In this study, we present solid phase extraction system for dissolved iron from a solution containing EDTA as organic ligand using molecular recognition technology gel; carrier modified the many layers of crown ether. Dissolved iron was quantitatively collected on the MRT gel from aqueous solutions containing a 100-fold concentration of EDTA, while the recoveries of ion-exchange and chelate resins were 10 to 50 percent. Dissolved iron was not completely collected using other solid phase extraction materials. The results indicate the MRT gel is available for separation of dissolved iron under large amounts of EDTA condition.
In this study, two municipal sewage treatment plants that employed modified oxidation ditch system for sludge reduction were assessed to evaluate its performance based on mass balance analysis. An analysis of operational records showed the peak of discharge during midnight due to the flow equalization effect. A preliminary study showed the higher organic concentration in effluent from modified system although the removal rate was almost same as that of the traditional oxidation ditch system. Mass balance analysis based on the round-the-clock survey revealed the removal rates of organic parameters, T-N and T-P were 84 - 98%, 64 - 78% and 54-87%, respectively. Of the two plants surveyed, the plant with lower treatment efficiencies in most parameters showed periodical carryover of SS, suggesting the high accumulation of sludge due to the lack of appropriate sludge withdrawal. Based on the mass balance analysis, it is estimated that the sludge production was reduced by ca.20% without the deterioration of effluent quality. To expect more reduction effect, it is necessary to find the optimum design and operational conditions of this system where the minimum withdrawal and maximum sludge reduction effect will balance.
The growth of harmful microalga, Prymnesium parvum, causes red tides in coastal environments, and can also cause damage to fisheries. The iron chemical condition in the coastal environments varies both spatially and temporally and changes the physiological characteristics of red tide microalgae regulating the algal growth. For investigating the molecular mechanisms of iron-stress microalgae, the iron limited culture of P. parvum was established, and the functional genes induced the transcription by iron stress was detected using differential display analysis. A number of differences in the gene transcriptional levels were revealed on the agarose gels and suggest that the algal cells under the iron stress induce the transcription of these functional genes to adapt to environmental stress.
In aquatic environments, the bacterial decomposition of organoarsenic compounds, such as dimethylarsinic acid, was important for evaluation of the dynamics of each arsenic species. The process of the arsenic cycle has been investigated by many researchers. For investigation of the bacterial decomposition activity of organoarsenic compounds in the lake water, dimethylarsinic acid ((CH3)2AsO(OH); DMAA) was added at final concentrations of 1 μmol⁄l and 0.05 μmol⁄l to the sample water. In addition, the sample was cultivated in an anaerobic or aerobic condition and light or dark condition. The DMAA was remarkably decomposed at the 30th day only in an anaerobic and dark condition. Denaturing gradient gel electrophoresis (DGGE) was performed after DNA extraction from the sample water. Two DNA extraction methods were compared to obtain more useful DNA for phylogenetic analysis.Sequence analysis of DGGE bands showed that beta-proteobacteria subdivision was predominant member in the sample water at the 30th day after the DMAA addition. Therefore, the members of beta-proteobacteria subdivision would decompose organoarsenic compounds.
The water fern (Azolla pinnata L.) was grown in culture solution with arsenate (As(V)) and dimethylarsinic acid (DMAA). Arsenic concentrations were measured in tissues of the plant after harvest. Plant of control and solution having lower phosphate concentration accumulated significantly higher amount of arsenate compared to that of higher phosphate solution. The Azolla pinnata L. accumulated about 7 folds arsenate than that of DMAA when the plants were grown in solution containing 4.0 μM of arsenate and no phosphate. With the increase of phosphate concentration in culture solution the arsenate uptake into the plant decreased significantly (p ‹ 0.001). The arsenate accumulation in Azolla pinnata L. decreased by 40% for the addition of 100 μM of phosphate in the solution. However, the Azolla pinnata L. accumulated 0.034±0.005 μmol g-1 dry weight of DMAA from solution having 4.0 μM of DMAA and no phosphate. The phosphate concentration did not affect DMAA uptake into the plant significantly. Arsenate uptake was clearly correlated with iron and phosphate uptake into the water fern though DMAA uptake was not. The results suggest that arsenate uptake in the macrophytes might be dependent on phosphate and iron uptake while DMAA was independent thereof.
Iron and Fe(III)-binding ligand size distributions in dissolved organic matter from the Tedori River (Japan) estuary were measured using size fractionation and electrochemical techniques. Estuary water samples showed natural concentration levels of particulate and dissolved iron. Dissolved iron (‹ 0.45 μm) was removed from the water column at high salinity (› 0.05%) and found to strongly correlate with Fe(III)-binding ligands at low salinity (‹ 0.05%). It is found that salinity and Fe(III)-binding ligands are related to the competitive complexation of iron with major seawater ions and with dissolved organic matter in the estuary. In dissolved iron, the colloidal form (10 kDa-0.45 μm) was prevalent instead of the truly dissolved form (‹ 10 kDa). Colloidal iron concentrations decreased significantly in saline regions. On the other hand, particulate iron (› 0.45 μm) concentrations were nearly constant regardless of salinity changes in the estuary. Colloidal iron likely converts to particulate iron, which is then rapidly removed via the precipitation and subsequent sinking of large particles.
Sapling cultivation technology was developed to improve the growth of afforested trees in salt-affected land. The reduction in the production of wheat, caused by salt-affected soils, had been reported in the wheat belt of Western Australia. A large amount of evaporation of groundwater from the soil surface results in the concentration of soluble salts on the topsoil. Therefore, it is necessary to sink the groundwater level for environmental restoration. One of the most promising ways to prevent the progress of saline soil is afforestation. With our technology, plants can use more underground water and be less affected by salt by growing deeper roots. We considered the results of our experiment from the following perspectives: height growth (growth in height), vertical distribution of root biomass, total biomass, and biomass allocation. In particular, Eucalyptus rudis x E. camaldulensis could promote the growth of deeper roots and achieve the largest biomass of the tested species. We also confirmed that the most suitable pipe size for this species was φ10 cm. In conclusion, the results suggest that this technique will be useful for effective afforestation in salt-affected land.
Conventional filters such as fabric filters show relatively low collection efficiency for the submicron particles. Electrostatic agglomeration could be one of the promising methods as a pretreatment of fine dust. In this work, the characteristics of electrostatic agglomeration of fine aerosol particles were closely investigated. A DC electric field was applied to induce the agglomeration of bipolarly charged particles. At the higher voltage in a Corona charging, the effect of DC electric field in the agglomeration zone was found more significantly. The length of agglomeration zone also affects the particle growth, so that the peer optimization on the dust flow channel should be followed based on dust characteristics.