Removal of Bisphenol S (BPS) by Adsorption on Activated Carbons Commercialized in Brazil.

This study assessed three powdered activated carbons (BETM, COCO, and SIAL) commercialized in Brazil at the bench scale in agitated reactors, analyzing their kinetic behavior and adsorptive capacity for BPS and BPA in ultrapure water. BETM exhibited the highest adsorption capacities (Q0max) for BPS and BPA at 260.62 and 264.64 mg/g, respectively, followed by SIAL, with a Q0max of 248.25 mg/g for BPS and for 231.20 mg/g BPA, and COCO, with a Q0max of 136.51 mg/g for BPS and 150.03 mg/g for BPA. The Langmuir isotherm model can describe the processes well. A pseudo-second-order model can describe the adsorption kinetics, and SIAL carbon had the highest rate constants (7.45 × 10-3 mg/g/min for BPS and 2.84 × 10-3 mg/g/min for BPA). The Weber-Morris intraparticle diffusion model suggests intraparticle diffusion as the rate-limiting step of all adsorption processes. Boyd's model confirmed more than the mechanism actuating in the bisphenol adsorption. The results suggest that adsorbents with basic surfaces, high specific surface areas, and high mesopore volumes tend to remove BPS and BPA efficiently. Therefore, activated carbons can effectively complement the existing treatment in Brazilian water treatment plants (WTPs).

Evaluation of the Removal and Effects of Cylindrospermopsin on Ripened Slow Sand Filters.

The occurrence of toxic blooms of cyanobacteria has been a matter of public health interest due to the cyanotoxins produced by these microorganisms. Cylindrospermopsin (CYN) is a cyanotoxin of particular concern due to its toxic effects on humans. This study investigated the removal and effects of CYN in ripened slow sand filters (SSFs) treating water from Paranoá Lake, Brasilia, Brazil. Four pilot-scale SSFs were ripened and operated for 74 days. Two contamination peaks with CYN were applied along the filtration run. The improvement of any of the evaluated water quality parameters was not affected by the presence of CYN in the raw water. The SSFs efficiently removed CYN, presenting concentrations lower than 0.8 µg/L in the filtered water. The microbiota of the SSFs were dominated by protozoa of the genus Euglypha and amoebas of the genera Arcella, Centropyxis, and Amoeba, together with some groups of rotifers. These microorganisms played a crucial role in removing total coliforms and E. coli. In addition, CYN was not identified as a determining factor in the microbiota composition.

Oxidation of Cylindrospermopsin by Fenton Process: A Bench-Scale Study of the Effects of Dose and Ratio of H2O2 and Fe(II) and Kinetics.

The cyanotoxin cylindrospermopsin (CYN) has become a significant environmental and human health concern due to its high toxicological potential and widespread distribution. High concentrations of cyanotoxins may be produced during cyanobacterial blooms. Special attention is required when these blooms occur in sources of water intended for human consumption since extracellular cyanotoxins are not effectively removed by conventional water treatments, leading to the need for advanced water treatment technologies such as the Fenton process to produce safe water. Thus, the present study aimed to investigate the application of the Fenton process for the degradation of CYN at bench-scale. The oxidation of CYN was evaluated by Fenton reaction at H2O2/Fe(II) molar ratio in a range of 0.4 to 4.0, with the highest degradation of about 81% at molar ratio of 0.4. Doubling the concentrations of reactants for the optimized H2O2/Fe(II) molar ratio, the CYN degradation efficiency reached 91%. Under the conditions studied, CYN degradation by the Fenton process followed a pseudo-first-order kinetic model with an apparent constant rate ranging from 0.813 × 10-3 to 1.879 × 10-3 s-1.

Influência do pH de coagulação e da dose de sulfato de alumínio na remoção de oocistos de Cryptosporidium por filtração direta descendente / The influence of coagulation pH and aluminum sulphate dose in removal of Cryptosporidium oocysts by down flow direct filtration

No presente trabalho, realizado em escala piloto, foi avaliada a influência do pH de coagulação e a da dose de sulfato de alumínio na morfologia dos flocos formados durante o processo de coagulação bem como na remoção de oocistos de Cryptosporidium por filtração direta descendente. As condições de coagulação testadas incluíram a dose ótima e superdose de coagulante em duas faixas distintas de pH. Os resultados mostraram que a eficiência de remoção dos oocistos de Cryptosporidium variou de 1,4 a 3,2 log durante a operação estável do filtro. Os experimentos realizados em valores de pH de coagulação mais baixo, em torno de 5, promoveram as melhores eficiências de remoção de oocistos de Cryptosporidium. A análise morfológica dos flocos mostrou uma tendência à formação de flocos mais porosos e irregulares ao se adotar superdosagem de coagulante.

This study, carried out in pilot scale, investigates the influence of coagulation pH and aluminum sulphate dosage on the morphology of flocs formed during coagulation and in the removal of Cryptosporidium oocysts by down flow direct filtration. Evaluated coagulation conditions included optimal and over dosages of coagulant in two distinct pH ranges. The results showed that the removal efficiency of Cryptosporidium oocysts ranged from 1.4 to 3.2 log during regular operation of the filter. Experiments carried out with lower coagulation pH values, around 5, presented the best removal efficiencies of Cryptosporidium oocysts. The morphologic analysis of flocs showed a trend to the formation of more porous and irregular flocs with the use of over dosages of coagulant.