Estudo da biodegradação anaeróbia de efluentes industriais

Mestrado em Engenharia do AmbienteNeste trabalho fez-se o estudo do tratamento anaeróbio de diferentes efluentes industriais em reatores UASB à escala laboratorial. Numa primeira fase, fez-se o estudo do tratamento anaeróbio de efluentes de uma indústria de mobiliário de madeira (efluente de uma cabine de pintura e envernizamento). Fizeram-se ensaios para testar a influência da carga orgânica e da velocidade ascensional da alimentação. Neste estudo os reatores UASB foram operados de forma descontínua com recirculação total do efluente tratado. Foram testadas cargas de 2,300; 1,150 e 0,671 g CQO.L-1 e velocidades ascensionais de 0,036; 0,072; 0,108 e 0,179 m.h-1. As condições operacionais que favoreceram o tratamento deste efluente foram a carga 0,671 g CQO.L-1 e a velocidade ascensional 0,036 m.h-1, condições para as quais se obteve uma eficiência de remoção de CQO de 86,9%, uma eficiência de metanização da CQO removida de 72,1% e uma biodegradabilidade de 62,6%. Verificou-se que a carga e a velocidade ascensional mais baixas favoreceram a eficiência de metanização e a biodegradabilidade. Os resultados obtidos ao longo dos vários ensaios realizados sugerem a adaptação da biomassa ao substrato aplicado. Conclui-se que o tratamento anaeróbio é uma opção viável para a gestão dos efluentes de cabine de pintura e envernizamento de indústrias de mobiliário de madeira. Numa segunda fase, foram estudadas diferentes estratégias de operação para o arranque de reatores UASB, inoculados com biomassa floculenta não adaptada ao substrato, utilizados no tratamento de efluentes de indústrias de lacticínios (efluente complexo contendo gorduras). As estratégias testadas foram: operação contínua, operação intermitente e operação intermitente com choques de gorduras. Foram realizados dois ensaios, o primeiro com uma carga orgânica de 5,0 g CQO.L-1. d-1 e o segundo ensaio com 8,5 g CQO.L-1.d-1. Em termos de remoção de CQO, as três estratégias de operação resultaram em valores semelhantes (de 51,3 a 60,4%). Nos dois ensaios verificou-se que a operação intermitente com choques de gorduras resultou nos valores mais elevados de metanização da CQO removida, com valores médios de 56,0% e 69,3% para o primeiro e segundo ensaios, respetivamente. Em comparação, para a operação intermitente, obtiveram-se eficiências de metanização médias de 53,4% e 60,7%, para o primeiro e segundo ensaios, respetivamente. Na operação contínua, as eficiências médias de metanização da CQO removida foram de 45,9% para o primeiro ensaio e 43,9% para o segundo ensaio. Verificou-se também que a operação intermitente com choque de gorduras teve um efeito benéfico em termos de sedimentabilidade da biomassa desenvolvida no reator, tendo-se observado a ausência de flutuação no topo do reator, ao contrário do que foi observado com a operação intermitente e com a operação contínua. Por outro lado, o modo de operação intermitente com choques de gordura apresentou a maior percentagem do grupo microbiano Syntrophomonadaceae, atingindo aproximadamente 20% da contagem total de microrganismos. Dos resultados obtidos conclui-se que a estratégia mais adequada para a adaptação da biomassa floculenta ao efluente de indústria de lacticínios é a operação intermitente com choque de gorduras.This work concerns the study of anaerobic treatment of different industrial wastewaters in laboratory-scale UASB reactors. The first phase of the work foccused on the anaerobic treatment of a wastewater from a wood furniture industry (wastewater from a dying hood). Tests were made to assess the influence of the organic load and the upflow velocity upon the performance of the process. In this research the UASB reactors were operated in a batch mode with total recirculation of the treated effluent. Loads of 2.300; 1.150 and 0.671 g COD.L-1 and upflow velocities of 0.036, 0.072, 0.108 and 0.179 m.h-1 were tested. The operating conditions that favoured the anaerobic treatment of this wastewater were a load of 0.671 g COD.L-1 and an upflow velocity of 0,036 m.h-1, conditions that lead to a removal efficiency of 86.9%, a methanization efficiency of the removed COD of 72.1% and a biodegradability of 62.6%. It was also established that the lower loads and the lower uplflow velocities favoured the efficiency of methanization of the removed COD and the biodegradability of the wastewater. Finally the results obtained throughout the series of tests performed suggest that the biomass adapted to the applied substrate. It was concluded that the anaerobic process is a viable option for treating the wastewaters from the dying hoods of furniture industries. In a second phase the work foccused on different startup strategies for UASB reactors, inocculated with flocculent biomass not adapted to the substrate, used for the treatment of dairy wastewaters (complex fat containing wastewaters). The tested strategies were: continuous operation, intermittent operation and intermittent operation with fat shocks. Two tests were performed: the first with an organic loading rate of 5.0 g COD.L-1.d-1 and the second with an organic loading rate of 8.5 g COD.L-1.d-1. In terms of COD removal the three tested strategies resulted in similar values (averages for all reactors from 51.3 to 60.4%). In both the tests it was verified that the intermittent operation with fat shocks resulted in the higher values of methanization of the removed COD with averages values of 56.0% and 69.3% for the first and second tests, respectively. In comparison for the intermittent operation the average methanization efficiencies of the removed COD were 53,4% and 60.7% for the first and the second tests, respectively. With the continuous operation the average methanization efficiencies of the removed COD were 45.9% for the first test and 43.9% for the second test. It was also verified that the intermittent operation with fat shocks had a beneficial effect in terms of biomass sedimentability. It was observed that no floating sludge layer was present in the top of the intermittent reactor with fat shocks in contrast with what was observed with the continuous and the intermittent reactors. On the other hand, the intermittent system with fat shock revealed that a high percentage of microbial group Syntrophomonadaceae, near to 20% of the total microbial count. From the results of this work it may be concluded that the most adequate strategy for the adaptation of flocculent biomass to dairy wastewater is the intermittent operation with fat shocks

Bio- e fotodegradação como estratégias para a remoção de estrogénios e antibióticos das águas residuais

Over the last few decades, the occurrence of emerging contaminants (EC) has raised concerns due to their ubiquitous presence in the environment and potential to cause undesirable ecological effects. Their main source are the discharges of wastewater treatment plants (WWTPs), which are not effective barriers to these pollutants. In order to assess the fate of EC, as well as to evaluate possible strategies to attenuate their presence, the study of natural processes is of the greatest importance. Adsorption, biodegradation and photodegradation appear as significant mechanisms of removal of EC in aquatic environments. Among the EC, two antibiotics, sulfadiazine (SDZ) and oxolinic acid (OXA), and two estrogens, estrone (E1) and 17α-ethinylestradiol (EE2), have received considerable attention because of their high consumption and persistence in the environment. Since SDZ and OXA resist to biodegradation and tend to remain in aqueous phase, while E1 and EE2 have high affinity to solid phase, in the present work, the photodegradation of antibiotics and the adsorption and biodegradation of estrogens were investigated. In what concerns SDZ and OXA photodegradation, the effect of environmentally relevant factors such as the pH, the presence of fractions of estuarine humic substances and salinity were evaluated. The results obtained indicated that at higher pH, and in the presence of photosensitizers, the SDZ photodegradation was much faster than in ultrapure water. Different results were obtained for OXA, with a significant decrease in its photodegradation in presence of photosensitizers. These observations may explain the results obtained in environmental matrices, namely the final effluent of a WWTP, fresh water and brackish water, in which the photodegradation of SDZ (t½ between 2.32 h and 3.48 h) was found to be much faster than in ultrapure water (t½ = 6.76 h). In contrast, OXA photodegradation was much slower in the final effluent of a WWTP, fresh water and brackish water (t½ between 1.65 h and 4.03 h) than in ultrapure water (t½ = 0.99 h). In WWTPs estrogens are mainly adsorbed onto sludge. Thus, a simple, reliable and inexpensive method for the quantification of E1 and EE2 in fresh sludge samples was developed. Recovery values of 103 % and 97 % were obtained for E1 and EE2, respectively. Regarding the estrogens’ removal under anaerobic conditions, the influence of different factors was investigated. A higher E1 removal from solid phase of sludge was obtained for higher temperatures (25 C and 34 C) and lower sludge content (2 g L-1). In the case of EE2, higher removal was obtained for lower sludge content (2 g L-1 and 3 g L-1). However, temperature had no effect on the removal of EE2. The presence of nitrate does not appear to influence the removal of both E1 and EE2 from sludge. Finally, the performance of continuous (CO) and intermittent operation (IO) of Upflow Anaerobic Sludge Blanket (UASB) reactors on the removal of E1 and EE2 was assessed. Higher biodegradation values (69.4 % vs. 43.3 % for E1 and 21.8 % vs. 8.0 % for EE2) and adsorption values (26.5 % vs. 5.7 % for E1 and 72.7 % vs. 31.0% for EE2) were found with the IO, compared to CO. Thus, the IO of UASB reactors can be a promising, sustainable, and robust alternative for E1 and EE2 removal from wastewaters.Nas últimas décadas, a ocorrência de contaminantes emergentes (CE) suscitou preocupações devido à sua presença no ambiente e ao seu potencial para causar efeitos ecológicos indesejáveis. A sua principal fonte são as descargas de estações de tratamento de águas residuais (ETARs), que não são eficazes na remoção destes poluentes. A fim de avaliar o destino de CE, bem como de avaliar possíveis estratégias para atenuar a sua presença, o estudo dos processos naturais é de maior importância. Adsorção, biodegradação e fotodegradação aparecem como mecanismos significativos de remoção de CE em ambientes aquáticos. Entre os CE, dois antibióticos, sulfadiazina (SDZ) e ácido oxolínico (OXA), e dois estrogénios, estrona (E1) e 17α-etinilestradiol (EE2), têm recebido especial atenção devido ao seu elevado consumo e persistência no ambiente. Uma vez que os antibióticos SDZ e OXA resistem à biodegradação e tendem a permanecer na fase aquosa, e os estrogénios E1 e EE2 têm grande afinidade com a fase sólida, no presente trabalho foram investigadas a fotodegradação dos antibióticos e a adsorção e biodegradação dos estrogénios. No que diz respeito à fotodegradação de SDZ e OXA, foi avaliado o efeito de fatores ambientalmente relevantes como o pH, a presença de frações de substâncias húmicas estuarinas e a salinidade. Os resultados obtidos indicaram que a pH mais elevado, e na presença de fotossensibilizadores, a fotodegradação da SDZ foi muito mais rápida do que em água ultrapura. Para o OXA foram obtidos resultados diferentes, tendo-se observado uma diminuição significativa da sua fotodegradação na presença de fotossensibilizadores. Estas observações podem explicar os resultados obtidos em matrizes ambientais, nomeadamente, o efluente final de uma ETAR, água doce e água salobra, nas quais a fotodegradação da SDZ (t½ entre 2,32 h e 3,48 h) foi muito mais rápida do que em água ultrapura (t½ = 6,76 h), enquanto que para o OXA foi muito mais lenta (t½ entre 1,65 h e 4,03 h) do que em água ultrapura (t½ = 0,99 h). Nas ETARs os estrogénios são principalmente adsorvidos às lamas. Assim, foi desenvolvido um método simples, fiável e barato para a quantificação de E1 e EE2 em amostras de lamas frescas. Foram obtidos valores de recuperação de 103 % e 97 % para E1 e EE2, respetivamente. Relativamente à remoção de estrogénios em condições anaeróbias, foi investigada a influência de diferentes fatores. Obtiveram-se remoções mais elevadas de E1 da fase sólida das lamas a temperaturas mais elevadas (25 C e 34 C) e menor teor de lamas (2 g L-1). No caso do EE2, foram observadas remoções mais elevadas com menor teor de lamas (2 g L-1 e 3 g L-1). No entanto, não foi observado qualquer efeito da temperatura na remoção do EE2. A presença de nitrato não parece influenciar a remoção, tanto do E1 como do EE2 das lamas. Finalmente, foi avaliado o desempenho do modo de operação contínuo (OC) e intermitente (OI) dos reatores de leito de lamas e fluxo ascendente (UASB) na remoção de E1 e EE2. Valores mais elevados de biodegradação (69,4 % vs. 43,3 % para E1 e 21,8 % vs. 8,0 % para EE2) e de adsorção (26,5 % vs. 5,7 % para E1 e 72,7 % vs. 31,0 % para EE2) foram obtidos com a OI em comparação com a OC. Assim, a OI dos reatores UASB pode ser uma alternativa promissora, sustentável e robusta para a remoção de E1 e EE2 das águas residuais.Programa Doutoral em Ciências e Engenharia do Ambient

Antibiotics in Aquaculture Wastewater: Is It Feasible to Use a Photodegradation-Based Treatment for Their Removal?

Aquacultures are a sector facing a huge development: farmers usually applying antibiotics to treat and/or prevent diseases. Consequently, effluents from aquaculture represent a source of antibiotics for receiving waters, where they pose a potential threat due to antimicrobial resistance (AMR) induction. This has recently become a major concern and it is expectable that regulations on antibiotics’ discharge will be established in the near future. Therefore, it is urgent to develop treatments for their removal from wastewater. Among the different possibilities, photodegradation under solar radiation may be a sustainable option. Thus, this review aims at providing a survey on photolysis and photocatalysis in view of their application for the degradation of antibiotics from aquaculture wastewater. Experimental facts, factors affecting antibiotics’ removal and employed photocatalysts were hereby addressed. Moreover, gaps in this research area, as well as future challenges, were identified

Aplicação da fotodegradação no tratamento de efluentes de aquacultura

Sem resumo disponível.publishe

Impact of UASB reactors operation mode on the removal of estrone and 17α-ethinylestradiol from wastewaters

This work aims to compare the performance of the continuous operation (CO) and intermittent operation (IO) of upflow anaerobic sludge blanket (UASB) reactors for the removal of estrone (E1) and 17α-ethinylestradiol (EE2) from wastewaters. Results suggest that the IO contribute to the improvement of the overall removal of estrogens (above 95% for E1 and EE2) when compared to CO (49% for E1 and 39% for EE2). For both CO and IO, biodegradation was the main removal mechanism for E1, while for EE2, adsorption to sludge was the major removal pathway. Moreover, a higher biodegradation of estrogens was obtained with the IO compared to CO (69.4% vs. 43.3% for E1 and 21.8% vs. 8.0% for EE2). The favourable effect of IO can be justified by effluent recirculation during the feedless period which promotes the adaptation of microbial biomass to estrogens' biodegradation.publishe

Photodegradation of sulfadiazine in different aquatic environments: evaluation of influencing factors

The pres­ence of an­tibi­otics, such as sul­fa­di­azine (SDZ), in the aquatic en­vi­ron­ment con­tributes to the gen­er­a­tion of an­timi­cro­bial re­sis­tance, which is a mat­ter of great con­cern. Pho­tol­y­sis is known to be a ma­jor degra­da­tion path­way for SDZ in sur­face wa­ters. There­fore, in­flu­enc­ing fac­tors af­fect­ing SDZ pho­todegra­da­tion in dif­fer­ent aquatic en­vi­ron­ments were here eval­u­ated in or­der to have a bet­ter knowl­edge about its per­sis­tence in the en­vi­ron­ment. Pho­todegra­da­tion of SDZ was found to be more ef­fi­cient at higher pH (t1/​2 = 6.76 h, at pH = 7.3; t1/​2 = 12.2 h, at pH = 6.3), in the pres­ence of hu­mic sub­stances (HS) (t1/​2 be­tween 1.76 and 2.42 h), as well as in the pres­ence of NaCl (t1/​2 = 1.00 h) or syn­thetic sea salts (t1/​2 = 0.78 h). Us­ing ˙OH and 1O2 scav­engers, it was pos­si­ble to in­fer that di­rect pho­tol­y­sis was the main pathway for SDZ pho­todegra­da­tion in ul­tra­pure wa­ter. Fur­ther­more, re­sults un­der N2 purg­ing con­firmed that 1O2 was not rel­e­vant in the pho­to­trans­for­ma­tion of SDZ. Then, the re­ferred ob­ser­va­tions were used for the in­ter­pre­ta­tion of re­sults ob­tained in en­vi­ron­men­tal ma­tri­ces, namely the fi­nal ef­flu­ent of a sewage treat­ment plant (STPF), fresh and brack­ish wa­ter (t1/​2 be­tween 2.3 and 3.48 h), in which SDZ pho­todegra­da­tion was found to be much faster than in ul­tra­pure wa­ter (t1/​2 = 6.76 h).in publicatio

Photodegradation of Aquaculture Antibiotics Using Carbon Dots-TiO₂ Nanocomposites

In this work, carbon dots (CD) were synthesized and coupled to titanium dioxide (TiO2) to improve the photodegradation of antibiotics in aquaculture effluents under solar irradiation. Oxolinic acid (OXA) and sulfadiazine (SDZ), which are widely used in aquaculture, were used as target antibiotics. To prepare nanocomposites of CD containing TiO2, two modes were used: in-situ (CD@TiO2) and ex-situ (CD/TiO2). For CD synthesis, citric acid and glycerol were used, while for TiO2 synthesis, titanium butoxide was the precursor. In ultrapure water (UW), CD@TiO2 and CD/TiO2 showed the largest photocatalytic effect for SDZ and OXA, respectively. Compared with their absence, the presence of CD@TiO2 increased the photodegradation of SDZ from 23 to 97% (after 4 h irradiation), whereas CD/TiO2 increased the OXA photodegradation from 22 to 59% (after 1 h irradiation). Meanwhile, in synthetic sea salts (SSS, 30‰, simulating marine aquaculture effluents), CD@TiO2 allowed for the reduction of SDZ’s half-life time (t1/2) from 14.5 ± 0.7 h (in absence of photocatalyst) to 0.38 ± 0.04 h. Concerning OXA in SSS, the t1/2 remained the same either in the absence of a photocatalyst or in the presence of CD/TiO2 (3.5 ± 0.3 h and 3.9 ± 0.4 h, respectively). Overall, this study provided novel perspectives on the use of eco-friendly CD-TiO2 nanocomposites for the removal of antibiotics from aquaculture effluents using solar radiation

Oxolinic acid in aquaculture waters: can natural attenuation through photodegradation decrease its concentration?

Quinolones, such as oxolinic acid (OXA), are antimicrobials commonly used in aquaculture. Thus, its presence in the aquatic environment surrounding aquaculture facilities is quite easy to understand. When present in aquatic environment, pharmaceuticals may be subjected to several attenuation processes that can influence their persistence. Photodegradation, particularly for antibiotics, can have significant importance since these compounds may be resistant to microbial degradation. OXA photodegradation studies reported in literature are very scarce, especially using aquaculture waters, but are markedly important for an appropriate risk assessment. Results hereby presented showed a decrease on photodegradation rate constant from 0.70 ± 0.02 h-1 in ultrapure water to 0.42 ± 0.01 h-1 in freshwater. The decrease on photodegradation rate constant was even more pronounced when brackish water was used (0.172 ± 0.003 h-1). In order to understand which factors contributed to the observed behaviour, environmental factors, such as natural organic matter and salinity, were studied. Results demonstrated that dissolved organic matter (DOM) may explain the decrease of OXA photodegradation observed in freshwater. However, a very sharp decrease of OXA photodegradation was observed in solutions containing NaCl and in synthetic sea salts, which explained the higher decrease observed in brackish water. Moreover, under solar radiation, the use of an 1O2 scavenger allowed us to verify a pronounced retardation of OXA decay, suggesting that 1O2 plays an important role in OXA photodegradation process.in publicatio

Olive oil mill wastewater to volatile fatty acids: statisticals study of the acidogenic process

The aim of the present paper was to study the feasibility of using olive oil mill wastewater (OOW) to produce a mixture of volatile fatty acids (VFA) adequate for producing polyhydroxyalkanoates (PHA) with better mechanical properties in a later aerobic phase. Hence, thiswastewater can be valorized rather than only treated, and its organic pollutant content can result in valueadded products with a sustainable origin. The influences of alkalinity addition and initial substrate concentration on VFA formation were evaluated in anaerobic batch fermentation experiments of OOW. The highest acidification degree (DA) (60 %) was obtained with an intermediate alkalinity of 5 gCaCO3 L−1 and a high substrate concentration of 14 gCOD L−1. These operational conditions produced a mixture of VFA (7.4 gCOD L−1) composed predominantly by acetic, n-butyric, and ncaproic acids. Regarding VFA valorization into PHA, recovering an adequate VFA composition is crucial to produce biopolymers that are more attractive industrially. The most suitable VFA mixture for PHA production was obtained at the highest alkalinity addition (7 gCaCO3 L−1), with an odd-to-even VFA ratio ranging from 0.42 to 0.61 with increasing COD load, predominantly composed of odd-equivalent acids, mainly propionic acid, although resulting in a significant decrease of DA to values close to 20 %. These experimental results suggest that VFA produced in this process can be used as substrate in a subsequent process for PHA production, regulating its monomer composition and polymer properties, solely by a proper adjustment of the operational conditions of the acidogenic fermentation step