continha ânodos de Ti/Pt/SnO2-Sb2O4 e de Ti/Pt/PbO2 (A); o outro sistema era formado apenas por um ânodo de BDD (B). As densidades de corrente em cada conjunto foram 20 mA cm-2 e 40 mA cm-2 para Ti/Pt/SnO2-Sb2O4 e Ti/Pt/PbO2, respetivamente, no sistema A, e 60 mA cm-2 para o BDD, no sistema B. Ambos os sistemas testados mostraram um comportamento semelhante na remoção de CQO, carbono dissolvido total, carbono orgânico dissolvido, azoto total de Kjeldahl, N-NH3 e azoto total. Os resultados mostraram a viabilidade dos elétrodos de óxidos metálicos em substituição do elétrodo de BDD em sistemas de oxidação; o conjunto A foi o menos eficiente na oxidação do azoto a NO3 -, apesar de mostrar um comportamento semelhante ao conjunto B para a produção de azoto gasoso, o que reduz a carga total de azoto presente nas amostras finais; a concentração de CQO funcionou como um importante fator inibidor para a remoção azoto total de Kjeldahl. Em relação ao consumo de energia, de uma maneira geral, o conjunto B apresentou o menor consumo.