When a high-density fluid flows into a small-scale water body, a density current is generated by the difference in mud concentration. Diffusion, mixing and overflow take place in the reservoir due to the density current. The influence of inflow on overflow in the reservoir should be estimated when the density of the outflow from the reservoir is regulated. The diffusion and mixing behavior of a density current in a reservoir was examined using a small-scale water body model. The difference in density affected the layer thickness of the density current after the reflection more than before the reflection at the downstream end of the reservoir. Dimensional analysis showed that changes in density for both the reservoir and overflow could be represented as functions of reservoir length, time and buoyancy flux. The empirical equation for the prediction of the overflow density with the functions of degree in dilution and time also was derived from the study.
Continuous hydrogen fermentation from a mixed substrate containing carbohydrates, proteins and lipids was investigated using microflora. The experiment was conducted with a chemostat-type reactor at 35°C by using dog food with a constant TS concentration of 100g/L. The hydraulic retention time (HRT) changed from 6.4 to 34.5 hrs at a constant pH condition of 6.5. Continuous and stable hydrogen production was obtained for a long period, ranging from 6.4 to 34.5 hrs. The highest hydrogen production rate was found to be 1.18 L/L/d at an HRT of 12.8 hrs, while the highest hydrogen yield was found to be 0.24 mol-H2/mol-glucose at an HRT of 34.5 hrs. Both the hydrogen production rate and hydrogen yield were significantly lower than those in a batch experiment, indicating that the continuous hydrogen fermentation of the mixed substrate with chemostat-type reactor is difficult. On the other hand, the acidogenic efficiency increased with the increase in HRT, and 40% was obtained at an HRT of 34.5 hrs. The main acidogenic products were acetate and butyrate while some propionate and ethanol were also produced. The results of this study indicate that a long HRT, such as 34.5hrs, is necessary to obtain a high hydrogen yield and acidogenic efficiency for a mixed substrate of dog food.
Micellar electrokinetic chromatography (MEKC) was used preliminarily to evaluate the simple, simultaneous analysis of nonylphenol polyethoxylates (NPnEOs) and their degradation products (NPnEOs: n=number of ethoxy units; 1-18, nonylphenol, nonylphenoxyacetic acid and nonylphenoxyethoxyacetic acid) in water. A 1000 ml water sample was loaded into a cartridge packed with Oasis HLB, copoly (N-vinylpyrrolidone-divinylbenzene) . After concentrating the eluate (104times), the concentrate was subjected to MEKC with sodium deoxycholate as the micelleforming reagent. More than 82% of the analytes spiked to the ma and Neya river waters were recovered with good reproducibility (relative standard deviation=3.0-15%) . Thus, the application of this simple method to the simultaneous analysis of nonylphenol polyethoxylates and their degradation products in water is promising, though further improvement is needed.
In order to measure the heavy metal content in fern plants, 133 samples were collected in seven areas in Hyogo prefecture. The results obtained by X-ray fluorescence spectrometry and atomic absorption spectrometry were as follows: 1) BothGleichenia japonicaandDicranopteris linearisshowed relatively high X-ray intensity for manganese. 2) Thousands of ppm of lead content were found inBlechnum niponicumpicked at the S1 area. 3) The lead content ofBlechnum niponicumfound in the rhizome, root and leaf blades was high.