Disinfection By-Products Formation from Chlor(am)ination of Algal Organic Matter of Chlorella sorokiniana.

Eutrophication in water reservoirs releases algal organic matter (AOM), which is an important precursor of disinfection by-products (DBPs) formed during water treatment. Chlorella sorokiniana is a microalgae which flourishes under conditions of high light intensity and temperature, thus its prevalence in algal blooms is expected to increase with climate change. However, Chlorella sorokiniana AOM has not been previously investigated as a DBP precursor. In this context, this study evaluated the effect of AOM concentration, humic acid (HA), and pH on DBP formation from chlor(am)ination of AOM Chlorella sorokiniana. DBP yields determined by linear regression for trichloromethane (TCM) and chloral hydrate (CH) were 57.9 and 46.0 µg·mg DOC-1 in chlorination, while the TCM, CH, dichloroacetonitrile (DCAN), 1,1,1-trichloropropanone (1,1,1-TCP), and chloropicrin (CPN) concentrations were 33.6, 29.8, 16.7, 2.1, and 1.2 µg·mg DOC-1 in chloramination. Chloramination reduced the formation of TCM and CH but increased CPN, DCAN, and 1,1,1-TCP yields. AOM Chlorella sorokiniana showed a higher DBP formation than 9 of 11 algae species previously investigated in the literature. At basic pH, the concentration of TCM increased while the concentration of other DBP classes decreased. Bromide was effectively incorporated into the AOM structure and high values of bromine incorporation factor were found for THM (1.81-1.89) and HAN (1.32) at 1.5 mg Br·L-1. Empirical models predicted successfully the formation of THM and HAN (R2 > 0.86). The bromide concentration had more impact in the model on the DBP formation than AOM and HA. These results provide the first insights into the DBP formation from AOM chlor(am)ination of Chlorella sorokiniana.

Multidrug-resistant Enterobacter spp. in wastewater and surface water: Molecular characterization of ß-lactam resistance and metal tolerance genes.

Among the ESKAPE group pathogens, Enterobacter spp. is an opportunistic Gram-negative bacillus, widely dispersed in the environment, that causes infections. In the present study, samples of hospital wastewater, raw and treated urban wastewater, as well as surface receiving water, were collected to assess the occurrence of multidrug-resistant (MDR) Enterobacter spp. A molecular characterization of ß-lactam antibiotic resistance and metal tolerance genes was performed. According to identification by MALDI-TOF MS, 14 isolates were obtained: 7 E. bugandensis, 5 E. kobei, and 2 E. cloacae. The isolates showed resistance mainly to ß-lactam antibiotics, including those used to treat infections caused by MDR bacteria. Multiple antibiotic resistance index was calculated for all isolates. It allowed verify whether sampling points showed a high risk due to antibiotic resistant Enterobacter spp., as well as to determine if the isolates have been in environments with a frequent antibiotic use. Twelve isolates showed ß-lactam antibiotic resistance gene, being the blaKPC widely detected. Regarding metal tolerance, 13 isolates showed at least two genes that encode metal tolerance mechanisms. Overall, metal tolerance mechanisms to silver, copper, mercury, arsenic and tellurium were found. New data on metal tolerance mechanisms dispersion and antibiotic-resistance characterization of the E. bugandensis and E. kobei species were here provided. The occurrence of MDR Enterobacter spp. in analyzed samples draws attention to an urgent need to put control measures into practice. It also evidences waterborne spread of clinically important antibiotic-resistant bacteria recognized as critical priority pathogens.

Predição da performance de carvão ativado granular para remoção de herbicidas com ensaios em coluna de escala reduzida / Prediction of granular activated carbon performance in removing herbicides with rapid small-scale column tests

RESUMO: Na região de Ribeirão Preto está localizado um dos polos produtores da cana-de-açúcar, com vasta área cultivada e uso intensivo de herbicidas, tais como o diuron e a hexazinona, os quais possuem elevado potencial de contaminação em águas superficiais e subterrâneas. Diversas tecnologias podem ser utilizadas para remover esses microcontaminantes da água, em função de, neste caso, não ser eficiente a técnica de tratamento em ciclo completo (ou convencional). Neste trabalho, estudou-se o desempenho do carvão ativado granular na remoção destes herbicidas. A água de estudo foi preparada em laboratório e fortificada com diuron e hexazinona. Foi construída e operada uma instalação piloto com colunas de adsorção em carvão ativado granular, cujos resultados obtidos mostraram que a difusividade intrapartícula predominante entre o carvão e os herbicidas diuron e hexazinona pode ser considerada constante, em relação ao tamanho do grão de carvão ativado. Eles também possibilitaram a validação do método de ensaios rápidos em coluna de carvão ativado em escala reduzida, com vista à predição do tempo para ruptura de um filtro de carvão ativado granular em escala real.

ABSTRACT: Ribeirão Preto has one of the producer poles of sugarcane, with a vast sugarcane plantation area and intensive use of herbicides, especially diuron and hexazinone, which have high potential of contaminating surface waters and groundwater. Several technologies can be used to remove these micro-contaminants from water, since the conventional treatment in complete cycle is not an efficient technique for this case. In the present study, the performance of the granular activated carbon in removing these herbicides was evaluated. The water sample was prepared in a laboratory and supplemented with diuron and hexazinone. A pilot granular activated carbon column was built and operated, and the results showed that the prevailing intra-particle diffusivity between carbon and diuron and hexazinone herbicides could be considered constant, with regard to the size of the activated carbon grain. The results obtained also enabled the validation of the rapid small-scale column test method to predict the full scale breakthrough time of a granular activated carbon filter.

Aplicacao da tecnica por cromatografia a gas para investigacao da formacao de sub produtos da desinfeccao em agua potavel / Application of gas chromatographic technique for investigation of the formation of by products in drinking water disinfection

O uso do cloro para a desinfecção e/ou oxidação nas estações de tratamento de água favorece a formação de subprodutos orgânicos halogenados (SOH), muitos deles carcinogênicos. O objetivo desta pesquisa foi validar uma metodologia analítica proposta para a quantificação simultânea de 12 subprodutos da desinfecção por cromatografia a gás com detector de captura de elétrons (CG-DCE). O método apresentou linearidade (r>0,998), repetibilidade menor que 0,15%, limites de detecção de 1 a 6 µg.L-1 e de quantificação de 3 a 21 Î1/4g.L-1, precisão (<10%), exatidão (93-120%) e recuperação (87-117%). Os resultados indicam que o método pode ser empregado para a investigação de SOH em água, garantindo confiabilidade analítica nos resultados.

The use of chlorine for disinfection and/or oxidation at drinking water treatment plants favors the formation of halogenated organic by-products (HOB), many of them carcinogenic. The purpose of this research was to validate an analytical method for the simultaneous quantification of 12 HOB from disinfection by gas chromatograph with electrons capture detector (GC-ECD). The method provided linearity (r>0.998), repeatability lower than 0.15%, limits of detection from 1 to 6 Î1/4g.L-1 and of quantification from 3 to 21 Î1/4g.L-1, precision (<10%), accuracy (93-120%) and recovery (87-117%). The results indicate that the method can be employed to investigate the formation of HOB in water, yielding analytically reliable results.

Toxicidade aguda dos herbicidas Diuron e hexazinona à Danio rerio / Acute toxicity of herbicides diuron and hexazinone to Danio rerio

O objetivo deste trabalho foi avaliar a toxicidade de herbicida comercial aplicado extensivamente nacana-de-açúcar, composto por diuron, hexazinona e ingredientes inertes, usando-se Daniorerio como organismo-teste. Os ensaios foram realizados em laboratório e seguiram recomendações da ABNT (2004) e USEPA (2002). Os parâmetros de controle da água foram pH, dureza total, condutividade, oxigênio dissolvido e temperatura, observando-se a atividade natatória e a mortalidade dos organismos. A CL50 do herbicida comercial para Daniorerio foi de 581,50 mg.L-1. Em concentrações a partir de 50 mg.L-1 do herbicida comercial foram observadas alterações comportamentais significativas, como hipoatividade relacionada ao movimento natatório em mais de 50% dos organismos. Para avaliação da toxicidade dos ingredientes inertes, responsáveis por 40% (m/m) da composição do herbicida, foram testados os compostos hexazinona e diuron separadamente.Nas concentrações estudadas, a hexazinona e o Diuron não resultaram em mortalidade ou alteração ao movimento natatório. Concluiu-se que os ingredientes inertes da composição do herbicida comercial foram os principais causadores da toxicidade aguda causada ao Danio rerio.

Pré-oxidação e adsorção em carvão ativado granular para remoção dos herbicidas Diuron e Hexazinona de água subterrânea / Preoxidation and adsorption in granular activated carbon for the removal of Diuron and Hexazinone from groundwater

O cultivo da cana-de-açúcar exige a utilização de herbicidas, destacando-se o Diuron e a Hexazinona. Alguns dos poços de abastecimento de Ribeirão Preto (SP) construídos no Aquífero Guarani estão situados em pontos de recarga, e a presença de solo de textura arenosa nessas áreas aumenta a vulnerabilidade da água subterrânea à contaminação por herbicidas. Neste trabalho foram monitorados alguns poços localizados na área de recarga e estudou-se a remoção de Diuron e Hexazinona por meio da adsorção em carvão ativado granular (CAG) e da pré-oxidação com cloro e dióxido de cloro em uma instalação piloto de escoamento contínuo. Verificou-se que o tempo de saturação do CAG no ensaio com a pré-oxidação foi inferior ao obtido no ensaio sem a pré-oxidação com ambos os oxidantes, possivelmente pela formação de subprodutos que competiram com a adsorção dos herbicidas.

The cultivation of sugarcane demands the use of herbicides such as Diuron and Hexazinone. Some supply wells from Ribeirão Preto, SP, Brazil, built in the Guarani Aquifer are located in recharge points, and the presence of sandy Quartzarenic Neosol in these areas increases the vulnerability of the groundwater to contamination from herbicides This paper reports the water quality monitored in some wells located in the recharge area and the removal of Diuron and Hexazinone by means of adsorption in granular activated carbon (GAC), preceded or not by preoxidation with chlorine and chlorine dioxide in a pilot plant. The results indicated that Diuron was more strongly adsorbed than Hexazinone and that the saturation time of the GAC in the test with preoxidation was shorter than in the test without preoxidation, which may have occurred mainly due to the formation of by-products that competed with the adsorption of the herbicides.

Cleaning of flattened root canals with different irrigating solutions and nickel-titanium rotary instrumentation.

The aim of this study was to evaluate the cleaning capacity of Profile .04 files combined with different irrigating solutions in flattened root canals using histological, morphometrical and SEM analyses. Eighty human mandibular incisors were prepared with Profile .04 instruments and randomly divided into 4 groups according to the irrigating solutions used (n=20): G1: distilled water (control); G2: 1% sodium hypochlorite (NaOCl); G3: 1% NaOCl alternated with 17% EDTA, and G4: 1% NaOCl with RCPrep cream. Ten teeth of each group were evaluated with an optical microscope to determine the percentage of root canal debris. The remaining teeth were evaluated under scanning electron microscopy (SEM). Data were analyzed statistically by ANOVA and Tukey's test (alpha=0.01).There was a significant difference (p<0.001) among the groups regarding the percentage of debris left in the canals (distilled water: 18.82 +/- 5.55; 1% NaOCl: 6.29 +/- 5.55; 1% NaOCl + 17% EDTA: 12.47 +/- 6.92; 1% NaOCl + RCPrep: 7.82 +/- 1.91). The SEM analysis showed the best results for 1% NaOCl + 17% EDTA on smear layer removal. It may be concluded that the combination of Profile .04 rotary instrumentation and the tested solutions was not able to totally remove debris and smear layer from flattened root canals.

Cleaning of flattened root canals with different irrigating solutions and nickel-titanium rotary instrumentation

The aim of this study was to evaluate the cleaning capacity of Profile .04 files combined with different irrigating solutions in flattened root canals using histological, morphometrical and SEM analyses. Eighty human mandibular incisors were prepared with Profile .04 instruments and randomly divided into 4 groups according to the irrigating solutions used (n=20): G1: distilled water (control); G2: 1 percent sodium hypochlorite (NaOCl); G3: 1 percent NaOCl alternated with 17 percent EDTA, and G4: 1 percent NaOCl with RCPrep cream. Ten teeth of each group were evaluated with an optical microscope to determine the percentage of root canal debris. The remaining teeth were evaluated under scanning electron microscopy (SEM). Data were analyzed statistically by ANOVA and Tukey's test (á=0.01).There was a significant difference (p<0.001) among the groups regarding the percentage of debris left in the canals (distilled water: 18.82 ± 5.55; 1 percent NaOCl: 6.29 ± 5.55; 1 percent NaOCl + 17 percent EDTA: 12.47 ± 6.92; 1 percent NaOCl + RCPrep: 7.82 ± 1.91). The SEM analysis showed the best results for 1 percent NaOCl + 17 percent EDTA on smear layer removal. It may be concluded that the combination of Profile .04 rotary instrumentation and the tested solutions was not able to totally remove debris and smear layer from flattened root canals.

O objetivo deste estudo foi avaliar a capacidade de limpeza dos instrumentos Profile .04 associados a diferentes soluções irrigantes, em canais radiculares achatados, por meio de análises histológica, morfométrica e MEV. Oitenta incisivos inferiores humanos foram submetidos ao preparo biomecânico com instrumentos Profile .04 e aleatoriamente distribuídos em 4 grupos de acordo com as soluções irrigantes usadas (n=20): G1 - água destilada (controle); G2 - NaOCl 1 por cento; G3 - NaOCl 1 por cento alternado com EDTA 17 por cento e G4 - NaOCl 1 por cento com RCPrep creme. Dez dentes de cada grupo foram avaliados em microscopia óptica para determinação da porcentagem de debris do canal radicular. Os demais dentes foram avaliados em microscopia eletrônica de varredura. A análise estatística mostrou diferença significante (p<0,001) entre os grupos ao considerar a porcentagem de debris remanescente nos canais (água destilada: 18,82 ± 5,55; NaOCl: 6,29 ± 5,55; NaOCl + EDTA: 12,47 ± 6,92; NaOCl + RCPrep: 7,82 ± 1,91). A análise em MEV evidenciou melhores resultados na remoção da camada de smear com o NaOCl 1 por cento alternado com EDTA 17 por cento. Pode-se concluir que a associação entre a instrumentação rotatória com Profile .04 e as soluções testadas não foi capaz de remover totalmente debris e camada de smear de canais radiculares achatados.

Formação de subprodutos orgânicos halogenados nas operações de pré-oxidação com cloro, ozônio e peroxônio e pós-cloração em água conténdo subtância húmica / Formation of halogenated organic byproducts using preoxidation with chlorine, ozone and peroxone and post-chlorination of water containing humic substances

Dentre os compostos orgânicos halogenados que podem ser encontrados na água distribuída à população, destacam-se: trialometanos, ácidos haloacéticos, haloaldeídos, halocetonas, halofenóis e halopicrinas. O presente trabalho teve como objetivo avaliar o efeito da formação de 22 subprodutos com a utilização dos pré-oxidantes: cloro, ozônio e peroxônio. A formação de subprodutos foi observada em água preparada com adição de substâncias húmicas extraídas de solo turfoso, por meio do uso da pré-oxidação, presença e ausência de coagulação, filtração e pós-cloração. Os subprodutos foram quantificados por cromatografia gasosa com detetor de captura de elétrons. Os resultados obtidos mostraram que o uso de pré-oxidantes alternativos, ozônio e peroxônio, associados à coagulação, filtração e pós-cloração, formam quantidades pequenas de subprodutos.

When chlorine is used as preoxidant, the formation of halogenated organic byproducts found in water treated and distriduted to the population, are: trihalometane, haloacetic acids, haloaldehyde, haloketone, halophenol and halopicrin. This research was performed to evaluate the formation potential of 22 byproducts using the following preoxidants: chlorine, ozone and peroxone. The formation of byproducts was simulated in water prepared with the addition of humic substances extracted from peat soil by the use of preoxidants, coagulation, filtration, and post-chlorination. Byproducts have quantified by gas chromatography with electron capture detector. The results obtained showed that the use of alternative preoxidants, such as ozone and peroxone, associated with coagulation, filtration, and post-chlorination form a low concentration of byproducts.

Chemical analysis of the flocculate formed by the association of sodium hypochlorite and chlorhexidine.

OBJECTIVE: The association of chlorhexidine (CHX) and sodium hypochlorite (NaOCl) to enhance their chemical properties during root canal biomechanical preparation can lead to a brown flocculate being formed. Therefore, this study evaluated the metals present in their association by atomic absorption spectrophotometry, and evaluated a possible reagent that could dissolve the flocculate, allowing its clinical use. STUDY DESIGN: Five concentrations of CHX and NaOCl were mixed (2.5% NaOCl + 0.2% CHX, 2% CHX + 0.5% NaOCl, 2% CHX + 5% NaOCl, 0.2% CHX + 0.5% NaOCl, and 0.2% CHX + 5% NaOCl). Methanol and hexane, acetic acid, and vinegar were evaluated to dissolve the flocculate. RESULTS: A flocculate was formed with all proportions and concentrations. Spectrophotometry analysis showed the presence of Ca, Fe, and Mg. CONCLUSION: It can be concluded that the association proposed led to the formation of brown flocculate regardless of concentration and proportion.