The objectives of this study were to investigate the effects of below-ground biomass reduction on the stability of eelgrass shoots in sediment to clarify the factors responsible for the loss of eelgrass shoots even with little disturbance by waves in Nagatsuraura Bay, Japan. The environmental conditions in eelgrass beds with and without root death were also investigated. Loss of roots without the dying-back symptoms led to the decrease in the stability of eelgrass shoots in the sediment, and would allow the uprooting of shoots with minimal disturbance. The decay of healthy root biomass of eelgrass was associated with a high sulfide concentration in sediment and/or low photosynthetic activity. In the sulfide concentrations between 0.5 mg/g D. W. and 2.0 mg/g D. W., eelgrass with high photosynthetic activity tended to experience less stunted roots compared to the shoots with low rates of photosynthesis. This result suggests that eelgrass with high photosynthetic activity seemed to prevent sulfide intrusion by supplying oxygen to below-ground tissues to maintain an oxic microsphere around the roots and by re-oxidizing sulfide to harmless sulfate.
The behavior of the adsorption of 1,4-dioxane (DOX) in water onto eight different activated carbons (ACs) was studied. All adsorption isotherms obtained using batch-type adsorption measurements, were found to fit a Freundlich equation. The amount adsorbed at an equilibrium concentration of 50 μg/L (q50) was obtained, and its correlation with microporosity and chemical properties of each AC was examined. The AC prepared from sawdust by direct activation adsorbed the most DOX (410 μg/g), while adsorption in the other ACs were in the range of 4.3 - 71.1 μg/g. No practical influence of specific surface area on the adsorption of DOX was found. We observed that log q50 mostly decreased linearly with an increase in mean pore diameter. The concentrations of acidic surface oxides and nitrogen in the ACs affected the hydrophilicity of the adsorbent and impaired q50. It was assumed that the main factor for the adsorption of DOX at trace concentration in water was surface chemistry rather than the microporosity of AC.
Fukuyama Port is a semi-enclosed harbor located in the central region of the Seto Inland Sea. During June 1998, no dissolved oxygen (DO) was present at the bottom layer of the water column. Low DO conditions continued until October, coinciding with a period of high water temperature. A study of the life cycle, distributive characteristics, and feeding type of Polydora cornuta Bosc, 1802, inhabiting the organically polluted port area, was performed. Polydora cornuta which lives in mud tubes in bottom sediments, was found to be unevenly distributed in the innermost part of the port. Taxonomic characteristics are modifications of setiger 5, which includes major heavy spines. Predicted life-cycle duration, based on the 11.5 - 18.2°C temperature of bottom mud during the normal life period for this species, was 40 to 59 days. Appearance of benthic life-stage individuals was limited to winter and spring (i.e., January to May). However, pelagic larval individuals were present throughout the year. The distribution and density of P. cornuta reflected the DO conditions of the bottom layer and sediment. Stable carbon and nitrogen isotope analysis indicated that this species is a suspension feeder.
Microorganisms have been used to improve soil structure in sandy soils; extracellular polysaccharide (EPS)-producing bacteria are believed to be useful for improving soil water-holding capacity. Some industries have already produced polysaccharides like xanthan and chitosan from microbes, but for economic reasons, growing microorganisms in situ to directly produce EPS is being considered. In this paper, we examined Lactobacillus sakei, a facultative anaerobic bacterium, as a potential producer of EPS in situ. Lactobacillus sakei strain CY1 is a member of a genus of microaerophilic bacteria known as food fermentation starters, which can produce bacteriocin and secrete polysaccharides. To determine the success of L. sakei CY1 as a biological agent for the improvement of soil quality, we examined the effect of L. sakei CY1 on soil aggregation in indoor experiments. The extent of aggregation was determined after 28 days of cultivation using a variety of carbon sources, such as glucose, fructose, galactose, xylose, and sucrose, on soil media. We compared these results with those obtained using organic fertilizer and commercial soil stabilizers like xanthan and chitosan. When the optimum nutrient sources were used in soil media (sucrose as a carbon source and ammonium chloride as a nitrogen source), the EPS-producing bacteria were just as successful at binding soil particles as the commercial soil stabilizers xanthan and chitosan. Lactoacillus sakei CY1 had caused 75 - 85% of soil particles to adhere to each other and build up macro-aggregates (> 250 μm). These results indicate that in sandy soils, L. sakei CY1 can potentially be used as a binder to improve soil structure.
Nitrifying granules were applied to high-speed nitrification of wastewater discharged from an electronic industrial factory. The behavior of the formation of nitrifying granules and the start-up performance of nitrification process were examined with three types of reactors: a column with a small diameter, a column with a large diameter and a rectangular-type reactor. As a result, the performance of the three types of reactors did not give significant differences in terms of the formation of nitrifying granules and the start-up trend of the reactor. A nitrification rate of about 2.0 kgN/m3/day was achieved in all reactors.
Activated carbon treatment and ozone oxidation were used for decolorization or total organic carbon (TOC) removal from an aqueous solution. Acid, neutral, and basic activated carbon (A-AC, N-AC, and B-AC) were prepared with particle sizes of 44 - 297 μm (S), 297 - 500 μm (M), and 500 - 840 μm (L), respectively. Methylene blue (MB) and orange II (ORII) were used as adsorbates, and the amount of MB or ORII adsorbed onto AC depended on the specific surface area of the AC. The adsorption data were fitted to the Freundlich and Langmuir equations, which suggested that the mechanism by which dye is adsorbed onto AC is that of monomolecular adsorption onto a heterogeneous surface. After ozone treatment, the MB and ORII structures were degraded and decolorized. However, TOC was not significantly reduced because the dye structure was broken down by ozone oxidation, which generated low-molecular-weight molecules but did not remove them. Activated carbon treatment after ozone oxidation was very effective for dye and TOC removal. This treatment enhanced the TOC removal by up to 20 - 30% from that achieved solely by ozone treatment.
The floating culture system is a water purification method using the ability of plants for nutrient removal. Since the appropriate management of the floating culture system in eutrophied water depends on the characteristics of the water body, like its shape or depth, it is impossible to make a general guideline. Therefore, as part of constructing a numerical prediction model of the flow and water quality in waters where the floating culture system is installed, a test tank experiment, using canna as plant, was conducted to parameterize the effect of the floating culture system, as a boundary condition, on the flow and water quality. The result of plant growth and water quality measurement shows that the growth rate of canna changes significantly with the phosphorus concentration in water; the relation between the removal rate of TP and the phosphorus concentration is unique. Regarding the DO concentration in tanks with floating culture system, it decreased because the system prevented aeration and blocked solar radiation at the water surface. Moreover, the water temperature measurement reveals that the shielding ratio of heat flux through the system depends strongly on the material of floating board and is approximately constant regardless of the plant's growth rate. It is concluded from the result that TP removal rate can be expressed by using phosphorus concentration in the water and heat flux shielding ratio can be set as a constant, using this canna floating culture system.
In this study, characteristics of chars from four types of woody waste biomass, namely, bamboo, bamboo leaf, reed, and rice husk, and their application to immobilization carriers for hydrogen fermentation were investigated. Fermentative hydrogen production capacities with woody chars were compared to select the most suitable char materials for fermentative hydrogen production. In comparison with the initial pH of the sterilized media alone, the addition of char materials shifted the pH level toward the alkaline side. Pore sizes of bamboo and reed were mostly distributed in the range of 1 to 10 μm, which corresponded to the sizes of the dominant species examined in this study (Clostridium perfringens and Klebsiella oxytoca). The highest hydrogen production rate and as well as glucose consumption were obtained with bamboo char, followed by reed char, bamboo leaf char, and rice husk char. Hydrogen production rate with bamboo char was 3 L-H2/(h·L-culture), about two times higher than the control (without bamboo char).
A simple, low-cost filtration system composed of a ceramic filter, an iron net and iron bacterial sludge was developed to remove arsenic (As) from groundwater. The ceramic filter, made of an 80% clay soil and 20% rice bran mixture on a weight basis, was combined with the iron net and the iron bacterial sludge in a reactor, and the assembly (As removal filter) was tested for its ability to remove As from synthetic groundwater. Synthetic groundwater with a varying composition of As(III), ferrous iron (Fe(II)) and phosphate phosphorus (P) was filtered on a daily basis. The results showed that both Fe(II) in groundwater and those released from the iron net were oxidized biologically and/or physico-chemically and that As and P were effectively removed by adsorption and/or co-precipitation processes. The concentrations of Fe(II) and P in groundwater were decisive factors in the removal of As . Groundwater Fe concentrations of ≥ 2 mg/L and P concentrations of ≤ 3 mg/L with an Fe/P molar ratio of ≥ 3.0 were required to achieve an effluent As concentration of less than 50 μg/L from raw water containing 500 μg/L of As(III). This simple, inexpensive filter could be used to treat As in contaminated regions.