[pt] O crescimento microbiológico em águas de sistemas de resfriamento pode resultar na formação de biofilme, o qual pode causar problemas de biocorrosão, perdas de carga em tubulações, redução de taxa de transferência de calor e obstrução de fluxo. Os principais e tradicionais biocidas utilizados no controle microbiológico de águas de resfriamento são os compostos à base de cloro. Entretanto, nos últimos anos o ácido peracético tornou-se uma alternava aos compostos clorados, uma vez que este biocida deixa como resíduo apenas o acetato o qual é biodegradável e não forma subprodutos organoclorados. Este trabalho analisou a aplicação do ácido peracético comparando-o com o hipoclorito de sódio no controle microbiológico e na corrosividade de materiais, empregando uma árvore de teste em escala de laboratório. Foi investigada a taxa de corrosão dos materiais metálicos de aço carbono, cobre e aço inoxidável, além da efetividade na redução da contagem bacteriana. Os experimentos foram realizados em condições de fluxo turbulento, pH 8 e temperatura de 32 C empregando uma água de estudo real, carregada de matéria orgânica (DQO = 350 mg/L). As concentrações usadas de ácido peracético foram 0,75; 1,0 e 3,0 mg/L e de hipoclorito de sódio foram 1,0 e 3,0 mg/L. O ácido peracético na concentração de 3,0 mg/L reduziu a carga bacteriana de 1,5x10 (elevado a 5) UFC/mL para 5,24x10 (elevado a 3) UFC/mL. Comparado ao hipoclorito de sódio, o ácido peracético foi menos corrosivo para o aço carbono em todas as concentrações. Na concentração de 1,0 mg/L a taxa de corrosão do cobre em ácido peracético foi menor do que na solução de hipoclorito de sódio. Já na concentração de 3,0 mg/L ocorreu o inverso. Não foi observada corrosão significativa no aço inoxidável para os biocidas estudados. / [en] Microbiological growth in cooling systems water may result in biofilm formation, which can cause problems of bio-corrosion, pressure drop in the pipes, reduction of heat transfer rate and flow obstruction. The main and traditional biocides applied in microbiological control of cooling waters are the chlorine based compounds. However, in recent years, peracetic acid has become an alternative to chlorinated compounds, since this biocide leaves as residue only the acetate, which is biodegradable and does not form chlorinated organic byproducts. This work analyzed the application of peracetic acid comparing to sodium hypochlorite in the microbiological control and material corrosivity using a laboratory scale test tree. The corrosion rate of carbon steel, copper and stainless steel alloys in addition to the effectiveness in reducing the bacterial count. The experiments were carried out under conditions of turbulent flow, pH 8 and temperature of 32 C using a real industrial test water loaded with organics (COD = 350 mg/L). Peracetic acid concentrations used were 0.75, 1.0 and 3.0 mg/L and sodium hypochlorite were 1.0 and 3.0 mg/L. Peracetic acid at the concentration of 3.0 mg/L decreased the bacterial load from 1.5x10 (raised to 5) UFC/mL to 5.24x10 (raised to 3) UFC/mL. Peracetic acid compared to sodium hypochlorite was less corrosive to carbon steel at all concentrations. At the concentration of 1.0 mg/L the corrosion rate of copper in peracetic acid was lower than in sodium hypochlorite solution. At the concentration of 3.0 mg/L, the reverse occurred. No significant corrosion was observed in stainless steel for the biocides studied.

Recirculating aquaculture offers a prospect for successful fish farming, but this form of aquaculture presents a great potential for pathogenic microorganisms to become established in the system through the formation of biofilms. Biofilms are capable of forming on all aquaculture system components, incorporating the various microflora present in the water. Pathogenic microorganisms released from the biofilms are capable of causing recurring exposure to disease in both fish and humans. With the increased consumption of raw and rare fish, the presence of these bacteria in or on the fish could lead to ingestion of pathogens. There is also the possibility of cross-contamination during processing. The objectives of this study were to increase the understanding of pathogen incorporation into biofilms in recirculating aquaculture systems and to determine the effectiveness of various sanitizers in eliminating biofilms. Seven freshwater and two saltwater facilities were sampled, with eight different types of materials tested. Pathogenic bacteria were identified using Bacteriological Analytical Manual methods and rapid commercial test kits. Most of the pathogenic bacteria identified were opportunistic organisms ubiquitous in an aquatic environment. The most significant human pathogens were Bacillus cereus, the Shigella species and the Vibrio species. The major piscine pathogens of concern were Photobacterium damsela, the Vibrio species, and Aeromonas hydrophila. The most significant variation in biofilm pathogens was observed between facilities and not construction material. Buna-N rubber, polyvinyl chloride (PVC), chlorinated PVC, glass, fiberglass and stainless steel disks were suspended in 79.2 liter (20 gallon) aquariums stocked with Nile tilapia (Oreochromus niloticus). The tanks were inoculated with a known amount of green fluorescent protein (GFP) modified Escherichia coli and samples were removed on days 1,3, 7 and 15. The modified E. coli were isolated on Luria Broth Agar and plate counts were performed under ultraviolet light. There was no significant difference in the growth of the surrogate pathogen on the different materials. The GFP E. coli was isolated in the largest numbers 24 hours after inoculation of the tanks, with an approximate 1-log decrease after day 1. Days 3, 7, and 15 showed equivalent growth of the target organism. Two sets of disks were suspended in another six 79.2 liter (20 gallon) aquariums. The tanks were inoculated with a known amount of the surrogate pathogen, GFP E. coli, and after 24 hours one set of disks was removed from each tank. The second set of disks was removed and treated by spraying with water, alkaline cleanser, sodium hypochlorite, quaternary ammonium compound, or peracetic acid. Ozone was bubbled directly into one tank to treat another set of disks. The modified E. coli were isolated and counted. Total aerobic plate counts and Enterobacteriaceae counts were performed. Statistical analysis indicated that the type of material had no significant affect on the effectiveness of the sanitizers. It was determined that sodium hypochlorite (99.4591 overall reduction) and peracetic acid (98.8461 % overall reduction) were the most effective sanitizers overall, and ozone (32.9332 % overall reduction) was the least effective. / Ph. D.

O objetivo desse estudo foi avaliar a ação de hipoclorito de sódio e ácido peracético na resistência à corrosão de titânio comercialmente puro, grau 4, (Ticp-4) em salivas artificiais, ácida e neutra, com diferentes períodos de imersão, por meio de ensaio de polarização potenciodinâmica anódica, microscopia eletrônica de varredura e espectrometria dispersiva de raios-X. Corpos-de-prova cilíndricos (5 mm x 5 mm) de Ticp-4 foram envolvidos com fio de cobre e fita isolante, este conjunto foi incluído em tubos de PVC (25 mm x 15 mm) e preenchidos com resina poliéster quimicamente ativada, após a polimerização da resina esses eletrodos de trabalho que foram polidos mecanicamente com lixas, feltros e pastas. Os 54 eletrodos de trabalho foram divididos em nove grupos (n=6) referentes às soluções e períodos de imersão: água destilada (controle), hipoclorito de sódio 1% (10 e 40 minutos), ácido peracético 0,2% (10, 30, 40 e 120 minutos) e ácido peracético 2% (30 e 120 minutos). Após serem imersos nas soluções, foram divididos em 2 subgrupos (n=3), pois os ensaios de polarização anódica foram realizados em triplicatas e utilizados dois eletrólitos, salivas artificiais pH 4,8 e pH 6,8. No ensaio de polarização anódica foi utilizada uma célula eletroquímica constituída por um eletrodo de referência do tipo calomelano saturado (ECS), um contra-eletrodo de platina e o eletrodo de trabalho constituído pelas amostras de Ticp-4, com taxa de varredura de 1 mV/s, partindo-se do potencial de corrosão (Ecorr) até 800 mVECS. Os dados do potencial de corrosão (Ecorr) e corrente de passivação (Ipass) obtidos das curvas de polarização foram analisados estatisticamente pelo teste t Student. Na comparação entre salivas ácida e neutra os valores de Ecorr e Ipass em todas soluções desinfetantes e períodos propostos não apresentaram diferença estatísitica. A comparação dos valores de Ecorr e Ipass entre água destilada (controle) e soluções desinfetantes em saliva ácida também não mostrou diferença, porém em saliva neutra houve diferença entre os valores de Ipass entre água destilada e hipoclorito de sódio 1% por 40 minutos e entre os valores de Ecorr entre água destilada e ácido peracético 2% por 120 minutos. Entre períodos de imersão, em saliva ácida, houve diferença entre os valores de Ipass do hipoclorito de sódio 1% 10 e 40 minutos e entre os valores de Ecorr do ácido peracético 0,2%. A microscopia eletrônica de varredura associada à energia dispersiva por Raio-X não mostrou diferença entre água destilada e as diferentes soluções desinfetantes frente as salivas ácida e neutra. Conclui-se que as curvas de polarização anódica foram similares em todos os ensaios, apesar das diferenças estatísticas salientadas para Ipass e Ecorr, não ocorreu corrosão superficial em quaisquer amostras após desinfecção e polarização em salivas ácida e neutra. A análise por microscopia eletrônica de varredura associada à espectrometria por dissolução de raios-X não revelaram alterações superficiais nas amostras de titânio comercialmente puro. / This study aimed to assess the corrosion resistance in a grade-4 commercially pure titanium (CP Ti-4) under action of sodium hypochlorite or peracetic acid, during different immersion periods, in acid or neutral artificial saliva for anodic potentiodynamic polarization test. Scanning Electron Microscopy (SEM) was used in conjunction with Energy Dispersive X-Ray Spectroscopy (EDS). This study aimed to assess the corrosion resistance in a grade-4 commercially pure titanium (CP Ti-4) under action of sodium hypochlorite or peracetic acid, during different immersion periods, in acid or neutral artificial saliva for anodic potentiodynamic polarization test. Scanning Electron Microscopy (SEM) was used in conjunction with Energy Dispersive X-Ray Spectroscopy (EDS). Cylindrical CP Ti-4 specimens (5 mm x 5 mm) were involved with copper wire and electrical tape, this set was enclosed in PVC pipe (25 mm x 15 mm) and filled with chemically activated polyester resin to obtain the fifty-four working electrodes which were, then, mechanically polished with sandpaper, felt and polishing paste. The 54 working electrodes were divided into nine groups (n = 6) for solutions and immersion periods: distilled water (control), sodium hypochlorite 1% (10 and 40 minutes), peracetic acid 0.2% ( 10, 30, 40 and 120 minutes) and 2% peracetic acid (30 and 120 minutes). After being immersed in the solutions, they were divided into two subgroups (n = 3), because the anodic polarization tests were performed in triplicate and two electrolytes were used: artificial saliva pH 4.8 and pH 6.8. A saturated calomel electrode (SCE) was used as a reference electrochemical electrode for the anodic polarization test with a platinum counter electrode and a working electrode consisting of CP Ti-4 samples with a 1 mV/s scan rate , starting from the corrosion potential (Ecorr) to 800 mVECS. Data for corrosion potential (Ecorr) and for passive current (Ipass) obtatined from the polarization curves were statistically analyzed by Students t-test. When comparing the Ecorr and Ipass values for acid and neutral saliva and disinfectant solutions during all the periods the statistics presented no difference. The comparison of Ecorr and Ipass values between distilled water (control) and disinfecting solutions in acid saliva also showed no difference, but in neutral saliva there was difference for the values of Ipass between distilled water and 1% sodium hypochlorite for 40 minutes and for the values of Ecorr between distilled water and 2% peracetic acid for 120 minutes. When comparing immersion periods, the acid saliva showed different Ipass values for 1% sodium hypochlorite in 10 and 40 minutes and between the Ecorr values for 0.2% peracetic acid. The scanning electron microscopy associated with Energy Dispersive X-Ray Spectroscopy showed no difference between distilled water and the different disinfectant solutions when in acid or neutral saliva. It is concluded that the polarization anodic curves for both acid and neutral saliva were similar in all trials, despite the statistical differences highlighted for Ipass and Ecorr, surface corrosion did not occur in any samples after disinfection and polarization in acidic and neutral saliva. Analysis by Scanning Electron Microscopy associated with Energy Dispersive X-Ray Spectroscopy revealed no surface changes in the commercially pure titanium samples studied.

O ser humano tem uma grande necessidade de se proteger de fontes de contaminação microbianas. Para tal, ao longo da história, diversos meios foram empregados, desde lavagem com água corrente até as mais modernas substâncias esterilizantes. Entre essas, o ácido peracético (APA) é o mais seguro, sob o ponto de vista ambiental, além de não ser cancerígeno ou tóxico para o corpo humano. O maior empecilho para a aplicação do APA em certas superfícies é seu caráter fortemente oxidante, que pode causar danos em materiais metálicos. Para que tal aplicação seja viável, é necessária a aplicação de inibidores de corrosão que reduzam os danos que o APA possa causar. Para tanto, foram estudadas sete substâncias empregadas comercialmente como inibidores de corrosão para aço inoxidável 304 em meio de ácido peracético a temperatura ambiente: benzotriazol (BTAH), molibdato de sódio, tungstato de sódio, fosfato monossódico, fosfato dissódico, hexametafosfato de sódio e dodecilsulfato de sódio (SDS) e, posteriormente, sinergismos entre os mesmos. Seus desempenhos foram estudados por diferentes técnicas eletroquímicas: potencial de circuito aberto, polarização linear potenciodinâmica, cronoamperometria, espectroscopia de impedância eletroquímica. A superfície do aço foi estudada por microscopia eletrônica de varredura (MEV). As técnicas eletroquímicas demonstraram que o aço 304 encontra-se passivado em meio de ácido peracético 0,2%. Sua resistência à corrosão pode ser significativamente aumentada com o emprego de BTAH, e de sua mistura com SDS, chegando a uma eficiência inibidora de 70%. Os outros inibidores ou pares de inibidores estudados apresentaram eficiências mais baixas. Ensaios microbiológicos foram realizados com o objetivo de se determinar se os inibidores de corrosão poderiam interferir no desempenho do APA como esterilizante. Os resultados obtidos comprovaram que a presença dos inibidores de corrosão BTAH e SDS não interfere sobre a ação esterilizante do APA. / The humanity has a great need to protect itself from microbial contamination. For that, through the history, several ways were employed, since running water washing until the most modern sterilizing substances. Between those, the peracetic acid (PAA) is the safest, under an environmentalist view, besides not being carcinogenic nor toxic to the human body. The great trouble to the application of PAA in some surfaces is its high oxidative property, which can cause damage to metallic materials. Therefore the application of corrosion inhibitor is necessary to reduces the damage that PAA might cause. For that, seven substances commercially applied as corrosion inhibitors for the 304 stainless steel in peracetic acid media were studied: benzotriazole (BTAH), sodium molybdate, sodium tungstate, monosodic phosphate, disodic phosphate, sodium hexametaphophate and sodium dodecilsulphate, as well as the synergism between them. Their per formances were studied through several electrochemical techniques: open circuit potential, linear polarization, chronoamperometry and electrochemical impedance spectroscopy. The steel surfaces were studied through scanning electronic microscopy (SEM). The electrochemical techniques showed that the 304 stainless steel presents passive behavior in 0.2% PAA media. Its corrosion resistance can be significantly improved through the application of BTAH alone, and in combination with SDS, achieving 70% of inhibitor efficiency. The other inhibitors and mixtures studied presented lower efficiency. Microbiological studies were performed aiming to define if the corrosion inhibitor could interfere with the PAA sterilizing performance. The results proved that the presence of BTAH and SDS corrosion inhibitors did not interfere with the sterilizing properties of PAA.

Peressigsäure (PES) hat seit kurzem als Desinfektionsmittel in der Aquakultur Einzug gehalten. Gegenüber anderen konventionellen Desinfektionsmitteln besitzt es in niedrigsten Konzentrationen (ca. 1 mg l-1) eine hohe Effektivität. Des Weiteren hat die Anwendung von PES kaum einen negativen Einfluss auf die Umwelt. Die Applikation von PES in Aquakulturanlagen erfolgt direkt über das umgebende Haltungswasser. Dies geht mit einem direkten Kontakt der Mikroorganismen und der Fische mit dem Wirkstoff einher. Aus diesem Grund ist generell ein Einfluss auf die Fischgesundheit und die Wasserqualität zu erwarten. Dieser hypothetische Einfluss ist bislang jedoch unzureichend untersucht worden. In der Praxis werden zumeist zwei Applikationsstrategien verfolgt: 1. Wiederholende Kurzzeitpulsapplikationen mit relative hohen PES-Konzentrationen (1-2 mg l-1) und 2. Die kontinuierliche Applikation mit relative geringen PES-Konzentrationen (≤ 0,2 mg l-1) in der Wasserzufuhr. Die potentiellen Unterschiede dieser zwei Strategien speziell auf die Fischgesundheit und die Wasserqualität sind bislang unklar. In der vorliegenden Studie wurden Effekte einer PES-Applikation auf die Fischgesundheit und die mikrobielle Aktivität in identischen Durchflussystemen untersucht. Diese Systeme garantieren eine optimale Wasserqualität. Regenbogenforellen wurde als Testorganismen gewählt. Verschiedene Stressparameter, Parameter des oxidativen Stresses, Wachstum, Kiemenhistologie und Parameter der angeborenen Immunantwort wurden zur Bewertung der Fischgesundheit herangezogen. Sauerstoff, pH und die visuelle Biofilmformation wurden kontinuierlich kontrolliert um die mikrobielle Aktivität zu interpretieren. Dazu wurde zweimal wöchentlich mit 1 mg l-1 PES (Pulsbehandlungen) im Haltungswasser und kontinuierlich mit 0,2 mg l-1 PES am Zulauf exponiert und verglichen. Die Ergebnisse belegen, dass die Pulsapplikationen mit 1 mg l-1 PES, im Gegensatz zur kontinuierlichen Applikation mit 0,2 mg l-1 PES die Fische stressten. Die Fische adaptierten sich jedoch an die PES-Pulsapplikationen. Dies wurde durch nachfolgend weniger heftige Reaktionen der Fische post applicationem, reduzierte Kortisolausschüttungen und unveränderte Reaktionen auf andere Stressoren deutlich. Obwohl die PES-Applikation leichte Hyperplasien in den Kiemen induzierte, war kein Einfluss auf das Wachstum und die angeborene Immunantwort feststellbar. Dies kann als ein Beleg für den fehlenden Einfluss der PES-Exposition auf die Fischgesundheit bewertet werden. PES induzierte unabhängig von den Applikationsstrategien oxidativen Stress in den Fischen. Als Antwort auf die PES-Applikation steigerten die Fische ihre antioxidative Antwort gegen die freien Sauerstoffradikale speziell in den Kiemen und im Serum. Unabhängig von den extrem geringen PES-Konzentrationen in der kontinuierlichen Applikation wiesen die Fische einen geringen oxidativen Stress auf. Der oxidative Stress der Fische in der Pulsexposition war hingegen periodisch nachweisbar. Daraus ist zu schlussfolgern, dass die Fische zwischen den Pulsexpositionen, wenn keine PES vorhanden war, Phasen der Erholung hatten. Das Fehlen dieser Erholungsphase in der kontinuierlichen Expositionsgruppe führte zu einer signifikanten Reduktion der Antiprotease-Aktivität im Serum. Dies impliziert das Risiko einer chronischen Entzündung. Die antimikrobiellen Effekte sind stark von der PES-Konzentration abhängig. Die Pulsapplikation mit 1 mg l-1 PES hemmte die mikrobielle Aktivität stärker als die kontinuierliche Exposition durch einen stärkeren oxidativen Stress. Dadurch wurde der Biofilm fast vollständig erodiert, und die mikrobielle Sauerstoffsverbrauch und nitrifikation inhibiert. Die PES-Konzentrationen in der kontinuierlichen Exposition waren zu gering um signifikante Effekte auf den Mikroorganismen auszuüben. Des Weiteren kann das PES-Zerfallsprodukte, die Essigsäure und Acetate, eine potentielle Kohlenstoffquelle für die Mikrobiota darstellen. Der daraus resultierende stärkere Biofilm kann durch die Besiedelung mit fakultativen Fischpathogenen eine Gefahr für die Fischgesundheit darstellen. Auf Grund des starken antimikrobiellen Effekts und des geringen Risikos die Fischgesundheit zu beeinträchtigen, werden periodisch regelmäßige PES-Applikationen in Konzentrationen von 1-2 mg l-1 empfohlen. Effekte einer PES-Applikation auf Spiegelkarpfen und die Wasserqualität in stark belastetem Wasser einer geschlossenen Aquakulturkreislaufanlage (RAS) wurde ebenso untersucht. Die Induktion einer schlechten Wasserqualität erfolge durch den Stopp der Wasserzufuhr zu den Tanks. Simultan zu den Wasserstopps erfolgte eine Applikation mit 1 mg l -1 PES. Die Stressantwort, Kiemenhistologie und die angeborene Immunantwort wurde mit nicht mit PES exponierten Kontrollfischen verglichen. Der Stopp der Wasserzufuhr steigerte die gesamte heterotrophen Bakteriendichte (GHBD) auf das Sechsfache. Im Gegensatz dazu wurde in den Expositionsgruppen die GHBD um 90% gesenkt. Der stark mikrobiozide Effekt der PES-Exposition verbesserte die Gesundheit der Kiemen, verhinderte bakterielle Infektionen welche in den Kontrollgruppen kurzzeitig festgestellt wurden. Zusammenfassend erhält PES appliziert periodisch in Konzentrationen von 1-2 mg l-1, im Fall der optimalen Wasserqualität, die gute Wasserqualität mit geringfügiger Beeinträchtigung der Fischgesundheit. In der Aquakulturproduktion, in welcher die Wasserqualität meistens durch die hoher Besatzdichte und organischer Belastung verschlechtert wird, verhindern regelmäßige prophylaktische PES-Applikationen Infektionen und begünstigen die Fischgesundheit. / Peracetic acid (PAA) has been recently introduced to aquaculture as a sustainable disinfectant. It has great advantages over conventional disinfectants by having high effectiveness and low environmental impact at very low concentrations (around 1 mg L-1). The application of PAA in aquaculture facilities is realized by adding PAA products to the rearing water. This leads to unavoidable exposure of fish and microorganisms (surface-attached and waterborne) to PAA. Consequently, a potential impact of PAA on fish health and microbial activities is expected. This potential impact, however, has been poorly studied. In aquaculture practice, two strategies are broadly used to apply PAA: short term high dose (1-2 mg L-1 PAA) periodic/pulse applications or continuous low dose (≤ 0.2 mg L-1 PAA) application related to the makeup water flow. The potential difference between these two strategies remains unclear, especially concerning their impacts on fish health and water quality. In the present study, the impact of PAA on fish health and microbial activities was tested in identical flow-through systems controlled with optimal water quality. Rainbow trout was selected as the model fish. Various parameters of stress, oxidative stress, growth, gill histology and innate cellular/humoral immunity were measured to indicate fish health. Oxygen, pH and visible biofilm formation were continuously monitored to interpret changes of microbial activities. In addition, the application strategies, biweekly pulse applications of 1 mg L-1 PAA in the rearing water and the continuous application of 0.2 mg L-1 PAA in the inflow, were compared. The results indicate that pulse applications of 1 mg L-1 PAA stressed the naïve fish during the first exposure, while the continuous application not. Fish could progressively adapt to PAA-induced stress, as indicated by less intensive behavioral reaction, reduced cortisol release and unaffected response to another stressor. Although the exposure to PAA induced slight hyperplasia in fish gill, the growth and innate immunity were affected, indicating unaffected overall health. PAA induced oxidative stress in fish, regardless of the application strategies. In response, fish enhanced their antioxidative defense, especially in gill and serum, to scavenge excessive free radicals induced by exposure to PAA. Despite of extremely low PAA concentration measured during the continuous application, the constant input of PAA induced a constant mild oxidative stress to fish. In contrast, the oxidative stress induced by pulse 1 mg L-1 PAA applications was periodic present. Consequently, fish had periodic recovery phases when the pulse PAA applications were absent. The lack of recovery phases in fish exposed to the continuous PAA application resulted in a significant reduction of antiprotease activity in serum. This implies a potential risk of chronic inflammation. The antimicrobial effect of PAA depended on applied concentration. The pulse applications of 1 mg L-1 PAA strongly inhibit microbial activities by inducing a strong oxidative stress. As a result, the biofilm in fish tanks was nearly erased, and the microbial oxygen consumption and nitrification were inhibited. In contrast, the PAA concentration during the continuous application was so low that only a minor antimicrobial effect was observed. In addition, the degradation products, acetic acid and acetate, were beneficial for the biofilm formation by providing organic carbon. The enhanced biofilm may become a potential risk by providing protective shed for opportunistic pathogens. Due to the strong antimicrobial effect and low risk to affect fish health, it’s recommended to apply PAA periodic at high concentrations (1-2 mg L-1) with sufficient intervals. The impact of PAA on fish health and water quality was also tested in a mirror carp recirculating aquaculture system (RAS) challenged with bad water quality. The challenge of bad water quality was realized by transient water stops in fish tanks. Simultaneous to the transient water stops, PAA at 1 mg L-1 was applied. The stress, gill histology and innate cellular immunity were compared in fish with or without simultaneous PAA treatments. The transient water stops caused a 6-fold increase of heterotrophic bacterial density in water, while the simultaneous PAA treatments caused a 90% decrease of heterotrophic bacterial density. The strong antibacterial effect of PAA significantly improved the gill health of fish, and effectively prevented bacterial infections, which were short-term present in fish exposed to transient water stops alone. To sum up, PAA applied periodically at 1-2 mg L-1 in optimal water quality is effective to maintain the water quality at a low cost of scarifying fish health. In production-scale aquaculture facilities, where the water quality is often deteriorated by high stocking density and organic load, regular applications of PAA are especially beneficial to enhance fish health and prevent potential infections.

O objetivo desse estudo foi avaliar a ação de hipoclorito de sódio e ácido peracético na resistência à corrosão de titânio comercialmente puro, grau 4, (Ticp-4) em salivas artificiais, ácida e neutra, com diferentes períodos de imersão, por meio de ensaio de polarização potenciodinâmica anódica, microscopia eletrônica de varredura e espectrometria dispersiva de raios-X. Corpos-de-prova cilíndricos (5 mm x 5 mm) de Ticp-4 foram envolvidos com fio de cobre e fita isolante, este conjunto foi incluído em tubos de PVC (25 mm x 15 mm) e preenchidos com resina poliéster quimicamente ativada, após a polimerização da resina esses eletrodos de trabalho que foram polidos mecanicamente com lixas, feltros e pastas. Os 54 eletrodos de trabalho foram divididos em nove grupos (n=6) referentes às soluções e períodos de imersão: água destilada (controle), hipoclorito de sódio 1% (10 e 40 minutos), ácido peracético 0,2% (10, 30, 40 e 120 minutos) e ácido peracético 2% (30 e 120 minutos). Após serem imersos nas soluções, foram divididos em 2 subgrupos (n=3), pois os ensaios de polarização anódica foram realizados em triplicatas e utilizados dois eletrólitos, salivas artificiais pH 4,8 e pH 6,8. No ensaio de polarização anódica foi utilizada uma célula eletroquímica constituída por um eletrodo de referência do tipo calomelano saturado (ECS), um contra-eletrodo de platina e o eletrodo de trabalho constituído pelas amostras de Ticp-4, com taxa de varredura de 1 mV/s, partindo-se do potencial de corrosão (Ecorr) até 800 mVECS. Os dados do potencial de corrosão (Ecorr) e corrente de passivação (Ipass) obtidos das curvas de polarização foram analisados estatisticamente pelo teste t Student. Na comparação entre salivas ácida e neutra os valores de Ecorr e Ipass em todas soluções desinfetantes e períodos propostos não apresentaram diferença estatísitica. A comparação dos valores de Ecorr e Ipass entre água destilada (controle) e soluções desinfetantes em saliva ácida também não mostrou diferença, porém em saliva neutra houve diferença entre os valores de Ipass entre água destilada e hipoclorito de sódio 1% por 40 minutos e entre os valores de Ecorr entre água destilada e ácido peracético 2% por 120 minutos. Entre períodos de imersão, em saliva ácida, houve diferença entre os valores de Ipass do hipoclorito de sódio 1% 10 e 40 minutos e entre os valores de Ecorr do ácido peracético 0,2%. A microscopia eletrônica de varredura associada à energia dispersiva por Raio-X não mostrou diferença entre água destilada e as diferentes soluções desinfetantes frente as salivas ácida e neutra. Conclui-se que as curvas de polarização anódica foram similares em todos os ensaios, apesar das diferenças estatísticas salientadas para Ipass e Ecorr, não ocorreu corrosão superficial em quaisquer amostras após desinfecção e polarização em salivas ácida e neutra. A análise por microscopia eletrônica de varredura associada à espectrometria por dissolução de raios-X não revelaram alterações superficiais nas amostras de titânio comercialmente puro. / This study aimed to assess the corrosion resistance in a grade-4 commercially pure titanium (CP Ti-4) under action of sodium hypochlorite or peracetic acid, during different immersion periods, in acid or neutral artificial saliva for anodic potentiodynamic polarization test. Scanning Electron Microscopy (SEM) was used in conjunction with Energy Dispersive X-Ray Spectroscopy (EDS). This study aimed to assess the corrosion resistance in a grade-4 commercially pure titanium (CP Ti-4) under action of sodium hypochlorite or peracetic acid, during different immersion periods, in acid or neutral artificial saliva for anodic potentiodynamic polarization test. Scanning Electron Microscopy (SEM) was used in conjunction with Energy Dispersive X-Ray Spectroscopy (EDS). Cylindrical CP Ti-4 specimens (5 mm x 5 mm) were involved with copper wire and electrical tape, this set was enclosed in PVC pipe (25 mm x 15 mm) and filled with chemically activated polyester resin to obtain the fifty-four working electrodes which were, then, mechanically polished with sandpaper, felt and polishing paste. The 54 working electrodes were divided into nine groups (n = 6) for solutions and immersion periods: distilled water (control), sodium hypochlorite 1% (10 and 40 minutes), peracetic acid 0.2% ( 10, 30, 40 and 120 minutes) and 2% peracetic acid (30 and 120 minutes). After being immersed in the solutions, they were divided into two subgroups (n = 3), because the anodic polarization tests were performed in triplicate and two electrolytes were used: artificial saliva pH 4.8 and pH 6.8. A saturated calomel electrode (SCE) was used as a reference electrochemical electrode for the anodic polarization test with a platinum counter electrode and a working electrode consisting of CP Ti-4 samples with a 1 mV/s scan rate , starting from the corrosion potential (Ecorr) to 800 mVECS. Data for corrosion potential (Ecorr) and for passive current (Ipass) obtatined from the polarization curves were statistically analyzed by Students t-test. When comparing the Ecorr and Ipass values for acid and neutral saliva and disinfectant solutions during all the periods the statistics presented no difference. The comparison of Ecorr and Ipass values between distilled water (control) and disinfecting solutions in acid saliva also showed no difference, but in neutral saliva there was difference for the values of Ipass between distilled water and 1% sodium hypochlorite for 40 minutes and for the values of Ecorr between distilled water and 2% peracetic acid for 120 minutes. When comparing immersion periods, the acid saliva showed different Ipass values for 1% sodium hypochlorite in 10 and 40 minutes and between the Ecorr values for 0.2% peracetic acid. The scanning electron microscopy associated with Energy Dispersive X-Ray Spectroscopy showed no difference between distilled water and the different disinfectant solutions when in acid or neutral saliva. It is concluded that the polarization anodic curves for both acid and neutral saliva were similar in all trials, despite the statistical differences highlighted for Ipass and Ecorr, surface corrosion did not occur in any samples after disinfection and polarization in acidic and neutral saliva. Analysis by Scanning Electron Microscopy associated with Energy Dispersive X-Ray Spectroscopy revealed no surface changes in the commercially pure titanium samples studied.

Made available in DSpace on 2017-07-24T19:38:05Z (GMT). No. of bitstreams: 1 Grasiele Cavallini.pdf: 1079338 bytes, checksum: 72df0086e3189309ac759c245ed41fed (MD5) Previous issue date: 2011-06-17 / This work aims to study the use of peracetic acid (PAA) to disinfect wastewater. Into this perspective, some methods were investigated to determine residual PAA, factors that interfere with its disinfecting action, its kinetic of degradation in wastewater and some possible by-products coming from its application. The results showed that the concentrations between 0,5 and 10 mg/L of PAA could be determined as for cerimetric/iodometric method as for spectrofotometric method using cromophore DPD. To concentrations between 01 and 05 mg/L only the method with DPD could be recommended. The disinfection tests with PAA demonstrated the grades of SST larger than 50mg/L implicated in an increase of 50% in disinfectant consume to inactivate total coliforms microorganisms and E.coli. The efficiency to inactivation of PAA related to the E.coli was also damaged in conditions of pH larger than 8. The time of contact had major influence in disinfection efficiency in dose up to 5mg/L of PAA. The kinetic tests showed that the degradation of PAA, about the studied wastewater, could be represented for a reaction of first order and its time of half-life in the wastewater was estimated in 79 minutes. The formation of by-products: nonanal, decanal, chlorophenols and 1-metoxi-4-methylbenzene weren’t observed in the wastewater, using the PAA dose of 10mg/L. With this same dose the physicochemical conditions like pH, BOD and COD of wastewater didn’t suffer prominent variation, however the DO got a larger increase of 60%, being this one of the most significant physicochemical contributions. Thus, the results with application of PAA indicated that its use in doses up to 10mg/L contributed to inactivate microorganisms and not altered significantly initial conditions of wastewater and there weren’t environmental damages demonstrated about the studied parameters. / Este trabalho tem por objetivo estudar a utilização do ácido peracético (APA) na desinfecção de efluentes sanitários. Dentro desta perspectiva foram investigados: métodos para determinação do APA residual, os fatores que interferem na sua ação desinfetante, sua cinética de degradação no efluente e alguns possíveis subprodutos provenientes da sua aplicação. Os resultados obtidos demonstraram que as concentrações entre 0,5 e 10 mg/L de APA puderam ser determinadas tanto pelo método cerimétrico/iodométrico como pelo método espectrofotométrico utilizando o cromóforo DPD. Para concentrações entre 0,1 e 0,5 mg/L apenas o método com DPD pôde ser recomendado. Os ensaios de desinfecção com APA demonstraram que teores de SST superiores a 50 mg/L implicaram em um aumento de 50% no consumo do desinfetante para inativação dos microrganismos coliformes totais e E. coli. A eficiência de inativação do APA em relação a E. coli também foi prejudicada em condições de pH superiores a 8. O tempo de contato teve maior influência na eficiência de desinfecção em dosagens até 5 mg/L de APA. Os ensaios cinéticos demonstraram que a degradação do APA, no efluente em estudo, pôde ser representada por uma reação de primeira ordem e seu tempo de meia-vida no efluente foi estimado em 79 minutos. A formação dos subprodutos: nonanal, decanal, clorofenóis e 1-metoxi-4-metilbenzeno não foram observadas no efluente, utilizando a dosagem de 10 mg/L de APA. Com esta mesma dosagem as condições físico-químicas, como pH, DBO e DQO do efluente não sofreram acentuada variação, porém o OD obteve um aumento superior a 60%, sendo esta uma das contribuições físico-químicas mais significativas. Assim, os resultados obtidos com a aplicação do APA indicaram que sua utilização em dosagens até 10 mg/L contribuíram para inativação de microrganismos e não alteraram de forma significativa as condições iniciais do efluente, além de não ter demonstrado prejuízos ambientais nos parâmetros estudados.

Listeria monocytogenes é o agente causal da listeriose, uma doença que pode atingir mulheres grávidas (e seus fetos), crianças, idosos e indivíduos com o sistema imunológico comprometido, A listeriose representa a maioria dos casos de morte decorrente de toxinfecções alimentares. Os alimentos são reconhecidos como fontes primárias da transmissão desta bactéria para o homem e L. monocytogenes já foi isolada de uma grande variedade de alimentos. Superfícies de equipamentos utilizados na produção de alimentos também podem estar contaminadas com este patógeno. Falhas em procedimentos de higienização podem deixar resíduos nos equipamentos de processamento de alimentos e L. monocytogenes pode se aderir a superfícies abióticas e iniciar sua multiplicação, dando origem a biofilmes. A interação com bactérias de outras espécies pode influenciar na forma formação de biofilmes por L. monocytogenes, constituindo um aspecto importante de estudo para auxiliar no controle da contaminação de alimentos por esta bactéria. Leuconostoc mesenteroides é uma bactéria lática normalmente encontrada em alimentos e algumas cepas podem interferir na multiplicação de L. monocytogenes pela produção de bacteriocinas com atividade antilisterial. Os biofilmes representam uma preocupação para indústria de alimentos, pois geralmente os microorganismos aderidos apresentam maior capacidade de resistir a tratamentos antimicrobianos. Neste trabalho, foram coletadas 30 amostras de presunto cozido fatiado, 30 de mussarela fatiada e 30 de superfícies de equipamentos de fatiar alimentos, em estabelecimentos do comércio varejista de Ribeirão Preto SP. As amostras forma avaliadas quanto à presença ou ausência de L. monocytogenes e também foi estudada a capacidade dos isolados em formar biofilmes em cultura pura e em testes de co-cultura. O sanitizante ácido peracético e a bacteriocina nisina foram testados para controlar a formação de biofilme por L. monocytogenes. Os resultados obtidos mostram que os isolados de L. monocytogenes formaram biofilme em superfície de aço inoxidável quando cultivados isoladamente ou em testes de co-cultura com L.mesenteroides. O tratamento da lâmina com ácido peracético inativou todas as células presentes no biofilme. Nas condições utilizadas, nisina não apresentou atividade contra L.monocytogenes em biofilmes. / Listeria monocytogenes is the causal agent of listeriosis, an infection that targets mainly pregnant women (and their fetuses), children, the elderly and immunocompromised individuals. Listeriosis represents the majority of fatal cases of foodborne diseases. Foods are recognized as primary sources of transmission of this bacterium to man and L. monocytogenes has been isolated from of a great variety of foods. Surfaces of equipments used in the production of foods can harbour L. monocytogenes. Failures in sanitization procedures can leave food residues adhered to equipments of food processing and L. monocytogenes can attach to abiotic surfaces, multiply and form biofilms. Interactions among bacteria of diverse species may influence biofilm formation by L. monocytogenes and this is an important issue to be studied to improve food safety. Leuconostoc mesenteroides is a lactic bacterium usually found in foods and some strains can interfere with the multiplication of L. monocytogenes by production of bacteriocins with antilisterial activity. Biofilms represent a special concern to the food industry, because adhered microorganism are generally more resistant to antimicrobial treatments. In this work, we collected 30 samples of sliced cooked ham, 30 of sliced mozzarella cheese and 30 of surfaces of food processing equipments, in the retail market of the city of Ribeirão Preto - SP. The samples were studied for presence or absence of L. monocytogenes. The ability of the isolates to form biofilms was also studied, in pure and in co-culture tests. The sanitizer peracetic acid and the bacteriocin nisin were tested to control biofilm formation by L. monocytogenes. L. monocytogenes formed biofilm on stainless steel coupons when cultivated alone or in co-culture with L. mesenteroides. The treatment of stainless steel coupons with peracetic acid inactivated the cells of the biofilm. Under the experimental conditions tested nisin did not present activity against L. monocytogenes in biofilms.

[pt] O objetivo deste estudo foi avaliar o efeito biocida do ácido peracético (APA) em águas de sistemas de resfriamento, de forma a buscar alternativas ao uso do cloro, que é corrosivo e reage com a matéria orgânica natural ou sintética presentes na água, formando subprodutos tóxicos. Para atingir este objetivo, experimentos utilizando amostras de água retiradas da bacia de uma torre de resfriamento de uma indústria química foram realizados. Ensaios foram executados utilizando-se uma solução comercial de APA, mantendo-se concentrações do biocida em 1,0 mgL-1 e 2,0 mgL-1 em pH 8,0 e 8,8. Cada condição de estudo foi monitorada ao longo de 5 dias, e contagens de bactérias heterotróficas mesófilas totais foram realizadas tanto antes da aplicação do biocida como em diferentes tempos de contato do biocida com a microbiota natural da água. Os tempos de contato monitorados foram de 5 min, além de 1, 2 e 4 h por dia considerando a aplicação do biocida em períodos totais de 4 h por dia. Com esta metodologia foi possível concluir que as duas dosagens aplicadas foram eficientes no combate aos microrganismos presentes naturalmente nas amostras de água, nos dois valores de pH estudados. A partir de uma carga microbiana natural da água de 106 a 107 UFC/mL, após o tratamento houve uma redução para contagens de no máximo de 104 UFC/mL em todos os experimentos, limite máximo esse adotado pelas indústrias para carga microbiana em águas de sistemas de resfriamento, entretanto, houve maior eficiência, cerca de 10 vezes maior, quando 2,0 mgL-1 de APA foi aplicado. Além disso, em pH 8,0 a ação do biocida também foi superior em 10 vezes em detrimento ao pH 8,8 para a mesma concentração de APA. / [en] The purpose of this study was to evaluate the biocidal effect of peracetic acid (PAA) in cooling water, in order to find alternatives to the use of chlorine, which is corrosive and reacts with natural and synthetic organic matter present in water, forming toxic byproducts. To achieve this goal, experiments using water samples taken from a basin of a chemical industry cooling tower were conducted. Experiments were performed using a commercial PAA solution, with concentrations of 1,0 mgL-1 and 2,0 mgL-1 and pH 8,0 and 8,8. Each study condition was monitored for 5 days and total mesophilic heterotrophic bacteria counts were made without biocide and after different contact times of the biocide and microorganisms present in water. The contact times were 5 min, and 1, 2 and 4 h per day, considering the application of the biocide in total periods of 4 h per day. This methodology has allowed concluding that two dosages applied were efficient in controlling microorganisms at the two pH values. From a water natural microbial count of 106 to 107 UFC/mL, after treatment there was a reduction to maximum counts to 104 UFC/mL in all experiments, that being the upper limit adopted by industries for microorganisms in cooling water systems. However, the results were 10 times more efficient when 2,0 mgL-1 of PAA were applied. In addition, at pH 8,0 the biocidal action was 10 times higher in comparison to pH 8,8 for the same PAA concentration.

The aim of the diploma thesis was to evaluate the influence of antiparasitic baths on selected biochemical and haematological parameters in the blood samples of fish. According to the results the application schema will be specified or amended such alterations will be substantiated. A test was performed on the fry of carp (naked and scaly form) to evaluate the influence of the peractetic acid with the help of biochemical and haematological parameters and with the histopathological examination. The common carp was exposed to the concetration 1 mg?l-1 and 2 mg?l-1 of PAA. Three days after application was taken the blood samples from fish and the biochemical and haematological parameters were determined. Than was taken a sample of skin with the musculature from fish to be sent for the histopathological examination in University of Veterinary and Pharmaceutical Sciences in Brno. Based on the results the naked form of the carp has been declared to be more sensitive to the application of PAA. All the observed changes in haematological and biochemical parameters were within physiological range, so it can be stated, that the application schema of PAA has not a signifiant negative influence on the health of the tested fish.