Knowledge of the effective radiation spectrum irradiating substrates from microwave powered electrodeless discharge lamps（MEDLs）, and the active species that directly oxidize substrates in the photolytic process, is...Knowledge of the effective radiation spectrum irradiating substrates from microwave powered electrodeless discharge lamps（MEDLs）, and the active species that directly oxidize substrates in the photolytic process, is fragmentary and unclear. In this work, we conducted a comparative study using MEDLs made with quartz envelopes（MEDL-quartz） and with borosilicate Pyrex envelopes（MEDL-Pyrex） targeting the degradation of Rhodamine B（Rh B）via radical-extinguishing tests. We found that UVC/UVB radiation is essential to generate·OH and H2O2 in the MEDL-quartz system. The degradation of Rh B mostly originates from·OH species, which account for a contribution of 53.8%, while the remaining contribution is attributed to oxidation by H2O2 and direct photolysis. This degradation is influenced by several parameters. Acidic and neutral p Hs, but not extreme alkaline p H, benefit the degradation. To ensure a high intensity of UVC/UVB, the optimum ratio of the MEDL volume to the aqueous solution volume（VL/VS） is 0.4. Concentrations of 0.15-0.20 mmol/L of Rh B are suitable to obtain an effective quantum absorbance in the MEDL-quartz system,showing a high decomposition rate of 5.6 × 10^-3（mmol/L）min-1. Moreover, two other substrates, Reactive Brilliant Red X-3B and Safranine T, were tested and found to be efficiently degraded in the MEDL-quartz system.展开更多
Drinking water treatment residuals（WTRs） have a potential to realize eutrophication control objectives by reducing the internal phosphorus（P） load of lake sediments. Information regarding the ecological risk of de...Drinking water treatment residuals（WTRs） have a potential to realize eutrophication control objectives by reducing the internal phosphorus（P） load of lake sediments. Information regarding the ecological risk of dewatered WTR reuse in aquatic environments is generally lacking, however. In this study, we analyzed the eco-toxicity of leachates from sediments with or without dewatered WTRs toward algae Chlorella vulgaris via algal growth inhibition testing with algal cell density, chlorophyll content, malondialdehyde content, antioxidant enzyme superoxide dismutase activity, and subcellular structure indices. The results suggested that leachates from sediments unanimously inhibited algal growth, with or without the addition of different WTR doses（10% or 50% of the sediment in dry weight） at different p H values（8–9）, as well as from sediments treated for different durations（10 or 180 days）. The inhibition was primarily the result of P deficiency in the leachates owing to WTR P adsorption, however, our results suggest that the dewatered WTRs were considered as a favorable potential material for internal P loading control in lake restoration projects, as it shows acceptably low risk toward aquatic plants.展开更多
基金supported by the National Natural Science Foundation of China (No. 5080167)
文摘Knowledge of the effective radiation spectrum irradiating substrates from microwave powered electrodeless discharge lamps（MEDLs）, and the active species that directly oxidize substrates in the photolytic process, is fragmentary and unclear. In this work, we conducted a comparative study using MEDLs made with quartz envelopes（MEDL-quartz） and with borosilicate Pyrex envelopes（MEDL-Pyrex） targeting the degradation of Rhodamine B（Rh B）via radical-extinguishing tests. We found that UVC/UVB radiation is essential to generate·OH and H2O2 in the MEDL-quartz system. The degradation of Rh B mostly originates from·OH species, which account for a contribution of 53.8%, while the remaining contribution is attributed to oxidation by H2O2 and direct photolysis. This degradation is influenced by several parameters. Acidic and neutral p Hs, but not extreme alkaline p H, benefit the degradation. To ensure a high intensity of UVC/UVB, the optimum ratio of the MEDL volume to the aqueous solution volume（VL/VS） is 0.4. Concentrations of 0.15-0.20 mmol/L of Rh B are suitable to obtain an effective quantum absorbance in the MEDL-quartz system,showing a high decomposition rate of 5.6 × 10^-3（mmol/L）min-1. Moreover, two other substrates, Reactive Brilliant Red X-3B and Safranine T, were tested and found to be efficiently degraded in the MEDL-quartz system.
基金supported by the National Natural Science Foundation of China(No.51278055)the Specialized Research Fund for the Doctoral Program of Higher Education(No.2012003110027)the National Key Technology R&D Program(No.2012BAJ21B08)
文摘Drinking water treatment residuals（WTRs） have a potential to realize eutrophication control objectives by reducing the internal phosphorus（P） load of lake sediments. Information regarding the ecological risk of dewatered WTR reuse in aquatic environments is generally lacking, however. In this study, we analyzed the eco-toxicity of leachates from sediments with or without dewatered WTRs toward algae Chlorella vulgaris via algal growth inhibition testing with algal cell density, chlorophyll content, malondialdehyde content, antioxidant enzyme superoxide dismutase activity, and subcellular structure indices. The results suggested that leachates from sediments unanimously inhibited algal growth, with or without the addition of different WTR doses（10% or 50% of the sediment in dry weight） at different p H values（8–9）, as well as from sediments treated for different durations（10 or 180 days）. The inhibition was primarily the result of P deficiency in the leachates owing to WTR P adsorption, however, our results suggest that the dewatered WTRs were considered as a favorable potential material for internal P loading control in lake restoration projects, as it shows acceptably low risk toward aquatic plants.
