Characterization of denitrifying granular sludge treating soft groundwater in an upflow sludge-blanket reactor

Nitrate removal from soft groundwater using ethanol as a carbon source in an upflow sludge-blanket reactor containing denitrifying granular sludge was investigated. At a hydraulic retention time of 0.83 h, influent nitrate was increased stepwise from 20 to 145 mg N/l (volumetric loading rates (VLRs), 0.60 to 4.2 g N/l/d, respectively) and sludge was periodically wasted to maintain a sludge bed of about 2 3 the liquid volume. Complete nitrate removal was achieved at influent nitrate concentrations up to 75 mg N/l(2.1 g N/l/d). MLSS increased from 20 g/l at a VLR of 0.6 g N/l/d to 51 g/l at a VLR of 1.9 g N/l/d, above which it decreased. VSS increased from 11 g/l to a maximum of 25 g/l at a VLR of 2.1 g N/l/d. Settling velocities showed the same trend with maximum values in a VLR range of 1.5 to 2.1 g N/l/d. However, granule size, calcium and magnesium contents of the granular sludge and protein, carbohydrate and nucleic acid contents of extracellular polymers decreased steadily with an increase in VLR throughout the range of testing. Within the VLR range of 0.6 to 2.1 g N/l/d, corresponding to complete nitrate removal and efficient sludge retention, the granular sludge had a high calcium content of 24 to 22%, magnesium ranged from only 0.7 to 0.1%, proteins from 3.2 to 1.3%, carbohydrates from 4.2 to 1.4%, and nucleic acids from 0.34 to 0.05% of the sludge dry weight. These results suggest an optimum operational VLR in terms of nitrate removal and sludge retention of about 2 g N/l/d.     

Formation of ferrihydrite and associated iron corrosion products in permeable reactive barriers of zero-valent iron

Ferrihydrite, which is known to form in the presence of oxygen and to be stabilized by the adsorption of Si, PO4 and SO4, is ubiquitous in the fine-grained fractions of permeable reactive barrier (PRB) samples from the U.S. Coast Guard Support Center (Elizabeth City, NC) and the Denver Federal Center (Lakewood, CO) studied by high-resolution transmission electron microscopy and selected area electron diffraction. The concurrent energy-dispersive X-ray data indicate a strong association between ferrihydrite and metals such as Si, Ca, and Cr. Magnetite, green rust 1, aragonite, calcite, mackinawite, greigite and lepidocrocite were also present, indicative of a geochemical environment that is temporally and spatially heterogeneous. Whereas magnetite, which is known to form due to anaerobic Fe0 corrosion, passivates the Fe0 surface, ferrihydrite precipitation occurs away from the immediate Fe0 surface, forming small (<0.1 microm) discrete clusters. Consequently, Fe0-PRBs may remain effective for a longer period of time in slightly oxidized groundwater systems where ferrihydrite formation occurs compared to oxygen-depleted systems where magnetite passivation occurs. The ubiquitous presence of ferrihydrite suggests that the use of Fe0-PRBs may be extended to applications that require contaminant adsorption rather than, or in addition to, redox-promoted contaminant degradation.     

Comparison of real-time reverse-transcription loop-mediated isothermal amplification and real-time reverse-transcription polymerase chain reaction for detection of noroviruses in municipal wastewater

The monitoring of NVs in municipal wastewater by both real-time RT-LAMP and real-time RT-PCR, and the comparison of these two methods with respect to NV detection were carried out. The change in NVs detected by real-time RT-LAMP agreed well with that detected by real-time RT-PCR. In contrast, the correlation between the copy number determined by real-time RT-PCR and the threshold time (Tt) determined by real-time RT-LAMP obtained during monitoring was not significant (0.1相似文献   

High-rate nitrogen removal from anaerobic digester liquor using an up-flow anammox reactor with polyethylene sponge as a biomass carrier

Here, the stable performance of nitrogen removal from digester liquor after partial nitrification was experimentally demonstrated in an up-flow anammox reactor with polyethylene sponge (PE sponge) as a biomass carrier. A high nitrogen loading rate of 8.4 kg-N/m(3)/day with a TN removal rate of 7.6 kg-N/m(3)/day was obtained in this study, indicating PE sponge carrier is effective to attain high nitrogen removal performance. This high NLR should be mainly attributed to the successfully operational strategy, the biomass carrier with strong adsorption as well as the functional microbial community. The reaction ratio of NH(4)(+):NO(2)(-):NO(3)(-) using the anaerobic digester liquor as feeding media was 1:1.09:0.14. In addition, the channeling phenomenon was investigated in this study, and the problem could be solved through keeping the sludge bed lower than 2/3 of the effective height of the reactor. Furthermore, the settling property of the anammox granules was enhanced significantly and the bacteria community was verified by DNA analysis. The new species of anammox bacteria (kumadai-1) and KSU-1 were confirmed to be the predominant species after stable anammox performance was obtained.     

Effect of inoculum conditioning on hydrogen fermentation and pH effect on bacterial community relevant to hydrogen production

The effect of conditioning for a variety of inoculums on fermentative hydrogen production was investigated. In addition, the effects of pH condition on hydrogen fermentation and bacterial community were investigated. The effect of conditioning on hydrogen production was different depending on the inoculum types. An appreciable hydrogen production was shown with anaerobic digested sludge and lake sediment without conditioning, however, no hydrogen was produced when refuse compost and kiwi grove soil were used as inoculums without conditioning. The highest hydrogen production was obtained with heat-conditioned anaerobic digested sludge, almost the same production was also obtained with unconditioned digested sludge. The pH condition considerably affected hydrogen fermentation, hydrogen gas was efficiently produced with unconditioned anaerobic sludge when the pH was controlled at 6.0 throughout the culture period and not when only the initial pH was adjusted to 6.0 and 7.0. Hydrogen production decreased when the culture pH was only adjusted at the beginning of each batch in continuous batch culture, and additionally, bacterial community varied with the change in hydrogen production. It was suggested that Clostridium and Coprothermobacter species played important role in hydrogen fermentation, and Lactobacillus species had an adverse effect on hydrogen production.     

Medium-chain fatty acid-containing dietary oil alleviates the depression-like behaviour in mice exposed to stress due to chronic forced swimming

Antidepressant-like effects of medium-chain fatty acid-containing dietary oil were examined by using mice forced to swim. This stress loading induced features typical for depression such as depressive symptoms and decreased the ratio of phosphorylated (p) extracellular signal-regulated kinases (ERK)1/2 to ERK1/2 in the hippocampus, demonstrating that our animal model prepared in mice was comparable to the general models using rats. Test diets containing structured medium- and long-chain triacylglycerols (MLCTs) and/or long-chain triacylglycerols (LCTs) as test oils and tap water were given freely during the stress period. Consequently, the intake of MLCTs resulted in a significant reduction in the immobility time in the forced swim test. Moreover, the ratio of pERK1/2 to ERK1/2 in the hippocampus was significantly higher in mice fed the MLCT diet than in those fed the LCT one. These results are the first evidence showing that MLCTs have a preventive effect against forced swimming-induced depression-like symptoms.     

Effect of high pressure gaseous carbon dioxide on the germination of bacterial spores

Effect of high pressure gaseous carbon dioxide treatment (HGCT) at 6.5 MPa, 35 degrees C on the germination of bacterial spores was investigated. Germination of bacterial spores was estimated by the decrease of heat tolerance. Approximately, 40% of Bacillus coagulans and 70% of Bacillus licheniformis were germinated by HGCT for 120 min at 35 degrees C, respectively. Germination was confirmed by phase contrast microscopy. The effect of hydrostatic pressure treatment (HPT) at 6.5 MPa, 35 degrees C on the germination of B. coagulans and B. licheniformis spores were also investigated. Spores did not germinate by HPT alone at 6.5 MPa for 120 min.