Yoichi Nakano

Ozone decomposition of hazardous chemical substance in organic solvents

Performance on the ozonation of hazardous chemicals in non-aqueous solutions, i.e. organic solvents, was studied in comparison with those in water. The specific conclusions obtained from this study are as follows: the rate of decomposition and the specific amount of decomposition per ozone consumption for orange II were higher in organic solvents like acetic acid, acetone, ter-butyl alcohol than in distilled water. The rates of trichloroethylene decomposition in organic solvents like acetic acid, acetone, and ethyl acetate were also higher than those in distilled water.

Evaluation of blast furnace slag as basal media for eelgrass bed

Two types of blast furnace slag (BFS), granulated (GS) and air-cooled slag (ACS), were evaluated as basal media for eelgrass bed. Evaluation was done by comparing BFS samples with natural eelgrass sediment (NES) in terms of some physico-chemical characteristics and then, investigating growth of eelgrass both in BFS and NES. In terms of particle size, both BFS samples were within the range acceptable for growing eelgrass. However, compared with NES, low silt-clay content for ACS and lack of organic matter content for both BFS samples were found. Growth experiment showed that eelgrass can grow in both types of BFS, although growth rates in BFS samples shown by leaf elongation were slower than that in NES. The possible reasons for stunted growth in BFS were assumed to be lack of organic matter and release of some possible toxins from BFS. Reduction of sulfide content of BFS samples did not result to enhanced growth; though sulfide release was eliminated, release of Zn was greater than before treatment and concentration of that reached to alarming amounts.

Relationship between growth rate of phenol utilizing bacteria and the toxic effect of metabolic intermediates of trichloroethylene (TCE)

The objective of this study is to clarify the effects of growth rate of phenol utilizing bacteria, on the toxicity of metabolic intermediates of TCE. The specific degradation rates of TCE in the reactor fed with TCE were around 20 to 50% of the reference reactors without TCE when the apparent growth rate was zero, whereas the degradation rates were almost the same when cells were kept in an exponential growth phase. Contrary to the previous studies, the cumulative amount of TCE degradation during one generation was not responsible for the toxic effects by metabolic intermediates of TCE. The toxic effects were dependent on the specific growth rate.

Benthic ecosystem development in an artificial tidal flat constructed from dredged spoil.

Dredged spoil (DS) was used as a silt and clay additive in the construction of artificial tidal flats from mountain sand (MS). As the ratio of DS in the sediment media increased, the number of emerging macrobenthos increased. The composition of the macrobenthic community was also affected by the addition of DS, and the changes might be dependent on the ratio of DS to MS. In addition, the macrobenthos in the artificial tidal flats was more abundant than that in the control tidal flat, which was constructed with natural tidal flat sediment. With a silt and clay content of 25%, polychaetes Ceratonereis erythraeensis and Capitella sp. and the gastropod Batillaria cumingii were dominant, whereas no bivalves were present. With less silt and clay (5% and 10%), the bivalves Ruditapes philippinarum and Musculista senhousia were observed in the artificial flats, while their numbers in the control tidal flat were lower.

Food waste mineralization and accumulation in biological solubilization and composting processes

The biological solubilization and mineralization system (BSMS) was compared to the composting system (CS) in terms of the rate of waste mineralization and accumulation under aerobic condition. A 25-L stainless steel reactor equipped with an impeller that mixed the contents every 30 min for 3 min at a rate of 10 rpm and a perforated plate at the bottom, was used as the experimental reactor for each run. Mineralization rate of food waste was higher in CS (0.24-0.36 kg m(-3) d(-1)) than in BSMS (0.09-0.24 kg m(-3) d(-1)) but the rate of waste accumulation was much higher in CS (0.03-0.15 kg m(-3) d(-1)) than in BSMS (0-0.05 kg m(-3) d(-1)). Abundant water supply in BSMS resulted in the ease of maintaining aerobic condition in the system causing most of the waste to be solubilized and mineralized rather than accumulated in the reactor. Investigation on the effect of food waste loading on waste mineralization and accumulation was also performed. When the loading was varied from 4 to 16 kg m(-3) d(-1), waste accumulation rate in CS was affected. Increased loading resulted in increased accumulation rate in CS while in BSMS there was no pronounced effect. Similarly, as the duration of operation goes beyond 30 d, waste accumulation increased in CS but remained almost the same in BSMS.

Macrobenthic succession and characteristics of a man-made intertidal sandflat constructed in the diversion channel of the Ohta River Estuary

We compared succession and characteristics of the macrobenthic community in a small-scale experimental intertidal sandflat constructed in the artificial diversion channel of the Ohta River Estuary with those of three natural intertidal sandflats at lower elevation in the same channel. The macrobenthic population density in the man-made intertidal sandflat increased significantly between 3 and 9 months after construction. Simplisetia erythraeensis was dominant (98% of individuals) after 9 months, but its proportion gradually declined with the increase in biodiversity until 26 months, indicating that succession of the macrobenthic community was nearly complete by 26 months. The macrobenthic community in the man-made intertidal sandflat differed from those of the three natural intertidal sandflats, and its population density was about double that at the natural sites, with smaller temporal fluctuation. The different structures of the macrobenthic communities in the man-made and natural intertidal sandflats were likely caused by differences in elevation.

Impact of flood events on macrobenthic community structure on an intertidal flat developing in the Ohta River Estuary

We investigated the effects of river floods on the macrobenthic community of the intertidal flat in the Ohta River Estuary, Japan, from 2005 to 2010. Sediment erosion by flood events ranged from about 2-3 cm to 12 cm, and the salinity dropped to 0‰ even during low-intensity flood events. Cluster analysis of the macrobenthic population showed that the community structure was controlled by the physical disturbance, decreased salinity, or both. The opportunistic polychaete Capitella sp. was the most dominant species in all clusters, and populations of the long-lived polychaete Ceratonereis erythraeensis increased in years with stable flow and almost disappeared in years with intense flooding. The bivalve Musculista senhousia was also an important opportunistic species that formed mats in summer of the stable years and influenced the structure of the macrobenthic community. Our results demonstrate the substantial effects of flood events on the macrobenthic community structure.

Construction of Algal Bed Substratum by Steel-making Slag

The objective of this study is evaluate algal bed substratum by steel-making slag. We carried out construction of algal bed substratum by steel-making slag that of particle size finer than natural rock. When algal bed substratum was constructed, the value of the turbidity and pH was almost the same as the surrounding sea area. It could not be confirmed increase in pH when steel-making slag was submerged into the sea. The steel-making slag had been maintained as algal bed substratum after one year. The algal species and amount of the constructed bed by steelmaking slag has been similar that of natural bed and constructed by natural rock.