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Bioclogging is a commonly encountered operational issue that lowers hydraulic conductivity and the overall performance of the infiltration systems. In this paper, a novel processing for alleviating bioclogging by filter media surface hydrophobic modification was presented. Two-dimensional porous media cells were used to observe the influence of hydrophobic modification on biofilm growth in the pore structure. Moreover, two continuous-flow columns packed with gravel, one of which half gravel was hydrophobically modified, were operated with artificial wastewater to verify the effect of hydrophobic modification on bioclogging alleviation. The results showed that the biofilm growth in the cell with hydrophobic modification was slow, and the biomass was less and liable to wipe off after hydrophobic treatment. Meanwhile, the hydraulic efficiency of the flow seepage field was also improved after hydrophobic treatment. The column tests results showed that the hydraulic conductivity of the filter bed with hydrophobic modification (Column B) decreased more slowly than that of another without hydrophobic modification (Column A). Column B had the hydraulic conductivity (k) of 0.66 cm/s in the final stage of the experiment, while the k of Column A was 0.14 cm/s. It verified that hydrophobic modification of partial filter media can alleviate the bioclogging problem of the infiltration systems to some extent. The results provide a new idea and potential technical support for solving bioclogging problem. [ABSTRACT FROM AUTHOR]

Novel magnetic molecularly imprinted polymers (MMIP) were prepared for selective removal of norfloxacin by effectively utilizing photocatalytic degradation and magnetic separation techniques. The imprinted material with titanium layer and multihole surface showed an excellent photocatalytic property. In this paper, the kinetics of photocatalytic degradation of norfloxacin by MMIP was explored, and the influences of environmental factors, including solution pH, humic acid, common ions and water media on photocatalytic performance of MMIP were elucidated. The results showed that MMIP had good adaptability and could degrade norfloxacin within 60 min, but the degradation rate constant decreased in surface water. Based on the identification of intermediate products, the possible degradation pathways of norfloxacin were analysed, speculating that it might be degraded into small molecules in the form of de-piperazine ring, de-carboxyl group and de-fluorine. Moreover, the mineralization ratio of norfloxacin could reach 84.2% after ultraviolet irradiation for 150 min, and the low cobalt release of MMIP enhanced the security of the material. The results of adsorption and degradation cycle tests showed that MMIP obtained by molecular imprinting technology had excellent performance in sustainable use for micro organic pollutants removal. [ABSTRACT FROM AUTHOR]

Batch experiments of photocatalytic bromate removal by F-Graphene-TiO2 (FGT) were conducted under different reaction conditions. The dosage of FGT, initial bromate concentration, pH, water temperature, and the coexisting substances including common halogen anions, oxyacid ion and humic acid factors affecting the efficiencies of bromate reduction were systematically discussed. Increasing the temperature or the dosage of FGT increased the bromate removal efficiency. The efficiency of bromate reduction was significantly increased by decreasing the pH from 6 to 5, because the isoelectric point of FGT samples was found at a pH of approximately 6.0. The coexisting anions, such as chloride ion, bromide ion, nitrate, chlorate and sulfate, had modest inhibitory effects on bromate removal under the experimental conditions, and the inhibitory effect from fluoride ion was relatively larger. These observations indicate that bromate reduction by FGT is a surface-mediated process, the competitive consumption of photogenerated electrons and the competitive adsorption by coexisting anions on FGT samples probably lead to the decreasing of bromate reduction efficiency. And the increase of appropriate dosage can partly eliminate the influence of coexisting ions. Over 90% of 100 μg/L bromate could be removed with a 0.05 g/L dosage of F1.0G0.1T in 15 min under UV irradiation at intensity of 26 μW/cm2 and pH of 5.2. Moreover, the specific roles of photogenerated electron–hole pairs and the mechanism of photocatalytic bromate reduction were also discussed. These findings suggest that photocatalytic bromate removal by FGT/UV can be a promising method for bromate from water. [ABSTRACT FROM AUTHOR]

Batch experiments of photocatalytic bromate removal by F-Graphene-TiO 2 (FGT) were conducted under different reaction conditions. The dosage of FGT, initial bromate concentration, pH, water temperature, and the coexisting substances including common halogen anions, oxyacid ion and humic acid factors affecting the efficiencies of bromate reduction were systematically discussed. Increasing the temperature or the dosage of FGT increased the bromate removal efficiency. The efficiency of bromate reduction was significantly increased by decreasing the pH from 6 to 5, because the isoelectric point of FGT samples was found at a pH of approximately 6.0. The coexisting anions, such as chloride ion, bromide ion, nitrate, chlorate and sulfate, had modest inhibitory effects on bromate removal under the experimental conditions, and the inhibitory effect from fluoride ion was relatively larger. These observations indicate that bromate reduction by FGT is a surface-mediated process, the competitive consumption of photogenerated electrons and the competitive adsorption by coexisting anions on FGT samples probably lead to the decreasing of bromate reduction efficiency. And the increase of appropriate dosage can partly eliminate the influence of coexisting ions. Over 90% of 100 μg/L bromate could be removed with a 0.05 g/L dosage of F 1.0 G 0.1 T in 15 min under UV irradiation at intensity of 26 μW/cm 2 and pH of 5.2. Moreover, the specific roles of photogenerated electron-hole pairs and the mechanism of photocatalytic bromate reduction were also discussed. These findings suggest that photocatalytic bromate removal by FGT/UV can be a promising method for bromate from water.