Luiz Di Bernardo

Removal of diclofenac by conventional drinking water treatment processes and granular activated carbon filtration

This study was carried out to evaluate the efficiency of conventional drinking water treatment processes with and without pre-oxidation with chlorine and chlorine dioxide and the use of granular activated carbon (GAC) filtration for the removal of diclofenac (DCF). Water treatment was performed using the Jar test with filters on a lab scale, employing nonchlorinated artesian well water prepared with aquatic humic substances to yield 20HU true color, kaolin turbidity of 70 NTU and 1mgL(-1) DCF. For the quantification of DCF in water samples, solid phase extraction and HPLC-DAD methods were developed and validated. There was no removal of DCF in coagulation with aluminum sulfate (3.47mgAlL(-1) and pH=6.5), flocculation, sedimentation and sand filtration. In the treatment with pre-oxidation and disinfection, DCF was partially removed, but the concentration of dissolved organic carbon (DOC) was unchanged and byproducts of DCF were observed. Chlorine dioxide was more effective than chorine in oxidizing DCF. In conclusion, the identification of DCF and DOC in finished water indicated the incomplete elimination of DCF through conventional treatments. Nevertheless, conventional drinking water treatment followed by GAC filtration was effective in removing DCF (⩾99.7%). In the oxidation with chlorine, three byproducts were tentatively identified, corresponding to a hydroxylation, aromatic substitution of one hydrogen by chlorine and a decarboxylation/hydroxylation. Oxidation with chlorine dioxide resulted in only one byproduct (hydroxylation).

Formação de subprodutos orgânicos halogenados nas operações de pré-oxidação com cloro, ozônio e peroxônio e pós-cloração em água conténdo subtância húmica

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.

Influence of the apparent molecular size of aquatic humic substances on colour removal by coagulation and filtration

This study aims to verify the influence of the apparent molecular size of aquatic humic substances (AHSs) on the effectiveness of coagulation with aluminium sulphate and ferric chloride. Coagulation-filtration tests using the jar test and bench-scale sand filters were carried out with water samples having a true colour of approximately 100 Hazen units and prepared with AHSs of different molecular sizes. Stability diagrams are presented showing regions of≥90% and≥95% apparent colour removal delineated for each water sample using plots of total metal ion concentration (Al3+ and Fe3+) versus coagulation pH. To achieve the same degree of colour removal, the water samples with smaller apparent molecular sizes and a higher percentage of fulvic acids required higher dosages of both aluminium sulphate and ferric chloride.

Uso de modelação matemática para projeto de câmaras mecanizadas de floculação em série em estações de tratamento de água

The existing methodology in the literature to optimize the velocity gradients in continuous flow completely mixed reactors using batch test data (static reactors) is based on mathematical models that describe the flocculation kinetics. Since this methodology has been shown to be inconsistent, as observed by several researchers, this work was carried out in order to propose a rational methodology to optimize the static reactors experimental data to obtain the design parameters of mechanized flocculation systems for water treatment plants.

Pré-oxidação e adsorção em carvão ativado granular para remoção dos herbicidas Diuron e Hexazinona de água subterrânea

The cultivation of sugarcane demands the use of herbicides such as Diuron and Hexazinone. Some supply wells from Ribeirao 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.

Influência das características das substâncias húmicas na eficiência da coagulação com sulfato de alumínio

Neste trabalho foi estudada a influencia das caracteristicas das substâncias humicas (SH), em especial a massa molar das moleculas, na eficiencia da coagulacao com o uso do sulfato de aluminio. Utilizando-se de agua proveniente de poco profundo, foram preparadas quatro aguas de estudo, todas com cor verdadeira de aproximadamente 100 uH. As SH foram extraidas de turfa e fracionadas em massas molares: i) SH filtradas em membranas de 0,45 µm; ii) SH filtradas em membranas de 0,45 µm e maiores que 100 kDa, iii) SH com moleculas entre 30 e 100 kDa; iv) SH com moleculas menores do que 30 kDa. Verificou-se que quanto maior a massa molar das SH maior foi a eficiencia de remocao da cor aparente, com as menores dosagens de coagulante.O pH de coagulacao otimo, esteve entre 6,0 e 7,0, para todas as aguas de estudo. Os estudos da porcentagem de acido humico (AH) e acido fulvico (AF) presentes em cada fracao de diferente massa molar mostraram que quanto maior foi a porcentagem de AF presente, maior foi a dosagem de coagulante exigida para se obter os melhores resultados de remocao da cor aparente.

Modelação da perda de carga na filtração direta ascendente em meio granular de areia grossa e pedregulho

Compreender e quantificar os mecanismos relacionados a perda de carga e a remocao de particulas em um meio filtrante granular e de importância fundamental para o estudo do processo da filtracao. Este trabalho apresenta o desenvolvimento dos modelos de perda de carga na filtracao em meios porosos e a proposicao da modelacao matematica semiempirica da perda de carga para meios filtrantes limpos e do desenvolvimento do perfil de perda de carga ao longo do tempo de filtracao a partir da equacao de Ergun. Objetivou-se a determinacao dos valores das constantes da equacao de Ergun para meio granular de areia grossa e pedregulho. Alguns exemplos de aplicacao dessa modelacao matematica sao tambem apresentados e discutidos pelos autores com base em dados experimentais obtidos em uma estacao piloto de dupla filtracao.

Avaliação da toxicidade aguda de uma cepa de Microcystis spp. por meio de testes com camundongos

This study was carried out to evaluate the toxicity of a strain of Microcystis spp, using acute toxicity bioassays with swiss albino mice and to characterize chemically the microcistins using high efficiency liquid chromatography with photodiode array detector (HPLC-PDA) and mass spectrometry with electrospray ionization (MS-ESI). The acute toxicity tests with mice showed that according to the classification proposed by Lawton et al (1994b), the toxic strain here tested corresponds to the degree of high toxicity with DL50 24h values for the dry extract lower than 100 mg/kg corporal weight (13,7 mg/kg corporal weight), while DL5024h for total microcystin - MCs concentration around 24,2 µg/kg corporal weight. and concentration of MCs in the dry material higher than 1,0 µg/mg dry weight (between 1.64 and 1.86 µg/mg d.w.).

Tratamento de água de reservatórios por dupla filtração, oxidação e adsorção em carvão ativado granular

This study evaluated the treatment of raw lake water using a double filtration (DF) pilot plant consisting of an up-flow gravel filter (UGF) in series with a down-flow sand filter (DSF) and followed by a post-treatment granular activated carbon (GAC) unit. Additionally, the study examines the effect of pre and inter-oxidation (between UGF and DSF) on overall efficiency in the treatment and the formation of halogenated organic byproducts (HOB). According to the results obtained, it was observed that the pre-oxidation improved the quality of the UGF effluent and the inter-oxidation favored lower values of turbidity and color in the DSF effluent. Also, the treatment process by adsorption on granular activated carbon, used as a post-treatment, was efficient to ensure the quality of final effluent in the tests, especially regarding the removal of organic matter, cyanobacteria, and color. The maximum concentrations of HOB found in the effluents from the DSF and GAC did not exceed the limits of the Brazilian drinking water standards (Portaria no 2.914/2011).

Removal of humic substances with different apparent molecular sizes using Fenton’s reagent

Abstract Fenton’s reagent was used as a coagulating agent in the treatment of water samples with high true color caused by humic substances (HS) extracted from peat. The effects of the apparent molecular size of HS on coagulation, flocculation, and flotation were studied. Four distinct water samples having the same true colors were prepared using HS with different molecular sizes obtained through ultrafiltration fractioning. Through optimization of the coagulant dosage and coagulation pH and the construction of coagulation diagrams for each water sample, it was verified that the sample with the smallest apparent molecular size of HS was the most difficult to treat, requiring higher coagulant (Fenton’s reagent) dosages than samples prepared with larger HS molecular sizes. Furthermore, filtration experiments after dissolved air flotation were carried out to simulate conventional treatment. The most representative results in filtered water were: absorbance at 254 nm ⩽ 0.016 cm−1; apparent color ⩽ 3 HU; and r...